Furnace question - Fiberglass RV


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Old 12-26-2019, 02:25 AM   #1
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Name: Anthony
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Furnace question

I can either roast myself out or freeze in my 2019 Scamp 13. When I check the thermostat it seems to lag by about half an hour to what the temperature actually is. With the thermostat set for 70 the time it actually comes on it is freezing (50 or thereabouts, but thermostat displays 68) inside and by the time it shuts off the heater it is well over 90 (the thermostat shows 70). Anyone else have this problem? Anyone figure out a fix? Or is it just a bad thermostat?
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Old 12-26-2019, 07:02 AM   #2
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Furnace question

Certainly check to make sure the thermostat is working correctly. If it tests good, here are some other things to try.

Move the thermostat. Itís tucked away in a dead zone on the sink end of the galley. Some people have moved it to the galley support (I think yours is the new tree style).

Consider a better thermostat. Some allow you to adjust the lower and upper bounds. But you may find if you set them too close to the desired temperature, the furnace cycles on and off excessively.

The real problem may simply be the lack of insulation and large windows. You will never get the even temperatures youíre accustomed to at home (though you should be able to do better than a 40-degree swing!). Adding Reflectix panels over the windows will help. Rigid foam sheets (shiny side facing inward) in the ceiling vents will also help.

Ours does have a noticeable swing between warm and cool as the furnace cycles. We havenít bothered with any of the mods I mentioned because we donít do much cold weather camping. We donít run it all night, just evening and morning, and weíre grateful after moving up from a tent to have heat at all!
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Old 12-26-2019, 07:34 AM   #3
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It is the same for me. I did experiments when I first got my 2019 Scamp and found that the thermostat is just EXTREMELY slow to react to temperature changes. I found that after about 24 hours of manually turning the furnace on and off, the thermostat would come close to the actual temperature and would control the furnace in an acceptable manner, with just about 5 or 6 degree fluctuations. (Still not very good, but tolerable)

I attribute it to a VERY poorly designed thermostat. Folks try to blame it on the location. I find, however, that other thermometers, and a remote, plug-in thermostat for my electric heater, placed right next to the installed thermostat correctly react, so I don't buy that explanation. You are not the only one who experiences this very poor performance.

If I were to primarily rely on the furnace for heat, I would definitely be replacing the Scamp provided thermostat.

Luckily, I normally just use an electric heater.
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Old 12-26-2019, 07:59 AM   #4
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Furnace question

Thatís disappointing, Lyle, but good information. I failed to mention I have the old-style analog thermostat. I expected the new digital style to work better. If I ever decide to go digital, Iíll spend a few extra bucks for a decent one, and I wonít bother relocating it.

I wonder if the initial temperature swings are due to starting with a cold cabin. The furnace quickly warms the air but not the contents. They have a much larger thermal mass and quickly absorb the heat from the air. Eventually- after multiple furnace cycles- the contents of the trailer warm up and act to stabilize the temperature.
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Old 12-26-2019, 10:55 AM   #5
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No. That is probably part of it, but not the major problem. The major problem is that the "thermometer" incorporated in the thermostat does not respond well. It takes it many hours to change the indicated temperature of the room. That is why I compare it to other thermostats/thermometers.

The other thermometers indicate a room temperature of, say, 68 degrees, while the room temperature on the Scamp thermostat still indicates 48 or 50 degrees. As I said, it takes that reading up to 24 hours to finally get up to the high 60s. Once it gets there, it works "ok".
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Old 12-26-2019, 11:52 AM   #6
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Understood. I can imagine a defective thermostat. I could even imagine two defective thermostats from the same batch, since you both have 2019ís. But I cannot imagine a properly working thermostat, even a cheap one, that cannot detect the ambient temperature within a few minutes.
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Old 12-26-2019, 02:29 PM   #7
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When I did my experiments with it, there were a lot of similar complaints. You may be correct, but I don't recall any of the responses claiming a good experience. I just treat it as a manual system for the first day or so.
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Old 12-27-2019, 08:46 AM   #8
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Thermostat adjustment

