New Honeywell Thermostat (Replacing Coleman Mach)

Triguy · 04-23-2012, 02:43 PM

I am posting this for those interested in swapping out the Coleman-Mach analog thermostat with a Honeywell programmable digital thermostat.

The Coleman-Mach thermostat supplied with my trailer has a very wide range of temperature control -probably close to 4-5 degree swings each way - and I have been meaning to replace it for a year now.

So, I followed what many others on our forum have done and replaced it with a digital.

Triguy · 04-23-2012, 02:45 PM

I opted for the Honeywell RTH221B Basic Programmable Thermostat because I wanted to set the furnace to come on automatically early in the morning just before we normally wake.

I also like the form factor of this model, specifically because there is no door to flip open to operate the Fan or Cool/Off/Heat switches. Because its vertical and replacing a horizontal unit, you will have to fill one old screw hole in your wall.

I paid $22.36 on Amazon, which is $5 more than the non-programmable RTH111B.

Triguy · 04-23-2012, 02:47 PM

Here is a picture of the Coleman-Mach and its circuitry. Note it uses six wires: Red, Yellow, White, Gray, Green, and Blue. The wiring from the factory to my Coleman-Mach actually matches colors correctly. Apparently, this is not always the case so examine the wires and note which terminal each wire is connected to.

Triguy · 04-23-2012, 02:48 PM

The Coleman-Mach has two screws and the wires are held tight in the wall due to the foam placed in the wall opening. Just pull the wires through gently. Some of the foam will flake off, which is fine. You should be able to pull out several inches as needed.

Make sure to tape up the wires to keep them from falling back into the hole. The foam holds it but better safe than sorry.

Next cut the wires and use wire strippers to cut and strip the protective coating off the wire. Do this for four wires: Red, White, Yellow, and Green. Leave Blue and Gray alone and further tape those ends to prevent shorts. You will not be using them.

I drilled small pilot holes and screwed in the wallplate for the Honeywell.

Triguy · 04-23-2012, 02:50 PM

The Honeywell RTH221B thermostat has terminals for 5 wires: "Y," "G," "Rh," "Rc," and "W." Note the jumper between the "Rh" and "Rc" terminals? Leave that jumper installed.

The wiring illustration is on the case and in the instructions. Place the bare wire in the appropriate side slot. Use a small Philips screwdriver to tighten as you go.

I opted to wire in order to use the fan on high as follows:

Red wire to “Rh” terminal (Rh and Rc utilize a jumper)
White wire to “W” terminal
Yellow wire to “Y” terminal
Green wire to “G” terminal
Gray (not connected)
Blue (not connected)

Triguy · 04-23-2012, 02:51 PM

Last, add two AAA batteries that you will supply and reattach the faceplate to the wallplate. Then test your thermostat. I have only tested for heat and everything works perfectly. I’ll test for AC later in the summer.

From soup to nuts, the whole thing took an hour.

OldCoot · 04-23-2012, 03:39 PM

Do you have hi & lo for the AC and does it work? I know you said you didn't try the ac, what was the reason why you didn't try it?

Triguy · 04-23-2012, 03:58 PM

I wasn't in an area with access to 30amp power so that will have to wait until I can move the trailer.

Triguy · 05-01-2012, 11:46 PM

Finally able to test the AC through the new Honeywell and it works perfectly. So all is good with furnace and AC. The T-stat does a great job keeping the temps steady.

Dunnnc, to answer your question, I opted to connect so that furnace and AC are both on high. This particular thermostat would need a mod in order to have both low and high fan.

foxhunt · 07-10-2012, 11:02 PM

I did this same mod and I have an issue with the AC only working when the Honeywell is set to "Fan ON." If the fan is on the "auto" setting, it makes no difference what the thermostat is set at, the AC will not come on. I'm completely baffled by this. I have the wiring connected just the way you did. Any ideas??

