Thermostat issue and solution

[rogerkathy]

Not really happy with our Dometic thermostat waiting 8 degrees before turning on our furnace in our 323MK Wildcat. Set for 68 but didn’t turn on until around 60 degrees. Noticed it was attached to an inner wall that surrounded our bathroom, furnace, and water heater. Found that wall tended to be warm when the furnace was in use and stayed warm for quite a while. Plus there was a quarter-sized hole behind it for the wiring which also let heat enter the thermostat. Solution? Put a light switch insulator foam piece with a small slit to allow for the wires. Works great now. Turns on when the temp drops 3 down degrees, which is acceptable to me. I found out I needed to make sure the insulation was slightly bigger than the inside section otherwise it tended to push into the thermostat parts which interfered with it working properly. I also used some tape to seal the precut punch out parts on the foam insulator to hold them flat and placed a thin (taco box) cardboard piece between the foam and the thermostat. Really pleased with the results so far.

[Rich5117]

Glad you were able to do something that worked. Had you taken it back for repair they would have replaced the stat and corrected nothing.

[rogerkathy]

Precisley why I try to figure things out first.

[WFD]

This is a perfect example why, in previous threads when people talk about replacing their thermostat, my suggestion to them is always insulate that wall while you are there and replacing the thermostat. It gets false readings from that wall cavity, would do the same in summer with regards to AC with heat build up in that wall.
Now if you really want to see an improvement, you could improve on that thermostat and get one that has a 1 or 1.5 degree variance from when it comes on or shuts down. Would make your unit much more comfortable and constant.

[rogerkathy]

I have considered that. Any suggestions as to which replacement thermostat to use? My current one has the traditional three wires. I believe (but could be wrong) that any LCD with batteries could be used but would like to get a good one that would switch on/off with a 1-1.5 degree variance.

[Iwannacamp]

I e-mailed Robershaw(why I chose them I don't remember) and posted this question based on a question on the FRF.

Hello,


I was wondering...does Robertshaw make a stat that would be usable in a 12V D.C. RV application?



Thank you,


Chetty Cherry


I cannot find the e-mail response, but the answer was no.

I have been working part-time on residential HVAC for 30+ years and I think the main question is the 2 speed fan control and having a 12V D.C. power supply for a stat that is normally powered by 24V A.C. or stat battery 1-2 1.5 D.C. AA batteries. Many people have successfully converted to some sort of Walmart/Lowes stat, but I would choose not to. I read quite a bit on Robertshaw and Honeywell's websites about recommendations and found no information based on RV applications. YMMV

[Bama Rambler]

RogerKathy -- If the thermostat you have is the Dometic LCD thermostat, it uses digital communications and therefore can't be replaced with a normal switching thermostat. When Dometic went to those digital thermostats, they prevented us from being able to replace them with standard household units.

However if yours is just for your furnace and it's an analog unit, you can easily replace it with a household unit that will have a lot closer deadband (tighter control).

[markb422]

To me, the best thing about all this is that he diagnosed and fixed the problem himself. One of the best things about camping/RVing and (most) campers is that the people seem to have some common sense. Especially true for most of the people on this forum. It used to be that way for our cars also but now you are lucky to be able to change your own oil. Are the RV's getting to that point also.

[The Newsoms]

Thank you for posting this. I’m going to see if it helps ours. I will be freezing before it kicks on.

[Dp26]

Clever, and now on my list, after opening a wall to insert a structure for a TV mount, and replacing my entry door...

[sgtlm17]

That thermostat comes from factory preset to wait 2 degrees before turning on ac or heat. You can change it to 1 degree. I changed mine from. The 2 degree preset to 1 degree and it keeps the coach much more even in temperature. Search YouTube for Dometic LCD RV thermostat and it shows you how to change it from 2 degrees to 1.

