Pellet Stove & Propane Heater Thermostat Control

Made a single 24vac thermostat control both my pellet stove as primary and my propane heater as secondary heat.

Diodes (x4)

Capacitor (1)

Buck Converter (1)

Relay (1)

PCB Board (1)

Wire to PCB Connectors (9 at least)

Terminal Box (1)

Thermostat (Google Nest)

Pellet Stove (Quadrafire Outfitter II)

Heating System ( Nacian Propane Heater)

5, 3 & 2 wires (thermostat wires, Lengths dependent on your project)

Light Switch

Get the Buck Converter, Diodes, Capacitor, PCB board, Wire terminals, and Relay following the diagrams. The Propane, HVAC, or Boiler uses 24VAC (I will be using Propane), and the Pellet stove uses a connection of a few millivolts to start. Connect three wires to the controller of the Propane, (R, C, W) (Power, Common, Activator), The R and C are connected to the corresponding connections on the thermostat. The Propane's W line is connected to either W2 or * to indicate it as the secondary heating source. Also, connect the C line to one side of the rectifying diodes; these diodes will turn the AC power into an unstabilized DC power. Connect the other rectifying diodes to the W1 thermostat wire. Add a capacitor to stabilize the DC to about 33VDC. I used a LM2596 Buck converter I had, but you can make one using the second diagram above. I used the Buck converter to turn the 33VDC to 12VDC, but convert it to whatever voltage you need for the relay you have. You can use a 24VAC fan relay to bypass all of this, but I didn't have one lying around. Connect the wires to each terminal of the light switch (Manual Bypass) and each of the thermostat connectors on the Pellet stove.

Wire it up. Experience or Confidence in fishing wires will help you here. Propane R -> Thermostat R. Propane C -> Thermostat C & Rectifier side 2. Propane W -> Thermostat W2 or (*). Thermostat W -> Rectifier side 1. Pellet Stove Thermostat connector 1 -> NO on Relay & NO on Switch. Pellet Stove Thermostat connector 2 -> Comm on Relay & Comm on Switch.

Install everything and test all the scenarios. The Thermostat I use does not turn on the Propane unless the temperature difference is >3.5 °F or the time it takes to warm up is more than 15 minutes, I believe. The light switch will allow the pellet stove to run even when the thermostat is not calling for heat, when you want to be warmer, or want it to stay on for longer than the minimum time you have your thermostat set to (mine is 30 minutes).