Converting Line Voltage Thermostat to Low Voltage

[atvkid4eva]

I currently have a single pole line voltage thermostat controlling my two overhead radiant heaters. I would like to convert to a low voltage thermostat so I have more options to use a digital thermostat for better accuracy. I have a few questions about doing this:

I currently have 120v coming into the thermostat box two wires (one black and one white). I believe I should use a Honeywell RC840T-120 to convert the 120V down to 24V. Here is the link:

https://www.supplyhouse.com/Honeywe...B0ecJFAu-orPy6iznBr0961OIbHvS4NsaArZ8EALw_wcB

Looking as the wiring diagram, it shows three wires a red white and black, I only have two wires coming into the box. Where would the third wire coming from the relay connect to?

Has anyone used this relay to accomplish what I am trying to do?

 

[dogdog]

I don't think that is a high current relay... it would work and would power your thermostat. you'll probably needed a higher amp rated 24V coil relay to drive your heater load. that thing is rated 22AMP @240V resistive loads.. so you'll have to check

If it is me, I would get the 24V transformer and a isolation relay ( it's just a contactor ) with proper amp rating of your heater.

wiring wise it's just like this except that aube thing have both the transformer and relay build in.

https://support.ecobee.com/hc/en-us...ermostat-installation-with-an-isolation-relay

 

[dogdog]

as far as wiring connections you can look at aube's installation instruction, it's in the link you provided.

https://s3.amazonaws.com/s3.supplyhouse.com/product_files/RC840T-120-Install.pdf

 

[PWC Repair]

You just need a plain jane transformer like this..https://www.supplyhouse.com/White-R...V-Primary-24V-Secondary-Foot-Mount-14929000-p
Along with a standard 2 pole contactor with 24v coil.https://www.supplyhouse.com/White-R...V-Primary-24V-Secondary-Foot-Mount-14929000-p
You could probably pick up used one from any HVAC company that has a pile of old units out back. Your 120v comes in to a box where it's attached to contactor, and jumpered off to the transformer. Other side of the contactor goes to your heaters. The 24v comes out of the transformer to power the new thermostat and the heat call out of the thermostat goes back onto the coil of the contactor. When the thermostat calls for heat, the 24v signal powers the coil and the contactor makes...powering the heaters.

 

[LS6 Tommy]

Get the 120/24VAC step down transformer previously listed and pull a new 4 or 5 conductor t-stat wire. You're going to need a "C" wire for just about all of the "good" smart stats unless you get an ecobee.

Tommy

 

[dfiler2]

Looking as the wiring diagram, it shows three wires a red white and black, I only have two wires coming into the box. Where would the third wire coming from the relay connect to?

Has anyone used this relay to accomplish what I am trying to do?

The item you posted will work fine, the red wire is for the load, it's what would be enrgized by the 24v thermostat to power your heaters.