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generator problem - Page 3

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Posted by Bruce Gordon on October 25, 2010, 6:36 pm

What you need is to run the power to the furnace thru an Isolation
Transformer, which will knock down the spikes in the power from the
genset. We used to have a whole bunch of SOLA Power Conditioners that
were BIG Heavy Ferro-Resonant Transformers with an LC Tuned Secondary
Winding, to take the Spikes out of our Generated Power for a big Xerox
Copy Machines and other sensitive loads.

Bruce in Alaska   add path before the @ for email

Posted by news on October 24, 2010, 11:46 pm

If the furnace doesn't like the power from the generator, it certainly
won't like the near-square-wave output of a typical UPS.  

We had a new high efficiency furnace installed and one of the first
questions I asked the installer was whether it would work from a
generator.  He said this specific Amana model would even work from an
inverter if needed.

Whether they work or not is VERY dependent on the design of the power
supply(s) used in the control circuits of the furnace.  

A pure sine wave inverter running from a battery might work; just use
the generator to keep the battery vharged.  Or build an alternate
power source with an old lawn equipment engine (mower, edger, etc)
powering a 12 volt alternator to keep the battery charged.  How to
pages here: http://theepicenter.com/tow082099.html

On the 180Hz reading, I agree that it's something internal to the
generator - worn brushes, dirty commutator or slip rings, marginal
voltage regulator.  Get a Kill-A-Watt (less than $0) and see what it
says the frequency is.  Mine reads fine on commercial AC and on two
different generators - but a frequency meter gives odd readings on one
of the generators.

If motor-driven appliances run OK, the frequency is close to correct.


Posted by Cat22 on October 26, 2010, 7:03 am
 On Sun 10/24/2010 4:46 PM, news@jecarter.us wrote:

My installer told me before i bought the furnce that it would run on a
generator, the guy who came to look at what was happening when i called
them said it should run on a generator but he didnt know why it wasnt

I'll look into that idea

They do, everything i throw at it works except this new furnace, the old
1995 carrier weathermaker 8000 had run on it several times

Posted by Josepi on October 25, 2010, 12:27 am
 Some things I observe.
The frequency is probably only a function of spikes (as another poster
stated) scrwwing with the zero crossing detector in the Fluke. Since the
freq. measured is a direct 3rd harmonic I would say that is a definite.
Heavier loads tend to disapate the 3rd harmonics or bury it in bigger
amplitude fundamentals for the meter.

Since you have a mechanical waveform generation, if your frequency varied
you would hear the motor increase in speed by that ratio. I doubt you are
hearing that freq. change.

Are there sepearte feedback sensor inputs for the generator regulator? Not
likely but, If so some other options come to mind.

The UPS may have more harmonics than your genny. Some fo these cheaper units
give off slightly filter squarewaves.

The line filters may help but I am not familiar with those ones usage or

Do you have a scope with memory?

I have a 5700 watt Mcculloch FG5700AK generator. When its under a
good load its ok,but when the load is light/none the freq jumps way
up. The speed sounds about normal, but the frequency measures 180 HZ
at very light/no loads and under quarter load or so the freq drops
back to close to 60 HZ.Output voltage is ~120vac and it does vary
some depending on load. I discovered this when we had a blackout and
i tried to run my new furnace on the generator, it would show fault
led's if the fridge kicked on (momentary voltage sag). or if nothing
else was running besides the furnace.
I measured the noload freq with a fluke meter t ~180Hz-  and at first
i thought i just didnt have a connection to the meter probe, but
under load (the lowest load i tried and still got 60Hz was 700 watts)
it drops back to right about 60Hz
Its a new Coleman CP9C Echelon furnace, my old carrier weathermaker
8000 worked fine on the generator. One big difference is the Coleman
draws very little power.

I had thought abut putting this on the furnace circuit:
  "Tripp Lite LC 1800 Line Conditioner / AVR System LC1800"
or maybe this:
  "Tripp Lite LCR2400 Line Conditioner - Automatic Voltage Regulation
with Surge Protection"
Would an ordinary Computer 1200VA UPS do?

Any ideas? Why does the freq act like that? Time for  new generator?


Posted by Cat22 on October 26, 2010, 7:05 am
 On Sun 10/24/2010 5:27 PM, Josepi wrote:

how can i determine if I have that?

no, i dont.

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