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Old 07-06-2012, 11:27 PM   #1
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Upgrading to Modern Thermostat


I just bought this very cool new thermostat called "Nest". I want to remove my current thermostat and install the nest. The problem I am having is knowing where to put each wire in the new nest unit.
My old thermostat has a white, orange, yellow, red, & green wire.
Can someone tell me where to place the wires in the codes labeled in the new unit?
Please see picture as reference.

Thanks
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Old 07-07-2012, 02:13 AM   #2
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Umm, look at the photo on the left. It tells you what colors go where. But I bet that you will find that your cur. system may not be compatible with the Nest. What type of system do you have, do you rent or own. Also, if you wanted to waste $300 on the Next, I could have just taken you to the local strip club and helped you stuff dollar bills in the trailer trash on the stage.

Sorry, but the Nest is a waste of money, and nothing more than a gadget, to say "Look what I wasted my money on".

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Old 07-07-2012, 06:53 AM   #3
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forget the colors on the old stat it is the letter to letter R,G,Y,C,W you need to transfer exactly and do the world a favor shut the furnace servcice switch OFF
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Old 07-07-2012, 07:06 AM   #4
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Quote:
Originally Posted by biggles
forget the colors on the old stat it is the letter to letter R,G,Y,C,W you need to transfer exactly and do the world a favor shut the furnace servcice switch OFF
Thank you Biggles. Ok, so letter to letter it is BUT the nest unit has a label titled O or B. I assume this orange or brown. Here is where I get confused. I have both and orange and brown wire going into the old thermostat.

Yes, I cut the power before working.
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Old 07-07-2012, 07:08 AM   #5
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Like biggles says.

Because old thermostat has neatly installed plug in a harness, you have to cut the wires so they are separate. Strip ends and screw onto equivalent color terminal of new thermostat. Jump RED wire onto both Rc and Rh if both cooling and heating will be used.

Looks like your brown wire gave you option of another fan speed at the thermostat. Not sure Nest will do that. You may have to change fan speed seasonally at the furnace or thermostat. BROWN = high fan for A/C, GREEN = low fan for heating.

O/B is for heat pump application. Your orange wire is for that and used for units other than Rheem and Ruud brands. If you don't have a heat pump, orange wire can be taped off and not used. Even if put on terminal of Nest, if you don't have a heat pump it won't do anything.

Last edited by diyorpay; 07-07-2012 at 07:20 AM.
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Old 07-07-2012, 07:17 AM   #6
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letter to letter the O/B are not colors IDs,they are system IDs for heat pump wires.......be caeful if you short the wires the transformer down in the funace will be shot....$$$ get off the colors ....go letter to letter

Last edited by biggles; 07-07-2012 at 07:19 AM.
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Old 07-07-2012, 07:19 AM   #7
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Quote:
Originally Posted by diyorpay
Like biggles says.

Because old thermostat has neatly installed plug in a harness, you have to cut the wires so they are separate. Strip ends and screw onto equivalent color terminal of new thermostat. Jump RED wire onto both Rc and Rh if both cooling and heating will be used.
Thanks diyorpay! Yes, this unit acts as both heating and cooling.
It doesn't look like the red wire is split in the current thermostat. As I mentioned above, the color to color thing makes sense until I get to the w or b input. But then again, if I have to now split the wires then it is getting much more complicated then originally anticipated.
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Old 07-07-2012, 07:25 AM   #8
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Gregzoll is right. You have a working, sophisticated thermostat that looks to have been installed by a pro. It has advanced features. The Nest isn't getting you much except maybe proposing slightly better efficiency gains.
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Old 07-07-2012, 07:25 AM   #9
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Quote:
Originally Posted by diyorpay
Like biggles says.

Because old thermostat has neatly installed plug in a harness, you have to cut the wires so they are separate. Strip ends and screw onto equivalent color terminal of new thermostat. Jump RED wire onto both Rc and Rh if both cooling and heating will be used.