Triguy · 07-11-2012, 12:19 PM

Hi Foxhunt,
I'm sorry but I could only guess why your unit is not working with the Auto Fan setting. The Auto fan works fine for me with the unit installed as described.

Guesses ...

Verify your wires are correct. I have read that some wiring may not have been done correctly by color so its always wise to have first labeled your wires regardless of color as you disassembled your old thermostat.

Try to switch the fan operation setting inside the t-stat between HE and HG and see if that has any effect (long shot but worth a try).

Good luck!

BBDAWG · 05-29-2014, 08:11 PM

Ok, Guys I have worked now for two days (nights) trying to make this stat work correctly.

My current symptoms are:
All works fine except the A/C fan comes on when the heat comes on. (not the a/c compressor, just the fan)

To get this far, I set the gas/electric switch to "electric". (moving this switch to the "gas" selection, the A/C fan only runs when fan mode is selected to "on". The a/c fan then also runs when the heat come on. NO fan period when set to auto.)

The wiring is set as follows:
A/c side Stat side
White to white
Yellow to yellow
Green to green
Red to R/Rh (with jumper on)

blue not used
grey not used

notes:
Blue, when touched to red "sparks"
Grey, when touched to red causes a/c fan to run (not sure if low or high)
Green when touched to red causes a/c fan to run (not sure if low or high)
connecting the green and grey together and installed in the G terminal does not seem to make the fan sound any different (unknown hi or low)

Like I said, all is working except that the a/c fan runs when the heat is turned on.
I have an Atwood 8535IVDCLP furnace

I called Honeywell support and after about 20 minutes, the guy told me this stat will not work on 12 volt systems. He left me hanging 2 time to go back and verify his statement.
He also told me I would have to bring in an a/c professional to resolve my digital thermostat needs.

I went through this whole same scenario last year with a Hunter stat in my old TT. We now have a new to us Fleetwood Pride 5th wheel and Atwood furnace and Honeywell stat. (Still love our Forest River Friends!!!)

Can anyone help me resolve this issue?

Thanks
Randy
(I am using this thread because I followed the wiring from TRrguy to get this far)

sdelam · 05-31-2014, 09:06 AM

On mine the green is the high fan and grey is the low fan. Make sure you didn't pop the 12v fuse for the furnace. Mine was a 7.5a fuse and I pooped it twice before figuring out my wiring.

BBDAWG · 05-31-2014, 10:16 AM

Quote:

Originally Posted by sdelam

On mine the green is the high fan and grey is the low fan. Make sure you didn't pop the 12v fuse for the furnace. Mine was a 7.5a fuse and I pooped it twice before figuring out my wiring.

Thank You for continuing to help. I know someone has the answer out there and I sure hope they will pop up and help figure this out.

Yes, I did blow the fuse, it was a 15amp. I also created another problem with the lights over the stove area (in a slide out) as they quit working at the same time. (4 lights on two switches) I have checked every fuse but no luck on fixing those yet.

Anyway, my a/c and thermostat are working except that one issues remains. When I turn on the furnace, the a/c fan comes on.
The furnace blower works the furnace ignites and seems to work as it should.

This one a/c fan issue is really bugging me and I know I have the stat he/hg set wrong but it is the only way it will work, as good as it is.

Randy

sdelam · 05-31-2014, 10:42 AM

My a/c fan also did this at first. I switched it from elec to gas and now it works like its supposed to.

Silly question but, did you wait a few minutes after turning it on and off initially to give the built in delay time to reset?

Witch Doctor · 05-31-2014, 11:12 AM

Take the green wire off and add the gray to the green terminal, then see what happens. Also look in your R/A and see if there is a green wire going to the board, it's easy to see. It hard to try and tell you how to wire it being all units are different. What will work on 1 unit may not work on yours. FR doesn't do anything consistently.

