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Buying a Generator – Considerations


Now that you have decided to purchase a generator, there are several considerations you must keep in mind when choosing which unit to buy, where to install it and how to install it. This guide will help you select a generator using a step by step method. Choosing the right machine is not difficult if you take the time to analyze your requirements carefully. Power World is here to help, if you get confused or have a question, ask us.

1.How to know generator set should be portable or Stationary?

Most homeowners first think of portable generators rather then stationary generators. If you want to haul a generator outside or put one outside in a shed and plug in cords when there is a power outage, it can be done. You will not necessarily save any money doing it but if you have a use for the portable generator for non-emergency times then it might be an alternative. It has been our experience that it is more economical and less hassle to purchase a stationary system and power the whole house or business. Not only do you get more power for the dollar but your family and/or employees don't have to do anything to have emergency power. Do you want your wife, children or employees hauling out equipment and plugging things in and starting up the system, switching the transfer switch and having to refuel? At some point all of this becomes ridiculous and costs you more in staff time and potential liability then its worth.

2.The difference of generator set Standby or Prime power?

The first determination you will need to make is whether you will require stand-by or prime power. Simply stated, prime power is required when you have no other source of power or you are using the system as you prime means of power. Any generator that is used everyday or on a fixed schedule to provide power is considered a prime power generator. Another word for prime is "continuous". If you need a prime power generator, use the generators prime or continuous rating as a a guide.
A standby set is a backup to normal utility power. Standby units are used only when your utility power is not available and will not be used frequently. Many stand by generators run at 3600 RPM and are not designed for constant daily use. Another word for standby is "emergency". If you need a standby power generator, use the generators standby or emergency rating as a a guide.

 3.How to know generator set Phases,Amperage?

Generator sets produce either single or three phase power. You should use the type of power your panel provides. Residences and small business generally use single phase. Three-phase power is used for medium to large businesses especially where power is used for motor starting and running. Three phase generators are set up to produce 120/208 or 277/480 volts. Single-phase sets are 120 or 120/240. Use the low voltage to run domestic appliances and the high voltage for your motors, heaters, stoves and dryers. Your service panel is either single phase or three phase, you don't need a three phase generator if your panel is only single phase. Check with your electrician before you begin your search.
Your service panel is a good place to start. Go and look at your service panel and see what the amperage is. If the panel is 100 Amps that tells you that your won't need more then 100 amps of power. As the panel gets bigger so will your generator needs. It is possible to install a generator to power only a small portion of your service panel, if you install appropriate sub-panels to sort out what will and will not be powered.

 4.The generator set fuel should be Gas or Diesel?

We recommend diesels due to their longevity and lower operating costs. Today's modern diesels are quiet and normally require much less maintenance than comparably sized gas (natural gas or propane) units. Fuel costs per kW produced with diesels is normally thirty to fifty percent less than gas units.
1800 rpm water cooled diesel units operate on average 12,000 to 30,000 hours before major maintenance is required.
1800 rpm water cooled gas units normally operate 6,000 to 10,000 hours because they are built on a lighter duty gasoline engine block. Gas units burn hotter (higher BTU of the fuel) so you will see generally see somewhat shorter lives than the diesel units
3600 rpm air-cooled gas units are normally replaced �C not overhauled at 500 to 1500 hours. These are "stand-by" generators, not intended to be run long hours or very often.

 5.How to check the operating Speed?

Electric equipment is designed to use power with a fixed frequency: 60 Hertz (Hz) in the United States and Canada, 50 Hertz in Europe and Australia. The frequency output of a generator depends on a fixed engine speed. To produce 60 Hz electricity, most engines operate at 1800 or 3600 RPM. Each has its advantages and drawbacks. 1800 RPM, four pole sets are the most common and least expensive in large generators. They offer the best balance of noise, efficiency, cost and engine life. 3600 RPM, two pole sets are smaller and lightweight, best suited for portable, light-duty applications. 3600 RPM sets are considered "Standby Generators" and can never be considered for prime power use.
In simple terms it's like operating your car at 90 mph, versus 45mph �C at 45mph your car will last longer, is quieter, less maintenance and longer life. Most 3600 rpm units are twin cylinder air cooled lawn mower engines, while the water cooled 1800 rpm units are comparable to those found in forklift and tractor engines. The bottom line is the 1800 rpm water cooled units will last longer, offer less maintenance problems and be more fuel efficient. In addition, 1800 RPM generators are designed to be rebuilt, 3600 RPM units are designed to replaced and are much lower in cost (most of the time). Some 3600 RPM stationary units and most RV and commercial power units can be rebuilt at least one or more times but this process is not inexpensive.

 6.What's the genset features & Benefits to look for?

Engine block. For long life and quiet operation we recommend four cycle, liquid cooled, industrial duty diesel engines.
Air or liquid cooling. Air-cooled engines require a tremendous amount of air and may require ducting and they are somewhat noisier. Liquid cooling offers quieter operation, more even temperature control and therefore longer engine life. Modern air cooled engines are suitable for many applications, especially short run,
Portable Or Standby Uses
Intake Air. All quality generators have intake air filters with replaceable filter elements. Today even small portables have replaceable air cleaners.
Mufflers. Most generator come equipped with an industrial grade muffler. One good investment is a residential or critical muffler that is much quieter and lasts longer. All enclosed generators should be equipped with at least a residential and preferably a critical muffler.
Lubrication. The lubrication system should have a full flow, spin-on oil filter. Larger generators should have a filter bypass. Most generators today have low oil alarms and shutdowns, make sure the generator you select has this valuable feature, its simply a must have protection
Major brand of engine. We do not know why people would even consider an inferior "scrap metal" unit or "off brand" engine, you will not be able to obtain the necessary parts, service and support. Many engines come with a box of spare parts including pistons, rings and bearings because your going to need them all. Save yourself some grief and buy a major brand of engine. If you buy a junk engine, we wont service it and most other reputable dealers won't either
Electrical system and circuit breakers. Standard 12 volt system should include at least the following: 1) Quality starter motor and battery. Larger generators should include a charging alternator with a solid state voltage regulator. 2) Larger diesel units should come with a pre-heat switch and all generators should have a start/stop switch. 3) Al generators should have a safety shutdown system to protect the engine in case of oil pressure loss, generator over-speed or over-crank and high water (or operating) temperature. 4) System circuit breaker to protect the generator. On small systems and portables there should be a circuit breaker on each circuit.
(The part that makes the generator "generate" electricity.)
AC generator should have a 4-pole revolving field. An automatic voltage regulator will provide “clean” power. Normal utility power is +/- 6% voltage regulation; most generators are even better ranging from +/- 5% or .25 % and even better. Most modern generators offer AVR – Automatic Voltage Regulation or some other proprietary brand of voltage regulation and can be safely used with modern electronics and computers.
Lifetime lubricated bearing. Cheap generators are not supplied with these bearings. They often require complete disassembly every two or three years for bearing replacement. Most modern power alternators, or generator ends, are provided with industrial quality lifetime lubricated bearings.
Upon determining the generator size you will need, make a list of optional and installation equipment you require. For noise abatement, we recommend a residential (not industrial grade) muffler. A good primary fuel filter/water separator is a must to protect your engine's fuel system. Stand-by sets may require a block heater to keep the coolant/water mix at an adequate temperature for easier starting and less smoking on startup.

 7.What Size set will i need?

Sizing is the most important step; nothing is more critical in your choice of a generator. A set that is too small won't last, will smoke and can do damage to your electrical equipment. If it is too large, the engine will carbon up, wet stack or “slobber” and this means excess fuel consumption and early failure. We recommend that a generator set never run continuously with less than 40% load - 50% to 75% is optimum.
Additional factors, which may affect efficient operation of your generator, are high altitude and high air temperature. These conditions will lower generator output. You must take into account your elevation, normal and extremes of temperature and other factors. Ask your sales engineer for de-rating information. Allow three (3) percent loss in efficiency for each 1000 feet above sea level minimum. Check the manufactures specifications and use the de-rating factor they specify. Nothing is worse than buying a generator that is too small.

 8.What is Load Bank, Why it is necessary, and how frequently should it be performed ?

Load Banking refers to the process of running a generator under a full load for an extended period of time - typically, two to four hours. The purpose of this process is to raise the operating temperature of a generator so as to burn off carbon build-up that is known as Wet Stacking. Wet-Stacking is a common problem with diesel engines which are operated for extended periods with light or no loads applied. When a diesel engine operates without sufficient load it will not operate at its optimum temperature. This will allow unburned fuel to accumulate in the exhaust system, which can foul the fuel injectors, engine valves and exhaust system, including turbochargers, and reduce the operating performance. More importantly, wet stacking can create a significant fire hazard.
Providing additional load from the building load may not be practical with critical computer, life safety or communication equipment. Any interruption of power to these loads may cause a loss of data, operations or jeopardize personal safety. In order for a diesel engine to operate at peak efficiency it must be able to provide fuel and air in the proper ratio and at a high enough engine temperature for the engine to completely burn all of the fuel. The proper load can be achieved by adding additional building load or by providing supplemental load through the use of a resistive load bank. These can be small portable load banks designed to be rolled up to the generator under test or they may be larger trailer mounted load banks for generator sets in the 1-3 MW range.
A generator needs to run under full load for several hours to get the engine and exhaust system back in shape. When the exhaust stack smoke is nearly invisible, the system is cleaned of the excess oil, fuel, and hydro carbons build up.


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