Carrier Control module 2-wire thermostat to smart thermostat

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Old 07-25-20, 07:31 PM
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Carrier Control module 2-wire thermostat to smart thermostat

Hello all,

We moved into a home where the previous home owner signed up for PSEG thermostat monitoring program for energy efficiency. The program ended. The thermostat installed was a Carrier And the control module located but the air handler in my garage. I removed the thermostat and I see 5 wires (2 white, 2 red, and a green), where only V+ & Vg were used. I know I need to bypass the control module if I want to use a smart thermostat. The question is do I need to run a new set of wires from air handler to the thermostat? I doubt the energy company did that when the installed the Carrier Thermostat, which is why there are 5 wires in the wall?
The thermostat controls only the center ac system, no heat.

Thank you



 

Last edited by PJmax; 07-26-20 at 11:14 AM. Reason: enhanced/resized pic
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  #2  
Old 07-25-20, 07:39 PM
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Welcome to the forums.

That's the thermostat side of a communicating system. You need to go to the air handler and find the other half of the system. It's probably a white box with the controller in it. We need to see how many wires are connected to it.

A basic split A/C usually only needs three wires......R, Y, G.... four with a powered thermostat.... C.
 
  #3  
Old 07-25-20, 07:54 PM
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Hello PJMAX,

This is from the control module.


Wire colors does not match what is by the thermostat.

Thank you
 
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Old 07-25-20, 08:53 PM
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No.... they won't.

The red and green on the left side go to the stat.

The wires below on the right side go to the air handler.....
Rc - red
C - blue
Y - yellow
G - green

I think Rh and 24vac go to a separate 24v transformer.
Post the model number from that EIM.
Basically the four wires on the right need to connect with four wires to the stat.
 
  #5  
Old 07-26-20, 08:08 AM
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All I see from EIM is Carrier 960-960020 on the cover, nothing behind the EIM.
Below are couple pictures of wiring from EIM to air handler.
The wires behind the stat do not match these wires by the air handler, how do I know which one corresponds to which? Again I doubt the energy company route new wires for V+&Vg to the stat, they just used the existing 5 wires I have but just used red and green as V+&Vg and discard the remaining 3 wires.


Close-up shot
 

Last edited by PJmax; 07-26-20 at 11:22 AM. Reason: cropped/resized/labeled pics
  #6  
Old 07-26-20, 09:03 AM
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Hi, it sounds like you want to remove the control module and just have a smart Tstat, correct ? There appears to be 2 sets of cables coming from the wall to the AC, where do the other cables go ? it seems the power co. may have cut them to splice in the module.
Geo
 
  #7  
Old 07-26-20, 10:56 AM
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Yes I do not want the control module.
the 2 sets of wires coming from EIM to air handler, then it goes up in the ceiling. I'm assuming it's going up to the stat?
 
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Old 07-26-20, 11:19 AM
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We see 5 wires at the stat.
Please confirm red, white and green in one cable and red and white in other cable.
I'll assume this to be correct and based on that.... the three wire cable goes to the A/C and is cable D.
The two wire cable more than likely goes to the heat and is unused.

Cables A and B go to the EIM.
Cable C probably goes to the outside condenser.
I need to see the cable A to cable C connections better.
Can you fan the wires out and post another picture.

Looks like only three usable wires to the stat. That means no usable C wire.
 
  #9  
Old 07-26-20, 12:12 PM
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At the stat: all 5 wires come out of same conduit, except a red & white were cut very short. Not sure if it's heat since I have heat thermostat at another location.
below are clearer pictures. Inside the EIM, I see RH jumper to 24VDC.
​​​​​

Wire sets A & C:



Wire set D:
​​​It's probably the 3 wires that goes to the stat. From the picture, red to red, yellow to white, green to green up to ceiling.... And that gets traced back into left side of EIM, V+&Vg.



Btw, I see a white/red wires here not connected at all and also go up to ceiling. Could these be the cut white/red wires at the stat?




 
  #10  
Old 07-26-20, 12:52 PM
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Hi, can you determine where the control panel is on the AH, see if you can determine where which cable is connected to the control board there.
Geo
 
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Old 07-26-20, 02:35 PM
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Yes....that cable with red and white probably goes to the stat. That means two cables at the stat because wire colors cannot duplicate in one cable. That's good.

I have everything I need. I'll work out the color connections for you.
 
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Old 07-27-20, 05:24 AM
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Thank you PJMax,

I hope it's as easy as I think.
 
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Old 07-28-20, 05:45 PM
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Hello Pete,

Please help with the color connections.


Thank you
 
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Old 07-28-20, 05:59 PM
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At the thermostat end.
Three wire cable......
red - R
white - Y
green - G
Two wire cable....
white - C. Tape this wire black so that it doesn't get confused with the white of the 3 wire cable.
red - spare
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
At the air handler. There are three cables we are interested in.
Stat 3 wire cable....
red stat to cond green
white stat to cond red
green stat to G wire coming out of air handler.
Cond 3 wire cable....
red cond to stat white
white cond to C blower wire and white wire (taped) black from that two wire cable we don't see.
green cond to red stat

Two diagrams. Look it over and see if it's clear.

Illustrating functions.


Actual wiring.

 

Last edited by PJmax; 07-28-20 at 06:49 PM.
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Old 07-28-20, 07:09 PM
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Wow more involved than I thought.... I will have to study it. I was thinking removing the wires on right side of the EIM and connect to the 3 stat wires + the extra white as C wire.
So after doing the way you drew out, I will have 4 wires at the stat with the extra white (labeled black) as the C wire? So I will be able to use smart stats? I was actually thinking to just get the Emerson WiFi stat.


​​​​​​Thank you
 
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Old 07-28-20, 07:14 PM
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It looks involved but actually you are just removing the EIM wiring.
That's why I actually drew the connections. As long as you know which cable is which... you can't go wrong.

Yes..... using that two wire cable will bring C to the thermostat. Just make sure you somehow change it's color at both ends so that's easy to see. I carry many color tapes with me. I'd make it blue but any color is ok.
 
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Old 07-28-20, 07:24 PM
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I will let you know if it works out, need to pickup Emerson WiFi stat to test.
​shutting down the handler power if enough to do this correct?

 

Last edited by gwei8; 07-28-20 at 07:45 PM.
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Old 07-28-20, 07:40 PM
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Yes.... shut off power to air handler.
I labeled the two wires as they were connected but more than likely those two wires go to a relay which means there is no connection polarity.
 
  #19  
Old 07-31-20, 01:22 PM
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Hi Pete,

I wired as you drew out... Installed the Emerson ST55.
However when I switched to cool mode, only fan comes on, condenser is not on.


Please help
 
  #20  
Old 07-31-20, 03:05 PM
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Hi, have you identified for sure which cable goes to the condenser?
Geo
 
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Old 07-31-20, 03:18 PM
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Yes it's labeled from Pete's picture
 
  #22  
Old 07-31-20, 05:22 PM
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Hi, if you jump R to Y at the Stat will the condenser start?
Geo
 
  #23  
Old 07-31-20, 05:26 PM
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ST55 stat does not require any jumper.

I have reinstalled my original stat back.
Will see what Pete suggests.

 
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Old 07-31-20, 07:15 PM
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You put all the wiring back on the EIM ?

Does the blower switch on and off correctly ?
You have the (3w) white wire on Y ?
Does the stat light up and appear to work ?
Did you allow for the 5 minute delayed condenser startup ?

Connecting the red and green from the COND cable should start the condenser.
If it doesn't...... follow the COND cable. It should connect to a transformer and splice to a two wire cable which would be the outside condenser.
 
  #25  
Old 07-31-20, 07:20 PM
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I disconnect from all the wire nuts and followed your diagram. I didn't touch anything inside EIM.

Yes I have the 3 wire white as Y, the other 2 wire white as C.

I turned the stat on "cool" mode and the blower comes on right away, but no condenser. I let it ran couple minutes.
The blower also turns on when I switched fan mode to on... So blower is turning on/off fine.

On my old stat, when I turn to cool mode, condenser starts up pretty much right away.

Right now I wired everything back to the way it was so I can have AC tonight. Now too sure why it wasn't working. Your diagram makes sense to me.

 
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Old 07-31-20, 07:29 PM
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Most new stats have a 5 minute built in delayed turn on.


The blower should come on immediately on high speed, followed by cold air circulation. The thermostat will indicate “Cooling” on the screen. Note that there can be up to a 5 minute delay for this process. This is indicated by a flashing setpoint temperature.
 
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Old 07-31-20, 07:34 PM
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The stat does show "cooling"... I know I didn't wait 5 minutes, probably 2 minutes at most.

Maybe I should try again and wait 5 minutes after blower kicks on to see if condenser comes on?

Btw, it's not the 2 green wires G&C out of the blower causing this right? Will swapping those connections do anything?
 
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Old 07-31-20, 07:52 PM
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That's not a typical air handler as there are usually more wires coming out at that point. You would normally see 24v, common and blower. We're only seeing common and blower which means it's getting the 24v from another location. As I mentioned earlier.... more than likely those two wires go to a relay. You should be able to reverse them with no change in operation.
 
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Old 07-31-20, 07:57 PM
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I guess the only thing I can do is to try again and wait 5 minutes and see if condenser kicks on. Hopefully that's the case.

I see this on Emerson site, but they state that this can be turned on with app. I was not using the app, maybe this is set by default?

A/C Protection
This feature helps prevent damage to your equipment when cooling is turned off and back on quickly. When the 5-minute delay is active on the Sensi Smart Thermostat, the temperature set point on the wall unit will flash. After 5 minutes, the air conditioner or heat pump will start.
 
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Old 08-01-20, 05:05 AM
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Hi, have you set up the account for that stat? The original stat was a Carrier and only had 3 wires connected, correct? I would still suggest that you remove the cover for the control panel and see where that 3 wire really terminates and also those 2 blue wires terminate, they were obviously pulled out though that opening to suit the power Co. I think there are too many assumptions being made.
JMO
Geo
 

Last edited by Geochurchi; 08-01-20 at 05:49 AM.
  #31  
Old 08-01-20, 07:45 AM
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Condenser doesn't come on after 7 minutes.... Still only fan.
New stat shows cooling but set point does not flash.

I do see the RH jumper to 24VAC inside EIM, does that mean anything?


 

Last edited by gwei8; 08-01-20 at 08:20 AM.
  #32  
Old 08-01-20, 10:06 AM
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That jumper looks to bridge power across the board.

It looks to me that the wiring is exactly how you see it and the poco extended it to the wall with two cables to get a better signal and a place to mount it.

Have you tried to trace the COND cable to where it goes ?
Have you tried just connecting the red and green on the cond cable ?
We have not seen any 24vAC source of power yet.

 
  #33  
Old 08-01-20, 10:45 AM
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I think you are right Pete, condenser is not getting 24VAC.

No I have not tried to just connect red and green Cond wires. Are you saying don't connect the white Cond wires to C wire and leave it off?
 
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Old 08-01-20, 10:49 AM
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We have 24v because the blower is working and the thermostat is working. Technically if I have those two right...... the condenser should also be right.

Did you try connecting the red and green together ?
That should supply 24v directly to the condenser.
 
  #35  
Old 08-01-20, 10:57 AM
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Sorry which red and green?
I have only wired it per your sketch so far.


 
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Old 08-01-20, 11:03 AM
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Have you tried just connecting the red and green on the cond cable
Previously mentioned.
Try following the cond cable. See where it goes.
 
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Old 08-01-20, 11:16 AM
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Just saw that outside also has 3 wires connected by the condenser.

I'll check the inside Condenser wires again but I think it just goes to ceiling...



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