# Generator won't run gas furnace



## CodeMatters (Aug 16, 2017)

Common issue. Don't think it's related floating neutral. Think it's a result 
of incredibly dirty sine wave produced by most generators. I'll find a link 
and post it in a little while.


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## CodeMatters (Aug 16, 2017)

Here's a discussion on this subject that took place over on ElectricianTalk.com:

http://www.electriciantalk.com/f2/clean-dirty-power-furnace-200057/


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## woodyl (Dec 7, 2017)

Thanks for the link. I knew that people have reported problems with some generators, but this one is an inverter and from what I've read, people have reported that it puts out a clean sine wave. I don't know how tight the frequency is or if that could be the problem. I will test some more and maybe try some of options discussed, i.e., a line conditioner or filter. I believe that the first time I tested this generator, it seemed to run the furnace ok, which makes me wonder if it might have something to do with the other loads on that are running at the same time.


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## CodeMatters (Aug 16, 2017)

woodyl said:


> Thanks for the link. I knew that people have reported problems with some generators, but this one is an inverter and from what I've read, people have reported that it puts out a clean sine wave. I don't know how tight the frequency is or if that could be the problem. I will test some more and maybe try some of options discussed, i.e., a line conditioner or filter. I believe that the first time I tested this generator, it seemed to run the furnace ok, which makes me wonder if it might have something to do with the other loads on that are running at the same time.


Those are good ideas. Might try asking the furnace manufacturer for 
suggestions as well.


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## Shadow99 (Nov 3, 2017)

woodyl said:


> Thanks for the link. I knew that people have reported problems with some generators, but this one is an inverter and from what I've read, people have reported that it puts out a clean sine wave. I don't know how tight the frequency is or if that could be the problem. I will test some more and maybe try some of options discussed, i.e., a line conditioner or filter. I believe that the first time I tested this generator, it seemed to run the furnace ok, which makes me wonder if it might have something to do with the other loads on that are running at the same time.


Testing the inverter/gen without other loads is a good start. You didn't mention the other loads in your initial post. If your really loading the gen, it could have issues.

Generally, Inverters have nice sine waves, so that probably isn't the issue.

Frequency output is the second problem. You may be affecting this by loading the inverter.

Third, is no ground reference. When you run a gen with floating neutral, it means it needs to be grounded at a 'remote' place. (ie, in the transfer switch or main panel).
Most portable gens and Inverter gens I've come across are neutral/ground bonded, because they pretty much are not interconnected with a xfer switch/panel.


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## joed (Mar 13, 2005)

You could try running the furnace through a UPS.


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## JACK HOTTEL (Dec 15, 2011)

Some gas furnaces prove ignition by sensing current flowing through the flame. This current is measured in micro amperes. Any voltage gradient between the incoming power supply neutral and safety ground will disrupt the sensing. These furnaces require a good connection between safety ground and neutral. In normal operation this is supplied by the neutral-ground bond in the main electric panel. If you are connecting such a furnace directly to a generator which you state has a floating neutral, you will need to connect that neutral to safety ground before it will work. The other comments about power quality are also valid
but inverter generators usually put out acceptable power. Good luck,
Jack Hottel


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## woodyl (Dec 7, 2017)

JACK HOTTEL said:


> Some gas furnaces prove ignition by sensing current flowing through the flame. This current is measured in micro amperes. Any voltage gradient between the incoming power supply neutral and safety ground will disrupt the sensing. These furnaces require a good connection between safety ground and neutral. In normal operation this is supplied by the neutral-ground bond in the main electric panel. If you are connecting such a furnace directly to a generator which you state has a floating neutral, you will need to connect that neutral to safety ground before it will work. The other comments about power quality are also valid
> but inverter generators usually put out acceptable power. Good luck,
> Jack Hottel


I don't think the ground is the problem. If I disconnect the equipment ground, the furnace still works fine on my regular AC power. The problem only shows up on generator power.


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## Oso954 (Jun 23, 2012)

Try measuring the generator voltage at one of the receptacles.
Hot to neutral, hot to ground, and neutral to ground.

Post your results.

It will give you, and others, a better basis to discuss your problem.


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## woodyl (Dec 7, 2017)

Oso954 said:


> Try measuring the generator voltage at one of the receptacles.
> Hot to neutral, hot to ground, and neutral to ground.
> 
> Post your results.
> ...


Ok, thanks for the suggestion. I will be travelling for several weeks. I'll do some more testing when I get back.


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## Oso954 (Jun 23, 2012)

I’ll give you my prediction, 60V hot to ground, 60v neutral to ground, 120V hot to neutral.

My guess is that grounding the neutral will not force the neutral voltage over to the hot as it would in a true floating neutral situation.

I am not suggesting that you attempt grounding the neutral. That might cost you the inverter.


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## woodyl (Dec 7, 2017)

Oso954 said:


> I’ll give you my prediction, 60V hot to ground, 60v neutral to ground, 120V hot to neutral.
> 
> My guess is that grounding the neutral will not force the neutral voltage over to the hot as it would in a true floating neutral situation.
> 
> I am not suggesting that you attempt grounding the neutral. That might cost you the inverter.


