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Ecobee v1 to Nest v3

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  • Feb 11th, 2019 8:36 pm
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[OP]
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Jul 4, 2009
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Mississauga area

Ecobee v1 to Nest v3

I just bought the Nest Thermostat v3 to replace the Ecobee that came with the house and opening it up, I see the wires as C RH G and W and Y together.
So I wired it to the Nest as C RH G and I took out the W/Y coupling and just attached it to W.
So now I have heat, but no cooling. Should I put the coupling back together and put the Y part to the Y? In the Nest guide, it said to remove any jumpers, not sure if this qualifies as a jumper and not sure if I can be ruining anything.

Any help would be greatly appreciated!
thermo.jpg
28 replies
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Oct 13, 2008
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You might want to check out the Ecobee wiring on their site and then compare it with the Nest wiring

On mine ... I originally had a Honeywell Programmable Thermostat (the ORIGINAL Thermostat was a very very old ... W / Y / G / Rc (jumper to R)

I took a photo of it before disconnecting and then labelled all the wires ...

IMG_20171226_092132.jpg



Pulled out the Nest and started to wire them ... and it looks like this:

IMG_20190118_165336.jpg
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May 23, 2009
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What kind of heating and cooling equipment do you have? Could be W or O/B based on your pictures. O/B is reversing valve for heat pump.

One cable in Y the other in O/B. Then you set O/B changeover in the Nest.

Like this
Image
[OP]
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Jul 4, 2009
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Mississauga area
I have a gas furnace and central air.

On the old Ecobee that I uncovered, I only have 4 wires.
That set up has:
1. black wire going into C
2. red wire going into RH
3. green wire going into G
4. white wire going into a split of W and Y -- W going into W, and Y going into Y.

So what I did with the Nest is black wire going into C, red wire into RH, green into G.
The problem is the white wire. I removed the split and put the white wire into W, now I have heat and fan control but no cooling. I mean obviously I don't need cooling now, but I will come summer.
I don't know if I should put the white wire back into the split thing and split W and Y like how the old owners did it, but to me that looks wrong.
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Oct 14, 2010
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I have never seen the small white unit where the Y and W wires seem to combine. So my comments are purely speculative. I don't think the white box is a simple coupling though. The system normally operates on 24 VAC, the white box may be as simple as this. It might have 2 diodes inside which send + voltage out the white wire when a request for heat is made , and sends out - voltage when cooling is requested. A similar unit at the furnace end of the wiring allows the + voltage to the W terminal and the - voltage to the Y terminal.

Since your system worked normally without a yellow wire, It looks like the white box works similar to the PEK (power extender kit) that is included with Ecobee. The PEK allows you to use a single wire for 2 purposes. Have you checked the furnace end of the wiring? Is there another white box that seems to take the single White wire and split it to the W and Y terminals on the furnace?,

Since this magic box worked previously, it might just work again with your new Nest. To be truly compatible you should have a yellow wire running to your thermostat if you have an AC unit. In the interim, you can move the white wire from the W terminal to the Y terminal (at both ends) as the seasons change.
Last edited by Rick007 on Jan 19th, 2019 9:40 am, edited 1 time in total.
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Nov 14, 2012
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AV-Fishing wrote:
Jan 18th, 2019 5:06 pm
You might want to check out the Ecobee wiring on their site and then compare it with the Nest wiring

On mine ... I originally had a Honeywell Programmable Thermostat (the ORIGINAL Thermostat was a very very old ... W / Y / G / Rc (jumper to R)

I took a photo of it before disconnecting and then labelled all the wires ...


IMG_20171226_092132.jpg




Pulled out the Nest and started to wire them ... and it looks like this:


IMG_20190118_165336.jpg

That wont work... need C com to power nest or use a "wire saver" box and grab common feed in equipment
Sr. Member
Nov 17, 2014
765 posts
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Ontario
AV-Fishing wrote:
Jan 18th, 2019 5:06 pm
You might want to check out the Ecobee wiring on their site and then compare it with the Nest wiring

On mine ... I originally had a Honeywell Programmable Thermostat (the ORIGINAL Thermostat was a very very old ... W / Y / G / Rc (jumper to R)

I took a photo of it before disconnecting and then labelled all the wires ...


IMG_20171226_092132.jpg




Pulled out the Nest and started to wire them ... and it looks like this:


IMG_20190118_165336.jpg
Have you had any problems because you don't have a common wire? When I originally hooked mine up I had no common wire and the thermostat kept draining battery as it only received power when the system was running. I read they really should have a common wire although Nest doesn't make it an actual requirement.

In my case I was lucky as whoever ran the wiring when the house was built left some spare wires in the wall, and even one right into the furnace that I could use a common wire, was just a matter of connecting it on both ends.

