VisionPRO IAQ to Nest Learning Thermostat

[Sdotnance1]

I have a Honeywell Vision Pro IAQ thermostat with an EIM module connected to a Trane Heat Pump and Trane A/C condenser and I need help eliminating the EIM to add a nest learning thermostat.  

[Sdotnance1]

My Equipment 

Air Handler: 
Trane:  ATEE3F40B1000BA

with heat strip BAYHTR1408+++

Condenser:  

Trane:  

4TWX5030A1000AA

Thermostat: 

Honeywell VisionPro IAQ 

TH9421C1004

[CoolingWizard]

Hello @Sdotnance1 , I saw your message that you had posted this and I took them home to read it. The key to success is if you have a thermostat cable that has seven conductors Running between The thermostat location and the air handler. 

Your Trane system can be controlled ising the Nest Thermostat. Can you advise me on how many conductor wires are in your thermostat cable?

AC Cooling Wizard

[Sdotnance1]

Yes sir! I have a 7 conductor cable going to my thermostat and only three conductors in use.

I’m not sure how to post pictures on here but I’ll try to post if I can.

In the meantime, this is currently how the wires are configured in the EIM.

Reference:

F-Furnace

HP-Heat Pump

T-Thermostat

F/HP- wire from both Furnace and Heat Pump

EIM wiring configuration 

1- Red to T

2- White to T

3- Green to T

C- Blue to F/HP

R- Red to F/HP

RC- jumper to R and RH

RH- Jump to DHM 1

HUM1- empty

HUM2- empty

DHM1- Jump to RH

DHM2- Pink to F

VNT1- empty

VNT2- empty

W1 OB- Orange to F/HP

W2 AUX- White to F/HP

W3 AUX2- empty

Y- Yellow to F/HP

Y2- empty

G- Green

[CoolingWizard]

The key is to ensure the color conductor are the same at each end. Basically thermostat cables have colored conductors to match terminal designators.  Y is typically Yellow and this terminal turns on the Compressor. 

IAQ allows three wires to digitally communicate to the air handler/Furnace.  So the colored wires going from the furnace control board are where you want to connect your cable coming from the thermostat to the IAQ.  Disconnect the three wires going to the IAQ. Then connect color for color where the wires from the IAQ connect. When connect say Red to Rc, remove the one from the IAQ. 

I hope this makes sense to you. 

AC Cooling Wizard

[Sdotnance1]

Ok great news that the nest is compatible.  So I understand color for color to eliminate the EIM but I do have a couple of questions regarding some of the terminations and placement of the wires on the nest thermostat. The nest has Y1, Y2, G, O/B, RC, W1, W2AUX, C, *, RH.

Y1- Yellow from F/HP

Y2- empty

G- Green from F

O/B - Orange from F/HP

RC- ?

W1- ? empty?

W2- white from F/HP

C- blue from F/HP

*- ?

RH- Black connected to Pink from Furnace

I’m not sure where the Red - from Furnace/HP would go on the Nest.  Also is it correct to take the pink from the furnace to RH using the black wire? And are my other connections correct as stated above?  

[CoolingWizard]

@Sdotnance1 ,

place the wires from the Furnace as follows:

Red to Nest RC

Yellow to Nest Y1

Green to Nest G

Orange to Nest *O/B

White to Nest W2

Blue to Nest C

of your Furnace is Gas or Oil, you have a “Duel Fuel Heating System”. Your heat pump is Electric, and the furnace is Gas.  On a Duel Fuel system, you need to determine at the temperature that the heat switches from Electric Heat Pump to Gas Furnace.  Basically this will be trial and error.  Since the cost of gas and the efficiency of your furnace are not known as of yet.  Simply accept the defaults. 

AC Cooling Wizard

[Sdotnance1]

I know that my system does not have gas and is an electric furnace.  We don’t have natural gas in the rural are where I live.  My electric furnace does have auxiliary electric heat strip. The only termination that is left would be the Pink wire coming from my furnace which is for the dehumidifier.  Would it get connected to the last remaining wire in the thermostat wire which is black? And where would it need to be terminated on the nest?

[CoolingWizard]

Since you have a wire that is on your DHum 2 of the IAQ, that can be controlled by the Nest if it is attached to * terminal.  If you use that Starr terminal for a dehumidifier, you will not be able to use it for emergency heat back up. So you’ll only have auxiliary heat, but no emergency heat support.

AC Cooling Wizard