Sorry, I don't understand what you mean. If there's 120v hot to neutral and grounding is not an issue, what would cause the problem I'm having? As I said before, I've already determined that my furnace will work with regular AC even with the equipment ground disconnected. Doesn't that suggest that grounding is not the problem? Or is it the grounding on the generator that's causing the problem?


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## Oso954 (Jun 23, 2012)

You really do not have a neutral. What you have is more like Two hots and a ground.
L#1 60v, L#2 60v and ground. No neutral. If the two “hots” are 180 degrees apart from each other, your voltmeter will read 120v between the two lines.

That’s the reason I suggested the “hot” to ground and “neutral” to ground measurement.

Since your flame sensor is expecting to see something near zero volts on the “neutral”, the 60 volts is confusing it. It is seeing something “wrong” and refusing to operate.


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## woodyl (Dec 7, 2017)

Oso954 said:


> You really do not have a neutral. What you have is more like Two hots and a ground.
> L#1 60v, L#2 60v and ground. No neutral. If the two “hots” are 180 degrees apart from each other, your voltmeter will read 120v between the two lines.
> 
> That’s the reason I suggested the “hot” to ground and “neutral” to ground measurement.
> ...


That could be the problem. Do you have any ideas of how to get the furnace to work in that situation? Is it likely that a UPS would change the situation?


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## woodyl (Dec 7, 2017)

Another question: I've read that shorting neutral to ground can fry an inverter, but I've also read that some people fixed problems by bonding neutral to ground separately from the generator, say, by using a neutral-ground bonded plug. I'd like to try this out, but I want to make sure that I don't damage my generator. Can somebody help me understand the issues with creating a neutral-ground bond?


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## mpoulton (Jul 23, 2009)

woodyl said:


> Another question: I've read that shorting neutral to ground can fry an inverter, but I've also read that some people fixed problems by bonding neutral to ground separately from the generator, say, by using a neutral-ground bonded plug. I'd like to try this out, but I want to make sure that I don't damage my generator. Can somebody help me understand the issues with creating a neutral-ground bond?


I cannot imagine that there is any issue with it. You should be able to bond neutral and ground just fine. Any inverter which cannot operate with neutral and ground bonded has a problem, I would say, and probably can't be UL listed. Many generators have a removable N-G bond to avoid parallel neutral paths when used with a transfer switch. For other uses though, portable generators should have neutral and ground bonded.

To address your earlier question about testing the furnace on utility power with the equipment ground removed, that test is not likely to be valid and you cannot draw any conclusions from it. It is questionable whether you can actually remove the equipment ground on the furnace at all. The furnace is presumably connected to metal ductwork and gas piping, all of which is likely bonded elsewhere. The equipment grounding conductor is only one of many probable bonding points. Did you check continuity between the furnace chassis and other bonded metal to verify that it was actually un-bonded?


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## woodyl (Dec 7, 2017)

mpoulton said:


> I cannot imagine that there is any issue with it. You should be able to bond neutral and ground just fine. Any inverter which cannot operate with neutral and ground bonded has a problem, I would say, and probably can't be UL listed. Many generators have a removable N-G bond to avoid parallel neutral paths when used with a transfer switch. For other uses though, portable generators should have neutral and ground bonded.
> 
> To address your earlier question about testing the furnace on utility power with the equipment ground removed, that test is not likely to be valid and you cannot draw any conclusions from it. It is questionable whether you can actually remove the equipment ground on the furnace at all. The furnace is presumably connected to metal ductwork and gas piping, all of which is likely bonded elsewhere. The equipment grounding conductor is only one of many probable bonding points. Did you check continuity between the furnace chassis and other bonded metal to verify that it was actually un-bonded?


Oh, that's a good point about the furnace being indirectly bonded via the ductwork and gas piping. I never considered that. It seems likely. I'll try bonding neutral and ground on the generator and see if that helps the problem.


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## Shadow99 (Nov 3, 2017)

I agree with MPoulton on the bonding of the gen.

I have heard of Inverters that specifically say in the manual, that they will short out if you bond the neutral to ground. I can't see that type of Inverter being used on a genset thou.

Worthwhile to look at the manual, and/or post which one you have. Someone can double check for you.


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## woodyl (Dec 7, 2017)

The model is a Champion 100302 "Digital Hybrid Portable Generator". The manual doesn't say anything about bonding, as far as I can see. The manual says this:



> Grounding
> The generator system ground connects the frame to the
> ground terminals on the power panel.
> – The generator (stator winding) is isolated from the
> ...


I'm not really sure how to interpret that.


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## CodeMatters (Aug 16, 2017)

Checked my own Generac iX 1600. 

Not running resistance:
gnd to neutral* - off scale
gnd to hot - off scale

running Vac:
hot to neutral - ~120
gnd to hot - <1
gnd to neutral* - <1 

*Not accurate to call this neutral but it seems the easiest way to describe 
where I was measuring. 

So it appears to me the gnd is not connected to anything in the current path. 
Likely connected to chassis parts. 

My manual doesn't say anything useful.


