Help with wiring new thermostat

[woodbender]

I am currently running a DOMETIC 3313195.000 SINGLE ZONE LCD THERMOSTAT.

 

Works fine to run the a/c and the furnace and will blow high or low or auto with the a/c.

 

I bought a Honywell RTH6350. This is one with battery power.

 

http://www.honeywellstore.com/store/products/honeywell-rth6350d-5-2-programmable-thermostat.htm

 

There are only three wires currently hooked up to the Dometic - red - yellow and orange in color. The other colors are snipped off.

 

I have terminals labeled as follows in the new thermostat:

 

Y2 W2 G W not used Y R Rc (the last two have a jumper connecting them.

 

What color wires should go to what terminals on the new thermostat?

 

 

[Chalkie]

You may have a problem there. That thermostat, which I have in my S&B home, operates on 24v.

 

As far as I know the thermostat you are replacing runs on 12v, since that is what we have in our RVs.

[Yarome]

You may have a problem there. That thermostat, which I have in my S&B home, operates on 24v.

 

Chalkie is correct. That particular unit requires 24v. There ARE battery operated residential thermostats (like Hunter) that can be used in either application, though. This one uses batteries for some functions, memory, backlighting, but the actual control board requires 24v.

 

If you follow the current thermostat wiring up into your A/C unit's control box, it should have a wiring diagram in the bottom of the cover.

 

 

On edit: Just FYI.. the jumper should remain in place unless you have both R and Rc wires.

Edited October 29, 2016 by Yarome

[Dutch_12078]

This is the way my Honeywell RTH221B programmable digital stat is wired.

 

 

 

Edited April 11, 2022 by Dutch_12078

[Yarome]

If you look at the bottom of page 11 of the installation manual you'll see the notation for 24v.

[Yarome]

This one Honeywell TH6220D would work. A dual powered.

[woodbender]

Thanks for the guidance, everyone. Looks like I need a new thermostat.

 

Below is a link to the manual for my a/c.

 

https://manuals.heartlandowners.org/manuals/Heating-Cooling/A-C_Units/Dometic/Dometic%20Installation_SZLCD%20with%20separate%20control%20box_3314378.000.pdf

 

Page 11 has the wiring diagram for my unit 3313379.000. You can see the three wires going out to the thermostat.

 

How would I hook up the wires with the Honeywell TH6220D?

 

More importantly, why would I tell my wife something like "Ok, honey. Sure, I'd love to go out for breakfast. Just lemme hook up this new thermostat real quick."

Edited October 29, 2016 by woodbender

[Wrknrvr]

Try reprogramming your thermostat. The new style Dometic single zone thermostats need to be reset occasionally. It is in the manual how to do it.

Probably reset 4 this year for my business and they all worked properly after being reset.

Although yours may be bad.

 

Quick enough to

[woodbender]

Thanks for that.

 

I'm trying to find a replacement for the single zone (which is working perfectly) so that I can set a timer for the furnace to warm things up in the am automatically.

[jc2]

Wrknrvr, on 31 Oct 2016 - 08:47 AM, said:

Try reprogramming your thermostat. The new style Dometic single zone thermostats need to be reset occasionally. It is in the manual how to do it.

Probably reset 4 this year for my business and they all worked properly after being reset.

Although yours may be bad.

 

Quick enough to

Has there ever been a reason given by the manufacture for having to "reset" these stats? We have a Nest stat in our house a I seriously question sometimes on why they are called a "smart thermostat"

[Dutch_12078]

Our Honeywell RTH221B digital stats do just what you're asking for, turning the heat down at night and up in the morning. I installed one for each furnace and A/C pair in our coach. They run about $22 each at Home Depot...

[Wrknrvr]

I would say that there is a small problem with the single zone thermostats. Not enough for them to do something about them. But as a Dometic dealer I do see that situation occasionally.

Had one about two weeks ago. No furnace Sunday am and we are planning something else. Told him to reset and it worked.

 

Safe travels. Vern

[woodbender]

Boy do I feel dumb.

 

I bought a Honywell RTH221B to replace my Dometic single zone thermostat.

 

Unfortunately, I'm still faced with my original challenge -

 

I do not have six wires going to the existing thermostat - I have only three.