As for OPs question I'm a little confused as to what the problem is? You only need a wire to either RC or RH. The Nest has an internal jumper that will make the switch for you depending on what mode you're in.
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kittypink wrote:
Jan 18th, 2019 10:28 pm
I have a gas furnace and central air.

On the old Ecobee that I uncovered, I only have 4 wires.
That set up has:
1. black wire going into C
2. red wire going into RH
3. green wire going into G
4. white wire going into a split of W and Y -- W going into W, and Y going into Y.

So what I did with the Nest is black wire going into C, red wire into RH, green into G.
The problem is the white wire. I removed the split and put the white wire into W, now I have heat and fan control but no cooling. I mean obviously I don't need cooling now, but I will come summer.
I don't know if I should put the white wire back into the split thing and split W and Y like how the old owners did it, but to me that looks wrong.
Please post a picture of the furnace side of the wiring
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Copper1212 wrote:
Jan 19th, 2019 6:04 am
Have you had any problems because you don't have a common wire? When I originally hooked mine up I had no common wire and the thermostat kept draining battery as it only received power when the system was running. I read they really should have a common wire although Nest doesn't make it an actual requirement.

In my case I was lucky as whoever ran the wiring when the house was built left some spare wires in the wall, and even one right into the furnace that I could use a common wire, was just a matter of connecting it on both ends.

As for OPs question I'm a little confused as to what the problem is? You only need a wire to either RC or RH. The Nest has an internal jumper that will make the switch for you depending on what mode you're in.
According to the Nest ... This is what the setup is. I'll take a photo of my furnace wiring later ...

IMG_20190119_074612.jpg
Stress is caused by NOT fishing enough.
JDM ONLY! No North American CRAP!
Megabass, Imakatsu, Jackall, GanCraft, OSP, EverGreen, YGK, Toray, Sunline, Nories, Shimano, Daiwa RULES!
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Nov 17, 2014
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Ontario
AV-Fishing wrote:
Jan 19th, 2019 7:48 am
According to the Nest ... This is what the setup is. I'll take a photo of my furnace wiring later ...


IMG_20190119_074612.jpg
Without a common wire you run the risk of the Nest battery draining, which is what happened to me, this led to my furnace acting up. The common wire provides constant power to the Nest, without it it only draws when the system is running.
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This is the wiring inside the furnace.

IMG_20190119_090301.jpg
IMG_20190119_090340.jpg
IMG_20190119_090510.jpg
Stress is caused by NOT fishing enough.
JDM ONLY! No North American CRAP!
Megabass, Imakatsu, Jackall, GanCraft, OSP, EverGreen, YGK, Toray, Sunline, Nories, Shimano, Daiwa RULES!
EVA Air Rocks ... Air Canada SUCKS!
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AV-Fishing wrote:
Jan 19th, 2019 9:07 am
This is the wiring inside the furnace.
Your photo of the furnace shows a white wire connected to the "C" terminal. Yet this white wire doesn't appear at your thermostat. It looks like they used CAT5 wiring from the furnace to the thermostat, but the white wire would not be part of that cable.

Since there is also a black wire on the Y terminal, it is likely that both the White and Black wires go to the AC unit, and not up to the thermostat, As others have said, you really should have a wire connected between the 2 "C" terminals.

PS How long has it been since you installed this new thermostat, and have you had any problems?.
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So you have a common wire running from the furnace but where does it go to?
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Rick007 wrote:
Jan 19th, 2019 9:32 am
Your photo of the furnace shows a white wire connected to the "C" terminal. Yet this white wire doesn't appear at your thermostat. It looks like they used CAT5 wiring from the furnace to the thermostat, but the white wire would not be part of that cable.

Since there is also a black wire on the Y terminal, it is likely that both the White and Black wires go to the AC unit, and not up to the thermostat, As others have said, you really should have a wire connected between the 2 "C" terminals.

PS How long has it been since you installed this new thermostat, and have you had any problems?.
I've had the Nest installed since December 2016 and haven't had any issues at all.

AC runs fine in the summer.

Heat works perfectly fine in the winter.

I just installed as per the manual that came with the Nest.

Furnace was original when home was built in 2006. We're the second owners.
Last edited by AV-Fishing on Jan 19th, 2019 9:39 am, edited 1 time in total.
Stress is caused by NOT fishing enough.
JDM ONLY! No North American CRAP!
Megabass, Imakatsu, Jackall, GanCraft, OSP, EverGreen, YGK, Toray, Sunline, Nories, Shimano, Daiwa RULES!
EVA Air Rocks ... Air Canada SUCKS!
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Copper1212 wrote:
Jan 19th, 2019 6:04 am
As for OPs question I'm a little confused as to what the problem is? You only need a wire to either RC or RH. The Nest has an internal jumper that will make the switch for you depending on what mode you're in.
The OP only has 4 wires to his thermostat. The "Y" and "W" terminals of the thermostat (cooling and heating requests) were combined into a magic white box, and traveled to the furnace on the single White wire.

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