and other things Ive learned about Generators
So, you want
a generator? Over the years,
Ive used quite a few, taken care of them, even specified new generators.
All of this is a quick summary of what Ive learned.
Of course your experiences might be totally different, but hopefully,
this will give you some things to either think about, or ask about.
Why do you
need a generator? Most
likely, to make power when the power company fails.
While we havent had any day-long state wide power failures like the
ones in the 1960s and 1970s, I think there is still a potential for such
an event. And in these
many years since the last major one, weve become far more power dependent. You didnt have a computer at home in 1965.
might give you some historical perspectives.
by itself, isnt enough if you have anything important.
Youll also need an Uninterruptible Power Supply (UPS) to supply power
while you or the automatic switch starts the generator.
options, gasoline, while easy to get after the lights have been off a while,
its very dangerous to store and transport.
Often a good
solution since theres no local storage.
But what if gas lines are interrupted?
What if the disaster that killed the power starts to effect the gas
store, very few environmental problems.
No way to transport more gas yourself.
Youll have to wait for delivery.
Same gas supply could be used for other purposes, like cooking and
especially for larger generators. Safer
to store, but new environmental demands make it expensive to store. Usually large above ground double lined tanks are
required. Also, diesel fuel
needs to be cleaned regularly if it isnt used.
Heres what happens: The
fuel and tanks sort of breathe.
As they expand and contract, humid air comes into the tank.
When that hits the colder tank walls, the water in the air condenses.
Now we have air, water and diesel.
Believe it or not, this is the perfect environment for a type of
bacteria. Yes, there is a
living thing that thrives on diesel fuel. When
that grows, it can clog the filter and engine.
Unless you go through the fuel every year, youll need to treat and
filter the stored fuel.
UPS versus the Generator
Why does my
new UPS reject power from my generator?
this confuses a lot of people.
A REAL UPS cares more about power than 'will it make light bulbs light
up?' There are many factors considered when a real UPS
goes to UPS mode and gives up on the AC source.
Is the voltage within a narrow range and stable within that range?
Is the frequency 60 Hz plus or minus a certain amount, and stable?
that you purchased a major UPS to protect your load, not just act like a dumb
transfer switch. It will
rightfully reject power from a generator that doesn't keep the frequency stable
when the load changes. When
I hear of this problem, I ask how the UPS reacts to the power line.
The answer is usually 'fine
it's just the generator.'
The UPS doesn't really listen for the exhaust... it's looking at the
power coming in and decides that your gen set is putting out power that could do
damage to a critical load, oh, let's say broadcast or computer equipment.
If the UPS has no problem with the power company, but rejects the
generator, it's trying to tell you something.
What can you
do about it? All those 'bells
and whistles' in that expensive UPS include a log that tells you exactly why it
rejected the AC source. Hook up a
computer to the UPS serial port and look at what it wants to tell you. Was it frequency or voltage?
Add an electronic governor to the gen set that will get the frequency
stable with changes in load. That
will keep the engine RPM steady even if the load changes quickly.
Sort of like a cruise control on your car.
Some will keep you more or less at 55 MPH, others are rock solid, no
matter how steep the hill.
Was it a
voltage sag? This means that
a large load was added to your generator and it took some time to get back to
the right voltage. When youre on
the power company, theyre more or less an infinite source of power (at least
your small load compared to all their generators.
But when 60 amps or air conditioning compressor comes on your 200 amp gen
set, thats quite a load. You
need to either get heavy cyclic loads off the gen set or get a bigger one. Examples of large loads that go on and off and can
cause a voltage dip include air conditioning systems and tower lights. There are
some tricks if youre on the border
does the A/C need to cycle while the
gen set is on? Constantly on
might make the room cold, but it could help your situation.
Maybe you could live with the tower lights on constantly while youre
on generator. Do you have a
non-emergency panel? There
are some things that just do NOT need to be on the generator.
Sprinkler pump? Water
heater? Or my favorite, the
jacket heater on the generator!
your gen set specs. It might
just be the wrong model for the application.
Gen sets are not created the same.
I had one installation that used a Dayton genset that was designed for
emergency building lighting. Just
fine to light hallways and exit signs, but it wasn't designed for computer
loads. It was replaced by a
Katight and that ended all the problems.
Ive been told its a function of the amount of copper in the
If you don't
care so much about your load, you can tell the UPS to not be so picky.
Say that the +/- 0.5 Hz window is too tight for you.
You can tell the UPS to allow +/- 1 Hz.
It's up to you. You might be
able to tell the UPS that 90 volts is just fine.
But don't blame your UPS when your equipment starts dying.
take the battery out of a smoke detector that keeps going off when there's some
smoke? Or would you put out
the fire? Fix the generator
and let the UPS work as it was designed to.
I learned a
lot real fast about the batteries used to start generators.
Heres a what happened with mine:
the battery is bad, you have a hunk of metal during a power failure. Make sure the battery is in good shape so it can start
up the generator, even if it takes a while to turn over.
Air is a
good thing for a generator. Make
sure your air intake is clean, and will be clean during a problem.
I dont mean just the carburetor intake. Also the fan. Ive
heard of generators failing during a hurricane.
A few things have happened: The
storm surge water comes up and starts to get sucked into the fan intake.
Or the barometric pressure has gone so low it has effected the air/fuel
mix. Or the wind from the
storm cancels out the needed air movement and the generator over heats.
Any of these causes a shut down.
If its an outdoor generator, you cant get outside to hit the reset.
that a generator needs more than fuel to run for days.
Dont get caught without engine oil if you have days of fuel on-site.
Some larger generators, even in top condition, can burn gallons of fuel
oil in a day.
generator, especially a diesel can be too cold.
You should have a crankcase heater, even in warm climates. The bottom of the engine should be hot to the touch,
all the time. This makes sure
the gen set will start and run smoothly within seconds of starting. This electric heater does NOT need to be on the
generator circuit. No need to
heat the generator if its already running.
does a few things
1. Is there a power failure?
What IS a power failure? No
power? Or poor power?
One phase low? How long does it need to be off before you start the
2. If there
is a power failure, order the generator to start.
that power from the gen set is stable and ready
4. Throw a
big double or triple pole, double throw switch to disconnect from utility and
connect to the generator.
the utility power. When it
has been stable for a certain amount of time, throw the big switch back to the
6. Let the
engine cool down
7. Shut down
8. Every so
often, usually weekly, go through all this as a test to make sure the generator
is ready for an emergency.
How well it
does all these things makes the difference between the good ones and the great
ones. Throw in some
telemetry, gauges, alarms and remote controls, and you have a nice bit of
of this is based on what I have learned over the years.
Your mileage may vary. But
if this gets you to ask your sales person, technician, architect, or neighbor
some questions, then Ive accomplished my goal.
01/14/2008 13:11:33 -0500