Replacing the Old Analog with this Honeywell

[weejumper]

I purchased this Honeywell thermostat today and was told it would work on a Dometic Roof Top ducted air conditioner. I have attached the wiring diagram on the old thermostat, pic number 1, and pic of the new one, pic 2 & 3. I will only wire in the high fan speed. Any help would be appreciated. Need help with wiring. Red 7.5 and Gnd giving me a fit.

[Chris_Bryant]

That thermostat should work fine, wired like I said:

I wrote:
Red- not used
Yellow- Y
White -W
Blue and Brown- G
Green - R

[weejumper]

All of you have been so helpful. I have a 2003 Salem with the Duo Therm that I am going to replace this fall or sooner if I make the wrong connection. LOL. The thermostat just quit controlling. Going to check all the wiring first. I will then try to wire in this Honeywell analog. I could not find the Duo Thern any cheaper than around 55.00 with shipping. The honeywell was recommended to me and was said to do the same thing for 16 dollars. I like Honeywell products but may need to go and but a digital or Duo Therm. I did not know it would be this complicated to wire this tstat up. So thank you all for the input. I really appreciate it.

[Chris_Bryant]

Billyboymr2 wrote:
From the way your current thermostat is wired, this is what you'll need:

Red wire from +7.5 - R on the new stat
Yellow wire from cool - Y on the new stat
White wire from furn - W on the new stat
Blue wire from hi fan - G on the new stat
(if you want to put low on there, it would be the orange wire on the G instead)
Tape off the green wire, it's not needed.

A few things to look out for when you do replace your thermostat:

Make sure to get a battery powered stat if you're using a homeowner version. They run off of 24V AC, not DC like the MH stat does. This one will work fine because it doesn't need power to work, but the nicer stats will need either batteries or 24V AC to work properly.

Also, most homeowner stats do not have a hi/lo fan switch, so that may need to be wired in to a separate switch and mounted somewhere close to the stat. If you know you're never going to use one speed or another, no need for the switch, just make sure you're putting the correct wire on the 'G' terminal.

I just purchased two of these for our MH, they're battery powered and work perfectly but do not have the hi/lo fan:

https://www.acwholesalers.com/Honeywell/TH5110D1022-1H-1C-FocusPro-Non-Programmable-Lg-Display-Thermostat/32359.ac?question=focuspro

Very nice, but none of that will work for the DuoTherm. I gave the correct wiring above- DuoTherm *grounds* the relays in the control box, they do not power them like RVP/Coleman does, and they use 2 relays for fan- the orange (or tan for newer models) is the power to the fan, the blue toggles between high and low, so if you just connect the blue, you get no fan at all.

If it's that difficult, why not just replace what you have- $35.

[weejumper]

Thanks Billyboymr2

[Billyboymr2]

From the way your current thermostat is wired, this is what you'll need:

Red wire from +7.5 - R on the new stat
Yellow wire from cool - Y on the new stat
White wire from furn - W on the new stat
Blue wire from hi fan - G on the new stat
(if you want to put low on there, it would be the orange wire on the G instead)
Tape off the green wire, it's not needed.

A few things to look out for when you do replace your thermostat:

Make sure to get a battery powered stat if you're using a homeowner version. They run off of 24V AC, not DC like the MH stat does. This one will work fine because it doesn't need power to work, but the nicer stats will need either batteries or 24V AC to work properly.

Also, most homeowner stats do not have a hi/lo fan switch, so that may need to be wired in to a separate switch and mounted somewhere close to the stat. If you know you're never going to use one speed or another, no need for the switch, just make sure you're putting the correct wire on the 'G' terminal.

I just purchased two of these for our MH, they're battery powered and work perfectly but do not have the hi/lo fan:

https://www.acwholesalers.com/Honeywell/TH5110D1022-1H-1C-FocusPro-Non-Programmable-Lg-Display-Thermostat/32359.ac?question=focuspro

[sonicsix]

RV Digital Thermostat Installation Guide - This is how we did ours.


.

[weejumper]

Old-Biscuit... Yes it is another analog t-stat. The Duo Therm t-stat bit the dust and this was recommended to get me through the summer. The whole unit will be replaced this fall. I was looking for something to get me through a few more weekends. Thanks

[Ski_Pro_3]

I recommend you google 'wiring code for thermostat'. Lots of info.

[Old-Biscuit]

Chris Bryant wrote:
I'll give it a shot- though that one is a bit odd.
Red- not used
Yellow- Y
White -W
Blue and Brown- G
Green - R

Reasoning- the DuoTherm grounds the relays to activate, plus needs both fan wires grounded for Hi fan.

:H

Isn't that just another analog t-stat?

[weejumper]

Just needed something for the summer. Having to put a whole new system in for next year. May do the Ac and Heat system.

[ScottG]

Honestly, that stat isn't much of an upgrade so it may not perform any better than what you had.

[Chris_Bryant]

I'll give it a shot- though that one is a bit odd.
Red- not used
Yellow- Y
White -W
Blue and Brown- G
Green - R

Reasoning- the DuoTherm grounds the relays to activate, plus needs both fan wires grounded for Hi fan.

[weejumper]

Now that was easy. Thanks Barney S...

[BarneyS]

Welcome to the forums!
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Barney