Author Topic: AC-Heat Thermostat Replacement  (Read 10902 times)

Steve Huber Co-Admin

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AC-Heat Thermostat Replacement
« on: June 18, 2015, 03:41:22 AM »
Has anyone replaced the PSG Signature (#7DE12-AH21-F) thermostat. If so what did you replace it with and did you maintain original functionality? Mine runs the basement AC compressors and sends a signal to the Hurricane for heat. Need to have a fan speed control so I can reduce fan speed to low when on 30 Amps.
Mike at BCS is checking for me and I've spent a number of hours on the web but no joy. Coleman has a line of RV thermostats but their rep looked at the PSG and said they didn't have anything that would work. Same answer from Newell (they used same AC units) and NW RV Supply.
The switches are shot on mine and I'd like to ID a replacement before I attempt to unsolder them from the PC brd.
Steve
Steve
2015-          07 Contessa Bayshore C9,  400 hp
2013-2015: 00 Marquis Tourmaline, C12, 425 hp
2005-2013: 01 Contessa Naples, 3126B, 330 hp

Edward Buker

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Re: AC-Heat Thermostat Replacement
« Reply #1 on: June 18, 2015, 08:35:03 PM »
Steve,

It seems to me the complication here is that two cooling units are run off of the same thermostat and the interactions of the unit is built in along with the selections you want to make. It would seem to me that you could use two separate thermostats side by side and enable one compressor for each. You could also set one thermostat a degree above the other to do the second one comes on if the first cannot keep up or simple turn one thermostat off if on 30amps. That would get you to a modern thermostat. You would have to understand the wiring and possibly make an intermediate mounting board with a routered cavity that would allow jumpering of the wires as needed.

This is similar to the thermostat that I have and in this PDF they mention dual compressor basement air conditioner application. Not sure if it would work for yours but maybe worth a read. They have controller boards also. May be worth a call to Dometic. The thermostat to controller wiring may be standard, basic power, ground, call for heat or cool, fan control etc. Operation and installation manuals below.

 http://media.channelblade.com/EProWebsiteMedia/1844/Duo_Therm_Comfort_Control_Manual.pdf

http://bryantrv.com/docs2/docs/ccc.pdf

Later Ed
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Steve Huber Co-Admin

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Re: AC-Heat Thermostat Replacement
« Reply #2 on: June 18, 2015, 09:14:38 PM »
Ed,
Thanks for the info. Mike at BCS was able to refer me to a Colman RV Comfort stat that will replace my unit so am good to go. Now to get the slide switches and see if I can repair the existing one w/o messing up the PC board.
Steve
Steve
2015-          07 Contessa Bayshore C9,  400 hp
2013-2015: 00 Marquis Tourmaline, C12, 425 hp
2005-2013: 01 Contessa Naples, 3126B, 330 hp

Steve Huber Co-Admin

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Re: AC-Heat Thermostat Replacement
« Reply #3 on: June 27, 2015, 11:53:50 PM »
The switches on my PSG Signature thermostat for the kitchen and front area of the Marquis were going bad. I first thought about replacing them but the idea of successfully unsoldering 10 connections per switch and not causing any damage to a relatively cheap PC board did not look like a sure thing.
Mike at BCS told me that they had some luck with the Coleman Mach 6536-335. I ordered one and installed it yesterday. It has the same controls as the PSG and seems to work fine. Wiring was relatively straight forward with a couple of wrinkles. The “freeze” wires on the T’stat have to be tied together and the 12V and Gnd for the Gas heater function need to be tied into the Elec 12v and Gnd circuit. Prior to doing this I had no 12v signals going to the AC compressors.

If anyone needs to replace their PSG T’stat here is the wiring layout.
                        
Beaver Wire   Coleman Wire   Signal      Orig PSG Terminal      Note
Small Red        Purple           Fan Low         GL   
Small Blk         Black            Fan High        GH
Orange           Orange         AC Comp 2     Y2   
Yellow            Yellow           AC Comp 1     Y1   
Red (large)     Red              +12V                R   
White(large)
& Small Blue   Blue             Gnd (-12v)       B   
Large Black     White/Blk    Elec Heat           W
                    Grey              Freeze                                 Tie to other Grey
                    Grey              Freeze                                 Tie to other Grey
                    Red             +12v (Gas)                            Tie to Large Red
                    Blue or
                    Blue/Wht     Gnd  (Gas)                            Tie to Large White
                    White             Gas Heat                              No Connection

The Coleman has 2 Molex style connectors, a 3 pin for gas and a 9 pin for elec, ac  & heat. I cut them off and used wire nuts to make the connections. The connectors wouldn't have fit in cabinet opening in any case.
Steve   
Steve
2015-          07 Contessa Bayshore C9,  400 hp
2013-2015: 00 Marquis Tourmaline, C12, 425 hp
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Dick Simonis

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Re: AC-Heat Thermostat Replacement
« Reply #4 on: June 28, 2015, 04:27:22 PM »
Steve, great report.  I'm also going to look at this real hard since this is still on my list.

Do you still have the same ability to lock out the 2nd stage compressor with the new thermostat??

Does the display give room temp as well as set point??

