Furnace Blows Hot on Generator - Cooler on 30 AMP Power

Handy · 03-06-2018, 09:14 PM

We have someone on the road using our RV and they told us the RV is running the furnace just fine on generator power (hot air) but on 30 amp shore power it runs a lot cooler air, warm, but much cooler than with generator power.

Any ideas why this would be? Cooking with LP works find so no supply issue.

Any help is appreciated since I'm not with the coach in person, I'll have to talk my user through it possibly.

2007 Jayco Melbourne 29D.

Thank you!

Handy · 03-06-2018, 09:25 PM

Note that I did notice a bit of a kink in the line leading out from the propane tank to the coach, but the propane flows fine since all burners work and the fridge works find on propane.. and the furnace blows hot on generator power... so why not shore power?

Isaacs · 03-06-2018, 09:45 PM

If, for some reason, the generator were not charging the coach batteries then this may result in a low voltage (12V) situation. The furnace blower would run slower and the air would feel hotter. Just a thought...

WinnieView · 03-06-2018, 09:52 PM

Had to think about it for a moment but could it be that the transfer switch is not working correctly?
So when connected to shore power there is no 12 volts being supplied to the furnace circuit and the flame is not on?
Check and reset all breakers?

Does it work with no shore or generator power??

jd99336 · 03-06-2018, 10:39 PM

Could it be your unit has the heatpump in the ac and they are selecting the heatpump instead of the gas furnace? I have done that on my 31DS by accident.

RVermont · 03-07-2018, 05:59 AM

Can you clarify that the unit is set up the same. Ie engine off, slides in or out? Only difference is gen on or gen off. Unit parked.
Do they hear the roar of the fire box or just the air blowing? Operationally on my unit when close to temperature set point the blower comes on. Then you hear the roar of the fire for a couple minutes until temperature is reached then fire stops and the blower continues for several minutes to cool the fire box.

As JD mentioned. If set on heat pump the furnace will come on for a few minutes then continue to blow awhile while moving to the ac units.

Sent from my iPhone using Tapatalk

Handy · 03-07-2018, 11:05 AM

Quote:

Originally Posted by 2008Seneca

Had to think about it for a moment but could it be that the transfer switch is not working correctly?
So when connected to shore power there is no 12 volts being supplied to the furnace circuit and the flame is not on?
Check and reset all breakers?

Does it work with no shore or generator power??

Great thought. I'm not with the coach but it might make sense. It works fine with the generator power, I'm not sure how well it works with battery power... but with shore power it is blowing cooler, not hot.

Handy · 03-07-2018, 11:10 AM

Quote:

Originally Posted by RVermont

Can you clarify that the unit is set up the same. Ie engine off, slides in or out? Only difference is gen on or gen off. Unit parked.
Do they hear the roar of the fire box or just the air blowing? Operationally on my unit when close to temperature set point the blower comes on. Then you hear the roar of the fire for a couple minutes until temperature is reached then fire stops and the blower continues for several minutes to cool the fire box.

As JD mentioned. If set on heat pump the furnace will come on for a few minutes then continue to blow awhile while moving to the ac units.

From what I gather, truck engine is off, unit is parked and connected to shore power. Slides would probably be out since they are at a campsite. I'll have to ask about the roar of the firebox.

Handy · 03-07-2018, 11:14 AM

I think the transfer switch is fine since the inverter doesn't need to be on to work the TV and other appliances work fine when connected to shore power.

Handy · 03-07-2018, 11:19 AM

I had them try to disconnect the batteries by using the disconnect switch on the coach and they said that all outlets and furnace blower and lights went off when they did that even when connected to shore power... so they just turned it back on. I'm new to the RV world but I would have thought that you could disconnect the batteries while on shore power if you want and the only affect would be to not charge the batteries and that all other functions would remain active. Apparently not.

WinnieView · 03-07-2018, 12:12 PM

Quote:

Originally Posted by Handy

I had them try to disconnect the batteries by using the disconnect switch on the coach and they said that all outlets and furnace blower and lights went off when they did that even when connected to shore power... so they just turned it back on. I'm new to the RV world but I would have thought that you could disconnect the batteries while on shore power if you want and the only affect would be to not charge the batteries and that all other functions would remain active. Apparently not.

No. The 12 volt DC disconnect switch disables the relay from the batteries and cuts power to the converter.

The microwave, AC, and any other 120 VAC appliances "should" still work.

RVermont · 03-07-2018, 02:47 PM

The furnace operates on 12 volts. This comes from the batteries, which are charged from the truck engine(maybe not sure in 2007), or through the converter which is supplied from the generator or shore power. Most unit are set up to be generator preference so when plugged into shore power and the gen running the power is supplied from the gen. Turn the gen off and it will switch to shore supply. To test, turn off the shore power breaker (gen off) at the pedestal. Give it a few seconds then turn back on listen very carefully and you should hear a loud thunk, that is the shore power moving the transfer switch.

Do you have anything in the unit that displays voltage of the batteries? If so that should show you the current level of battery charge. Possibly the shore power is not charging the batteries due to transfer switch. Still need to see if the fire box is actually firing up it is pretty loud when it cycles.

Sent from my iPhone using Tapatalk

You may also like: