No heat when on generator

[Denray]

Have a new 95+ Rheem heater. 
When the power is out, and on a generator, only the fan will come on, but burners won't light. My old 80% would light up no problem. 
Any ideas?

[Marc]

3 hours ago, Denray said:

Have a new 95+ Rheem heater. 
When the power is out, and on a generator, only the fan will come on, but burners won't light. My old 80% would light up no problem. 
Any ideas?

I assume this is a gas-fueled furnace. Grounding and correct polarity of the incoming power is vital in order for ignition to function. The ignition card will detect if the polarity is incorrect and fail the ignition every time.

[Denray]

Thanks for the replay Marc
I plug it into the 3 prong outlet of the generator the same way I did with the 80. 

[Marc]

1 hour ago, Denray said:

Thanks for the replay Marc
I plug it into the 3 prong outlet of the generator the same way I did with the 80. 

The ignition card on the old 80 may not have had the polarity sensing feature of the 95+.

[Jim Katen]

Do the burners try to light and fail or does the ignition cycle not even start? 

[Denray]

Ignition no start. 
Could be something about generator not grounded. If so, wondering about proper way to ground a small generator to the furnace?

[Jim Katen]

If this is a portable generator with an extension cord, the grounding shouldn't matter as long as you're using an extension cord with a grounding wire and intact connections at each end. 

If this is a permanent setup with a transfer switch, the generator should have its own grounding connection to the earth, just as you'd have at the power company's service point. 

Grounding problems to a furnace usually result in the flame sensor not working properly, in which case the unit would at least try to start up, but then shut down when it couldn't prove the flame. If the flame doesn't even try to start, something else it probably wrong, but I couldn't say what. Try calling Rheem. 

[Denray]

Rheem sent me to an online that was going to cost. Which I didn't try.

Been told it's a polarity issue that somehow relates to grounding. Very new 95+ and full of computerish hardware. I have no warranty on this rig, but I think it's not it's fault. Heater installer has large output generator at his house wired into service panel for his same as mine furnace. Mine runs fine on house electric.

 

[Denray]

Just read some furnaces don't work with inverter supplied power.

[Marc]

1 hour ago, Denray said:

Rheem sent me to an online that was going to cost. Which I didn't try.

Been told it's a polarity issue that somehow relates to grounding. Very new 95+ and full of computerish hardware. I have no warranty on this rig, but I think it's not it's fault. Heater installer has large output generator at his house wired into service panel for his same as mine furnace. Mine runs fine on house electric.

 

I spend a lot more time on recreational vehicle FB pages than I do here. Lots of appliances and power filtering devices will give trouble if your power plant isn't grounded. It's all the new electronics.

Check if your power plant is already grounded. If it isn't, you need to do it somewhere on your premises wiring. Just be absolutely sure that it isn't grounded twice.

[Denray]

It's portable eu1000i Honda. Should I run a ground wire from it's internal metal frame to house ground rod, or to metal frame of the furnace?

 

[Jim Katen]

If it's a portable generator that only uses extension cords, then there is no reason to make a connection to the earth. The frame of the generator is the "ground." As long as the extension cord has an intact equipment grounding conductor and as long as the grounding wire's socket and pin are it good condition, then the furnace will see this as grounded. 

Also, a generator is not an inverter and the furnace should not see it as one. 

Is this how your system is set up, or are you using a transfer switch? 

[Denray]

This is how it is advertised by Honda

Honda EU1000i - 900 Watt Portable Inverter Generator w/ CO-MINDER™ (CARB)

Extension cord connection only. My furnace installer friend has his furnace, same as mine, connected to a standard generator, when our power goes out.

[Marc]

5 hours ago, Denray said:

This is how it is advertised by Honda

Honda EU1000i - 900 Watt Portable Inverter Generator w/ CO-MINDER™ (CARB)

Extension cord connection only. My furnace installer friend has his furnace, same as mine, connected to a standard generator, when our power goes out.

That's an excellent choice of generator. I'm saving for the EU 3000 myself for my travel trailer.

I suspect most good generators don't automatically ground the neutral because it isn't known if the RV, or whatever you connect it to, is also grounded. Two separate grounding points introduce neutral currents into the ground wire, which is to be avoided. Look at the schematic that came with the generator. If it doesn't show a bonding point between neutral and ground, ground it yourself and see if the furnace works.

Edited January 19, 2023 by Marc

[Denray]

Thanks for the replies everyone. You all still rock!

[Jim Katen]

According to the instructions ( https://www.electricgeneratorsdirect.com/manuals/Honda EU1000i Manual 2013.pdf  page 38), the equipment grounding wires are bonded to the frame of the generator but not to the neutral. This makes little sense  because the EGCs will never clear a fault that way. This also explains why your furnace won't work while connected to it. The instructions don't mention it, but there should be a bonding strap that bonds the neutral to the EGC. I'd make that connection and try again. 

[Les]

I guess I can ask a stupid question even when I think I know everything. 

Isn't a 900watt generator a bit small for this application?  I  have four generators for my use;  smallest is 3500 for the barn. 

 

[Jim Katen]

That's a great question. I didn't even look at the capacity of the generator. Most furnaces are going to need 8-10 amps, not the 7.5 that this one produces. It's possible that the generator just isn't producing enough power. 

[Marc]

Makes sense. That generator is rated 7.5 amps steady-state. The blower on my 3 ton Rheem is 8.6 amps FLA.

[Denray]

No AC here, just the blower and the blower starts no problem.

I'll get back to you once I, if I, can figure it out.

Thanks a bunch for all your insight.

[Jim Katen]

Look at the furnace's rating plate - it's almost certainly going to be greater than 7.5 amps. 

Then just try bonding the grounding terminal to the neutral at the generator - even temporarily as a troubleshooting measure. 

[Denray]

"Then just try bonding the grounding terminal to the neutral at the generator - even temporarily as a troubleshooting measure".
So, we did that and the fan turned on, but then there was this click click noise? And then the burners lit up. And a little later there was warm air coming out our vents. 
Color us happy!
Thanks again for your help on this. 
Pulled off the panel holding the outlets on the generator and right on the back side there was a hole to push the jumper in and a screw right next to it to complete the bonding. Piece of cake.

[Jim Katen]

I see that the minimum circuit ampacity is 10 amps . . . though if it's working, I guess that's all you need.