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## Shadow99 (Nov 3, 2017)

woodyl said:


> The model is a Champion 100302 "Digital Hybrid Portable Generator". The manual doesn't say anything about bonding, as far as I can see. The manual says this:
> 
> 
> 
> I'm not really sure how to interpret that.


Well, pretty much says it's a floating gen.
They don't mention specifically 'not' to bond the neutral to ground, but as @*Oso954* said in post #12 , the inverter may not like it.

I suggest calling Champion and asking them. From my experience their tech support is pretty good.


As a side note** I never heard of an Inverter that would blow up with neutral/ground bonded, until this thread !! Really, wtf ?
A quick google found this http://gpelectric.com/files/gpelectric/Docs/Manuals/Go_Power_MAN_Inverter_GP-1750HD-2500_vA.pdf
On page 7, it states DO NOT BOND !
I've worked with quite a few Inverter chargers, often fed from a bonded generator, no issues at all.

I can't see any mfr ever putting this type of inverter on a Gen, but stranger things have happened.


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## woodyl (Dec 7, 2017)

I'm going to be away from home for several weeks, so I won't be able to test anything until I get back. It couldn't hurt to talk to the manufacturer, but I'll not always confident that the person I'm talking to really knows what's going on.

This generator has a 30 amp RV plug and is clearly intended to work with an RV. I don't know if an RV would typically have a neutral-ground bond at the panel, or if it expects to see the bond at the pedestal. If an RV does have a bond at the panel, then I would expect that this generator would need to be built to tolerate it.

This generator


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## mpoulton (Jul 23, 2009)

woodyl said:


> I'm going to be away from home for several weeks, so I won't be able to test anything until I get back. It couldn't hurt to talk to the manufacturer, but I'll not always confident that the person I'm talking to really knows what's going on.
> 
> This generator has a 30 amp RV plug and is clearly intended to work with an RV. I don't know if an RV would typically have a neutral-ground bond at the panel, or if it expects to see the bond at the pedestal. If an RV does have a bond at the panel, then I would expect that this generator would need to be built to tolerate it.
> 
> This generator


An RV would sometimes (but not always) have a N-G bond, especially if it was ever set up for a permanent electrical service. They certainly couldn't guarantee that it wouldn't, so the generator would have to handle it.


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## woodyl (Dec 7, 2017)

Ok, to follow up on this, I talked to a very helpful technical support person at Champion, and he said that bonding the ground and neutral is a good practice and will not damage this generator. He thought that there's a good chance that doing that will fix the problem I'm having running my furnace off the generator. I haven't tested it yet, but I will soon.


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## woodyl (Dec 7, 2017)

I finally got around to testing the generator again. I made the neutral-ground bond at the panel and this time the furnace ran ok. So, for anybody else having the problem, make sure you try that.


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## Oso954 (Jun 23, 2012)

What panel did you make that bond in ? Is this a house main panel, house subpanel, or an rv panel ?
Could be a huge safety problem.


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## woodyl (Dec 7, 2017)

Oso954 said:


> What panel did you make that bond in ? Is this a house main panel, house subpanel, or an rv panel ?
> Could be a huge safety problem.


It's a small panel with a few breakers. The whole setup is completely separate from my home electrical service. I wired it to some dedicated generator outlets.


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## JG44070 (Aug 1, 2020)

Oso954 said:


> You really do not have a neutral. What you have is more like Two hots and a ground.
> L#1 60v, L#2 60v and ground. No neutral. If the two “hots” are 180 degrees apart from each other, your voltmeter will read 120v between the two lines.
> 
> That’s the reason I suggested the “hot” to ground and “neutral” to ground measurement.
> ...


I agree with your analysis, well thought out. I took the readings as you suggested and they are as you predicted. Jumpering the neutral wire to furnace case solves the problem but I don't like this for safety reasons. Do you have a suggestion for a permanent fix to this issue. I was thinking about lightly fusing the neutral to case (.5 amp) then adding a inline gfci to handle the safety issue. Opinion? Thanks.


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## woodyl (Dec 7, 2017)

@JG44070 
This thread is a little old, but what worked for me was to bond the neutral to the ground. Because my setup runs everything through a small breaker box, it was convenient for me to do the bonding there. Otherwise. I would have bonded the neutral to the frame of the generator to accomplish the same thing.

This was what worked with my generator. I don't know if that would be the way to go with yours or not.


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## deanh1608 (Nov 13, 2021)

CodeMatters said:


> Common issue. Don't think it's related floating neutral. Think it's a result
> of incredibly dirty sine wave produced by most generators. I'll find a link
> and post it in a little while.


I thought so too, so I sold the champion generator at a loss and then purchased an inverter generator for $500 more. SAME PROBLEM. when I bonded the neutral-ground together like this No Shock Zone and worked great. problem solved! Should have done this first!


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## deanh1608 (Nov 13, 2021)

deanh1608 said:


> I thought so too, so I sold the champion generator at a loss and then purchased an inverter generator for $500 more. SAME PROBLEM. when I bonded the neutral-ground together like this No Shock Zone and worked great. problem solved! Should have done this first!


better link Generator Ground-Neutral Bonding | No~Shock~Zone


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