Magnetic Pickup

Magnetic pickups (MPUs) are speed sensors that detect the speed of a prime mover, typically an engine or turbine. They are the communication link between your engine and a Woodward electronic governor control. The MPU is installed next to a drive shaft gear made of a material that reacts to a magnetic field. As each gear tooth passes the MPU, the gear interrupts the MPU's magnetic field, and an alternating voltage is developed. The frequency of this voltage is translated by the speed control into a signal that accurately depicts the speed of the prime mover.

Magnetic PickUp Principle

Generator Frequently Asked Generator Questions

Q1. How large a generator do I need for my home or small business? 

A. Every home or small business is different. The size of the generator is based on the type of appliances, equipment, pumps, air-conditioners and other electrical devices requiring power.

Your service panel is normally rated at 200 amps @ 240 volts and the average home uses approximately 140 to 160 amps of 240 volts power to operate everything at the same time. Your larger appliances (well pump, kitchen stove, water heater, electric dryer, electric heater and heat pump system) will typically use 240 volts power and the lights and other smaller appliances will use 120 volt power. It is important to consider this difference in doing the load calculations because the important calculation is to determine just how many amps and watts you will need. For example, if you want to operate your refrigerator (20 amps x 120 volts = 2400 watts), freezer (20 amps x 120 volts = 2400 watts), electric hot water heater (20 amps x 240 volts = 4800 watts), washer (20 amps x 120 volts = 2,400 watts) and electric dryer (30 amps x 240 volts = 7200 watts) all at the same time you will need approximately 19,200 watts to meet the breaker requirements for these appliances. In reality the breakers are typically oversized for safety by 10 to 15% and the above appliances will not all operate at peak at the same time and the above load can be handled with a 15,000 watt (15 kW) generator set (GenSet).

The major appliances, pumps, or other motor driven devices that you plan to operate with your generator system need to be considered when calculating the minimum size of a generator. Sizing a generator system requires you to honestly assess your needs and wants. Generally you can cut through all this stuff with these simple rules. If you have 100 Amp service panel, use a 8-12 kW GenSet (use larger if you have air conditioning). If you have a 200 Amp service panel, use a 15-20 kW GenSet (again use the larger size if you have air conditioning or large well pump). If you have a 400 amp service panel, use a 30-50 kW GenSet (if you have lots of air conditioning or other larger loads use the large size in the range).There are some other power requirements that will help you establish a minimum size generator system:

1) Well pumps usually require 2-3 times the run watts to start the pump.

2) Combination heat pump/air-conditioner systems are normally on 60 amp (14400 watts) breakers and use 30 amps (7200 watts) for the heat cycle and the same for the air-conditioning function.

3) Electric furnaces are typically on 50 amp breaker. (6,000 watts at 120 volts)

4) Hot water heaters normally use between 20 amps (4,500 watts) and 25 amps (6,000 watts) depending on the size and efficiency design

5) Electric kitchen stoves are usually on 50 amp (6,000 watts) breakers.

6) Air-conditioners come in a variety of sizes and ratings which need to be calculated based on the BTU output. A 2-ton unit is rated at 24,000 BTU's 20 amps (5000 watts) to start the unit and 15 amps (3,600 watts) to operate it.

Q2. Do generators have advantages over Battery  Systems.
 Yes of course. But these two systems have different advantages compared to each other. So you should now where they are advantegous and not.  In homes we can roughly say generators are better than battery systems. 

Q3. Single or Three Phase? Is a 3-phase generator suitable for the average homeowner or small business? 

A. Yes and No. Some manufacturers use an over-sized 12-wire 3-phase generator end for single-phase applications. This allows the generator system to be used for both single-phase and 3-phase applications. The advantage of using an over-sized generator in a 3-phase or single-phase application is to meet motor starting requirements without having to use an overly large diesel engine. For most residential applications are 1 phase (single phase) and using a 3 phase generator is a waste of money and fuel. If you have a 3 phase service you will need a 3 phase generator otherwise use a unit built as single phase. Be cautious, some dealers will try to sell you a 3 phase generator "strapped" for single phase. You will lose 30% of the generators output and use 30% more fuel to make single phase power.

If your generator system will power air-conditioning units, pumps, heat pumps, well pumps, welders, or irrigation pumps you need assistance calculating your service size let us know. We will make sure you get the right size. GeneratorJoe provides this service free. We will insure that the when your generator is built that the voltage is set and the GenSet is tested at the factory before shipment 

Q4. What is the function of the electronic controller on a GenSet? 

A. Most of the engine/generator controllers used today are digital and are designed to provide control of the generator set. (GenSet). The controller system monitors the operation of the engine and generator functions. Typical safety items include low oil pressure, high temperature, engine start over-crank, over/under frequency (speed), low coolant level etc. Modern digital controllers for residential or small business applications are typically a simplified LED indicators a start-stop button with or without auto-start. If the generator has auto-start, the controller can be used to interface with an automatic transfer switch or inverter/battery system to start and stop automatically. Usually manual controls are provided on al generators including those with auto-start. Advanced controllers provides real time monitoring of volts, hertz and amperage in addition to the basic engine/generator safeties and auto-start functions. Complex controllers typically installed on larger generator systems provide engine safeties and shutdowns for low oil pressure, high temperature, engine start over-crank, over/under-speed, low coolant level and also have indicators for low fuel level, KVA output, KW output, power factor (PF), engine & generator gauges in real time. Larger generators often have a communication capability for remote monitoring and starting. 

Q5. Can I use a portable generator for an automatic starting system? 

A. Generally No. Most portable generators do NOT have the capability to auto-start. The generator must have an electric starter, electric choke (for gasoline units) and the start and stop controls and safety sensors to be able to start and stop automatically. The cost of auto-start and safety equipment generally increases the price of portable equipment so much that no one would buy them, so they are not manufactured. 

Q6. What kind of generator should I purchase - gaseous or diesel? 

A. There are a number of factors to consider in evaluating the differences between a gaseous (natural gas or propane) powered engine. 

GeneratorJoe recommends the use of liquid-cooled diesel engine GenSets in hurricane environments where the potential for long run times is high or for prime duty applications where the generator is the prime source of power. GeneratorJoe carries a number of high quality diesel powered generator products designed to provide years of trouble-free operation. 

Q7. Do 3600 RPM diesel generators last as long as 1800 RPM GenSets? 

A. Generally the 1800 RPM engine speed will out last the 3600 RPM units. Most small diesel portable generators in the 3 kW to 6 kW class are air-cooled 3600 RPM engines are designed to keep the weight and cost down. Generally air cooled GenSets are for temporary use and have short lives. If you need a long term solution or have several outages a year or long outage times use a liquid cooled 1800 RPM GenSet. 

Q8. We want the power generator to supply power to a computer system in our home or business; what are the issues involved? 

A. Most generators sold by GeneratorJoe are designed to power computers. The majority of 1800 RPM and 3600 RPM liquid-cooled generators use automatic voltage regulated (AVR-Electronic module) generator systems that provide from 1% to 2% voltage regulation, which meets or exceeds the local utility power specifications. Some portable generators with capacitor regulation (voltage control from 5% to 10% or without AVR) can present a problem for some computer systems if the computer is plugged directly into the electrical circuit and does not use a battery regulated power supply or UPS. Another factor that impacts computers is the speed control, (which effects frequency in hertz) which is normally 3-5% with an engine mechanical governor regulation and .25% to .5% regulation with an electronic engine governor system. Mechanically governed systems are normally sufficient to provide clean power for sensitive electronics like computers. For computer service centers and other communication applications like radio and TV stations that use a UPS system, they usually use of an electronic governor. Electronic governors not only maintain engine speed more accurately but with a much quicker response time to no-load to load conditions which helps prevent voltage drop. Most industrial diesel engines equipped with auto-start can be equipped from the factory with an electronic governor depending on the manufacture and engine design, however the costs will be much higher than a mechanical governor and may not be necessary for most uses. GeneratorJoe has developed a series of Cummins diesel powered open and sound enclosed GenSets rated for both standby (emergency service less than 500 hours per year) or prime (main power source over 500 hours per year). The new GeneratorJoe Cummins powered Warrior and Gladiator Series represents one of the most competitively priced full featured quality diesel generators on the market today. 

Q9. What does the term "Wet Stacking" mean in a diesel engine? 

A. Diesel engines are designed to operate with a load. When a diesel engine operates considerably below the rated output level the engine can start to over-fuel or "Wet Stack". Diesel engines perform most efficiently in the 70-80% range of rated output. When an engine operates for a prolonged period of time below 40% of the rated output it begins to over-fuel. This is similar to driving a car in the City at slow speeds for long periods. Wet Stacking occurs because the injection tips began to carbonize and disrupt the fuel spray pattern. Commercial generator systems often have widely varying loads with some low output conditions often have wet stacking problems because of the diverse load applications and owners artificially load the generator with an automatic load bank. A load bank will place a "false" load on the generator system to keep the diesel engine properly loaded. Once a diesel engine begins to "wet stack" the only way to correct the problem is to load the engine for a couple of hours to burn off the excess fuel and clean up the engine. This is seldom necessary in a residential or commercial application. Generally, electronically controlled engines and engines with advanced emission systems are less likely to "wet stack". It is for this reason that proper sizing and design is important. GeneratorJoe can help you with all your sizing and design considerations. 

Q10. What kind of maintenance will my diesel generator need and how complicated is it for the average homeowner or small business? 

A. Diesel engines require routine maintenance for long-life service. The normal maintenance requirements are about the same as owning a diesel powered vehicle - oil, oil filter, air filter and fuel filter. In tropical and cold climates it is advisable to have a water-fuel separation filter system installed. Water or moisture in diesel fuel can be damaging to a diesel engine because the water properties create advanced ignition and accelerated detonation.

The engine will need an oil change every 250 to 500 hours depending on the dust conditions or annually in the case of standby generators. Change the oil filter when you change the oil. Air filters need to be changed when they appear dirty. Check air filters whenever you inspect the generator or change the oil. Fuel filters are normally changed every 250 to 300 hours depending on how clean the fuel is. Inspect fuel filters when you fill the tanks, during oil changes and any time you inspect the generator. If the generator has a service schedule, follow it.

The generator end (AC alternator) will not require any service unless you live in a dusty environment. In dusty environments we recommend you use a high pressure (50 PSI) air hose and occasionally blow out the dust from the generator system. Dirt and heavy dust particles can cause shorts in the internal wiring coatings under the right conditions. 

Q11. Will the GenSet I purchase from GeneratorJoe have adequate operating instructions and service manuals? 

A. Every GenSet sold by GeneratorJoe comes complete with an operators manual for the engine, generator and controller if applicable. We will include any special instructions for added options or features, if available. Some manufactures offer factory service and parts manual kits as an option 

Q12. How do transfer switches work and can I install one myself? 

A. GeneratorJoe recommends that transfer switches be installed by a licensed electrician. A transfer switch is a box that only allows power to be supplied to the distribution panel from the utility or the generator system, but not both at the same time.

There are basically three types of transfer switches to consider. 

1) Manually operated panels providing 6 to 10 pre-selected circuits that can be used during any generator supplied power situation.  These types are used primarily for portable generators.

2) Manually operated Service rated (e.g. 100A, 200A, or 400A) NEMA-1(indoor rated) or NEMA-3R (outdoor rated), UL rated panels for either single or 3-phase applications.

3) Automatic operated Service rated panels. .

For manual switches. The normal sequence of events to transfer a manual switch when the power goes off, follow these simple steps. 1) Leave the transfer switch in the utility position. 2) Start the generator and allow it to properly warm up. The generator breaker should be in and stay in the on position; 3) Once the generator engine is warmed up move the transfer switch to the generator position. When the power returns from the utility the sequence of events is reversed: 1) Simply move the transfer switch to the utility position 2) After the generator engine has run with no-load and cooled down for approximately 5-minutes shut the generator engine down.

Automatic switches do all the functions needed to go from utility to generator power and back, without any intervention by a person. If you are often away from home working, leaving your spouse and kids at home alone, use an automatic system. You don't want them going outside and trying to transfer equipment they are not familiar with. Automatic systems also exercise the generator every month to circulate oil and charge the batteries.

Three phase systems should always use automatic transfer switches because they include in-phase monitoring controls that prevent power transfers when the transfer will damage a out-of-phase equipment.

Q13. What is the difference between standby/emergency/maximum and prime/continuous duty applications? 

A. Most products have a "maximum" rating, also called standby and emergency rating. This value is the most that a generator can produce under normal conditions although it may still have some peak reserve for surges. The prime or continuous rating is the rating that the equipment should not exceed under normal running on a continuous basis. Even though small portables have both ratings that does not mean that they are designed for continuous use. A prime power generator must be 1800 RPM and liquid cooled. Any air cooled or 3600 RPM generator is a standby generator no matter what other dealers may tell you. Most residential generators are standby rated. You should use a prime rated, 1800 RPM, liquid cooled generator when the number of hours per year will exceed 500 and the use is on a regular basis. If you start the generator many times a year for short periods you may also need a prime power rated generator. You must use a prime power rated generator when the generator is used 24 hours per day and 7-days per week. If you use a standby generator in a prime power situation the generators life expectancy can be shortened considerably and the potential for premature failure is increased dramatically. Buying a GenSet rated for standby duty and using it for prime or prime continuous application is just dumb and will normally void your factory warranty as well. Your generator system should be considered a long-term investment and should be sized and selected properly. 

Q14. Why do well pumps, air-conditioners, welders and other electrical motor driven appliances require special consideration when sizing a generator? 

A. Appliances and equipment with electric motors, especially compressors and well pumps, have a much higher start up amperage called Locked Rotor Amps (LRA), than the running amps shown on most nameplates. As a general rule of thumb is a minimum of at least twice the amperage to start a device as to run it. However, some devices can require up to 6 or 7 times the amperage to start as to run. If you have water wells, large air-conditioners, sump-pumps, or other heavy duty motor applications you need to find out what the locked rotor amps of the largest piece of equipment is. GeneratorJoe can assist you with all of your motor starting calculations and we can supply you with generator systems designed to provide the best performance and size for heavy duty motor starting applications. 

Q15. How are decibel levels calculated on generators? 

A. Most generator manufactures, but not all, calculate dBA levels at full load operation. The USA standard is based on the sound level at 21 feet (7 meters) and the European standard is based on the sound level at 23 feet but its close enough to compare. The calculation of dBA levels involves a complicated mathematical formula. The relative noise level is the best way to understand the relationship of one sound to another. Human conversation is 60 dBA. below are typical descriptions of sound levels. Take all sound levels provided by manufactures with a grain of salt. You cant tell the difference in 5 dBA without a lot of experience and a sound meter. See our noise table at NOISE.