Dick

Steve Huber Co-Admin

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Re: AC-Heat Thermostat Replacement
« Reply #5 on: June 28, 2015, 06:16:49 PM »
Dick,
The T'stat has a Fan Auto/On and a High/Low fan setting, same as teh PSG. Setting the fan on Low should lock out AC2 same as the PSG. However, I'll throw the AC2 breaker in the future when on 30a to be sure.

Display shows ambient temperature and switches to set point on first push of the up or down temp setting switches.
Steve
Steve
2015-          07 Contessa Bayshore C9,  400 hp
2013-2015: 00 Marquis Tourmaline, C12, 425 hp
2005-2013: 01 Contessa Naples, 3126B, 330 hp

Dick Simonis

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Re: AC-Heat Thermostat Replacement
« Reply #6 on: June 28, 2015, 07:01:30 PM »
I had the AC guys in Bend come over and check a couple of items while I was at BCS last week and the guy screwed something up so it's not quite working correctly but I reached a point where all I wanted was him OFF MY COACH.  Figured I could do a better job with the controls.

However, I did sort of figure out what the HIGH/Low switch really does which was a boon.  Seems it only changes the fan speed which is a bit redundant so I'm thinking of other uses for that which like running the second stage compressor through it instead.

Very glad the display shows room temp as that is something I wanted.  I may just order it and make the change after I give you a week or so to uncover any issues.

Dick

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David T. Richelderfer

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Re: AC-Heat Thermostat Replacement
« Reply #8 on: June 29, 2015, 03:17:33 PM »
I use the high-low-auto fan button often.  When in the bedroom I set the bedroom air conditioner to low fan speed to cut down on the noise so the TV can be heard.  When in the living room I set the living room air conditioner fan speed to low so that TV can be heard.  Otherwise, all three air conditioners are usually set to auto.  Note:  When I purchased the coach, as I recall, I was told in order to speed up or skip the air conditioners' start up delay, then turn on the air conditioners and set their fan buttons to either low or high.  But, if all the fan button does is set fan speed, then I suspect the start up delay cannot be circumvented.
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Dick Simonis

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Re: AC-Heat Thermostat Replacement
« Reply #9 on: June 29, 2015, 04:07:04 PM »
Steve,  does this T-stat fit between the two switches??? Any chance of a pic showing the new unit???

Also, do you have a copy of the manual....can't find one on line.

Thanks.

Dick

Steve Huber Co-Admin

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Re: AC-Heat Thermostat Replacement
« Reply #10 on: June 29, 2015, 08:19:35 PM »
Dick,
Here's pix. Will email pdf of manual.
Steve
Steve
2015-          07 Contessa Bayshore C9,  400 hp
2013-2015: 00 Marquis Tourmaline, C12, 425 hp
2005-2013: 01 Contessa Naples, 3126B, 330 hp

Dick Simonis

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Re: AC-Heat Thermostat Replacement
« Reply #11 on: July 09, 2015, 03:18:37 PM »
Bit of an update.

Replacing the thermostat on our 2002 Marquis is slightly different than on Steves coach.  Ours has a different OEM thermostat and an additional switch for controlling the fan speed.

I have received the Coleman T-Stat and have gotten as far as checking all the wire for color and functionality.  Once the change is complete, I'll update the wire matrix for others to follow.

Right now my intention is to use the separate rocker switch to control the 2nd stage compressor and use the T-Stat to control fan speed.  That will make living on 30 power quite easy.  The SCS T-Stat did not allow manual fan speed selection in Auto which I guess is why Beaver added the extra switch.  My biggest problem is the the distance between the two switch is not enough to for the new T-Stat so I will do a temp mounting with it rotated 90 degrees until I get home.  Fred knows how to drill rectangular holes so we will just move the High/Low switch left an inch or so.
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Dick Simonis

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Re: AC-Heat Thermostat Replacement
« Reply #12 on: July 11, 2015, 02:36:59 PM »
I now have the new Coleman T-Stat installed and operational but the SCS T-Stat did have some differences.

With the SCS fan speed was can not be manually changed while operating in Auto so Beaver added a separate switch beside the unit for that purpose.  Interestingly, BCS told me the High'Low switch was for both fan speed and #2 compressor....that was incorrect, it's only the fan speed and #2 compressor is disabled by placing the T-Stat switch in "Low". 

For my purposes I took the T-Stat orange wire to the center contact of the switch than connected the coach Large Orange wire to the the lower terminal.  This allows me run both AC compressors in "High" and #1 compressor only in "Low".  Manual fan speed is controlled by the T-Stat fan speed selector.  Once all the wiring was complete, the AC control is excellent.

Getting the heat to operate properly was not so straightforward.  On the first attempt I ran the set temp up about 10 degrees over room temp and NADA, no heat. Steve had to fool the T-Stat into thinking we had a heat pump by directly connecting the relay coil to 12 VDC and using the electric heat wire (white/Blk) for the Aqua Hot control.  Normally this works fine but the T-Stat has a safety feature that shuts off the heat pump if the set temperature is more that 5 degrees above room temp and calls for auxiliary gas heat through the white wire.  Connecting the white (gas heat) to the white/blk (heat pump) solved this issue and now all is well.

Thanks again to Steve for blazing this path and saving me some aggravation.  I was going to use a Honeywell T-Stat but the Dometic has some clear advantages.