Furnace Issue

[ock91299]

Hi All,

I have a 2005 Jayflight 29fbs. I have the trailer plugged in (to house electric) and just parked in the driveway unoccuppied. Last night I heard puffing sound coming from the exhaust outlet for the furnace, like it was going on and off. I opened the door the the trailer and heard a clicking sound coming from return vent cover under the fridge. The thermostat was off, and the propane was off. I removed the vent cover and did a once over look at the furnance and didn't see anything out of sorts...(i'm no mechanic and only been camping for 6 months, don't even know what i'd be looking for!!!!). The furnance kept making this clicking sound and revving constantly like it was starting up, shutting down...etc and air was puffing out of the vents throughout trailer. We were out all day, so i'm not sure how long it was doing this. I tried shutting off breaker but it kept doing it i guess because it was running off the battery. So I turned breakers back on, opened propane tanks and turned on thermostat and the furnace came on and ran normal. Then I shut off thermostat, then fan kicked off a short time later and the clicking started again. So I unplugged the battery and came in and turned off all the breakers and everything stopped. Any thoughts on what thats all about?? Odd that it started to do that when no one was in there and thermostat was off. Thanks

[eldermike]

Did you try setting the temp down to where it would not be calling for heat? The reason I ask is to help isolate the issue. If it quits doing it by setting it all the way down then it's most likely a bad thermostat in the slide switch area. What this would tell you is that you have control of the furnace temp but not control of the off setting.

[Doug]

Originally Posted by eldermike

Did you try setting the temp down to where it would not be calling for heat? The reason I ask is to help isolate the issue. If it quits doing it by setting it all the way down then it's most likely a bad thermostat in the slide switch area. What this would tell you is that you have control of the furnace temp but not control of the off setting.

X2, good advice

Doug

[ock91299]

I'll check that out and get back. Thanks

[Threebutchers]

Another thought based on your symptoms....

Is it possible you are not flipping the switch far enough to turn off the furnace? My thermostat switch is VERY hard to slide from off / on. So difficult, it feels like I'm about to wring the thermostat off the wall or snap the on / off lever. My Dealer told me they are all that way for safety so they don't accidentally get jarred to the on position during travel.

[clutch]

It sounds like it was trying to start with no propane available.

[Threebutchers]

Originally Posted by clutch

It sounds like it was trying to start with no propane available.

X2.....that's why I'm thinking the propane is being shut off....but the thermostat on / off switch isn't getting flipped over all the way

[ock91299]

so far so good, turned the thermostat all the way down so it wouldn't be calling for any heat and made sure the switch was all the way off. Just took our last trip this weekend and furnace worked great, no repeat issues. Time to winterize. Thanks again.

[usmc616]

Originally Posted by clutch

It sounds like it was trying to start with no propane available.

That is exactly what I was thinking.

[msturtz]

Ok, a bit of information on how RV propane furnaces work. RV propane furnaces operate differently than residential furnaces or small propane heaters work. Because RVs are small and are usually insulated well they have very limited air for combustion. So under code regulations air for combustion must be drawn in from outside the RV and then exhaust must exit to the outside. If you look closely at the exhaust tube on the outside you will see a center hole and then a hollow outer section. The hollow outer section draws in combustion air while at the same time insulating the hot exhaust allowing tighter clearance to combustible materials. Also per code RV Furnaces use forced draft (induction) to prevent inadvertent backflow. So, given this information the furnaces does the following to start up:
Thermostat calls for heat
Induction fan turns on to draw in combustion air from outside and exhaust burned gases
Propane valve opens to allow the flow of propane to the furnace burner
DSI (Direct Spark Ignition) fires to provide spark to ignite the propane (This is the crackling or clicking sound you heard.)
A thermocouple determines if the burner has lit
After x seconds if the ignition has failed then the gas valve will close
Assuming the burner is lit then the furnace blower automatically starts to blow air throughout the RV. (Note: some furnaces are configured to automatically turn on the blower as soon as the induction fan turns on. It sounds like your furnace is configured this way.)
As soon as the heat set point is reached the propane valve closes.
The forced induction fan runs for several minutes to allow cool off
The blower fan runs to allow cool down of the heat exchanger
After cool down the induction fan and blower shut off

the benefit of this setup is you get dry warm air in your RV with no carbon monoxide or water vapor inside our RV. The drawback is it uses more electricity than ceramic heaters etc. If the propane is shut off or runs out depending on the setup of the propane heater. Some heater will try x times to start and then give up until you power them off at the thermostat (there is a small switch that turns the heater on and off) others may continue to attempt to start every so often.

I hope this helps you understand the operation of your RV furnace.

[outofhere]

Thanks that was informative I had the basic but that help to put it in the correct order