Industrial Quiet well designed enclosure with air-scoop and dense foam. 69 to 75 dBA - noticeable noise level at 10-feet / loud conversation at 21-feet.

Residential Quiet well designed enclosure with air-scoops and foam. 64 to 68 dBA - quiet but noticeable at 10-feet / normal conversation at 21-feet.

Super Quiet special sound attenuation enclosure normally with air-scoops and dense foam. 61 to 63 dBA - normal conversation at 10-feet / quiet operation at 21-feet. 

Ultra Quiet special sound attenuation design for rental fleets or residential applications. 56 to 60 dBA - barely hear the unit operate at 10-feet / normal conversation at 10-feet. 

Entertainment Industry Quiet Special and expensive sound attenuated and designed GenSets. 50 to 55 dBA - barely hear the unit operate at 3-feet / normal conversation next to GenSet.

For the average residential application, the residential levels shown about are adequate. Some engines tend to be noisier than others and will have some effect on the overall dBA rating of the unit. Obviously, a 10 kW generator is typically quieter than a 40 kW if all other conditions are equal. The abatement of noise in all GenSets is normally a function of the enclosure design, air-flow and the quality and type of insulation used. Front air-scoops are ypically used to remove radiator sound. Special residential grade muffler systems are used to help reduce the engine noise. 

Q16. What are the most important things to consider when purchasing a standby/emergency generator system? 

A. Here is a list of important things to consider:

1) A generator is a major purchase and should be amortized over it's expected life. A generator can last 10 to 20 years if properly taken care of. For most residential applications a quality generator will last a life time if used for standby/emergency backup. For this reason we recommend the purchase of a quality GenSet with suitable features for your application. A cheap or bargain price will become an expensive lesson when your buying the second or third generator or when the power goes out and the cheap unit fails. Buy right the first time, spend a little more on quality. Don't be cheap at first and spend more in the long run.

Chinese (or other foreign) generators sold on the internet look like good deals but they are not. Here's why: 

(a). Most Chinese generators are copies of U.S. Made units but they are not good enough copies to use U.S. manufacturers spare parts. Even Chinese spare parts are such poor quality they wont fit. 

(b). Many Chinese generators do not really have EPA approval and they have phony environment certificates. It is very hard to verify there certificates and the Chinese makers know that, so they just claim they have EPA approval. Most don't. 

(c). Most foreign made non-EPA compliant generators have terrible fuel economy, produce excessive emissions and consume oil. Many of the countries that make these generators are the biggest polluters in the world so they don't have or enforce any environmental controls. 

(d). Buying foreign generators hurts America!. Buying this junk not only pollutes our environment but it puts Americans out of work, contributes to the trade deficit, devalues the U.S. Dollar and ships U.S. economic power to foreign countries. BUY AMERICAN!

2) If your backup requirements are "occasional" and you only need limited power during an outage an inexpensive generator system will most likely meet your needs (air-cooled, 3600 RPM gasoline, diesel or gaseous GenSets will work. 

3) If you live anywhere on the East Coast, Florida, or in the Caribbean you are likely to need a heavy duty diesel GenSet and one with high quality features. Most modern gaseous or diesel engines are reliable and fuel efficient. Block heated diesel models provide easy starting in cold weather. An 1800 RPM, liquid cooled generator will provide better fuel efficiency and longer life but cost more initially. 

4) The generator end is the usually the last thing to fail with heavy use. The insulation coatings on the windings are based on heat ratings and 'F' is good and 'H' is better. Some major brands manufacture their own generator ends and parts and repair is usually only available through the manufacturer. Most manufacturers use off-the-shelf industrial brands like Marathon, MeccAlte, Newage and Somers because parts are readily available and any qualified service repair center can service the generator end. 

5) Controllers are a vital part of most generator systems. The controller monitors the generator engine speed for hertz, the oil pressure and water temperature and other engine and generator functions. It shuts down the engine if one of the threshold settings for these controls fails. It also provides the auto-start function for the automatic transfer switch or inverter if one is used. Buy a unit with adequate controls. Don't buy glitz and features you do not need, just more things to take care of and go wrong. All GeneratorJoe models come with digital control panels. 

6) A generator is a mechanical and electrical device that over time will need some service or parts. Make sure you are purchasing a generator system that will be supported in the future from a company that will be there to support you. Someone reliable brands like GeneratorJoe or Winco are best. 

7) Know what you intend to run with your generator and make sure the generator you purchase will handle your load. GeneratorJoe can help you with design considerations, load calculations and motor starting considerations. 

Q17. What size transfer switch do I need? 

A. The transfer switch is sized to match the service or sub-panel on the building. The transfer switch must also be the same size in amps (or larger) than themaximum output of the generator you select. Example: If you have a 12 kW generator operating at 120 VAC single phase, (100 Amps) and a 200 amp building service you need a 200 Amp transfer switch or you must install a 100 Amp sub-panel. Transfer switches should be installed by a licensed electrician. 

Q18. How does a transfer switch work? 

A. The automatic transfer switch monitors utility and generator power. When utility power fails or is unsatisfactory, the transfer switch control starts the generator set, checks the generator speed and voltage output and transfers the load to the generator set. When utility power is restored the transfer switch automatically transfers back to utility power. The generator is llowed to cool down for a short period and then shuts down. The system instantly resets itself and is ready for the next power interruption. No action is required by the user. 

Q19. Can I save money buying a manual transfer switch? 

A. Generally no. Most modern automatic transfer switches have a manual mode so they do not switch until you change the switch position to transfer or automatic. New switches are electrically operated and when they change position they use power from the utility or generator to move. They DO NOT have handles on the sides of them like old fashioned switches. You may save $100 or so on a manual switch and you cannot retrofit the switch later to make it automatic. For portable generators buy a manual switch from Reliance Controls. We carry a full line of automatic and manual switches. 

Q20. Do I need an indoor (Nema1) or outdoor (Nema 3) switch. 

A. If you can install the switch inside a building you can use an indoor switch. Inside means in a heated garage or building. An unheated, drafty, damp tool shed is considered outside. In most cases it cost a few dollars to a few hundred dollars to upgrade to an outdoor Nema 3R switch. We always recommend that you buy an outdoor switch because they are water resistant and tighter than indoor switches. If there is any chance water will be sprayed around a transfer switch, an outdoor version is always a good investment. Any moisture inside a transfer switch will cause it to fail at the very time you need it. 

Q21. Is there a way to get a competitive price on a number of different transfer switches? 

A. Yes. At the top of every page there is a button that called Transfer Switch Find. It looks like this. >

There are also buttons like this on every product page on the website. You can go to the finder anytime, even if you have items in the shopping cart. 

Q22. What size generator do I need? 

A. Every home or small business is different. The size of the generator is based on the type of appliances, equipment, pumps, air-conditioners and other electrical devices requiring power.

Your service panel is normally rated at 200 amps @ 240 volts and the average home uses approximately 140 to 160 amps of 240 volts power to operate everything at the same time. Your larger appliances (well pump, kitchen stove, water heater, electric dryer, electric heater and heat pump system) will typically use 240 volts power and the lights and other smaller appliances will use 120 volt power. It is important to consider this difference in doing the load calculations because the important calculation is to determine just how many amps and watts you will need. For example, if you want to operate your refrigerator (20 amps x 120 volts = 2400 watts), freezer (20 amps x 120 volts = 2400 watts), electric hot water heater (20 amps x 240 volts = 4800 watts), washer (20 amps x 120 volts = 2,400 watts) and electric dryer (30 amps x 240 volts = 7200 watts) all at the same time you will need approximately 19,200 watts to meet the breaker requirements for these appliances. In reality the breakers are typically oversized for safety by 10 to 15% and the above appliances will not all operate at peak at the same time and the above load can be handled with a 15,000 watt (15 kW) generator set (GenSet).

