Furnace turning off and on all night

[Toyhauling]

Hello everyone,
I have a problem when in cold weather and I am wondering how others have dealt with it. My furnace cycles on and off a few times an hour when the temps are less than 30 degrees and I have the thermostat at 40 degrees. I have considered a catalytic heater, but the risks seem too high for me (dogs, kids, CO, etc.)
Has anyone tried putting a heat sink in front of a furnace to collect and distribute the heat more evenly? I was thinking about a descent sized piece of iron. I.e. Scrap railroad rail.
Is there a thermostat on the market that you could program to cycle less often? I.e. Turn on at 40 degrees, off at 50 degrees?
Is there a catalytic heater with outside air exchanger similar to my forced air furnace?
Thanks in advance.

 

[Mr Lars]

Sounds like your furnace is working fine.

 

[PaulBates]

Your experience is similar to mine. I've determined that one problem is where the thermostat is located, placed for convenience, not function.

I've heard others here mention, and we're going to try next week on our next trip: a portable indoor electric unit from home... That assumes you have shore power.

 

[Rene T]

Your experience is similar to mine. I've determined that one problem is where the thermostat is located, placed for convenience, not function.

I

That’s interesting. How about starting the furnace then tape a piece off insulation over the thermostat to prevent heat from getting to it and see if it continues to run.

 

[Mark_K5LXP]

Yep, insulating/shielding the thermostat is automatic hysteresis, sometimes called differential. Frequent cycling can also be resolved by putting the thermostat somewhere else. If it's located where heat blows or otherwise warms up quickly than other areas of the room, it will cycle more.

Mark B.
Albuquerque, NM

 

[PaulBates]

In addition to the not optimal room location, it's mounted parallel and next to the oven (to be the fair to the designer, I'm not sure there is an optimal location... maybe "least worse" location)

I'd like a tstat like I have for my house that allows multiple battery sensor remotes and averages them. This feels like the same problem solved at my house, just much smaller scale. Maybe on "the list" one day.

Edit: and a 2 degree dwell instead of kicking on/off at each degree

 

[John From Detroit]

Sounds like your furnace is working fine.

Yup. it's workign as it should.

 

[Domo]

re: Fresh Air Exchange; I'd think the vents on the outside of the RV at the furnace are the intake and exhaust for the burner only - there should be no mixing of the outside air with the cabin unless that fresh air intake is faaar away from the exhaust of the furnace.

 

[Toyhauling]

Domo. Yes, that is why we like the inefficient, noisy furnace, it seems very safe compared to the catalytic heaters. Especially, when our trailer feels very full of (combustible) stuff with the whole family in it. I can just imagine the dog bed catching on fire, while the family is unconscious from a lack of oxygen.
I will definitely try shielding the thermostat! I did not think of that.
Thank you everyone for your comments.

 

[Gary RV_Wizard]

There are a few thermostats that have adjustable dwell (differential). The Ecobee smart thermostat, for example, allows you to program dwell to as much as +/- 3 degrees, i.e. when set to 60 it could be made to cycle on at 57 and off at 63. The cycles are fewer but longer. Robershaw & Lux also make some thermostats with adjustable dwell time.

However, the biggest problem in RVs is the (often unavoidable) poor thermostat/sensor locations. Some of the common problems include:

• Nearly every wall is an outside wall, heating or cooling at different rates than the interior air
• Located in the path of air blowing from heat or a/c vents
• Located adjacent to a stove, oven or incandescent light
• Uneven air circulation within the RV (hot or cold spots)

Baffles or shrouds can sometimes alleviate errant breezes. In other cases, a small fan, e.g. a computer cooling fan, may help keep the air stirring near the tstat. On exterior walls, ir may help to mount the thermostat on an insulating backer board.

In my last coach, the front zone thermostat sensor was cleverly located under a cabinet, next to a halogen light and over the cooktop. Lots of heat, trapped under the overhang. Duh! The rear zone sensor was also adjacent to a hot halogen bulb. Changing to Led bulbs helped some.

