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Old 12-26-2009, 04:07 PM   #1
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Generator and furnace


Greetings,
I plugged my HE furnace into a cheap generator a month ago. It worked but now I have control problems. I thought it was the T-stat, so I jumped the red and white. The furnace worked fine. I thought the RTH6300B T-Stat might be loaded up with bad harmonics, so I drained & reprogrammed it, and used the default energy star schedule. Put it back and everything worked fine all Christmas Day. Next day furnace got to within -4F of set point and shut down. Vent motor kept running and HSI started, gas valve opened then shut abruptly.
I shut it all down and jumped out the T-stat. The furnace ran for about 10 minutes and shut down with the jumpers still connected.
I re-drained the Stat put it back in now everything is fine (but I have a feeling it won't be tomorrow morning)

So my question is does the HE furnace poll the circuit for the heat anticipator and thereby know that the furnace is not connected to a T-stat?
Don't know if I smoked the board, the T-stat, or if the T-stat was jumbled up?
Why would the furnace shut down with the red and white still jumped? Thanks


Last edited by okrite; 12-26-2009 at 04:14 PM. Reason: grammer
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Old 12-26-2009, 04:27 PM   #2
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The issue with cheap generator is the power supply from the generator is not very clean plus what more cheap generators do not run at excat 60 HZ at all escpally unloaded it will run about 61 or 62 HZ depending on how it set up.
But once you get loaded up it should be on 60 HZ but not always the case I have see them run low as 57 HZ even lower that can really screw up some items.

that two thing that will shut down the electronic items and power surge can wreck hovac on electronic circuit board.

Hang on one of the members will offer you a soulation but let me address this how you hook up this furnace to generator ?

Merci,Marc

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Old 12-26-2009, 05:54 PM   #3
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It sounds to me like one of your safety's are shutting it down (flame sensor, high temp, combustion blower pressure switch) When you jumped red to white does the AHU blower come on? Is the air flow good?
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Old 12-26-2009, 05:54 PM   #4
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Thanks Marc,
During power outage it is manually connected to L14-30 male back-feed inlet, then through a BF rated 30 amp breaker.

The main panel is a GE 100A and I have a double lock in-lock out device to prevent simultaneous connection to the POCO. [GE Generator Interlock Kit]

The generator is a Champion 3500w-4000pw 120-240v, 3600 RPM-60Hz

Once the IC board is subjected to the "dirty" power, is it ruined?

Regards, how are things up North?

Last edited by okrite; 12-26-2009 at 07:35 PM. Reason: [clarity]
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Old 12-26-2009, 06:05 PM   #5
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Ok sound like you have very good legit set up there so we are fine with that part.,

Now let do little trobleshooting here do the furnce work very well on normal power source if so then next step is generator related issue one simple test is get a standard electric clock not the digtial one type get one with hand sweep type so you can able timmed in 10 minutes so you know how fast it is running if both clock is matched with your watch or other verifed source like portable wind down timer which you used for kitchen for cooking to set at 10 min and if both are the same then the speed is good if not you know something is not right.

As far for other part for furance check it out with Wirenut suggest check the burner door to see anything funny on normal power source if ok then get on generator power if that act up then you know the circuitboard is not reading correct.

Speaking of weather I am in France now it is not too bad got some snow but not much probly about 3 inches but in Wisconsin that diffrent matter eastern Wisconsin got some rain and snow mixed but western wisconsin and Minnestoa got socked pretty hard I heard but not confimed but stated over 22 inches and Nord Dakota et Iowa and most of Minnesota pretty much shut down the interstates.

Heard couple power outage but how much that I not getting confirmed answer yet.

Merci,Marc
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Old 12-26-2009, 06:24 PM   #6
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Quote:
Originally Posted by wirenut1110 View Post
It sounds to me like one of your safety's are shutting it down (flame sensor, high temp, combustion blower pressure switch) When you jumped red to white does the AHU blower come on? Is the air flow good?
Greetings wirenut,

15 second venter purge, HSI glow, gas valve open, ignition fine, AHU blower starts, good airflow.
Checked furnace after cut off, did not seem to be over heated.

