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 design5) 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.
GeneratorJoe provides: Sales: Competent and knowledgeable salespeople to discuss all your requirements and application and to properly size and calculate all motor starting requirements.Customer Service: parts and warranty assistance on all products purchased from GeneratorJoe.Technical Support: trouble-shooting service via phone, fax, or e-mail. Shipping to your door or export freight forwarder Products: We have the best products on the market at the best Prices. We don't sell junk equipment, cheap imports, cheap hardware store brands or low price volume products that most generator companies wont sell. If we sell it, its quality.

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.
See our Generator Fuel chart for a list of positive and negative factors of fuel and generator types. 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.