Changing my thermostat

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MartyB

MartyB

Well-known member
Joined
Oct 3, 2015
Posts
66
Location
Woodstock, Ontario
My current thermostat sucks.  The operating range is too big.  We are either too hot, or too cold.  Goldilocks wouldn't last a day.  I want to replace it with just a normal "Honeywell" type 'stat.
My dilemma.  I don't think it will work with the propane furnace / Heat pump combination in my 5er.  Am I correct?  Any idea's?  Thanks for you time gang.

Marty
 
All I know about the situation is that I replaced my regular factory installed cheap thermostat with a digital one. I got it off eBay. It's a Coleman mack. Just changed it to a digital. What I don't like about my system is that I want to run the fan all the time but it won't let me in the heating or cooling modes. My old TT with the same thermostat allowed this. I need to wire it differently or something. Not sure if you can use a Honeywell home thermostat in a tt. Search this site and check for old posts that can help.
 
There are plenty of RV-style thermostats available with all sorts of capabilities, including multiple zones, heat pumps, LP furnaces, digital displays, etc. If MartyB would describe his HVAC system completely and what t-stat he has now, maybe somebody could make a suggestion.

At this point its not clear his problem is the thermostat design or simple its placement. RV's heat/cool control often goes awry simply because the temperature sensor is located where the output of furnace or a/c blows on it, or it's on an outside wall and affected by wall temperature, or similar issues. Replacing it with a Honeywell or similar doesn't necessarily solve the problem. Besides, most Honeywells require 24v DC power, which is standard for a residential HVAC primary wire.  There are, however, battery powered digital t-stats that will mostly work in an RV. The typically don't have two speed fan control, though.
 
I replaced both of our analog Duo-therm thermostats with Honeywell 7-day programmable digital stat. As I recall the instructions included information for both standard heat/AC systems and heat/heat pump systems. I don't know if it's adaptable to your specific setup or not though. The model RTH2510b that I have uses two AAA batteries that last at least a year.
 
Thanks for that Gary.  I'll have to get back to you.  My trailer is in storage for the winter and I can't get to it right away.  I know it can be done.  I've seen videos on Youtube.  However I don't think any of them actually address a heat pump / gas system.
 
There is nothing particularly magical about a heat pump vs a/c. The t-stat just sends a "heat needed" or "cool needed" signal and the HVAC controls does the rest. The t-stat just needs to be able to deal with multiple sources, since there are two heats (pump and furnace) plus cooling.  And maybe multiple zones if you have two heat pumps.  Most residential thermostats allow for auxiliary heat with a heat pump, but may not offer flexible control for the auxiliary source and rarely handle two-speed fans.

Although you cannot get info on your system right now, could you describe better what the problem is?  Often RV thermostats lack fine temperature control, i.e. they don't switch on until the room temp drops 1 or 2 degrees below the Set temp, and then stay on until the room temp reaches +1 or +2 over Set temp. That makes for a 2-4 degree swing in room temperature and is indeed less that satisfactory.  Something like the Dometic/Atwood Comfort Control System t-stat might be an improvement.  Or one of the Coleman Mach RV Comfort models (see http://www.airxcel.com/docs/default-source/coleman-mach/thermostats/thermostat-catalog.pdf).

But if the problem is caused by rapid changes in wall or air temperature by the thermostat (or its remote sensors), changing thermostats won't help.
 
I should have added to my post that I modified our Honeywell digital stats with a mini-toggle switch for two speed A/C fan operation. Other folks just select a single speed and leave it at that.


 

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Gang.  Have a look at the attached picture.  I am asking questions blindly.  I don't have the trailer to reference.  My T stat has a setting for gas OR electric heat.  I am just assuming there will be wiring to match.  A residential T  stat probably wouldn't.  Correct
 

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My residential Honeywell has Cool, Heat, and Auxiliary (aka Emergency) heat.  Cool & Heat are wired to the heat pump, while Aux/Emergency is wired to my secondary heat source (happens to be electric in my Florida home, but could be most anything.

If you do not have it already, this article from RV Comfort may be helpful.  It describes how the heat pump & gas furnace are controlled together.
http://old.rvcomfort.com/rvp/pdf_documents/t_stat_electric_heat_function.pdf

The RV Comfort HP is a pretty good t-stat, though I think it maintains the room temperature one degree from the set temp (plus/minus one degree). It is, however, very sensitive to the room ambient and if located on an exterior wall or where sunshine or drafty air currents can reach it, the temperature it maintains can be 3-4 degrees off from other parts of the room. This is a very common problem with any thermostat in an RV. The RV manufacturers place the thermostat wherever it is handy (usually more for the installer than the owner) and you suffer the consequences.
 
Gary RV_Wizard said:
There are plenty of RV-style thermostats available with all sorts of capabilities, including multiple zones, heat pumps, LP furnaces, digital displays, etc. If MartyB would describe his HVAC system completely and what t-stat he has now, maybe somebody could make a suggestion.

At this point its not clear his problem is the thermostat design or simple its placement. RV's heat/cool control often goes awry simply because the temperature sensor is located where the output of furnace or a/c blows on it, or it's on an outside wall and affected by wall temperature, or similar issues. Replacing it with a Honeywell or similar doesn't necessarily solve the problem. Besides, most Honeywells require 24v DC power, which is standard for a residential HVAC primary wire. There are, however, battery powered digital t-stats that will mostly work in an RV honeywell home thermostat remove cover. The typically don't have two speed fan control, though.
Click to expand...
Installed a new Model RTH7600 Honey Programmable Thermostat. The temp
in the house was around 63F based on my trusty alcohol thermometer.
But my $99 RTH7600 read a temp of 72F. Waited for 20 minutes and now
it read 68F. Furnace finally kicked in (I had it set at 68F) the
RTH7600 still read 68F. Ran for 15-20 minutes.

My questions:

1. Does this thermostat need time to get an accurate indoor temp
reading?
2. Is there a way to calibrate the indoor temp? Or reset the entire
thing?
3. Should I return it?

Thanks
 
I don't know the answer, but I suspect that someone who does would like to know where the "trusty alcohol thermometer" was and where the thermostat was at the time of reading. Even in a house, let alone in an RV, even a foot or two distance between the two can show a considerable difference in temperature, in addition to the fact that neither of them will change instantly -- they need at least a few moments to adjust.

Likely someone who knows more will be along shortly.
 
We put Z-Wave thermostats in our Bus. Fan runs on high or low automatically. Fan can be run manually. Heat pump, AC, and furnace work. It's a simple install and the T-stats weren't overly expensive. They run on 3 AAA batteries that last a year or so. Here's the article of the guy that figured it out.

MOD: Smart Thermostats in an RV? YES!
 
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