Many basic thermostats have an adjustable feature inside called an ďanticipatorĒ. Google it and you will get more info on the anticipator than you ever wanted. Itís likely in need of adjustment. Many electronic t-stats have ďmagicĒ inside to prevent big temperature swings.
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Old 12-27-2019, 09:34 AM   #9
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one problem is that the thermostat is mounted to the same cabinet that the furnace is in.
The cabinet heats up and delays the thermostat.
If you don't care to move the thermostat, you could insulate the wall behind the thermostat from inside the cabinet with maybe reflectix or a piece of solid styrofoam. That could reduce the lag time and make the heat more even.
Another good thing is to cut reflectix to fit the windows, when it is cold out the windows cascade cold. The reflectix will help the furnace cycle less.
The reflectix panels will just press fit into the windows and are easy to install and remove.
You will see an instant improvement with warmer feet and face.
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Old 12-27-2019, 03:16 PM   #10
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Originally Posted by floyd View Post
one problem is that the thermostat is mounted to the same cabinet that the furnace is in.
I had to go look in my 16' Deluxe, and the thermostat is on the passenger side and the furnace is on the driver's side with mine. I have layout 4. I wonder if different layouts have the thermostat on different sides.
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Old 12-27-2019, 06:51 PM   #11
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the thermostat on our Casita was taking way too long to come on, then running too long til it was too hot, rinse repeat.

I noted that when I carefully and slowly move the temp setting lever up enough for it to click 'on', then back to it clicks 'off' was a much wider spread than I expected

in the center of the control dial on many old fashion mechanical thermostats is a dial with a pointer that is labeled with decimal fractions. I adjusted this dial down to a much smaller fraction (or maybe it was a larger one?) til the difference between 'on' and 'off' was only about 5 degrees, after that the furnace worked much better.

ah, here it is! it was set to like 1.2 which is the max 'longer cycle' setting, I turned it down to 0.25 where it is in the picture, and much better cycling.

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Old 12-27-2019, 10:39 PM   #12
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Quote:
Originally Posted by lisantica View Post
I had to go look in my 16' Deluxe, and the thermostat is on the passenger side and the furnace is on the driver's side with mine. I have layout 4. I wonder if different layouts have the thermostat on different sides.
The OP's trailer is a 13.
The factory location is pretty much the same on all 13s
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Old 12-27-2019, 10:41 PM   #13
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Originally Posted by floyd View Post
The OP's trailer is a 13.
The factory location is pretty much the same on all 13s
Ahhhh, I see, thank you Floyd for the information. I'm always learning something new on this website.
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Old 12-27-2019, 10:56 PM   #14
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I went with a cheap digital thermostat in the Casita. Works well and easy to hook up. Not sure what the model is but It was about $20 CDN at Walmart. It does take 2 AA batteries and it has lasted years now on those batteries.
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Old 12-27-2019, 11:47 PM   #15
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I replaced my analogue thermostat with a Honeywell digital to get rid of the loud click when the analogue turned the furnace on in the night, waking me up.
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Old 12-28-2019, 07:27 AM   #16
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one of the problems with these heaters in a small trailer is overshoot due to the cool down cycle of the furnace. It runs on after hitting its target and you can pump quite a bit more heat into the trailer than what you have the temp set to. Also the thermostat location can be a problem, ours is a about 2 1/2 feet from the floor so the upper level can get pretty warm before the thermostat shuts down. The newer casitas have moved it up higher. Good thing is that you can heat these units up pretty fast in the morning! Now to get heat into the bathroom or icebox as we call it. Yes we do tend to leave the bathroom door open at night.
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Old 12-28-2019, 09:07 AM   #17
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You could buy the world’s most accurate thermostat but I doubt you are going to obtain the heating accuracy you desire .
Too many variables—-windows , outside ambient temp , furnace type and location ,air movement , thermostat placement , infiltration , insulation , trailer being one long hallway ,etc etc etc .
Our current trailer has a Dometic CT digital thermostat and it works only slightly better than the $5 analog thermostat in our Casita
Instead if being 10 deg off it’s only 8 deg off , hardly a major improvement !!
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Old 12-28-2019, 10:15 AM   #18
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I guess, my point is that the $30 or $40 dollar LUX remote thermostat that I plug my electric heater into works very good at maintaining a constant temperature.

The installed thermostat for the gas furnace (sitting within inches of the LUX) does not even come close to maintaining any level of comfort, and it does NOT indicate the proper room temperature until up to 24 hours after the trailer has been heated. This tells me the installed thermostat is a very poor design.

If I were the only one with this problem, I would assume I had a defective thermostat, but since it is a very common complaint, I can only assume it is a defective design.
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Old 01-01-2020, 12:37 PM   #19
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I bought a small circulating oil heater for my 19ft Escape and it helps to keep the temperature even during cold weather. Doesn't take up much space and I warm my pajamas on it before going to bed! (but if you do this, don't cover up the vents)
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Old 01-01-2020, 01:54 PM   #20
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Quote:
Originally Posted by Barb Hunt View Post
... I warm my pajamas on it before going to bed! (but if you do this, don't cover up the vents)
Very good advice there. NEVER cover the vents in your pajamas.
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