I finally filled my system yesterday and I am now ready to start with the control side. As always I need help from you guys. I purchased a 2 stage heat thermostat that I would like to control my propane furnace and secondary circulator pump/furnace fan. I have an adjustable thermostatic switch screwed into the top of my storage tank and a 24volt / 120 volt relay. My furnace has a 24volt transformer inside and I just ran new thermostat wire with 8 circuits inside. I was planning on putting the thermoswitch and relay in series with the first stage heat(W1) so I could control that circuit based on storage temperature. I was going to wire W1 to the Fan on circuit on the furnace control board so W1 would turn on the fan only but it looks like it would back feed the green wire (G) circuit. When I ordered the relay and thermoswitch I didn't completely understand how a thermostat worked. I didn't realize that the thermostat closed the fan contact (G) and the heat(w) contact at the same time for heat the the same for cooling, (G) and (Y). I thought it only closed (W) or (Y) and the furnace controlled the fan on its own. Since this is not the case I have the issue with backfeeding on the (G) fan wire. Hope I didn't confuse everyone.