The manual says the heat anticipator should be set at .6 amps (40 ohms?) I wondered if these new furnaces can sense the existence of a T-stat?
(maybe it can be jumped for only 10-15 minutes without interrupt)

I trust will know more in the morning.

happy 2010
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Old 12-26-2009, 06:49 PM   #7
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[quote=frenchelectrican;372337]Ok sound like you have very good legit set up there so we are fine with that part.,

"...one simple test is get a standard electric clock not the digtial one type get one with hand sweep type so you can able timmed in 10 minutes so you know how fast it is running if both clock is matched with your watch or other verifed source like portable wind down timer which you used for kitchen for cooking to set at 10 min and if both are the same then the speed is good if not you know something is not right.."

hi Marc
I am on POCO power now not really worried about the outage. Trying to get the furnance to work on "good" power.

I saw that clock as a tachometer idea before--a beautiful thing! I will get to that later (when I visit the antique store or the goodwill)

Not sure I'll be connecting the furnace without a power conditioner.

Kind of funny the generator (it is still new) was $159.00 at Kragen in 2007 they are now $549.00. A power conditioner is $600.00 for two capacitors, a coil and couple resistors.

its not what, its how

happy 2010
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Old 12-29-2009, 07:45 PM   #8
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Fault codes said it is one of the following: pressure switch; blocked flue; blocked drain; weak blower; incorrect pressure switch setting, etc.

Main flue drain fitting was blocked and hoses had crud in them.

Measured the condensate discharge after cleaning. Putting out about ten pounds of water per therm---which is about right according to NG Combustion 101.

Had nothing to do with the generator. Furnace had not been serviced for 3 years except for filters and some temp and air tuning. Still have to add two ducts this spring.

the fault codes?, duh.

thanks
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Old 12-29-2009, 09:54 PM   #9
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You can get an "online" "true sine" UPS (for computer power backup typically) which always makes its own electricity and creates a perfect "sine wave" like the electric company provides. Check for prices here...
http://www.google.com/products?hl=en...-8&sa=N&tab=wf

Then here is what "dirty power" looks like...
(The first picture is what it should look like.)
http://www.jkovach.net/projects/powerquality
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Old 12-29-2009, 11:57 PM   #10
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[quote=Billy_Bob;373730]You can get an "online" "true sine" UPS (for computer power backup typically) which always makes its own electricity and creates a perfect "sine wave" like the electric company provides. Check for prices here...

Billy_Bob
good pics of the oscilloscope, sine and square waves, what does it mean?
do you think brand new Champion generator (Honda clone) can damage furnace board?

i know the avr & hz is not real good
. don't know about harmonics.
not worried about the motor.
does 24vac transformer attenuate dirty power at all?


knowing now that coincidence emerged (plugged condensate drain) wonder if ok to run furnace off cheap machine.

hooked up for test run seemed ok, cr tv worked fair (some flicker), flat screen tv worked perfect.

my late father an EE said, "it most likely won't hurt the board".

think so?

thanks


coincidence invented murphy's law


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Old 12-30-2009, 12:10 AM   #11
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It can transmit thru the transfomer but how bad it depending on which type it is and some are very senstive and some are not.

Most cheap generator is pretty easy to set the voltage due the HZ and V/R is straghtfoward it is liner 2volts to 1 HZ so like example at 60 HZ you should have perfect 120 volts if reading 118 then you are running at 59 HZ simuir with higher than 120 volts.

That one thing about cheap generators they don't have very good surge resevration at all and some of them don't even produce clean power at all they can wreck hovac on some electronic stuff.

I know Honda Generators are pretty good and the best what I heard is the inverter generator they make super clean sine wave quality so that is very safe with computer and other electronic stuff plus what more the inverter generator have variable engine speed so if the load is very light the engine run at lower RPM's until the load get higher the engine speed up a bit to keep up with it.
That is nice thing due very low noise and pretty fuel effecency unit.


I deal with much bigger generators it have seperated voltage reguator so I can able finetune it.

Now for the other parts of furance the key issue is the condisante drain you have to check from time to time to make sure it is not plugged up few furance have that feature so if plugged it will shut down the burner to prevent flooed combustion chamber. { from the condendationing }

senice with my furnace it run on oil I don't have that issue at all but I have drain hose from A/C so I used blow gun to blow out any debries before I turn it on late spring and check the hose to make sure there is no kink at all.


Merci,Marc
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Old 12-30-2009, 09:50 AM   #12
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I've seen some generators lately which claim to be "electronics friendly". Here is a google.com search for those...

http://www.google.com/#hl=en&source=...c9c32d20fe6232

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