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Terminology and Technology you need understand.
Decisions...
STAND-BY OR PRIME?
Will you require stand-by or prime power supply? Simply stated,
prime power is required when you have no other source of power.
A stand-by generator set is a backup to utility power
Why
differentiate? The rating of a generator for backup power assumes
the generator will be in occasional use for periods of several hours or
days. Prime power generators are expected to run 7/24 for 365 days per
year. Generators are rated are higher for backup use than for prime
power.
USED as an Option
There are good deals to be found within the used market. We come
across generators which have been installed for many years as backup with
incredibly low hours on the equipment. However, if your application
is critical or you require the unit for prime power you must understand
that parts, although available, may not be readily available or on hand at
your local engine dealer for older engines.
GENERATOR
TYPES & FEATURES
Generator sets produce either single
or three phase power. Choose a single phase generator if you do not have any
motors above five horsepower. Three-phase power is better for motor starting
and running. Homeowners usually require single phase whereas industrial or
commercial applications frequently require three phase power.
Three phase generators are set up to
produce 120/208 or 277/480 or 347/600 volts. Single-phase sets are 120 or 120/240.
Large heaters, stoves and dryers frequently use 240V volt power. 120V is
the voltage available at your normal household electric outlets.
GENERATOR
RATINGS
Generators are rated in
either kVA (Kilovolt amperes) of kW (kilowatts), Kilo meaning 1000. kVA is always higher than the kW. All
of our three phase water-cooled generators are rated with a power factor
of 0.8 and single phase generators have a power factor of one.
GAS OR
DIESEL?
Diesel generators while initially more expensive are frequently
the best alternative due to their longevity and lower operating costs. 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.
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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.
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3600 rpm diesel generators. It is difficult to categorize 3600
rpm diesel generators because there is a huge spectrum of engines
within this category. Generally, small light-weight 3600 rpm
diesel engines are not as durable as 1800 rpm engines. However,
companies such as Deutz and Lombardini make excellent and durable air
cooled units, some of which are designed to operate at 3600 rpm.
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3600 rpm air-cooled gas and gaseous units are normally replaced –
not overhauled at 500 to 1500 hours depending on
manufacturer.
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No matter which manufacturer you use, you will get substantially
shorter longevity from the gas and gaseous fuelled engines than diesel
powered units because the gas units are built in a lighter fashion and
because they burn hotter (higher BTU of the fuel).
OPERATING
SPEED
Electric
equipment in North America is designed to use power with a fixed frequency:
60 Hertz (Hz); and 50 Hertz in Europe, Africa and Australia. The frequency
output of a generator depends on a fixed engine speed.
Frequency (Hz) is measured
in Hertz (cycles per second) and
basically it is the number of times that an
AC supply oscillates in one second. The standard frequency in
Canada and
the US is
60Hz. Frequency is held constant by the mechanical and or electronic
governor mounted on the generator. An excellent level of frequency control
is 1% while a 2-5% level of control is usually adequate.
To
produce 60 Hz electricity, most engines operate at 1800 or 3600 RPM. Each
has its advantages and drawbacks:
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1800 RPM, four
pole gensets are the most common in larger units and in quality
generators and are more expensive to manufacture.
They offer the best balance of noise, efficiency, cost and engine life
but are heavy and are only considered portable when mounted on trailers.
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3600 RPM, two pole sets are smaller and lightweight,
frequently best
suited for portable, light-duty applications.
- 3600 rpm engines tend to
use more fuel than 1800 rpm engines per kilowatt hour produced by about 10
to 15% (not usually an issue for a backup generator)
- 3600 rpm engines almost
always produce more horsepower from the same size engine running at 1800
rpm. This means a smaller engine can drive a bigger generator. Smaller
engines cost less than larger ones, saving money.
- 3600 rpm engines are
usually about 4X noisier than 1800 rpm engines (usually 85dB vs 76dB)
- We have not noticed a
difference in longevity within 3600 vs 1800 diesel engines when two quality
engines from the same company are compared.
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 or single cylinder gasoline powered air cooled
lawnmower 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: Select four cycle, liquid
cooled, industrial duty diesel engines for long life and quiet operation.
Air or liquid cooling:
Air-cooled engines require a tremendous amount of air and may require ducting.
They're noisier too. Liquid cooling offers quieter operation and more even
temperature control but these units weigh and cost more.
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DC electrical system. Standard 12 volt system should include:
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Starter motor and battery charging alternator with a solid
state voltage regulator
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Diesel units may come with a pre-heat switch and start/stop
switch.
Pre-heating comes in many forms including glow plugs to warm the
combustion chamber and manifold pre-heaters to warm the incoming air.
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Safety shutdown system to protect the engine in case of
oil pressure loss, generator overspeed or overcrank and high water temperature
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DC system circuit breaker to protect the battery charging
system.
GENERATOR UNIT
AC
generator should have at least a 4-pole revolving field. Automatic Voltage
Regulator (AVR)
provides “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
ENGINE ACCESSORIES AND CONTROLS
After determining the generator size
you will need, make a list of optional and installation equipment you require.
For noise abatement, we recommend purchasing a sound attenuated generator.
A good primary fuel filter/water separator is a must to protect your engine's
fuel system.
AC SWITCHGEAR AND CONTROLS
Switchgear can be as simple or complex
as you want or can afford. As complexity increases, so does cost. Balance
and a good electrical advisor are the keys here.
All generator systems require a circuit
breaker and a distribution panel.
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The circuit breaker protects the generator
set from short circuit and unbalanced electrical loads.
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The distribution panel divides and routes
the connected loads and includes circuit breakers to protect these loads.
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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 generator unit and back
so that both aren't on at the same time.
Auto-start, auto-transfer systems
are available but are costly. Your contractor can help you determine
what you will need.
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