 

I have a yellow wire which goes to 12v, a red which goes to 12v+, and an orange wire which goes to the comms connection on the existing thermostat.

 

I could REALLY use some guidance as to what three terminals on the new thermostat I should use to connect these three wires.

[Yarome]

I could REALLY use some guidance as to what three terminals on the new thermostat I should use to connect these three wires.

 

Did you look up in the control box on the AC unit itself to get the wiring diagram? It should show you which leads need to be pulled down (from the control box) to your new thermostat.. and should coincide with the diagram Dutch posted up in #4.

[woodbender]

Hopefully the image above appears in the final post. (first time trying to post an image)

Just as an example, far as I can tell, the wiring diagram above makes no reference to the brown wire I see in Dutch's drawing.

Nor can I find a green wire in the maze of wires in and around the control box in the A/C except for the green wire in the thermostat bundle which is currently connected to nothing.

Just a thought -- might the green (ground) wire be labeled as 12v- (as opposed to 12v+)?

Edited November 21, 2016 by woodbender

[Yarome]

goes to the comms connection

 

OHHhh.. crap! One of those... I should have read that more carefully. Sorry.

 

You're not going to want to hear this.. but unfortunately.. it's not possible to wire in a new digital thermostat without rewiring the AC control box itself in order to bypass the "brain". The "com" connection passes codes back and forth from the "thermostat" to the "brain".

 

You used to be able to get an analog replacement control box that would make a conversion possible, but I haven't seen any around for quite a while.

 

Your current thermostat looks like this, right?

 

Hmm. I can't think of a work around for what you want do at the moment.. let me think on it. Other's might chime in as well.

 

 

[Yarome]

Inside looks like this?

 

[Dutch_12078]

Hmmmm, X2 what Yarome said. I have no idea how to wire an aftermarket replacement stat for that one.

[woodbender]

Well, the good news is I don't feel quite so dumb.

 

Thanks for chiming in everyone. If there's a workaround, I"m IN!

 

Yup, that's the existing thermostat.

 

All I'm really trying to do is get my new 110volt Suburban furnace to kick off in the morning on a timer.

Edited November 21, 2016 by woodbender

[Yarome]

I don't feel quite so dumb.

 

Yup, that's the existing thermostat.

 

All I'm really trying to do is get my new 110volt Suburban furnace to kick off in the morning on a timer.

 

Evidently smarter than we are since you already figgered you canna do it.

 

That's what I was afraid of. Yup.. not possible without a rewire.

 

I've never done it, but it seems to me that you might be able to stick a 12v timer in-line of the furnace 12v supply. The thermostat can still call for heat, but if you kill the 12v feed to the furnace during programmed intervals then it would effectively kill the furnace from cycling. I can't think of any reason.. or harm.. that could be done.

 

Something like this maybe?

[mptjelgin]

Can you just leave the A/C on the current thermostat and shift the furnace over to a new programmable thermostat. As far as I know nothing says that your furnace has to be on the same thermostat as you A/C. In fact, on our Hitchhiker the A/C - Heat Pump is on one thermostat, and our two-speed furnace is on another.

[Yarome]

shift the furnace over to a new programmable thermostat.

 

THERE's a good idea!! K.I.S.S.

[woodbender]

Yarome, that would work, I think, but here's what I want to do:

 

I'd like to run the furnace at, let's say 55 degrees at night, but then fire it up to 68 degrees at 6:00am so when the boss gets up, it's nice and toasty.

 

Sounds like the timer idea would shut it down completely for the night, then crank it up in the am.

 

Close... very close but not quite what I'm trying to do.

[Yarome]

Sounds like the timer idea would shut it down completely for the night, then crank it up in the am.

 

Exactly. Following Mark's suggestion would get you where you want to be.. and you already have the right Thermostat for the job so it's a pretty simple matter to just clip the wires leading out of the dometic control box and wire directly to your furnace.

 

That would be my first choice.

[woodbender]

whoops, I missed Mark's great suggestion. Sorry Mark. I'm going to try that.

 

So.... I have a red wire and a white wire going to the furnace.... two wires going to and from the control box.... so I clip...

 

I believe the furnace is either on or off, and just touching the red and white wires turns it on.... so....

 

What two terminals would you guys suggest I use in the new thermostat??

Edited November 21, 2016 by woodbender