Witch Doctor · 05-31-2014, 11:27 AM

The green wire might be a ground. All you need are the white and red to bring your furnace on blower will start then burner. A/C side red hot, yellow compressor, blue or gray high and low speed (normally). Fan only for your unit would be red to gray/blue only use one. when set to on not auto should just bring on the a/c blower. Like I said it's hard to tell how they wire it. When you call for a/c your sub base will bring on the compressor yellow and the gray for the blower in auto or fan on without the compressor kicking in. It's the best I can say with out seeing it, SORRY you should not see a spark touching the blue to red the blower should come on only. The way triguy told you is correct but remember this is FR. Make sure it is set to gas not electric. I'll check back at 1:30 PM East time let me know what happens. easy way to check your wire is disconnect them all from the stat with red to yellow only compressor will come on, red to gray a/c fan only , red to white furnace should start, It sounds like they made your blue wire ground and the green low speed. Your lighting problem sounds like a fuse to me. Also you have a different stat then triguy, Honeywell might be right just noticed that, but hard to read his model #

BBDAWG · 05-31-2014, 12:24 PM

Ok, first off what is the R/A?
Yes, I did wait for the time limit, not at first with the other stat.
When I touch red to Yellow, compressor come on, no fan
When I touch red to white, the furnace come on
When I touch red to grey, a/c fan comes on
When I touch rd to green, a/c fan comes on
When I touch red to blue - SPARKS

If I put the hg/he switch to h/g, the a/c compressor comes on but NO FAN (with the Green attached to the G stat lug). Heater seems to work OK.
e
Can I take photos of anything and post them?

We are having a large storm right now so will have to do this later.

Thanks so much for the help but gotta run now.
Randy

Witch Doctor · 05-31-2014, 12:44 PM

Quote:

Originally Posted by BBDAWG

Ok, first off what is the R/A?
Yes, I did wait for the time limit, not at first with the other stat.
When I touch red to Yellow, compressor come on, no fan
When I touch red to white, the furnace come on
When I touch red to grey, a/c fan comes on
When I touch rd to green, a/c fan comes on
When I touch red to blue - SPARKS

If I put the hg/he switch to h/g, the a/c compressor comes on but NO FAN (with the Green attached to the G stat lug). Heater seems to work OK.
e
Can I take photos of anything and post them?

We are having a large storm right now so will have to do this later.

Thanks so much for the help but gotta run now.
Randy

The green and gray are high and low speed, for some reason the blue is ground causing the spark or it's touching something and grounding out. . Use the gray only and hook it up as you stated do not use the green or blue tape them off. Reinstall and it should work. Lets cross our fingers make sure your batteries are in. I'll check back in the am. If your a/c is on the roof you have a split panel in the ceiling 1 side you will see with twist black knobs, that is where your return air filter is located and your a/c control board from the stat. what is hg/he stand for in your install book? Then turn down the a/c to 60 to make sure it comes on, then shut it off to 90 and put your fan switch to on the fan will come on only I hope. Your furnace is fine you just need the white and red.

BBDAWG · 06-01-2014, 10:16 AM

ALRIGHT!
I removed the green and attached the grey to the "G" terminal. I set the switch back to (HG) for the gas furnace setting. I turned the breaker back on and waited for the protect circuit to kick in and it came on.

Then checked the heat cycle and there was no a/c fan with the heater running. SUCCESS!

final step - the a/c fan still sounds like it is in "lo" speed so I went back and added the green wire to the grey and reinstalled it.

The fan now seems a little louder, not much sound difference but I do think it is louder (faster) I'm going to leave it like this for a while and see if all goes well but I do think it is all working again.

I know I had this config once or twice before and I had the problems. I guess I was wrapped around the axle and not seeing things (or remembering) correctly.

I really appreciate YOU Guys stepping in to help us wayward mechanic wanna be's, dig ourselves out of these holes..

Now I have to figure out what I did to the circuit with 4 - 12 volt lights that quit working. I have checked each fuse in the two fuse boxes so I need to do more digging. Ugghhh

(and NO, I am not having fun yet!!)

Thanks again!!
Randy

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