Register                
Results 1 to 3 of 3

Thread: How many Nest's on one common?

  1. #1
    Junior Member

    User Info Menu

    How many Nest's on one common?

    Hello. I have a Argo arm-4p Thermostat Controller. It only has one common connection, and one 24v 1VAH connection. I currently have one nest, and one ecobee hooked up and there sharing that common wire connection. I need to add one more nest, but was wondering how many Smart Thermostats can that common connection theoretically handle. That controller is ment to handle up to 4 zones. So I figured it should be good up to 4 common connections...but I'm no expert.

    P.S. there are two connections next to each other one says common, and the other says 24v @ 1VAH....what's the difference? I thought that common was 24v anyways.

  2. #2
    Administrator

    User Info Menu

    I am not familiar with Argo but I did find a manual online and it looks like you should be good to add the third thermostat to the common.



    Quote Originally Posted by OneAn9ryN00b View Post
    P.S. there are two connections next to each other one says common, and the other says 24v @ 1VAH....what's the difference? I thought that common was 24v anyways.
    Typically the common is grounded and the 24v would have 24vac

  3. #3
    Junior Member

    User Info Menu

    I agree that you will be fine adding a third powered WiFi thermostat. I think that the 1VA label is just to cover their butts to tell people not to attach anything significant to those terminals.

    In Argo's documentation it shows using a replacement 20VA transformer to power the board which comes with 30VA so there is at least 10VA spare. (a lot more since the 6 port also uses it). Other way to calculate is that it also shows that the 30VA transformer can power up to 15 zones. So at 4 zones you are using less than half power. For sizing a WiFi thermostat normally takes up to 4VA. So going to 4 powered thermostats would be shaky but the numbers work for 3.






    For power you need two wires normally labeled R and C in the HVAC world. Not quite the same but think of it as the + and - on a battery. The ARM Common terminal is C and the 24vac terminal is R which is also connected to all of the TR terminals.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •