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How to choose the right Generator for you
02/11/12
Once you've decided to purchase a generator set, there are several considerations
you must keep in mind when choosing which set to buy, where to install it and
how to install it.
This guide will help you make informed decisions during the selection process.
Choosing the right machine is not difficult if you take the time to analyze
your requirements carefully. Electric Generator Mart sales engineering staff
is available to help you with all steps of the generator selection and sizing
process.
You will also need to know a few terms and have a basic understanding of the
different types of generator sets and their operating principles.
Installation requires expert assistance and a strict adherence to local codes
and regulations. We recommend that you have a contractor do your installation.
STAND-BY OR PRIME?
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. A stand-by set is a backup to normal utility power
GENERATOR TYPES & FEATURES
Generator sets produce either single or three phase power. Choose a single
phase set if you do not have any motors above five horsepower. Three-phase power
is better for motor starting and running. Most homeowners will require single
phase whereas industrial or commercial applications usually require three phase
power. 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.
GAS OR DIESEL?
We recommend diesels (see Why Choose Diesel) 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 12-30,000 hours before
major maintenance is required. 1800 rpm water cooled gas units normally operate
6-10,000 hours because they are built on a lighter duty gasoline engine block.
3600 rpm air-cooled gas units are normally replaced – not overhauled
at 500 to 1500 hours.
Because the gas units burn hotter (higher btu of the fuel) you will see significantly
shorter lives than the diesel units.
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.
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.
In simple terms it’s like operating your car at 90 mph, versus 45mph
– 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 1800 rpm water cooled units will last longer,
offer less maintenance problems and be more fuel efficient.
FEATURES & BENEFITS TO LOOK FOR
ENGINE
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. They're noisy too. Liquid cooling offers quieter operation
and more even temperature control.
Intake and exhaust. Time and money savers include a large, integral air cleaner
with replaceable filter element and a residential muffler, which is built into
the exhaust manifold. This saves the need for an additional muffler.
The lubrication system should have a full flow, spin-on oil filter with bypass.
Major brand of engine – We do not recommend you purchase a Chinese built
unit or off brand engine, you will not be able to obtain the necessary follow-on
parts and service support available with our machines!
DC electrical system. Standard 12 volt system should include:
Starter motor and battery charging alternator with a solid state voltage regulator
Diesel units should come with a pre-heat switch and start/stop switch
Safety shutdown system to protect the engine in case of oil pressure loss,
generator overspeed or overcrank and high water temperature
DC system circuit breaker.
GENERATOR END
AC generator should have a 4-pole revolving field. An automatic voltage regulator
will provide “clean” power. Normal utility power is +/- 5% voltage
regulation; our 1800-rpm models are even better +/- 2%! All of our models offer
AVR – Automatic Voltage Regulation
Lifetime lubricated bearing – some less expensive units – are not
supplied with these bearings…they often require complete disassembly every
two or three years for bearing replacement. All Power Generators units are provided
with industrial quality lifetime lubricated bearings
ENGINE ACCESSORIES AND CONTROLS
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.
AC SWITCHGEAR AND CONTROLS
Switchgear can be as simple or complex as you want or can afford. Of course,
as complexity increases, so does cost. Balance and a good electrical advisor
are the keys here. The diagrams at right illustrate basic configurations for
prime power and stand-by systems. All generator systems require a circuit breaker
and a distribution panel. The circuit breaker protects the generator set from
short circuit and unbalanced electrical loads. The distribution panel divides
and routes the connected loads and includes circuit breakers to protect these
loads. Stand-by systems also require a main circuit breaker between the utility
source and the transfer panel. The transfer panel switches power from the utility
to the gen-set and back so that both aren't on at the same time. Auto-start,
auto-transfer systems are available but are costly. Your supplier or contractor
can help you determine what you will need.
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