Question about digital thermostats

giadiep

Active Member
Sep 5, 2015
494
Syracuse, NY
I have a 2011 Starcraft 187 TB hybrid. I want to replace my thermostat with a digital one. It controls the furnace only. I see that some of you guys have ones that uses batteries. Is there a specific reason for this? Also, do you have to get one that is made specifically for DC vs the home ones that are for AC? I appreciate the recommendations but also want to know the "why". Looking forward to some of you guys dropping some knowledge on me.

Thanks.
 

Snow

Super Active Member
Jul 19, 2007
11,895
Ontario
Can't offer any insight into which type of t-stat to get.. If you look around (maybe) on this site and definitely on google you can find where folks have mod'ed the t-stat wiring to make an extension cord of sorts so the new t-stat can sit up on the table or counter instead of down near the floor to provide better comfort..
 

BaysideJim

Active Member
May 5, 2015
146
Denver, Colorado
I have a 2010 Coleman Bayside. I replaced the sorry Atwood analog Thermostat with a digital one that I found at Home Depot (about $17 I think sorry don't recall the brand) It does require a battery and it works fine much better than the unreliable Atwood
 

tombiasi

Super Active Member
Sep 1, 2012
6,700
Northwestern New Jersey
A thermostat closes a switch upon reaching a preset temperature. That's all any of them do. There are different way to sense the temperature and different ways to display the temperature. A digital thermostat shows the temperature digitally.
 

kitphantom

Super Active Member
Platinum Supporting Member
Dec 26, 2009
13,541
Albuquerque, NM
We used a Lux brand, with a momentary back light, which made it easier to see. We bought a Hunter for the first replacement in our TT, but changed to the Lux after a year or so of needing a flashlight to see it at night.
Although we never had issues with the Hunter in cold weather, both Lux ones were rated to a lower temperature. Apparently some thermostats don't work in the lower temeratures garages, cabins, and campers may exprience before heat is turned on.
 

tenttrailer

Art & Joyce - Columbus, O
Jul 18, 2013
3,758
Thornville, OH
I used a honeywell that only had heat on/off. No cooling or fan switch. It works great. But do remove the batteries when you put it into storage.
 

xvz12

Super Active Member
Apr 6, 2017
923
ID
I too have a cheap Honeywell digital, it is capable of both heat or cool, but I have it set up for heat only, since all i need it for is my furnace. 2 wire hookup, easy peasy. Yes, it requires a battery, butnot a big deal... put a fresh one in when you open the pup up for the year, remove & recycle battery at the end of the season.
 

tenttrailer

Art & Joyce - Columbus, O
Jul 18, 2013
3,758
Thornville, OH
The wires in a popup provides 12V DC. A house thermostat that is powered by the furnace is running off 24V AC. You need the batteries to operate the thermostat, it had no problem passing th 12 VDC through it's switches.
 

daschnoz

Active Member
Feb 9, 2015
273
Don't worry about the battery life in these thermostats. We had a 5+2 programmable thermostat on the wall at our old house (heating and cooling). It was powered by a single 9V battery. I replaced the battery on that one once per year - whether needed or not.

The LUX that I installed (link in previous post) uses 2x AA (3V circuit) batteries. I put new batteries in the thing at the beginning of the season and they last until I close the thing up in late October.

If you really want to nerd out (and I think I feel the need to), you could make a small regulator circuit to get the voltage down to what you need and run it off of the PUP. Over-engineered solution to a problem that has already been solved, YUP - it's what we do here. [LOL]
 

giadiep

Active Member
Sep 5, 2015
494
Syracuse, NY
Tenttrailer & Daschnoz,

Thanks for the explanations. I am interested in understanding the why as well as finding a good solution. I have a business contact that manufactures all the thermostats for Coleman-Airxcel. Spoke to him today. He's the owner and an engineer by trade. He actually just gave me a digital one to try out and a manual one that has better gradient temp swing control than the standard ones that come in RVs. Neither requires batteries since they are designed for RVs. I'm going to try them both this fall to see which one regulates the temperature better. These will control the furnace in my HTT so I have to wait until temps are lower.
 

daschnoz

Active Member
Feb 9, 2015
273
The short answer to why they run on battery power - different systems run different voltages. "Standard" home systems run 24Vac control circuits. Your PUP runs 12VDC. Making something that is universally device powered would require a power conditioning circuit. Assuming that the thermostat circuit needs 3VDC, the power circuit would need to take both 24Vac AND 12VDC and convert it to 3VDC. It's not super difficult to do, but it would add to the cost and size of the final product.

SO

What they do is make a thermostat that is battery powered, and the relay that turns the HVAC system on (heating or cooling) is nothing more than a dry contact. Land whatever voltage here, when the relay closes, that voltage is passed through and back to the HVAC device - triggering it to do its thing.
 

kitphantom

Super Active Member
Platinum Supporting Member
Dec 26, 2009
13,541
Albuquerque, NM
Tenttrailer & Daschnoz,
I'm going to try them both this fall to see which one regulates the temperature better.
We have found that a big piece of the puzzle for temperature control is not the type of thermostat, but the location.
in our pup, it was in a nice a few inches off of the floor, on the wall of one of the dinette benches. We added the long wire so it was more easily and safely reachable for me. Having it on the counter made the temperature swings far smaller. That alone helped comfort.
We haven't moved the one in the TT, though we did change it out for a digital one. It is on the wall, across the floor and around a corner from the furnace. We have a cold spot in the front of the trailer, since the thermostat clicks the furnace off before the warm air reaches the front corner of the trailer. We don't see any place for the thermostat that would eliminate that cold spot, without creating other issues, so we're leaving it as is. (If we're camping in cold weather with power, we use a small fan to keep the air moving; same in hot weather with a/c, which requires power anyway.)
 




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