Replacing Carrier thermostat with Nest.

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Old 12-14-16, 08:26 AM
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Replacing Carrier thermostat with Nest.

Hi All, I really Hope someone can help, and I am sure you can.

my Wife and i have just purchased our first home. crazy excited, and as a gift we received a nest Thermostat, I am big into 'Smart' things so was super excited.

i went to install it and after removing my current Thermostat, a Carrier one, i noticed only two wires a V+ and a Vg. so according to the nest website, and the online support, my system is not compatible. which to me is very hard to believe considering my current thermostat controls both Heat and Cooling, we have an AC unit and a Forced hot air Furnace.

I have attached pictures of Thermostat and wiring.

PLEASE HELP... Thanks you so much Mark

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Old 12-14-16, 09:43 AM
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I think they are right the nest is not compatible with your system.
 
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Old 12-14-16, 10:32 AM
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Welcome to the forums.

I'm not sure of the proper name but you have a Carrier multiplexed system. The thermostat is connected to an electronic control module (EIM) at the furnace end. It will be a box with a lot of thermostat wiring going into it.

It can probably be removed.
You will also need to check and see how many conductor cable was run.
You may need 6-8 conductors requiring a new cable to be run to thermostat.

When I went back and looked at your picture again.... it looks like they used SPT-1 two conductor lamp cord. That will definitely need to be replaced.

Pictures of the wiring at the furnace would be helpful. http://www.doityourself.com/forum/electrical-ac-dc/534445-how-insert-pictures.html
 
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Old 12-14-16, 11:00 AM
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Hi, And thank you for your response.

yes i read about the EIM, when i get home this evening i will look and take picture of the wiring at the furnace EIM,

How will i know and find about the conductor cables? can i not remove the EIM and run the wiring from my furnace through the walls to my thermostat?

Thank you for your help, i am Hand and know most things, but am completely in the dark about all of this HVAC and wiring, and after the house purchase and moving cant afford to have a pro come look at it all, so i really do appreciate the help more than you know.
 
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Old 12-15-16, 07:39 AM
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Hi PJMax,

so last night I was searching around and i found the EIM that you talk off connected to my furnace. so it should be as easy as connecting wires to the existing ones and feeding them through the wall to the Nest thermostat location? Correct?

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Thanks again Mark
 
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Old 12-15-16, 10:26 AM
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First thing you'd do is to label or document what terminal each wire is connected to.

The EIM would be removed from the system.
Your new stat wire would go directly into the furnace.
It looks like you may have a two wire cable that goes to the A/C float switch.
 
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Old 12-15-16, 11:28 AM
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Can i not just run a New Stat wire, through to the furnace and attach it to the screws on the EIM and just not use the V+ and Vg wires, so 'Bypassing the EIM'

whats the "a two wire cable that goes to the A/C float switch" mean?
 
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Old 12-15-16, 11:55 AM
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You will require at least 5 conductor wire to be run to the location of the thermostat on the wall.
There's a second wire coming in that looks to break R, probably a float switch shutdown. That will have to be rewired in.
 
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Old 12-15-16, 12:11 PM
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OK yeah, i have a 5 conductor wire, and its easy to run from the Thermostat to the furncae, and i can just attach it to the screws on the EIM correct, (to match the existing Rh C W etc etc) How would i go about re wiring in the wire that 'Breaks R' and what does float switch shutdown do
?
 
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Old 09-08-17, 06:56 PM
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Nest install

Did you get this too work with Nest? I have the very same type setup.
 
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Old 09-08-17, 07:04 PM
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Did you get this working? I have the very same thermostat with a Carrier heat pump.
 
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Old 09-09-17, 01:05 AM
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ccapps...... did you read the thread ?
You need to locate the EIM module at the furnace.
You will need 5-7 thermostat wires depending on functions needed.
 
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Old 09-09-17, 05:17 PM
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the carrier thermostat you have is likely a much better product that can control the equipment better than the nest with fewer wires.

what wire terminals are hooked up at the eim?

What's the model of the furnace.

The nest has a lousy reputation and if you want a smart stat, you would be better off selling it on ebay or something and buying an ecobee 3.
 
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