Generally you can cut through all this stuff with these simple rules. If you have 100 Amp service panel, use a 8-12 kW GenSet (use larger if you have air conditioning). If your have a 200 Amp service panel, use a 15-20 kW GenSet (again use the larger size if you have air conditioning or large well pump). If you have a 400 amp service panel, use a 30-50 kW GenSet (if you have lots of air 

Q23. Do I need a fuel tank? 

A. Industrial diesel generators require a tank either under it (called a sub-base tank) or near it (called an external tank). We sell both types and they are listed as options in each generator product. RV generators require an external tank on the vehicle, we do not sell these tanks. Propane generators require an external propane tank, we do not sell these tanks. Portable generators have tanks installed on them and they are not expandable 

Q24. What is included with each generator? 

A. At the bottom of each product description on the product page is RED text that describes what is included with each generator. It looks like this: "Included Equipment: Generator engine and alternator, open skid mount platform, weather enclosure, no tank, flexible fuel lines, oil drain cock, digital control panel, electronic governor, residential muffler (enclosed models), industrial muffler (open models), spring isolators, 12 volt electric starter, included charging alternator, air filter, radiator, blower fan and guards, battery tray, battery cables, owners manual and warranty. Other options are NOT included please purchase the options from the option lists." 

Q25. What is the difference between single and three phase? 

A. Single phase has only one phase using two wires and three phase has three phases using three or four wires. Generally homes are single phase and business are three phase. If you go out to your main breaker panel you can usually tell if you have a single or three phase service. Single phase is 120/240 and three phase can be 120/240, 120/208 or 277/480. There are other voltages but these are the most common. If you are not sure what your power is, have an electrician come and look at your service or call your utility company. 

(This information was taken from a website called generatorjoe ! )

Generator Frequently Asked Generator Questions

Q1. How large a generator do I need for my home or small business? 

A. Every home or small business is different. The size of the generator is based on the type of appliances, equipment, pumps, air-conditioners and other electrical devices requiring power.

Your service panel is normally rated at 200 amps @ 240 volts and the average home uses approximately 140 to 160 amps of 240 volts power to operate everything at the same time. Your larger appliances (well pump, kitchen stove, water heater, electric dryer, electric heater and heat pump system) will typically use 240 volts power and the lights and other smaller appliances will use 120 volt power. It is important to consider this difference in doing the load calculations because the important calculation is to determine just how many amps and watts you will need. For example, if you want to operate your refrigerator (20 amps x 120 volts = 2400 watts), freezer (20 amps x 120 volts = 2400 watts), electric hot water heater (20 amps x 240 volts = 4800 watts), washer (20 amps x 120 volts = 2,400 watts) and electric dryer (30 amps x 240 volts = 7200 watts) all at the same time you will need approximately 19,200 watts to meet the breaker requirements for these appliances. In reality the breakers are typically oversized for safety by 10 to 15% and the above appliances will not all operate at peak at the same time and the above load can be handled with a 15,000 watt (15 kW) generator set (GenSet).

The major appliances, pumps, or other motor driven devices that you plan to operate with your generator system need to be considered when calculating the minimum size of a generator. Sizing a generator system requires you to honestly assess your needs and wants. Generally you can cut through all this stuff with these simple rules. If you have 100 Amp service panel, use a 8-12 kW GenSet (use larger if you have air conditioning). If you have a 200 Amp service panel, use a 15-20 kW GenSet (again use the larger size if you have air conditioning or large well pump). If you have a 400 amp service panel, use a 30-50 kW GenSet (if you have lots of air conditioning or other larger loads use the large size in the range).There are some other power requirements that will help you establish a minimum size generator system:

1) Well pumps usually require 2-3 times the run watts to start the pump.

2) Combination heat pump/air-conditioner systems are normally on 60 amp (14400 watts) breakers and use 30 amps (7200 watts) for the heat cycle and the same for the air-conditioning function.

3) Electric furnaces are typically on 50 amp breaker. (6,000 watts at 120 volts)

4) Hot water heaters normally use between 20 amps (4,500 watts) and 25 amps (6,000 watts) depending on the size and efficiency design

5) Electric kitchen stoves are usually on 50 amp (6,000 watts) breakers.

6) Air-conditioners come in a variety of sizes and ratings which need to be calculated based on the BTU output. A 2-ton unit is rated at 24,000 BTU's 20 amps (5000 watts) to start the unit and 15 amps (3,600 watts) to operate it.

Q2. What is the advantage of buying a generator direct over the internet through GeneratorJoe as opposed to buying from a local dealer? 

A. GeneratorJoe supplies many of the best generator products available in the world today at the most competitive prices available. Our factory direct program removes the middle man and generally saves the customer 10-30% off the normal dealer price. Retail stores are usually restricted to one brand. We have a wide selection of products so you get the best model for your application at the best possible price. GeneratorJoe gives you the selection and services needed to make it easier to own a generator system.

Q3. Single or Three Phase? Is a 3-phase generator suitable for the average homeowner or small business? 

A. Yes and No. Some manufacturers use an over-sized 12-wire 3-phase generator end for single-phase applications. This allows the generator system to be used for both single-phase and 3-phase applications. The advantage of using an over-sized generator in a 3-phase or single-phase application is to meet motor starting requirements without having to use an overly large diesel engine. For most residential applications are 1 phase (single phase) and using a 3 phase generator is a waste of money and fuel. If you have a 3 phase service you will need a 3 phase generator otherwise use a unit built as single phase. Be cautious, some dealers will try to sell you a 3 phase generator "strapped" for single phase. You will lose 30% of the generators output and use 30% more fuel to make single phase power.

If your generator system will power air-conditioning units, pumps, heat pumps, well pumps, welders, or irrigation pumps you need assistance calculating your service size let us know. We will make sure you get the right size. GeneratorJoe provides this service free. We will insure that the when your generator is built that the voltage is set and the GenSet is tested at the factory before shipment 

Q4. What is the function of the electronic controller on a GenSet? 

A. Most of the engine/generator controllers used today are digital and are designed to provide control of the generator set. (GenSet). The controller system monitors the operation of the engine and generator functions. Typical safety items include low oil pressure, high temperature, engine start over-crank, over/under frequency (speed), low coolant level etc. Modern digital controllers for residential or small business applications are typically a simplified LED indicators a start-stop button with or without auto-start. If the generator has auto-start, the controller can be used to interface with an automatic transfer switch or inverter/battery system to start and stop automatically. Usually manual controls are provided on al generators including those with auto-start. Advanced controllers provides real time monitoring of volts, hertz and amperage in addition to the basic engine/generator safeties and auto-start functions. Complex controllers typically installed on larger generator systems provide engine safeties and shutdowns for low oil pressure, high temperature, engine start over-crank, over/under-speed, low coolant level and also have indicators for low fuel level, KVA output, KW output, power factor (PF), engine & generator gauges in real time. Larger generators often have a communication capability for remote monitoring and starting. 

Q5. Can I use a portable generator for an automatic starting system? 