[rogerkathy]

Tried doing that but it did not help until I insulated the thermostat from the wall

[hdmtnrider]

rogerkathy, I like the fix you did for your thermostat. I have the same one in my TH and I would like the to do this to mine. Only question is, Does the thermostat just pull off the base plate? Would like to know before I brake something. TIA for you time.

[Jim-LP240FS]

Thanks Rogerkathy. I think that you have solved the thermostat problem in my new RV. I have the new Dometic Capacitive Touch Thermostat in my Leprechaun 240FS but it appears to work exactly like your thermostat but with capacitive touch buttons rather than the tactile touch buttons on yours. My thermostat is on the wall between by bedroom and bathroom and when I removed it there was a ¾” hole in the wall. I applied 1/8” Frost King Self-Adhesive pipe wrap insulation tape to the back of my thermostat and also wrapped the wire to plug the hole in the wall.

As sgtlm17 pointed out, it is easy to reset the temperature differential on these Dometic thermostats from 2 degrees to 1 degree.

Instructions from my Dometic Capacitive Touch Thermostat Operating Instructions:

To set temperature differential, system must be Off. Press V button and simultaneously press and hold ON/OFF Mode button for three seconds. Press ^ button to toggle between “d1”, “d2”, and “Co”. “d1” is for a 1° differential and “d2” is for a 2° differential. “Co” is for “COOL ONLY” Mode. The “COOL ONLY” configuration should be selected if the RV system does not have a furnace.

NOTE: My rig has a furnace and I didn’t see the “Co” “COOL ONLY” Mode.

[rogerkathy]

Hdmtnrider, I put my thumb under the bottom edge and gently lifted my thumb out and upwards, pretending the top edge was hinged. Then I lifted the whole cover up and out. Tried sending a photo but it keeps asking for a url of my image. No clue what or how to do that.

[hdmtnrider]

Originally Posted by rogerkathy

Hdmtnrider, I put my thumb under the bottom edge and gently lifted my thumb out and upwards, pretending the top edge was hinged. Then I lifted the whole cover up and out. Tried sending a photo but it keeps asking for a url of my image. No clue what or how to do that.

Thank you very much for the information.

[rjshiflet]

Our furnace (and heat pump) thermostat is on the rear/outside wall and when it's really cold, the furnace runs until it's way too hot in the fifth wheel. When the sun hits that wall in the daytime warmer months - the A/C seems to run constantly. I think I need to look into the insulation solution as well.

[5picker]

Originally Posted by rogerkathy

Hdmtnrider, I put my thumb under the bottom edge and gently lifted my thumb out and upwards, pretending the top edge was hinged. Then I lifted the whole cover up and out. Tried sending a photo but it keeps asking for a url of my image. No clue what or how to do that.

From the "Forum 101" section...

How to add photos to a post
Click reply and scroll down to bottom of text box.
Click "go advanced" add text to message window and then scroll down.
Click "Manage attachments" A separate window will pop up.
Click "browse" Then select the file to be uploaded. Be sure that the photo is appropriately sized. 620 x 620 pixels (or smaller) and no more than 50K. Forums software will automatically reduce the size, but smaller size photos will upload much faster. You may select several photos to upload at the same time by repeating the last step.
Click "Upload" After pics have loaded close the pop-up window
Click "submit reply" to mount the text of your message - photos will automatically appear at the bottom of your post.

How to embed an image stored on another site:
You can do this by using image tags. Upload the image to a service like imageshack and then copy the URL of the image and put that between [IMG] tags. That will work well, as long as the host site stays in business and doesn't disable your image for overuse of bandwidth etc.

You can also paste in the location of a photo stored here in a photo gallery.

To do this: Paste the url of the image into your post. Then add the following code on either side of the url (with no extra spaces):

[IMG]url here[/IMG]

The image will appear where the url was in your text.

[270S]

Nice for posting the 1 vs 2 degree cycling, but there is still no calibration setting for pathetic actual temp input. Will need to replace thermostat. Another few threads on that subject.

[rogerkathy]

Thanks so much 5picker for the info on photos. It really should not be so involved.