Open Roads Forum

Print  |  Close

Topic: Using Atwood 1H2C Thermostat with Dometic A/C ??

Posted By: BillMartin on 11/22/14 08:43pm

I am attempting to replace a Duo-Therm Thermostat Model# 3107612.008 with an Atwood Model# 1H2C. Neither the furnace, A/C compressor, or A/C fan will operate with the Atwood. All functions are good with the Duo-Therm.

The Atwood documentation claims that it "has been designed to operate standard air conditioning units in conjunction with an RV furnace".

Furnace: Atwood Model# 8535IVDCLP
A/C: Dometic Model# 620426.331

Duo-Therm Thermostat connections:
Terminal Wire
-------- ----
+7.5 Red
Cool Yel
Fur Wht
Fan Hi Blu
Fan Tan
Gnd Grn

Atwood Thermostat connections:
Terminal Wire
-------- ----
1) Gnd Grn
2) n/c
3) +12VDC Org (voltage verified)
4) +7.5VDC Red (voltage verified)
5) Compressor Yel
6) Fan Hi Blu
7) Fan Lo Tan
8) Furnace Wht

1) The Orange wire in the thermostat cable was not used for the Duo-Therm thermostat installation, and was not connected at either end of the thermostat cable run. The Atwood thermostat requires a source of +12VDC. The Orange thermostat wire is now connected to a wire labeled "+12VDC" in the A/C wiring compartment. This "+12VDC" wire appears in a cable from the coach wiring, supplying the A/C unit. Have verified that the Orange thermostat wire is at +13.5VDC with respect to the Green ground wire. The Atwood thermostat display "powers up" upon connection of the Green and Orange wires. The Orange thermostat wire IS NOT connected to "CON 1" of the A/C controller, which apparently would be the case for a Heat-Pump / Heat-Strip application, which I do not have.

2) I note that all of the thermostat connections (with the exception of the added Orange +12VDC wire) connect directly to the A/C controller. The A/C controller provides a pair of terminals which connect to the furnace's thermostat circuit. The furnace does not connect directly to the thermostat.

3) Have experimented with the "heat" function with no thermostat connected to any wiring. The furnace goes "on" when the furnace "White" wire is connected to the ground "Green" wire.

4) Have experimented connecting to the Atwood t-stat all wires except the furnace "White" wire. The A/C compressor and A/C fan do not operate.

5) On the Atwood thermostat, there is an undocumented "dot" in the lower left corner of the display which appears to be a "Call" indicator. This appears to be functional, is "on" in "heat" mode with setpoint above room temperature, is "on" in "cool" mode with setpoint below room temperature, otherwise "off".

Does anyone have any ideas why the Atwood won't work?






Posted By: Old-Biscuit on 11/22/14 10:00pm

I'm not positive but thought that the control board for that old analog t-stat had to be replaced with one compatible with digital


Is it time for your medication or mine?


2007 DODGE 3500 QC SRW 5.9L CTD In-Bed 'quiet gen'
2007 HitchHiker II 32.5 UKTG 2000W Xantex Inverter
On the Road Debt Free April '07
Off the road still Debt Free Jan. '14


Posted By: BillMartin on 11/22/14 10:46pm

Old-Biscuit wrote:

I'm not positive but thought that the control board for that old analog t-stat had to be replaced with one compatible with digital


According to the instruction sheet it should be able to directly replace an analog thermostat.

[image]

* This post was last edited 11/22/14 11:03pm by BillMartin *


Posted By: Old-Biscuit on 11/22/14 11:19pm

The Duo Therm T-stat #3107612.008 is obsolete.
NEW Duo-Therm Dometic Thermostat Part #3106995.032 Must Use With #3107541.009 Relay Kit.

And that analog t-stat was discontinued.
Dometic 3313189 Digital Replacement Kit for Dometic 3106995.032 Analog Thermostat

So you may need the different relay board to use a digital t-stat


Posted By: BillMartin on 11/23/14 11:41am

Thanks


Posted By: Chris Bryant on 11/23/14 02:32pm

If you want to use the thermostat you have, you cannot change the board in the air conditioner, only change it if you want to use the Dometic thermostat.
The Atwood should work with what you have.