A. Generally No. Most portable generators do NOT have the capability to auto-start. The generator must have an electric starter, electric choke (for gasoline units) and the start and stop controls and safety sensors to be able to start and stop automatically. The cost of auto-start and safety equipment generally increases the price of portable equipment so much that no one would buy them, so they are not manufactured. 

Q6. What kind of generator should I purchase - gaseous or diesel? 

A. There are a number of factors to consider in evaluating the differences between a gaseous (natural gas or propane) powered engine. 

GeneratorJoe recommends the use of liquid-cooled diesel engine GenSets in hurricane environments where the potential for long run times is high or for prime duty applications where the generator is the prime source of power. GeneratorJoe carries a number of high quality diesel powered generator products designed to provide years of trouble-free operation. 

Q7. Do 3600 RPM diesel generators last as long as 1800 RPM GenSets? 

A. Generally the 1800 RPM engine speed will out last the 3600 RPM units. Most small diesel portable generators in the 3 kW to 6 kW class are air-cooled 3600 RPM engines are designed to keep the weight and cost down. Generally air cooled GenSets are for temporary use and have short lives. If you need a long term solution or have several outages a year or long outage times use a liquid cooled 1800 RPM GenSet. 

Q8. We want the power generator to supply power to a computer system in our home or business; what are the issues involved? 

A. Most generators sold by GeneratorJoe are designed to power computers. The majority of 1800 RPM and 3600 RPM liquid-cooled generators use automatic voltage regulated (AVR-Electronic module) generator systems that provide from 1% to 2% voltage regulation, which meets or exceeds the local utility power specifications. Some portable generators with capacitor regulation (voltage control from 5% to 10% or without AVR) can present a problem for some computer systems if the computer is plugged directly into the electrical circuit and does not use a battery regulated power supply or UPS. Another factor that impacts computers is the speed control, (which effects frequency in hertz) which is normally 3-5% with an engine mechanical governor regulation and .25% to .5% regulation with an electronic engine governor system. Mechanically governed systems are normally sufficient to provide clean power for sensitive electronics like computers. For computer service centers and other communication applications like radio and TV stations that use a UPS system, they usually use of an electronic governor. Electronic governors not only maintain engine speed more accurately but with a much quicker response time to no-load to load conditions which helps prevent voltage drop. Most industrial diesel engines equipped with auto-start can be equipped from the factory with an electronic governor depending on the manufacture and engine design, however the costs will be much higher than a mechanical governor and may not be necessary for most uses. GeneratorJoe has developed a series of Cummins diesel powered open and sound enclosed GenSets rated for both standby (emergency service less than 500 hours per year) or prime (main power source over 500 hours per year). The new GeneratorJoe Cummins powered Warrior and Gladiator Series represents one of the most competitively priced full featured quality diesel generators on the market today. 

Q9. What does the term "Wet Stacking" mean in a diesel engine? 

A. Diesel engines are designed to operate with a load. When a diesel engine operates considerably below the rated output level the engine can start to over-fuel or "Wet Stack". Diesel engines perform most efficiently in the 70-80% range of rated output. When an engine operates for a prolonged period of time below 40% of the rated output it begins to over-fuel. This is similar to driving a car in the City at slow speeds for long periods. Wet Stacking occurs because the injection tips began to carbonize and disrupt the fuel spray pattern. Commercial generator systems often have widely varying loads with some low output conditions often have wet stacking problems because of the diverse load applications and owners artificially load the generator with an automatic load bank. A load bank will place a "false" load on the generator system to keep the diesel engine properly loaded. Once a diesel engine begins to "wet stack" the only way to correct the problem is to load the engine for a couple of hours to burn off the excess fuel and clean up the engine. This is seldom necessary in a residential or commercial application. Generally, electronically controlled engines and engines with advanced emission systems are less likely to "wet stack". It is for this reason that proper sizing and design is important. GeneratorJoe can help you with all your sizing and design considerations. 

Q10. What kind of maintenance will my diesel generator need and how complicated is it for the average homeowner or small business? 

A. Diesel engines require routine maintenance for long-life service. The normal maintenance requirements are about the same as owning a diesel powered vehicle - oil, oil filter, air filter and fuel filter. In tropical and cold climates it is advisable to have a water-fuel separation filter system installed. Water or moisture in diesel fuel can be damaging to a diesel engine because the water properties create advanced ignition and accelerated detonation.

The engine will need an oil change every 250 to 500 hours depending on the dust conditions or annually in the case of standby generators. Change the oil filter when you change the oil. Air filters need to be changed when they appear dirty. Check air filters whenever you inspect the generator or change the oil. Fuel filters are normally changed every 250 to 300 hours depending on how clean the fuel is. Inspect fuel filters when you fill the tanks, during oil changes and any time you inspect the generator. If the generator has a service schedule, follow it.

The generator end (AC alternator) will not require any service unless you live in a dusty environment. In dusty environments we recommend you use a high pressure (50 PSI) air hose and occasionally blow out the dust from the generator system. Dirt and heavy dust particles can cause shorts in the internal wiring coatings under the right conditions. 

Q11. Will the GenSet I purchase from GeneratorJoe have adequate operating instructions and service manuals? 

A. Every GenSet sold by GeneratorJoe comes complete with an operators manual for the engine, generator and controller if applicable. We will include any special instructions for added options or features, if available. Some manufactures offer factory service and parts manual kits as an option 

Q12. How do transfer switches work and can I install one myself? 

A. GeneratorJoe recommends that transfer switches be installed by a licensed electrician. A transfer switch is a box that only allows power to be supplied to the distribution panel from the utility or the generator system, but not both at the same time.

There are basically three types of transfer switches to consider. 

1) Manually operated panels providing 6 to 10 pre-selected circuits that can be used during any generator supplied power situation.  These types are used primarily for portable generators.

2) Manually operated Service rated (e.g. 100A, 200A, or 400A) NEMA-1(indoor rated) or NEMA-3R (outdoor rated), UL rated panels for either single or 3-phase applications.

3) Automatic operated Service rated panels. .

For manual switches. The normal sequence of events to transfer a manual switch when the power goes off, follow these simple steps. 1) Leave the transfer switch in the utility position. 2) Start the generator and allow it to properly warm up. The generator breaker should be in and stay in the on position; 3) Once the generator engine is warmed up move the transfer switch to the generator position. When the power returns from the utility the sequence of events is reversed: 1) Simply move the transfer switch to the utility position 2) After the generator engine has run with no-load and cooled down for approximately 5-minutes shut the generator engine down.

Automatic switches do all the functions needed to go from utility to generator power and back, without any intervention by a person. If you are often away from home working, leaving your spouse and kids at home alone, use an automatic system. You don't want them going outside and trying to transfer equipment they are not familiar with. Automatic systems also exercise the generator every month to circulate oil and charge the batteries.

Three phase systems should always use automatic transfer switches because they include in-phase monitoring controls that prevent power transfers when the transfer will damage a out-of-phase equipment.

Q13. What is the difference between standby/emergency/maximum and prime/continuous duty applications? 