Looks like your brown wire gave you option of another fan speed at the thermostat. Not sure Nest will do that. You may have to change fan speed seasonally at the furnace.

O/B is for heat pump application. Your orange wire is for that and used for units other than Rheem and Ruud brands. If you don't have a heat pump, orange wire can be taped off and not used. Even if put on terminal of Nest, if you don't have a heat pump it won't do anything.
Very educated response. Much appreciated.
In order to "dumb it down" for me, the red wire still needs to be split? Which red would it go into? Where would I put in the brown wire?
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Old 07-07-2012, 07:32 AM   #10
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Looks to me like the photo you took of your existing tstat shows the wiring harness between the stat and the base. You're interested in the wiring AT THE BASE - this is typically a brown wire that penetrates from the wall, with 4 or more solid core wires (4 is generally for gas/electric heat, 5+ is generally for heat pump).

THAT wire is the one where you should matching colors, not on the harness. If you can take a pic of that brown tstat wire and the connections, we might be able to help you further.

According to the NEST site, you don't need to jumper Rh and Rc, even if they're jumped on the old tstat.

I've never known the Brown wire to manage different fan speeds - generally that's a Common wire or a secondary Heat wire.
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Old 07-07-2012, 07:38 AM   #11
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RED goes on both Rc and Rh, maybe. We're only seeing the buttons on the Nest. They may be jumped internally as scott says.

Since you don't have terminals on Nest (I am no expert on Nest) for multiple fan speed (your old one did), GREEN would be default wire on G terminal. That's the low speed setting typically used for heat. If you put the BROWN wire on G terminal instead, fan speed will be high, typically used for A/C. Your old thermostat and control board on the furnace let you manually set fan speeds from the thermostat, a nice feature. Can't see front of your old thermostat but that is implied by wiring stated on back in your pic.

Read the Nest literature if multiple fan speeds are possible from the thermostat.
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Old 07-07-2012, 07:42 AM   #12
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Quote:
Originally Posted by scottmcd9999
Looks to me like the photo you took of your existing tstat shows the wiring harness between the stat and the base. You're interested in the wiring AT THE BASE - this is typically a brown wire that penetrates from the wall, with 4 or more solid core wires (4 is generally for gas/electric heat, 5+ is generally for heat pump).

THAT wire is the one where you should matching colors, not on the harness. If you can take a pic of that brown tstat wire and the connections, we might be able to help you further.

According to the NEST site, you don't need to jumper Rh and Rc, even if they're jumped on the old tstat.

I've never known the Brown wire to manage different fan speeds - generally that's a Common wire or a secondary Heat wire.
So here is a picture of the wiring pulled out from the wall. Does this help?

Thanks!
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Old 07-07-2012, 07:48 AM   #13
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Hmmm ... could be a factory wiring harness? Does the wire on the wall side of that plug go all the way to your air handler/furnace? Or does it connect to another wire in that junction box?

What brand of HVAC system do you have? Can you take a picture of the outdoor unit and/or the indoor unit?

Last edited by scottmcd9999; 07-07-2012 at 07:52 AM.
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Old 07-07-2012, 07:58 AM   #14
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if you have a solid state module in the furnace those wires out of the wall connect to letered termials...R,G,Y,W,C on the board
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Old 07-07-2012, 08:02 AM   #15
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Quote:
Originally Posted by scottmcd9999
Hmmm ... could be a factory wiring harness? Does the wire on the wall side of that plug go all the way to your air handler/furnace? Or does it connect to another wire in that junction box?

What brand of HVAC system do you have? Can you take a picture of the outdoor unit and/or the indoor unit?
The unit is by Whalen. It is a high rise condo building so there isn't really anywhere to take a picture.
I know other residents in the building have switched to the nest (and they are super happy with it) so it is compatible. Each resident said they paid over $200 to have it professionally installed and each said that it took no time and could have probably been done themselves.
however, none of the residents were able to take a picture of their finished install to help me out. It is a good thing I have all of you.

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