-- Chris Bryant
My RV Service Blog
The RV.net Blog


Posted By: Old-Biscuit on 11/23/14 09:51pm

Chris Bryant wrote:

If you want to use the thermostat you have, you cannot change the board in the air conditioner, only change it if you want to use the Dometic thermostat.
The Atwood should work with what you have.


Then how does he wire it.........furnace is only thing working?


Posted By: Chris Bryant on 11/24/14 08:26am

Atwood provided faulty instructions- the so called 7.5 volt is not used- terminal 4 on the thermostat needs to be hooked to ground. If Atwood had just used standard terminology it would be easier- they show terminal 4 as relay common- a.k.a. rc and rw combined. Because DuoTherm switches the ground side of the relays, you need to provide a ground to rc and rw.
Given that they made that error, I'm not sure if the high fan will work correctly, because DuoTherm uses a relay for fan, then a relay to toggle between high and low. RVP uses a high relay and a low relay- IOW, both fan relays need to be energized for high fan for DuoTherm, single relays need to be energized for RVP. I assume that the note about the jumper deals with this issue...

The new Dometic digital system will ONLY work with the Dometic thermostat- it is a single comm wire setup, truly digital, not just a digital display on an analog setup, like all of the standard Hunter, et.al.


Posted By: Fisherguy on 05/27/15 08:03pm

Bill Martin, did chris' suggestion work for you? I have the same thermostat and want to try installing it. Do you have the 2 speed fan for the AC?


06 Dodge Ram 3500 Cummins 6 spd std with a few goodies.

2007 Komfort 274TS, SteadyFast stabilizers, Trimetric 2025RV, PD9280, Honda EU2000i, Xantrex SW600, shocks and EZ-Flex suspension, Reese Strait-Line
480 watts of solar



Posted By: Fisherguy on 05/27/15 08:08pm

oops


Posted By: Fisherguy on 05/29/15 09:05am

Atwood says I need to run another 12v lead to the thermostat, will see if that works.


Posted By: clarinet on 06/01/15 04:26pm

I'm looking to do the same thing. Did the suggested change to the ground wire (move from position 1 to position 4) work? Help!


Posted By: Fisherguy on 06/01/15 10:10pm

No, Chris' suggestion didn't work, neither did running a new power source, I could hear relays clicking but nothing from the furnace or ac.
My bud gave me the thermostat after he tried it and also couldn't get it to work. He's looking for his receipt, if he finds it I'll see if I can get a new one.

Here's the way the Atwood tech told me to wire it.
Blue from duo therm hi fan to Atwood 6
White from duo therm furnace to Atwood 8
Yellow from duo therm cool to Atwood 5
Brown from duo therm fan to Atwood 7
Red from Atwood 7.5 volt to Atwood 2
Ground to Atwood 2
New 12 volt to Atwood 3

Would like to get it to work but will be leaving for 3 weeks on Thursday, put the old duo therm back and it works fine.


Posted By: clarinet on 06/02/15 07:09am

How do you install the new 12 volt wire?


Posted By: Chris Bryant on 06/02/15 07:39am

Atwood's instructions say to hook the +7.5 (red) to 2 & 4. I still think Atwood doesn't know how the Dometic analog system works, though- they need to switch the grounds to activate any relays.
It would really help if they used anything close to standard terminology with this.


Posted By: Fisherguy on 06/02/15 08:05am

clarinet wrote:

How do you install the new 12 volt wire?


To test it I jumpered to a light fixture near the thermostat, if it worked I was going to try fishing the ceiling and the wall by removing the trim around a roof vent to help run the wire.



Chris Bryant wrote:

Atwood's instructions say to hook the +7.5 (red) to 2 & 4. I still think Atwood doesn't know how the Dometic analog system works, though- they need to switch the grounds to activate any relays.


Not from what I can see:

Atwood Instructions

Have you actually installed one of these and been successful? Dometic AC and Suburban furnace?


Posted By: Chris Bryant on 06/02/15 08:15am

Further proof that Atwood is relatively clueless- see page 14 of the service manual, which gives the instructions I gave.
No- I haven't dealt with one of these.


Posted By: Fisherguy on 06/02/15 08:25am

OK, so would that be why I heard relays clicking but nothing out of the AC or furnace?

