Daisy chaining thermostats

Users who are viewing this thread

Jessielogue

New Member
Messages
6
Reaction score
0
Points
1
Location
Indiana
Hey all

I have an outdoor wood boiler for heating and also have a heat pump. I am wanting to mount a second thermostat below my homes original one but I want to know what wires to use to just make the just the fan turn on when the second one would call for heat (owb)
 

jadnashua

Retired Defense Industry Engineer xxx
Messages
32,753
Reaction score
1,171
Points
113
Location
New England
You'd want to connect the 'Red' wire to the R-terminal of both thermostats, and on the one for the fan, connect the 'Green' wire on the W terminal.

The red and white would go on the one for heat.

WHen the thermostat calls for heat, it closes a switch inside it to connect the R-wire to the W-terminal.

On the one you want to control the fan, the G wire is normally connected to the manual fan control line, but since you want it switched automatically via the thermostat, using the terminal to activate the heat would turn the fan on instead. If you want to manually turn the fan on as well, jumper from the W to G, and when you flip the fan from auto to manual, the R wire would also connect to the fan line to activate it manually.
 

Jessielogue

New Member
Messages
6
Reaction score
0
Points
1
Location
Indiana
You'd want to connect the 'Red' wire to the R-terminal of both thermostats, and on the one for the fan, connect the 'Green' wire on the W terminal.

The red and white would go on the one for heat.

WHen the thermostat calls for heat, it closes a switch inside it to connect the R-wire to the W-terminal.

On the one you want to control the fan, the G wire is normally connected to the manual fan control line, but since you want it switched automatically via the thermostat, using the terminal to activate the heat would turn the fan on instead. If you want to manually turn the fan on as well, jumper from the W to G, and when you flip the fan from auto to manual, the R wire would also connect to the fan line to activate it manually.
The one I’m wanting to add so I just tie into the red wire to the r terminal and green wire to the w terminal, I won’t need to turn the fan on manually so then that’s it?
 

jadnashua

Retired Defense Industry Engineer xxx
Messages
32,753
Reaction score
1,171
Points
113
Location
New England
You don't need the G wire in the second thermostat to be connected at all. Think of the thermostats as temperature controlled switches. On the original, it turns the heat on. The second one, you want to turn on a pump at a specific temperature, so you hook the wire that normally would control the fan in a furnace to the heating line.

Now, if you wanted to turn the fan on when the heat rose to a particular value versus off when it drops, you'd use the a/c terminal. Then as the temperature rose, it would be trying to turn the a/c on, and turn off when the temperature dropped. The a/c line on the thermostat is the Y or yellow terminal.
 

Jessielogue

New Member
Messages
6
Reaction score
0
Points
1
Location
Indiana
You don't need the G wire in the second thermostat to be connected at all. Think of the thermostats as temperature controlled switches. On the original, it turns the heat on. The second one, you want to turn on a pump at a specific temperature, so you hook the wire that normally would control the fan in a furnace to the heating line.

Now, if you wanted to turn the fan on when the heat rose to a particular value versus off when it drops, you'd use the a/c terminal. Then as the temperature rose, it would be trying to turn the a/c on, and turn off when the temperature dropped. The a/c line on the thermostat is the Y or yellow terminal.
All I want is the second thermostat to kick the fan on. I have a water to air heat exchanger from my boiler built into my plenum below my furnace, so say I have the second thermostat set at 75
First one set at 65 for my heat pump
I only want to heat with the second one, I just need the fan to kick on for the fan air to go thru that heat exchanger
So I know red to R terminal, but I know I need another wire for the fan to kick on
 

jadnashua

Retired Defense Industry Engineer xxx
Messages
32,753
Reaction score
1,171
Points
113
Location
New England
The G wire is typically used to control the fan manually. If you want the thermostat to do it automatically for you, connect it to the W terminal on the thermostat. So, when the temperature falls to the turn-on point, it would connect the R wire to the G wire, and turn the fan on. Once the temperature rises to the set point, it would turn the fan off.
 

Jessielogue

New Member
Messages
6
Reaction score
0
Points
1
Location
Indiana
The G wire is typically used to control the fan manually. If you want the thermostat to do it automatically for you, connect it to the W terminal on the thermostat. So, when the temperature falls to the turn-on point, it would connect the R wire to the G wire, and turn the fan on. Once the temperature rises to the set point, it would turn the fan off.
Ok thanks a lot
I really appreciate it
 

Fitter30

Well-Known Member
Messages
2,873
Reaction score
459
Points
83
Location
Peace valley missouri
By just adding a 2nd stat and wiring it R to G at air handler/ furnace good possibly that a feed back will happen back through the 1st stat. 16521234274581247412525.jpg
 
Last edited:
Top
Hey, wait a minute.

This is awkward, but...

It looks like you're using an ad blocker. We get it, but (1) terrylove.com can't live without ads, and (2) ad blockers can cause issues with videos and comments. If you'd like to support the site, please allow ads.

If any particular ad is your REASON for blocking ads, please let us know. We might be able to do something about it. Thanks.
I've Disabled AdBlock    No Thanks