2955RL Furnace Problem

[budbon]

We picked up our new 2010 2955RL in Mesa, Az on Jan. 22nd of this year and love it. We had a few little warranty items that were tended to by the dealer. We also had one that has become a problem. The furnace will fire up and run for maybe 8 to 15 minutes and then shut down before getting up to the thermostat defined temperature. After a few minutes it will come on and run for a few minutes and shut down. In time it will get to the thermostat defined temp but only after a number of these starts and stops. To further explain, we usually shut the furnace off at night as we like to sleep cool. This past week during a Moab, Utah trip the inside temp got down to about 48 degrees. I turned the furnace on and set the temp to 70. It took more than an hour with numerous starts and stops to get to temp. I own an older Mobile Home Park and a number of trailers.

The dealer has been in contact with the furnace manufacture and has replaced the thermostat twice, replace some sort of sensor near the AC (I think that is what they said). The dealer is going to work further on the problem but we are in Colorado and won’t return to Arizona until November. Another problem is in Arizona the overnight temps don’t get very low so I don’t know if they will be able to experience these many starts and stops of the furnace. I do a little work on furnaces and as such I thought it was probably a limit switch problem. I guess the dealer and manufacture see’s something different. Having said that I believe the furnace should continue to run until the thermostat temp is reached.

Because I don’t like to shop our local Montana dealer even for parts, taking it there is out of the question so I will wait until November and hope the situation can be dealt with. In the mean time I would appreciate any ideas from you folks. Have any of you had such an experience?

[DnDatGrdJct]

Bud,

The furnace in our 2008 model 3075 does exactly the same thing. This is the first time we have used the furnace to any extent so we were wondering if that is the normal mode of operation.

Will be interested in any replies you receive.

We are also in Colorado and going through propane at a dealers delight rate.

Hope that our situations are not normal as this furnace cycling is a real annoyance at night.

Dean

[budbon]

DNDatGrdJct, I will try to keep you posted on the furnace problem. There is no way this is normal for a furnace. I know what you mean about the cycling thru the night being annoying.
By the way, we live out of town here in Durango and use propane for our home. We had a "wet line" installed on our propane tank enabling me to fill our tanks at home. The price is cheaper than filling at a station and much more convent although slower.

[Ozz]

This could be a limit switch, shutting the furnace off, then cooling off, then starting back up because of a blockage. There may be an obstruction in the discharge air, or intake air causing the furnace to overheat.
I would have to see exactly what is happening to be of more help. I would check, or have them check for a blockage, or something in the fan blades causing it to not move much air.
Can you feel a forceful air discharge?

[DnDatGrdJct]

Ozz,

Do not want to hijack Bud's question but his and our problems seem to be very similar so thought I would just add how ours is behaving in hopes of helping solve the issue.

I can't speak for Bud but in our case there is considerable air flow from all the registers. if we put a piece of newspaper over the register it will easily get blown off.

Have timed the rate of cycling and it appears to be about 10 minutes from start of on-heating to off for a bit to start of on again. This is with an outside temperature of about 20 degrees lower than the inside.

Bud, please excuse my butting in on your question.

Dean

[mhs4771]

There was another post some time ago about a similar situation. It was suggested to pull the thermostat from the wall and plug the rather large hole that was made to run the control wire through. The thought being that heat to the underbelly was traveling up through the wall to the back of the thermostat causing a pre-mature shut-down. Mine does the same exact thing, but have haven't gotten around to plugging the hole yet as we're just getting into our usage season (warmer weather that won't need the furnace). Not sure if this will fix the problem, but think it's worth a try. Let us know if it works, then I'll know for sure to do it on mine.

[budbon]

The dealer supposedly checked the heat duct for obstructions. You are not hijacking DnDatGrdJct, this seems to be a common problem and any input is desired. I'll check the hole behind the thermostat and see what is there.

[klash]

I had the same problem with my 2007 Montana 2955RL. The thermostat is mounted on the
wall on the left hand side going up the steps to the bedroom. There is a hole in the behind the thermostat the size of a silver dollar. The basements in our units have some heat
directed down there. The hollow portion of the walls connects with all the void spaces in the basement, and eventually some of the heat will enter the back of thermostat through the large hole, and this will then shut down the furnace. This will go on and on, and of course the inside of the unit will not reach your desired set point. I fixed he problem by putting some low expansion foam in the hole, or you could jam in a wadded p piece of butyl tape, then I cut a small slit in a piece of duct tape, smaller than the back of the thermostat, placed
it around the wires, and stuck the tape on the wall. No more problems.

[dmacy]

The lower the outside temp the longer the cycles. This behavior is normal.I have had many rvs in my 25 years plus rving and all my furnaces have performed the same way.