Interesting page 14 is dated 6/19/02 and the instructions that came with the unit (and the one I linked to above) are dated 9/21/04, they're newer, you'd think the newer ones were correct...?


Posted By: Chris Bryant on 06/02/15 08:28am

Really, the only relay that could click without activating something would be the high/low fan relay- the compressor and fan relay should run those if they click.
They simply do not give enough info on operation, so I don't know what terminal 2 is on the t-stat.


Posted By: Fisherguy on 06/02/15 08:45am

We're leaving for a trip in 2 days, I don't think I'll have time to try it with 2 jumpered to 4, maybe I'll take it woth me on the trip and play with it while away.

One of the Atwood techs sent me this when I was trying to get it to work.

[image]


Posted By: Chris Bryant on 06/02/15 09:00am

On that diagram they hook up #2, with nothing on #4, they also list #2 (and the black out of the control box) as both +7.5 *and* ground. I wish I knew what terminal 2 actually was- terminal 4 they list as relay common, which makes sense- on a standard t-stat that would be terminal R (C or H).


Posted By: Fisherguy on 06/02/15 09:17am

These Atwood thermostats are not cheap, the instructions suck.
For less money someone could buy the Dometic thermostat that includes the parts for the Dometic AC unit, bet Atwood doesn't sell a lot of these.

My bud gave the Atwood to me after he gave up on trying to make it work, he put the Dometic in and had absolutely no problems with the install.

Removing the board from the unit and turning it over, looks like it was made by Channel Products Inc.


Posted By: Fisherguy on 06/28/15 06:55pm

Chris Bryant wrote:

On that diagram they hook up #2, with nothing on #4, they also list #2 (and the black out of the control box) as both +7.5 *and* ground. I wish I knew what terminal 2 actually was- terminal 4 they list as relay common, which makes sense- on a standard t-stat that would be terminal R (C or H).


Tried that today, set it to AC and what do you know the AC came on, I could also change the fan speed, HI or LO, only thing is it would not turn off when my set temp was lower than the current temp, and the furnace didn't come on at all.

Will contact tech support again tomorrow.
How can they sell these things for more than the Dometic is beyond me ...?


Posted By: clarinet on 06/28/15 08:07pm

I gave up an returned the Atwood 1H2C thermostat for credit. I am going to install a LUX DMH110a thermostat and adding a single pole double throw (SPDT) switch. It's the simplest install and have great support from LUX.


Posted By: Fisherguy on 06/28/15 09:14pm

clarinet wrote:

I gave up an returned the Atwood 1H2C thermostat for credit. I am going to install a LUX DMH110a thermostat and adding a single pole double throw (SPDT) switch. It's the simplest install and have great support from LUX.


One of these?
LUX


How'd you figure out how to wire it?


Posted By: clarinet on 06/28/15 09:50pm

Yes, exactly. Here's what I got for directions. (copy of email)
Converting from Dometic Analog thermostat. The wiring is as follows:
Red is 7.5v
Black is Cool
White is Furnace
Blue is Hi Fan
Orange is Low Fan
Green is Ground

LUX wrote:


Wire the DMH110c as follows:



Red / 7.5 dc = Rh w/jumper to Rc

Black / Cool = Y

White / Furnace = W

Blue / Hi Fan = G (usually used in cooling mode)

Orange / Low Fan = G (usually used in heat mode)

You would have to manually change the Lo & Hi speed wires to the ā€œGā€ terminal to control multiple fan speeds. Our unit has only 1 G/Fan speed terminal.

Green / Ground = TAPE OFF, Do Not Use.



Joel-Tech 856-234-8803 x 7


My additional notes for fan speeds: I used a SPDT rocker switch and cut out a piece from thermostat mounting plate.
Take Green/Ground attach to to neutral pole on switch then connected hi fan to one pole and low fan to other pole.




Thermostat model number

DMH 110c

Message


Posted By: Fisherguy on 06/28/15 09:58pm

THanks, if I can't get this thing to work that will be something to think about, 17 bucks and backlit seems like a bargain compared to this Atwood POS.

* This post was edited 06/28/15 10:15pm by Fisherguy *


Posted By: clarinet on 06/29/15 05:11am

I made one small error in my post. You do not use the ground wire. What you need to do is get a piece of 18 gauge thermostat wire and connect it from the "G" on the thermostat to the center/neutral pole on the rocker switch. By the way you can get the rocker switch from the GoRving parts catalog on line. Good luck. Saves a little bit of money.