 

[Contributor]

Mine behaves the same way. I attribute it to the fact that my small trailer warms up quickly and then does a poor job of retaining the heat due to typical low R value of the construction.

Besides the noise, it keeps the interior at the desired temperature. Other option is to turn it off and add a down comforter to the bed and turn on the furnace during my last pee run before morning.

 

[Old_Crow]

The front sensor in my coach is located on the bottom of a cupboard right over the place where my coffee maker sits. Not a big issue, but when I had a cheap Mr Coffee that kept the coffee warm on a burner I had to set the t/stat at a higher setting than with the Keurig I use now.

 

[DutchmenSport]

In my Montana, I have 2 of these Dometic, single zone thermostats - click here.

You may have something different. But with mine, there is only a 1 or 2 degree tolerance (that can be set by pushing the buttons) between the on and off, and off and on cycle. That's not much in temperature change and yes, it does cycle on and off a lot. In time though, we got use to it. Now, if it doesn't cycle, I think something is wrong.

Since we do a lot of cold weather camping (and we do not boom-dock), we use the camper's electric fireplace for heat and we have 2 ceramic space heaters we use. Ours also has a air conditioner / heat pump. So we have multiple sources for electric heat when we are hooked up to 50 amp service and the outside temperature is above 32 (freezing).

When outside temperatures reach 32 or less, we make sure the furnace is running as that is absolutely necessary to keep the underbelly warm and pipes from freezing.

Yes, drafts blowing on your wall thermostat can make it cycle on and off more. The best thing you can do is crawl under your camper and look for any holes or gaps in the underbelly covering and pump it full of foamy stuff used to fill holes in houses and around pipes. Anywhere there is a hole, that air will find a path to the inside of your camper.

 

[Toyhauling]

The thermostat is in small walkway into the front "bedroom", about 5' from the non-ducted furnace. My current toy hauler has terrible insulation. A big part of leaving the heater on at night is keep to the fresh water pipes from freezing, they are in the same cabinet space as the furnace. My plan is to loosely cover the thermostat with some aluminum foil and see if I can create that 5+ degree difference between the furnace being off and on, just to cut down on the cycling.
Great comments and advise on the adjustable dwell thermostats. Thank you.

 

[Heli_av8tor]

A funny side story:
Our coach has two furnaces, one in the bedroom and the other one in the main living area. They use remote mounted thermistors to sense the temperature, one on an interior bedroom wall and the front on under a cabinet in the living area. The dual Dometic thermostat control is common to both.

It got to just below freezing on our maiden voyage. I set the front to 50° and the bedroom to 65° and went to bed. We awoke to 95° in the bedroom and 40° in the front.

A couple hours of research and troubleshooting revealed that someone had switched the front and rear thermistor wires at the control unit. Could have been that way from the factory and the original owner never set much of a differential temp.

 

[NY_Dutch]

Our living area furnace thermostat is properly located on an inside wall, but it's too close to a floor vent that was causing it to cycle too often. I fixed that with a simple swap of the fixed vent to one with directional vanes from a local hardware store. About $6 as I recall...

 

[touchracing]

Whenever I get into temps that cold I like to supplement the furnace with electric heaters.

 

[Old_Crow]

Whenever I get into temps that cold I like to supplement the furnace with electric heaters.

My coach also has a front and rear furnace. I've got an electric heater that I'll use in the front of the coach, but once I found out that the rear furnace also heats the basement to keep the pipes from freezing, I won't run an electric heater in the back.

 

[Heli_av8tor]

I can tell you from last years front furnace failure on the way to Arizona that my rear furnace does NOT keep my pipes from freezing.

 

[Old_Crow]

I can tell you from last years front furnace failure on the way to Arizona that my rear furnace does NOT keep my pipes from freezing.

I suppose I've been lucky so far then. Since I quit using the electric heater in the rear I haven't had a freeze up.
It's currently 27* here in the eastern Sierra's. Hope the snow melts by Friday when I'm due to leave.