[budbon]

dmacy - I agree that the lower the temp the longer the cycle, but I believe there should only be one cycle from start to set point, not many. My experience with furnaces has been that there are two limit switches on the furnace. One is the fan limit in which after the furnace fires it reaches a certain temp before the fan comes on thus warm air is directed to the ducts. Note: on my Monty the fan comes on before the furnace fires - maybe this is the way it is designed. The second limit switch I call the high limit. This switch is a safety switch that limits the total maximum temp before shutting down. Both switches can control the gas valve opening. The only other control over the gas valve opening would be the thermostat.

Having said that, it would seem the high limit switch is causing the unit to shut down pre thermostat set point unless, as mentioned above, where heat is reaching the thermostat more directly than by ambient air. Also as mentioned above, some things that would cause the unit to overheat and trigger (open) the high limit switch could be not enough air flow either thru the air ducts or possibly return air restrictions. I assumed (you know what they say about that) the service people took into consideration these factors. Perhaps the furnace is improperly spec-ed for the unit. One of many questions I have is why does the blower fan come on before the heat?

Disclaimer: I am not a furnace repair tech. I own an older mobile home park along with 19 mobiles. Over the years I have learned to tend to some of the minor furnace issues on these units. I would and will certainly embrace input from anyone. This is a great site.

[budbon]

I pulled the thermostat and covered any excess hole area behind. There seems to be plenty of air flow. I'm still leaning toward the high limit switch.
Now to get the dealer to agree. I suggested this to the service department back in January and they seem to be stuck on something other than the limit switch. Oh yeah, they said they checked the sail switch. Limit switches are not to expensive. Maybe I'll change it myself and take a chance it won't void the warranty.

[farmboy]

I have a 2005 2955 with the remote stat. and it does not work as yours does. That being said I do not like how it does work though.

[alandaudrey]

The reason your fan comes on before your furnace ignites is the "sail switch". It has to sense air flow and close a micro switch before it will let gas flow.

It is possible that there have been a bad batch of switches installed or that they are set incorrectly. That could be the same for the "high temp cutout" switch. Either switch being faulty could cause this problem.

I think the easiest thing to check would be the air flow coming into the thermostat from the wiring channel. That would be a quick check.

[Bob Pasternak]

This probably has no bearing on your problem, but on an '03 2955RL we had, birds got into the outside furnace vents and built a nest while it was in storage. Had to practically dismantle it to get it out. I put a screen over it and on the 3000RK we got later.

[ARJ]

quote:Originally posted by Bob Pasternak

This probably has no bearing on your problem, but on an '03 2955RL we had, birds got into the outside furnace vents and built a nest while it was in storage. Had to practically dismantle it to get it out. I put a screen over it and on the 3000RK we got later.

I agree-there may be an obstruction in the exhaust. Check and then put a screen over the exhaust vent. One other stupid idea, is the thermostat in some of the air flow when the furnace is running?

[Johnnyg]

We have the same problem as Bodbon with the furnace short cycling on our 2010 3665RE although the AC unit runs continusouly until the set temperature is reached which leads me to beleive my problem is related to the furnace and not the thermostat.
Now I'm not sure if it's related but last weekend the temp dropped over night and we turned the furnace on. I noticed it was short cycling as usual.About half way thru the evening the furnace quit running altogehter. I swithched tanks and it restarted without further problem but the first tank was not MT. Getting to my point, is it possible the furnace is starving for LP causing it to short cycle and somehow restarting on its own?

[SlickWillie]

quote:Originally posted by Johnnyg

We have the same problem as Bodbon with the furnace short cycling on our 2010 3665RE although the AC unit runs continusouly until the set temperature is reached which leads me to beleive my problem is related to the furnace and not the thermostat.
Now I'm not sure if it's related but last weekend the temp dropped over night and we turned the furnace on. I noticed it was short cycling as usual.About half way thru the evening the furnace quit running altogehter. I swithched tanks and it restarted without further problem but the first tank was not MT. Getting to my point, is it possible the furnace is starving for LP causing it to short cycle and somehow restarting on its own?

Were you running on the side with the red regulator? 18 PSI IIRC. There have been issues with these regulators. I know my furnace would try to fire up, so I called an RV service. Before they came, I figured out the red regulator was full of pipe thread compound. I'm running without it now.

[DnDatGrdJct]

We tried the remedy the Klash suggested. Found the wire hole big enough to load a 50 amp power cord through. They must have put the hole in with a hammer head. We taped over the hole and found that made a very noticeable difference in the cycle times and the ability to run to set temperature without recycling.

When I put my finger in the hole there was a very noticeable movement of air.

Hopefully this will solve the recycling problem.

Dean

[Johnnyg]

No, it was the the other side but I'm sure worth checking.

[Johnnyg]

Though I'd take a look behind the thermostat as Klash had recommended and sure enough there it was a hammer size hole. I blocked it off with some insulation and duct tape.