Posted By: Fisherguy on 08/10/15 07:49pm

Clarinet, got my Luxtoday, do you have a pic on the switch you installed?
You say you put it in the base of the unit but the base is angled on mine, curios to see how you did it.
Thanks


Posted By: bearwayne on 08/11/15 04:57pm

I looked at the wiring diagram of how I wired my thermostat and it is similar to what th Lux Tech told you EXCEPT I did not use the +7.5V and connected Rh/Rc to the GND (Green)wire from the control module. This correlates with what Chris Bryant said about having to take the relays to ground to activate. You might try that if what the Lux Tech said doesnt work.

In this thread is the diagram of how I connected my analog thermostat.

link


Posted By: Fisherguy on 08/11/15 05:19pm

bearwayne wrote:

I looked at the wiring diagram of how I wired my thermostat and it is similar to what th Lux Tech told you EXCEPT I did not use the +7.5V and connected Rh/Rc to the GND (Green)wire from the control module. This correlates with what Chris Bryant said about having to take the relays to ground to activate. You might try that if what the Lux Tech said doesnt work.

In this thread is the diagram of how I connected my analog thermostat.

link


What kinda thermostat are you talking about? Chris was talking about the Atwood, Clarinet was talking about the Lux.


Posted By: bearwayne on 08/11/15 06:53pm

I was referring to the Lux.


Posted By: Fisherguy on 08/11/15 07:59pm

Interesting.

The link you posted was for a Hunter thermostat..?

I better contact Lux, lotsa other posts for the Hunter say you don't use the 7.5 volt wire and connect the ground as you say.


Posted By: bearwayne on 08/12/15 05:52am

The point of my post about my Hunter install was to show the wiring diagram. The brand of thermostat does not matter--I think all home thermostats are similarly wired and I -think- the terminal names are pretty much standardized. There are tons of posts on here about analog thermostats with various RC AC systems. That's how I figured out how to install mine. Btw, that Hunter I installed was terrible--I replaced it with an inexpensive Honeywell (not all Hunter thermostats are bad, just the model I bought.)


Posted By: Fisherguy on 08/12/15 06:53am

What was wrong with your Hunter? With the Lux you can adjust the temp swing, not sure if they all allow that.

I've given up on the Atwood.


Posted By: bearwayne on 08/12/15 05:32pm

The Hunter was difficult to use. It would take several presses on the screen to change settings. The worse thing is that on multiple occasions, it turned on the heat continuously even though the thermostat was set to "System Off"! The reviews for the Hunter on Amazon are pretty bad!

I like that the Lux has an adjustable temp swing. I was looking on their website to see if it did. My Honeywell does not as far as I know. I like a temp swing of +/- 1degree F. Otherwise, I notice wider swings.


Posted By: Fisherguy on 08/19/15 10:10pm

OK, got my Lux, wired up the switch but with my setup I need to have the LO and the HI connected to get the fan to come on high speed.
I know I've seen other people's wired up like this, always thought you should only have the HI or LOW connected but doing it that way my hi speed wouldn't work.


Posted By: bearwayne on 08/22/15 08:03am

I'm glad you got your thermostat working! I'm curious though--did you end up using the +7.5 or Gnd?i think it's good to provide those details for folks who find this thread in the future. I wonder if Clarinet got his thermostat working.


Posted By: Fisherguy on 08/22/15 09:25am

I used the ground. His works too, I didn't ask him if he used the ground or the 7.5 volts, but I think most other threads for these other thermostats also used the ground.
For the switch I removed the circuit board to put the switch in the front piece then put the board back:

[image]

[image]


Posted By: clarinet on 08/22/15 10:03am

Hi! This is Clarinet. I never got my Lux thermostat to work properly. I contacted the Lux rep and he told that I should return the thermostat becauseit will no work in my application. A complete 180 from my original contact.


Posted By: Fisherguy on 08/22/15 10:19am

Really, what hapened? Earlier you said it was working, did you use the power or the ground?
Mine works fine using the ground, not the 7.5 volts.

* This post was edited 08/23/15 11:42am by Fisherguy *


Print  |  Close