A. Most products have a "maximum" rating, also called standby and emergency rating. This value is the most that a generator can produce under normal conditions although it may still have some peak reserve for surges. The prime or continuous rating is the rating that the equipment should not exceed under normal running on a continuous basis. Even though small portables have both ratings that does not mean that they are designed for continuous use. A prime power generator must be 1800 RPM and liquid cooled. Any air cooled or 3600 RPM generator is a standby generator no matter what other dealers may tell you. Most residential generators are standby rated. You should use a prime rated, 1800 RPM, liquid cooled generator when the number of hours per year will exceed 500 and the use is on a regular basis. If you start the generator many times a year for short periods you may also need a prime power rated generator. You must use a prime power rated generator when the generator is used 24 hours per day and 7-days per week. If you use a standby generator in a prime power situation the generators life expectancy can be shortened considerably and the potential for premature failure is increased dramatically. Buying a GenSet rated for standby duty and using it for prime or prime continuous application is just dumb and will normally void your factory warranty as well. Your generator system should be considered a long-term investment and should be sized and selected properly. 

Q14. Why do well pumps, air-conditioners, welders and other electrical motor driven appliances require special consideration when sizing a generator? 

A. Appliances and equipment with electric motors, especially compressors and well pumps, have a much higher start up amperage called Locked Rotor Amps (LRA), than the running amps shown on most nameplates. As a general rule of thumb is a minimum of at least twice the amperage to start a device as to run it. However, some devices can require up to 6 or 7 times the amperage to start as to run. If you have water wells, large air-conditioners, sump-pumps, or other heavy duty motor applications you need to find out what the locked rotor amps of the largest piece of equipment is. GeneratorJoe can assist you with all of your motor starting calculations and we can supply you with generator systems designed to provide the best performance and size for heavy duty motor starting applications. 

Q15. How are decibel levels calculated on generators? 

A. Most generator manufactures, but not all, calculate dBA levels at full load operation. The USA standard is based on the sound level at 21 feet (7 meters) and the European standard is based on the sound level at 23 feet but its close enough to compare. The calculation of dBA levels involves a complicated mathematical formula. The relative noise level is the best way to understand the relationship of one sound to another. Human conversation is 60 dBA. below are typical descriptions of sound levels. Take all sound levels provided by manufactures with a grain of salt. You cant tell the difference in 5 dBA without a lot of experience and a sound meter. See our noise table at NOISE.

Industrial Quiet well designed enclosure with air-scoop and dense foam. 69 to 75 dBA - noticeable noise level at 10-feet / loud conversation at 21-feet.

Residential Quiet well designed enclosure with air-scoops and foam. 64 to 68 dBA - quiet but noticeable at 10-feet / normal conversation at 21-feet.

Super Quiet special sound attenuation enclosure normally with air-scoops and dense foam. 61 to 63 dBA - normal conversation at 10-feet / quiet operation at 21-feet. 

Ultra Quiet special sound attenuation design for rental fleets or residential applications. 56 to 60 dBA - barely hear the unit operate at 10-feet / normal conversation at 10-feet. 

Entertainment Industry Quiet Special and expensive sound attenuated and designed GenSets. 50 to 55 dBA - barely hear the unit operate at 3-feet / normal conversation next to GenSet.

For the average residential application, the residential levels shown about are adequate. Some engines tend to be noisier than others and will have some effect on the overall dBA rating of the unit. Obviously, a 10 kW generator is typically quieter than a 40 kW if all other conditions are equal. The abatement of noise in all GenSets is normally a function of the enclosure design, air-flow and the quality and type of insulation used. Front air-scoops are ypically used to remove radiator sound. Special residential grade muffler systems are used to help reduce the engine noise. 

Q16. What are the most important things to consider when purchasing a standby/emergency generator system? 

A. Here is a list of important things to consider.

1) A generator is a major purchase and should be amortized over it's expected life. A generator can last 10 to 20 years if properly taken care of. For most residential applications a quality generator will last a life time if used for standby/emergency backup. For this reason we recommend the purchase of a quality GenSet with suitable features for your application. A cheap or bargain price will become an expensive lesson when your buying the second or third generator or when the power goes out and the cheap unit fails. Buy right the first time, spend a little more on quality. Don't be cheap at first and spend more in the long run.

Chinese (or other foreign) generators sold on the internet look like good deals but they are not. Here's why: 

(a). Most Chinese generators are copies of U.S. Made units but they are not good enough copies to use U.S. manufacturers spare parts. Even Chinese spare parts are such poor quality they wont fit. 

(b). Many Chinese generators do not really have EPA approval and they have phony environment certificates. It is very hard to verify there certificates and the Chinese makers know that, so they just claim they have EPA approval. Most don't. 

(c). Most foreign made non-EPA compliant generators have terrible fuel economy, produce excessive emissions and consume oil. Many of the countries that make these generators are the biggest polluters in the world so they don't have or enforce any environmental controls. 

(d). Buying foreign generators hurts America!. Buying this junk not only pollutes our environment but it puts Americans out of work, contributes to the trade deficit, devalues the U.S. Dollar and ships U.S. economic power to foreign countries. BUY AMERICAN!

2) If your backup requirements are "occasional" and you only need limited power during an outage an inexpensive generator system will most likely meet your needs (air-cooled, 3600 RPM gasoline, diesel or gaseous GenSets will work. 

3) If you live anywhere on the East Coast, Florida, or in the Caribbean you are likely to need a heavy duty diesel GenSet and one with high quality features. Most modern gaseous or diesel engines are reliable and fuel efficient. Block heated diesel models provide easy starting in cold weather. An 1800 RPM, liquid cooled generator will provide better fuel efficiency and longer life but cost more initially. 

4) The generator end is the usually the last thing to fail with heavy use. The insulation coatings on the windings are based on heat ratings and 'F' is good and 'H' is better. Some major brands manufacture their own generator ends and parts and repair is usually only available through the manufacturer. Most manufacturers use off-the-shelf industrial brands like Marathon, MeccAlte, Newage and Somers because parts are readily available and any qualified service repair center can service the generator end. 

5) Controllers are a vital part of most generator systems. The controller monitors the generator engine speed for hertz, the oil pressure and water temperature and other engine and generator functions. It shuts down the engine if one of the threshold settings for these controls fails. It also provides the auto-start function for the automatic transfer switch or inverter if one is used. Buy a unit with adequate controls. Don't buy glitz and features you do not need, just more things to take care of and go wrong. All GeneratorJoe models come with digital control panels. 

6) A generator is a mechanical and electrical device that over time will need some service or parts. Make sure you are purchasing a generator system that will be supported in the future from a company that will be there to support you. Someone reliable brands like GeneratorJoe or Winco are best. 

7) Know what you intend to run with your generator and make sure the generator you purchase will handle your load. GeneratorJoe can help you with design considerations, load calculations and motor starting considerations. 

Q17. What size transfer switch do I need? 

A. The transfer switch is sized to match the service or sub-panel on the building. The transfer switch must also be the same size in amps (or larger) than themaximum output of the generator you select. Example: If you have a 12 kW generator operating at 120 VAC single phase, (100 Amps) and a 200 amp building service you need a 200 Amp transfer switch or you must install a 100 Amp sub-panel. Transfer switches should be installed by a licensed electrician. 

Q18. How does a transfer switch work? 

A. The automatic transfer switch monitors utility and generator power. When utility power fails or is unsatisfactory, the transfer switch control starts the generator set, checks the generator speed and voltage output and transfers the load to the generator set. When utility power is restored the transfer switch automatically transfers back to utility power. The generator is llowed to cool down for a short period and then shuts down. The system instantly resets itself and is ready for the next power interruption. No action is required by the user. 

Q19. Can I save money buying a manual transfer switch? 

