Bryant 926TB 2 stage gas furnace installed smart thermostat wiring help

[indiana]

Hello,

I just had the Bryant 926TB installed in my home and I currently have the NEST thermostat.  My old furnace was a single stage gas furnace and had only 4 wires going to the thermostat.  The new installer stated that I didn't need additional wires for the new 2 stage furnace.  I believe he's incorrect but I want to confirm this before calling up the company and complaining to them to make this right.

Shouldn't I have a wire for the 2nd stage of the heat going to this smart thermostat that can manage a 2 stage furnace?

Thank you,

[indiana]

Looking through the service manual, it mentions that a single stage thermostat can control the 2 stage furnace.  That's great but I have a 2 stage thermostat.  The wiring diagram shows 7 wires running to the thermostat in the book and I currently have 4. 

Shouldn't they have run new wiring to enable additional control? 

[Admin]

There is really not alot of difference between letting the furnace or thermostat control staging.  Unless it's easy to install more wiring I wouldn't worry.  Are you using the Nest power connector for 5 wire hookup?

[Sergroum]

Furnace itself is able to control its own staging. Thermostat can be more precise, but will require extra wiring. If you genuinely want to pay the installer to run a new wire, then it's your choice. Whether you'll notice a difference, or not  ... Another question.

[indiana]

You mention the furnace can control it's own staging.  My understanding is the furnace is just set to an amount of time and then switches from stage 1 to stage 2.  Is that true?  If so then the thermostat would have a lot more data and control on how to adjust between the stages to make the house more comfortable.  Also the manual mentions a dehumidifier wire D to the thermostat.  I don't believe the furnace could do the dehumidification option without that wire.  Is that true? 

[indiana]

There is really not alot of difference between letting the furnace or thermostat control staging.  Unless it's easy to install more wiring I wouldn't worry.  Are you using the Nest power connector for 5 wire hookup?

I have only a 4 wire hookup at the moment.  No power connector.  The manual shows 7 wires should be run to thermostat. 

Manual has:
Heat Stage 2. W2
Heat Stage 1. W1
Cool Stage 1.  Y
Fan                G
24 V Hot         R
Dehumidify.    D
Common        C

[Sergroum]

Furnaces do not dehumidify. Air conditioners, or dehumidifiers wired in with the furnaces (they use the furnace blower fan) dehumidify.   Same thing with humidifiers. They are seperate appliances that can be wired in with the furnace.

You can ask the installer to run more wires for you, but I assure you, you will need to pay for it. Might also involve some holes in drywall, depending on what's involved in running the wire.

[indiana]

Correct it's the AC Coil that would dehumidify.  The manual says that setting runs the blower at a slower speed to remove more humidity. 

[Admin]

You need a communicating thermostat to use that feature with that furnace.