True air replacement thermostat

[jimandsue60]

Is there a homestyle replacement thermostat for the True Air Coleman Mach thermostat? I would like to be able to program temps and times.

Thanks
Jim

[jimandsue60]

Is there a homestyle replacement thermostat for the True Air Coleman Mach thermostat? I would like to be able to program temps and times.

Thanks
Jim

[John_Canfield]

Jim - I seriously doubt it. The thermostat does some "magic" about starting one or two compressors due to the limited power we have to work with in the coach. But this is only a guess so maybe you will get a more qualified opinion from somebody else.

[jimandsue60]

John, plus the fact that it has 2 heat modes. I have not seen any like that in the stores.

Thanks
Jim

[Ed Gardiser]

Jim and John
All thermostats that I have access to both residential and commercial are 24 volt AC.There are many commercial thermostats that come with up to three stages of heating and cooling.But here is the issue our thermostats are 12 volts DC.
Ed Gardiser
Escondido,Ca.
04 Vectra
87 Nissan PickUp
FMCA

[swyates]

I've done a bit of research on this as I plan to replace mine because I don't particularly like the programming on the Coleman, and I also want to cool off the motor home at night. I believe it woud be possible to use a high end dual stage AC/dual stage Heat programmable heat pump thermostat. It would have to be heat pump compatible, and have dual stage heating and cooling. The one thing that I want that I cannot find in a replacement programmable thermostat is the ability to set when the 2nd stage heat comes on independant of the 1st stage.
If you have not already done so, you would need to get the wiring diagrams for the thermostat, heat pumps and LP furnace from Winnebago's web site. It will require special wiring, and doing this incorrectly could damage your equipment.
1. While true that residental control circuits are 24VAC, usually the programmable thermostats actually run on AA batteries and use relays to cycle heat/ac/fan modes. While this should be verified by tracing the circuits on the thermostat, it makes since that nothing in the thermostat really uses the 24VAC because all the electronics would require low voltage DC.
2. As for power management, this is done by the powerline system and the thermostat never really knows whether one or two compressors are running. The thermostat just sends 12V to the relays in the heat pump (and LP furnace) and if the powerline is sending AC to that circuit, it comes on.
3. In heating mode, you would connect the 1st stage of the thermostat to the heat pump. In heating mode, Coleman tries to run both compressors (depending on power availablity) all the time. The 2nd stage could be connected to the LP furnace. Note however this seriously changes the nature of how the 2 heat sources work. The orig thermostat runs the heat pump until the temp drops 5 degrees below set point and then turns on LP. It repeats this cycle 3 times, then locks out the HP for a few hours (doc says 2, but it seems longer on mine). With most programmable thermostats, 1st stage comes on at either .5 or 1 degrees below setpoint, and 2nd stage cycles at 2 degrees below setpoint.
4. In cooling mode, you would connect 1st stage cool to compressor 1 circuit, and 2nd stage to compressor 2 circuit. This would work identical to the orig Coleman thermostat.
Please note that this is all theory at this point as I have not attempted to do this yet.

[tderonne]

Some great info here.

And while on the subject. We needed to replace our thermostat. There are two different ones in the Winnebago catalog (besides black and white). They appear the same except for a choke coil. Are they? When would the choke coil be required?

[troth]

swyates: Consider this link 3 heat/2 cool Thermostat

tderonne, here's good info about using a Hunter Thermostat (from Home Depot or Lowes):
Hunter T'stat

[jimandsue60]

Thanks troth, I will follow up on those threads.

Jim

[Ed Gardiser]

swyates
jimandsue

You made me think
Look at a Honeywell TH8000 VisionPro
#TH8321U1008 Touch Screen Thermostat
Either 24 volt ac or battery operated
3 stages of heat
2 stages of cool
Programmable
Conventional and or heat pump
Ed Gardiser
Escondido,Ca.
04 Vectra
87 Nissan PickUp
FMCA

[AdrianLee]

Ed,

Thanks for the idea on the Honeywell Thermostat. I have been thinking of doing something like this too.

[Duner]

Well I did manage to replace the stock Coleman-Mach thermostat with a $79 full-featured digital touch screen unit from Home Depot. The slide switch on the Coleman was getting more & more flaky, and my warranty was gone. To avoid spending $150-300 for another featureless stock Coleman, I was highly motivated to figure how to adapt a digital setback model. This job took me many, many hours to figure out the wiring. I had to measure voltage swings on all the wires, in all the different conditions, break down and understand the schematics of the heat pump unit, the Coleman stat, an the RiteTemp schematics. I sure didn't want to blow out the control circuits or bypass the delay function that protects the compressors.

I found that a RiteTemp Model 8085C for a dual stage heat pump with control for auxiliary heat strips fit the bill. It is battery operated and has floating contact closures to control the heat pump unit and kick in the gas furnace if the heat pump can't keep up or if you set the temp more than 4 deg warmer than ambient. It doesn't have the 2 speed fan switch so you wire it for hi speed only, but the Winnie Energy Management System will still cut the speed to low to save power on 20 or 30 amp service.

It has some really great features:
---It records the number of hours of actual furnace run time and will notify you to clean/replace the filters when it hits the hrs you preset.
---You set the swing temp for up or down to get the cycling time that suits you & your coach conditions.
---You can off-set the temp reading to be calibrated to a more accurate temp somewhere else (like next to your favorite chair).
---Backlite touch screen with very large numbers and very intuitive to use.
---Measures humidity and can set a limit to control a humidifier if you really need one.
---It comes programmed with an "Energy-Star"� program which works great for us. But if you want, it has 4 program periods/day on Program A, and 2 or 6 periods/day on program B.
---If the coach is too hot/cold, just tap the display up/down a few degrees to override program.

I have a hand sketch of the wiring that is working in my '04 Winnie coach, but I would have to clean it up so it could be used to show exactly what wire goes where. I'm thinking a drawing that shows existing Coleman stat terminal connections crossed over to new RiteTemp terminals is all that is needed. I believe all the Winnie's with basement AC/Heat pump use the same Coleman thermostat for many years. It'll take me a few days to pull all the info together to publish here. Also I don't know how to upload a pdf to the forum when I have a schematic ready. If someone could PM the info to me that would be helpful.

This link will take you to the RiteTemp website where you can download the Installation Guide and Operation Guide:
8085C

Here's the 29 page application guide:
Download Professional Application Guide

Happy Trails,
Bill

[Charles99]

I believe that the True air is actually a 3 stage unit. You have two compressors and a furnace. Only one compressor runs if the temperature is close to set point and if it is over two degrees from set point, both compressors come on. Then you also have the furnace to deal with.

[troth]

Wow, nice job Duner! I look forward to seeing the wiring schematic and how it hooks up to your coach.