Atwood Furnace

[jbrack]

I'm a little frustrated with my Atwood furnace. I have a 2018 5th wheel that I bought at the RV show in Sacramento. I hit the road to Arizona and almost immediately had trouble with the furnace. For example, if the temp was 60" inside the coach and I set the thermostat on 70", the furnace would come on and cook for about 5 minutes and then the burner would shut off. The fan was still blowing and then in about a minute, the burner would fire back up. It would cycle on and off like this until if reached the desired 70". I took it in to a mechanic in Tucson and they replaced the circuit board. About 10-12 months later, the fan when I wanted heat, the fan would come on but the burner would not light. I took it in again (Camping World in Vacaville, CA) and they replace the Sail Switch. Now it lights right away but is back to that cycling operation from before. I called Dometic who took over Atwood, and they can't help me. They said I just need to take it back to a mechanic. My furnace is accessed through the storage compartment or basement. Each time I have to remove all of my gear and take down the walls so the guy can crawl in there. It's a royal pain the butt. Anyone have a guess why its cycling like this? None of the mechanics seems to know.

[BFL13]

Can this happen if you close off some of the duct vents to different places (at the room ends using the variable closures) while leaving others wide open?

[wa8yxm]

That is one possible cause of Short Cycling.. Another is thermostat placement relative to the heat vents.. The T-Stat quickly heats as the furnace blows on it then shuts down then cools down and tries again. Annoying true.

ON my RV the original T-Stat was the front A/C. the sensor is actually in the grill assembly.. Well it tended to be influenced by "Cold" leaking in from outside. I had to put a fan on it to control temp.

Today the T-stat is in the hall, away from heat vents and The A/C.

[Flyfasteddie]

I'm in the same boat as JimK. Mine has always done this. It puts out a massive amount of heat for a little 23' MH and as it gets over 63 degrees or so in the MH the burner will shut off maybe every 10 minutes and then come back on after 5 minutes or so until it reaches the thermostat set temp or I turn it off. I just always thought that the furnace was oversized for the application.

[JimK-NY]

My furnace has always done this. It puts out plenty of heat so there does not seem to be an issue. Then after a few minutes, the burner shuts off, plenty of heat comes out and the burner goes back on within a minute or so. I suspect the furnace is just oversized for the amount of duct work and size of my RV.

[midnightsadie]

#1 don,t go to cw ,just my .02cts worth. hire a mobile rv tech. talk to him on the phone ,and when he gets there show him old biscuits post. p.s that mobile tech comes to you.

[Old-Biscuit]

Burner cycling on then off/back on/off is called 'limiting' which is when the airflow has been restricted and heat exchanger high temp limit switch is opening (too hot) then fan continues to run so temp drops...high temp limit switch closes and burner lights back off

You have something obstructing/blocking either the furnace discharge air flow OR the return air to furnace
Could be closed/blocked register, could be crushed ductwork, could be how/where stuff is stored


Fan runs cause high temp limit switch opened.burner keeps firing back off cause thermostat temp set point has not been met....high temp limit switch controlling burner shutting down/relighting

[BFL13]

Seems similar--with my ( older model) it was not the high limit switch, but the main board so it was easy to fix.

https://www.rv.net/forum/index.cfm/fuseaction/thread/tid/29853782/gotomsg/29853808.cfm#29853808