# Configuring 2-stage furnace with new 2-stage thermostat



## Billly4325 (May 27, 2018)

I have a CARRIER 59TN6A060V17-14 60000 BTU, UP TO 96% AFUE, MULTI-POSITION, TWO STAGE, VARIABLE SPEED GAS FURNACE controlled by an ECOBEE 4 2-stage thermostat. There is no air conditioning unit, but one may possibly be installed in the future. The ECOBEE 4 replaced a Pro1 T705 1-stage thermostat. *After installing the ECOBEE 4 I believe I am not taking advantage of the 2-stage functionality of the Carrier furnace. Also, I cannot operate the fan-only to circulate air without the furnace being on.* Please refer to the attached document which shows photos and configuration tables. Any advice is appreciated and I apologize if this was the incorrect message board to post this inquiry. Thank you.


----------



## user_12345a (Nov 23, 2014)

How many wires do you have at the thermostat?

You'll need 5 to stage the furnace, have a common and control continuous fan. I recommend a 7 or 8 wire cable for future expansion - a/c, control humidifier, etc.

There's a dip switch that needs to be changed on the control board to disable the upstage timer.

From there, you'll need the following terminals connected with wires, between furnace and stat.

R
W1
W2
G
C for powering without batteries.

The stat should have a settings menu, set to 2 heat/no cooling.


----------



## Billly4325 (May 27, 2018)

There is a 5-wire from the main board to thermostat. I will have to pull another 2 or 5 wire should an AC unit be added.

I re-purposed the yellow wire as it was not used. I connected the yellow wire to W2 on both main board and thermostat.

I then changed the DIP switch SW1-2 from OFF to ON. 

The Ecobee 4 then detected the furnace as a 2-stage system.

I believe it is now working with your advice. Thank you for your advice.


----------



## user_12345a (Nov 23, 2014)

Run the furnace for 20 minutes on low fire (u may have to disconnect w2 temporarily) so make sure it doesn't auto updates after the board's 16 minute delay.

Then reconnect W2 and see if when you run the heat and turn the stat up, it cycles to second stage right away.


----------



## Billly4325 (May 27, 2018)

I disconnected the W2 wire from the main board. I ran the furnace on low fire for 20 minutes. The furnace remained on Stage 1. Stage 2 did not engage. Seems like that is working.

I reconnected the W2 wire. I ran the furnace and turned up the stat from 70F to 90F. The furnace remained on Stage 1 for 10 minutes. After 10 minutes Stage 2 was engaged. You mention the furnace should immediately go to Stage 2. 

The Ecobee has a setting called "Heat Stage 2 Temp Delta". It is set to Auto by default. You can set a value of 1F to 10F.

The Ecobee has a setting called "Heat Stage 1 Max Runtime". It is set to Auto by default. You can set a value of 10 to 120 minutes.

I would assume that if both of the settings above were set to Auto (which they are currently), and I raise the temperature from 70F to 90F, Stage 2 should immediately engage, but it does not. Stage 2 engages only after Stage 1 was running for 10 minutes.

I believe I changed the appropriate DIP switch as mentioned previously. Could you please confirm this is the correct setting per the attachments in the original post. 

Thank you.


----------



## user_12345a (Nov 23, 2014)

It sounds like the ecobees have a staging delay - minimum run time before second is engaged, unlike honeywells which bring it on pretty quick.



> he Ecobee has a setting called "Heat Stage 1 Max Runtime". It is set to Auto by default. You can set a value of 10 to 120 minutes.


Set this to 120 minutes. The whole idea is to allow continuous operation on low with it switching to high as needed, then back to low. You don't get that with a 10 minute max runtime before bringing on high.



> The Ecobee has a setting called "Heat Stage 2 Temp Delta". It is set to Auto by default. You can set a value of 1F to 10F.


1F will result in it bringing on the second stage before you notice a temp drop.

This is what I would try using first.


----------



## Billly4325 (May 27, 2018)

"Heat Stage 1 Max Runtime" is now set to 120 min. System runs on low fire for over 20 minutes.

Then "Heat Stage 2 Temp Delta" is set to 1F. Stage 2 immediately runs. I assume this means everything is configured correctly. If that assumption is correct, do you recommend the value to be changed from 1F to something more practical like 5F for very cold days?

Thank you.


----------



## user_12345a (Nov 23, 2014)

It's a matter of personal preference.

When set to a higher setting, it may let the temperature drop quite a bit before bringing on the second stage.

When it's brutally cold, as soon as the first stage isn't keeping up, for best comfort the second stage should start cycling on and off.



> to something more practical like 5F for very cold days?


Set it to 5F and you could be cold and the house will take a long time to warm up when you raise the temperature.


----------



## Billly4325 (May 27, 2018)

My interpretation of "Heat Stage 2 Temp Delta" is if this value is exceeded, turn ON Stage 2. For example, if the value is 5F, the current room temperature is say 60 and I have the thermostat set to 66, Stage 2 would immediately start on the cold days. Am I misunderstanding?


----------



## user_12345a (Nov 23, 2014)

That's my interpretation too.

But you wouldn't want it getting down to 60 to 61 when set to 66f.

For comfort would want it to come on as soon as it starts dropping from 66f.

The entire point of 2-stage is to avoid temperature swings.

In the real world, most furnaces are oversized by a large margin and first stage satisfies even in the coldest weather. It's a shame - don't get the continuous runs.

---------------------------

I don't know how the ecobee stats work, it sounds like they always wait for a certain differential before bringing on second stage.

The honeywells in comparison monitor rate of change and bring the second stage on as needed to maintain the setting.


----------

