# My Home Furnace Wont Run Off My Generator No More!



## z-family




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## ember

I just overheard part of a conversation on this topic at the electrical supply store, unfortunatly didn't really pay too much attention, but the best I can relay to you, is something about the two 'machines' have different interface languages. Not the help you were looking for I know, but maybe in the paperwork for the two units it has a "conversion" table. In my defense, I am NOT an electrician, I was picking up an order for a friend of ours who is an electrician, but I was in the neighborhood of the electrical supply store.
TTFN
Ember


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## Northern Wind

Hey Rob, it's probably some safety switch for the gas supply, having something to do with constant voltage supply from the generator. Even the best cycle to some extent and can throw high and low spikes. Thats what our furnace man told us this year when we installed the new furnace, he told me I would have to have at least a 6000 W Diesel to get by all the safety's on the new furnace. Of course he didn't mention this until after it was installed!

Steve


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## z-family




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## N7OQ

I'm a HVAC tech and I'm surprised it wont work. A few things come to mind, a Invertor generator might have a clean 60 cycles but it also puts out RF energy, this is something I'm dealing with my Generator, it wipes out a couple of HF bands on my radio so I'm getting ready to build a filter that will remove this RF hash. So you may be interfering with motherboard.

I know Hams with the Honda 2000 that are able to use their generator by taking the negative lead from the 12v dc out put and connecting it to the generator ground terminal and the noise will go away. You could also try clamp on fairite chokes on the extension cord closest to the generator. A good power strip will also have some filtering in it so you could try a power strip at the generator then plug the extension cord into the power strip. You might have to go with a brute force filter to get rid of the RF noise, this is what I'm building for my Generator.

I have to ask did you try the generator on the furnace after AC power came back on? The reason I ask is there might be a safety that comes from another device that gets its power from a different source.

If you want give me the model number and I will research it and ask our suppliers if they might have a answer.


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## z-family

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## N7OQ

z-family said:


> Wow thanks Bill... Its a Trane XR90 high efficient natural gas forced air unit. I did try the generator and furnace again after power was restored and I did all the grounding work but it still faulted. Plugged it back in the wall and its running strong.
> 
> Rob


I made a couple of phone calls to friends who work for a company we do business with these are design engineers and both said the same thing. You are on the right track with the ground. Flame rectification proofing works at very low voltages and a voltage difference of as little a 50mv between ground and neutral will cause it to fail. Most backup generators tie into the service panel with a transfer switch so the neutral and ground stay bonded and there is no problem. But they said that when a portable generator is used there is no real ground they said that if you were to open your generator you would see the ground is connected to nothing or it is only connected to a external ground lug and the neutral is not connected the the ground so even if you do ground the generator the neutral is still floating.

I asked about just tying the ground and neutral together and he said that might work but what he finds what always works is to make a pigtail where the neutral and ground from the house stay connected to the furnace and the generator provides the power, like a Y cable but don't connect the the hot to the plug that goes to the house so you don't back feed power to the grid but get the benefit of a good house ground. He also that if just connecting the ground to neutral works than just go with that.

Anyway keep us posted if it works or not it would be a good thing for everyone to know. I also use my generator when we loose power and my Furnace works OK the way it is but I will be changing it out soon to something more efficient so I might have to do the same thing.

Here are the codes I found you might already have them but thought I would post them just in case you don't.

* Flashing slow: Normal - no call for heat
* Flashing fast: Normal - call for heat
* Continuous on: Replace IFC (circuit board)
* Continuous off: Check power
* 2 Flashes: External lockout (retries or recycles exceeded)
* 3 Flashes: Pressure switch error
* 4 Flashes: Open limit device
* 5 Flashes: Flame sensed when no flame should be present
* 6 Flashes: 115 VAC power reversed polarity or poor grounding
* 7 Flashes: Gas valve circuit error
* 8 Flashes: Low flame sense signal
* 9 Flashes: Check igniter


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## z-family




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## z-family




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## California Jim

Excellent read and info guys


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## Sayonara

Good info. Ill have to check mine before the power goes out in the winter. Thanks!


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## N7OQ

Good Deal Rob glad it worked it is really a good thing to have heat when you lose power. Sayonara brings up a good point everyone should check out their generator connections before it is needed.

A lot of people don't realize that a Gas fired furnace will work off a portable generator, but a gas fired furnace doesn't really use that much current. Most gas furnaces only have a blower motor and some might have a small fire box motor too. So check your gas furnace if it had a cord that plugs into the wall then just unplug it and plug it into your generator, it will make going through a winter power loss more comfortable. A oil furnace might work as well but I have never worked on a Oil fired furnace only oil fired boilers.


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## Oregon_Camper

Glad to hear you got it resolved.

And way to go to all the Outbakers..especially Bill, for going out of his way to help.


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