A. Generally no. Most modern automatic transfer switches have a manual mode so they do not switch until you change the switch position to transfer or automatic. New switches are electrically operated and when they change position they use power from the utility or generator to move. They DO NOT have handles on the sides of them like old fashioned switches. You may save $100 or so on a manual switch and you cannot retrofit the switch later to make it automatic. For portable generators buy a manual switch from Reliance Controls. We carry a full line of automatic and manual switches. 

Q20. Do I need an indoor (Nema1) or outdoor (Nema 3) switch. 

A. If you can install the switch inside a building you can use an indoor switch. Inside means in a heated garage or building. An unheated, drafty, damp tool shed is considered outside. In most cases it cost a few dollars to a few hundred dollars to upgrade to an outdoor Nema 3R switch. We always recommend that you buy an outdoor switch because they are water resistant and tighter than indoor switches. If there is any chance water will be sprayed around a transfer switch, an outdoor version is always a good investment. Any moisture inside a transfer switch will cause it to fail at the very time you need it. 

Q21. Is there a way to get a competitive price on a number of different transfer switches? 

A. Yes. At the top of every page there is a button that called Transfer Switch Find. It looks like this. >

There are also buttons like this on every product page on the website. You can go to the finder anytime, even if you have items in the shopping cart. 

Q22. What size generator do I need? 

A. Every home or small business is different. The size of the generator is based on the type of appliances, equipment, pumps, air-conditioners and other electrical devices requiring power.

Your service panel is normally rated at 200 amps @ 240 volts and the average home uses approximately 140 to 160 amps of 240 volts power to operate everything at the same time. Your larger appliances (well pump, kitchen stove, water heater, electric dryer, electric heater and heat pump system) will typically use 240 volts power and the lights and other smaller appliances will use 120 volt power. It is important to consider this difference in doing the load calculations because the important calculation is to determine just how many amps and watts you will need. For example, if you want to operate your refrigerator (20 amps x 120 volts = 2400 watts), freezer (20 amps x 120 volts = 2400 watts), electric hot water heater (20 amps x 240 volts = 4800 watts), washer (20 amps x 120 volts = 2,400 watts) and electric dryer (30 amps x 240 volts = 7200 watts) all at the same time you will need approximately 19,200 watts to meet the breaker requirements for these appliances. In reality the breakers are typically oversized for safety by 10 to 15% and the above appliances will not all operate at peak at the same time and the above load can be handled with a 15,000 watt (15 kW) generator set (GenSet).

Generally you can cut through all this stuff with these simple rules. If you have 100 Amp service panel, use a 8-12 kW GenSet (use larger if you have air conditioning). If your have a 200 Amp service panel, use a 15-20 kW GenSet (again use the larger size if you have air conditioning or large well pump). If you have a 400 amp service panel, use a 30-50 kW GenSet (if you have lots of air 

Q23. Do I need a fuel tank? 

A. Industrial diesel generators require a tank either under it (called a sub-base tank) or near it (called an external tank). We sell both types and they are listed as options in each generator product. RV generators require an external tank on the vehicle, we do not sell these tanks. Propane generators require an external propane tank, we do not sell these tanks. Portable generators have tanks installed on them and they are not expandable 

Q24. What is included with each generator? 

A. At the bottom of each product description on the product page is RED text that describes what is included with each generator. It looks like this: "Included Equipment: Generator engine and alternator, open skid mount platform, weather enclosure, no tank, flexible fuel lines, oil drain cock, digital control panel, electronic governor, residential muffler (enclosed models), industrial muffler (open models), spring isolators, 12 volt electric starter, included charging alternator, air filter, radiator, blower fan and guards, battery tray, battery cables, owners manual and warranty. Other options are NOT included please purchase the options from the option lists." 

Q25. What is the difference between single and three phase? 

A. Single phase has only one phase using two wires and three phase has three phases using three or four wires. Generally homes are single phase and business are three phase. If you go out to your main breaker panel you can usually tell if you have a single or three phase service. Single phase is 120/240 and three phase can be 120/240, 120/208 or 277/480. There are other voltages but these are the most common. If you are not sure what your power is, have an electrician come and look at your service or call your utility company. 

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(This information was taken from a website called generatorjoe ! )

YOUR GUIDE TO THE DIESEL POWERED GENERATOR

OVERVIEW

Any electric generator produces electricity by rotating magnetic field in its stator. The rotational force is normally produced by an engine that burns fuel. It is the main component that determines the type and basic properties of a generator. 

Technically speaking, a diesel engine (DE) is a compression ignition reciprocating engine. The fuel in DE is ignited within a cylinder without a spark.. 

A Diesel Genset

Like a gasolineengine, it is an internal combustion engine that typically use a four-stroke or two-stroke cycle. The main difference is diesel fuel is injected into the combustion chamber after the air has been compressed, and the high temperature caused by the compression ignites the mixture. This is in contrast to a gasoline devices, in which the fuel is injected into the air as it is drawn into a cylinder, and ignition is initiated by a spark.

Since in DE only air is compressed, and fuel is injected at the end of the combustion process, compression ratios can be much higher without threat of detonation. This greatly increases the device efficiency. 

The term "diesel fuel" (DF) generally refers to any fuel for a compression ignition engine. Most commercial diesels is made from petroleum and is often called petrodiesel. There are also non-petroleum types of such fuel, such as biodiesel.

Crude oil naturally contains some sulfur, a portion of which is converted to sulfate particulates in the exhaust and contribute to so-called particulate matter (PM) emission. To reduce PM and to enable some advanced emissions control devices for better air quality, many countries set the limits to sulfur content of DF. Particularly, in U.S. starting in June, 2006, EPA required at least 80% of the on-highway DF to be Ultra-Low Sulfur Diesel (also called ULSD or S15), with maximum sulfur level of 15 parts per million (ppm). Gas pump could still sell DF with 500 ppm sulfur until December 2010. In US by 2014 DF for all categories of equipment has to be ULSD. Note that in European Union and Japan ULSD means less then 10ppm sulfur.

Older engines should probably work normal on ULSD -- they may just have a small reduction of efficiency. However, newest engines with advanced pollution-control technology designed for ULSD, may be damaged by fuel with high sulfur content.

DIESEL POWER GENERATOR USES

DGs are widely used both as a prime energy source in places where grid is not available and as an emergency backup power source for grid connected buidings. Depending on the size, they can be used for small loads, such as electric tools, and for large loads like factories, commercial buildings, and hospitals. However, because of the high cost of standby diesel systems, they are used primarily in industrial and commercial applications. Private homes more often use natural gas or propane models that you can get for less. Diesel standby systems are widely used as an emergency backup source in hospitals, fire and police stations because of their shortest warm up time. For example, the standard NFPA 99 for health care facilities requires the genset to pick up the load and meet the requirements of the emergency system within 10 seconds after loss of main power. DG is probably the only type of gensets that can reach rated power within ten seconds. This type of devices is also used in remote locations in hybrid off-grid solar systems as an auxiliary power generator. Portable diesel generators are popular on jobsites because typically they have 2-3 times longer life than gasoline-powered models. High-power stationary DG may cost around $500-$2000 per kilowatt. Mid-sized portable diesel gensets typically run for $130-500/kW. As a rule, the higher wattage the lower cost per watt. 

The chart below summarizes basic advantages and disadvantages of diesel generators.

PROs 

The most reliable and maintenance-free of all types of emergency backup generators: no ignition systems, carburetors, nor spark plugs (just regular oil and filter changes);

Lowest fuel consumption (typically it would burn half the amount of fuel that would be required for a same-size gasoline generator);

The fuel can be stored in large tanks (up to 2 years with fuel preservatives), it is less flammable than other fuels and is the safest fuel to store. The most expensive type;

CONs

The gas pumps may not operate and the fuel may not be available during blackouts;

This fuel contains paraffin waxes that become solid at freezing temperatures- needs low temperature operability additives;

High emissions (such as nitrogen oxides - a smog-forming pollutant) and unpleasant odor. According to WHO, diesel fumes are carcinogenic.

In conclusion, diesel-powered gensets are more reliable and have higher efficiency than other gensets, but they are also the most expensive and the most polluting of all types. Such devices are used primarily in industrial and commercial applications. 

Home Type Generators

Our everyday life depends on the continuous flow of electricity probably more than we realize. While a few hours without power may be just an inconvenience, losing it for days or even weeks can be costly and life threatening. 

Besides spoiled food, an ordinary blackout may result in the loss of central heat in the winter, the loss of air conditioning in the summer, a flooded basement, inoperative security systems, and a faltered business. All of the above are good reasons to consider some kind of an emergency power source for your home. If you do an online search for home generators, you will find models for sale ranging anywhere from $120 into thousands of dollars. Which type do I need for power outages? Why would I pay $4,000 for a permanent electric genset plus $2000-$5000 for the installation when I can buy a portable one for $600-$1000 and run a bunch of extension cords? These are the commonly asked questions. In this guide I'll answer these questions and provide you with practical facts and information you need to know to buy the right system for your home.

AVAILABLE TYPES 

You probably know already that there are two basic types of home generators: stationary and portable. They are often called gensets because they are actually the sets comprising of an alternator and an engine.

Unfortunately, the numerous buying guides and articles available everywhere do not always emphasize all the drawbacks and the issues associated with each of these types. Before going over the details, let's start with a quick background information. 

Stationary (standby) systems are permanently connected to your house and hooked up to a fuel source. Normally this would be the same source you use for the heating: natural gas, propane or diesel. An indoortransfer panel isolates home wiring from input lines during utility power failure (see simplifed connection diagram). The wattage of the available air cooled standby systems intended for home use ranges from 6 kilowatt to 20 kW, so you can always select the right model that can supply the whole house including central a/c, sump pump, etc. In automatic mode such a system will start by itself without your involvement when it detects a power interruption. Likewise it will shut down when utility voltage is restored.

Portable devices range from 500 W to almost 20,000 W. When you need to use a portable genset, you have to moved to the place where you want to use it, fill with fuel and start up. Then after a short warm up period you can connect it to your equipment. There are no auto start portables. Gasoline and diesel models come with an on-board fuel tank; propane and natural gas models have to be connected to an external tank or fuel line. All the devices with an on-board tank have to be refueled several times a day if you load them to their maximum capacity.

All engine-driven units can be run only outdoors. A stationary device always sits outside just like a central a/c. A portable one is normally stored elsewhere and connected only when you need to use it. There are detailed descriptions and reviews of different generators in our SMPS site. Here we will just discuss the basics.

PROS AND CONS OF DIFFERENT TYPES 

As you realize, all types of gensets have pros and cons. Fixed systems provide the highest level of comfort, but of course it comes with a price tag. Depending on wattage and options, complete systems with a changeover switch may sell for $2000 to $5000. You may also need to spend several thousand dollars for electrical wiring and fuel hook up. Before the installation, you will likely need to obtain permits from your utilities and pass the inspections after the work is done. All this, obviously, takes time. So, if you are looking for an emergency generator because there is a hurricane or an ice storm in tomorrow's forecast, it is too late to consider a standby type. Another issue is service. A hard-wired appliance that weights 400-500 pounds is not something you can easily disconnect and ship back or bring to a repair shop. Should you need a repair, you'll have to wait for a service technician to come to your place or for the manufacturer to send you a replacement part. 

Portable generators are much cheaper-- their prices start at around $120 for a 1000W model. Unlike stationary devices, they don't have to be hardwired to your house unless you choose to-- their control panel has several outlets of various types into which you can plug cables from your electric loads. This can be both an advantage and a disadvantage. On one hand, you can start using such device, so to speak, right out of the box. However, this would work only if you want to run "cord and plug" appliances, such as refrigerators and window air conditioners. You can just unplug them from the wall outlets and connect via extension cords to the generator. However, when it comes to lights, furnaces and everything else that is wired directly into your house electrical lines, you'll face problems powering them up. This is something homeowners often don't realize while dealers may neglect to mention to you. You might ask, why can't I just hook up my genset to a wall outlet? First of all, it is illegal and dangerous to connect any voltage source into any electrical wiring connected to the grid. By trying to energize your house you are also feeding voltage back into the utility lines. This may hurt line workers or your neighbors who may think the mains is down. Aside from this, unless you are the only one who lost power, you would actually be trying to power up all the neighbors houses who lost electricity. This would likely overload your generator and trip its circuit breaker. Because of all of the above, if you want to run your built-in appliances and lights from a portable backup source you still need a redundant switch. In this case it has to be a manual one though. Such a connection is the safest one, but you would still have to deal with the professional installation, permits, inspections, etc. Technically, it is possible to isolate your house wiring by flipping the main circuit breaker to OFF position. However it leaves a possibility of a human error and is not recommended (see portable generator connection for more details and wiring diagrams). 

You would also have another hurdle to overcome if you buy a portable model equipted with GFCI and grounded neutral. In such a model the GFCI will trip when you use it with a regular transfer switch. This is something the manufacturers and retailers may not always mention you. So, if you choose a genset with GFCI, you need to buy a special 3-pole transfer switch or otherwise discounnect genset's ground wire in the transfer switch. In any case, such a setup is still cheaper than a stationary for two reasons: because portables cost less than standbys and because manual switches cost less than automatic ones. In case of emergency, if you have no choice and you really need to connect your genset into a wall outlet, first flip the "disconnect switch" on the main service panel. This would isolate your house from the outside lines. This is not a recommended method though. You also need to remember that a standard outlet is rated for 15A. So, you can't use it for more than 120x15=1800 volt-amps. If you draw a higher current you may overheat the socket and the wires, which is a fire hazard.

WHAT GENERATOR DO I NEED? 

My pick for standby genset for a typical house with a central a/c: Generac Guardian 17 kW home generator model 5873. (An included 100A auto transfer switch is installed indoors).

Well, buying the right model for the home involves several key decisions:

How much power do you need?

How soon do you need to use it? 

How often do you expect to use it and for what duration of time?

Are you able to move around a few hundred pound device?

Here is when you definitely need a standby home generator system: 

Your house requires more than 17 kW power, or 

You want to be prepared for long-term power outages, or 

You want fully automatic operation, or 

You don't want to move around a heavy device. 

Here is when you should buy a portable genset: 

You need emergency power immediately; 

You are looking to spend less than $1,500 (maybe even a few hundred dollars). 

In all other cases, either type might work for you. You just need to choose between cost and convenience.

For standby gensets, my pick is the Generac Guardian® series available in the range from 8 kW and 45 kW. For my advice on portables, see my picks of best portable generators for home. For more buying choices also see my guide to cheap generators.

Whatever genset you choose, remember that all engine driven devices have a common disadvantage- they all require maintenance, such as frequent oil changes. If you don't feel like getting involved into this, you may want to consider a maintenance-free battery backup solution. More details are provided in my review of different types of power generators, which compares traditional and alternative power systems. If you are interested in "green" energy, check out the tutorials on residential wind generator and to solar-powered system.