I have a rental house where the renters tore off old t-stat, purchased a Hunter heat only T-stat to install. The problem is, it only has two wires for T-stat. One is red which has 24V and one blue. Question is, there are 3 other wires that has been snip off, to check for volts on red wire I had to go to snip white to read volts on red, there are no volts on blue, which I think is the heat or fan, not sure. Can a gas furnace and T-stat run on two wires only? or do I need another wire to complete circuit. It's a Hunter model #40020 T-stat. Thanks for any HELP....Sam
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not all digital thermostats are compatible with the manufacturers circuit control boards in the furnace. Hunter has had this problem several years ago. Other than that you may have miss wired the unit. usually the furnace is used as backup heat (during defrost) or emergency heat if your heat pump konks out. Are you switching to emergency heat for a furnace call?
The Red and White wires coming from the furnace are the only ones that call for heat. the Green wire turns on the fan continuously, the yellow is for AC. If you have another wire color, it may be a Common wire and should not be used if your t-Stat has batteries. If no batteries, it goes to the C screw.
Here is some basic info to help you. On the thermostat the letters mean... G is for your blower fan, and is usually green, Rc and Rh are power for the heating and cooling circuit (24v) and are usually red; Y (or in this case Y/O) is power to the cooling contactor (outside the house) and is usually yellow, and W (or in this case W/B) is the common wire, and is usually white. It kind of sounds like the people who installed the old thermostat followed these guidelines, so your best chance is to go to the heating unit and seeing where the wires connect to. Hope this helps
Depending on where the wires were connected on the old thermostat, would be the best place to start, but if that is not an option you could try to trace the wires back to your furnace and see where they connect to. It appears you have either an oil fired furnace, or a single stage heat pump. If you need more assistance please just provide type of heat used. Hope this helps
The wire colours mean nothing. If your old one didn't have letters or you already disconnected it, you will have to go to the furnace. Under one of the panels there will be a control board to which the thermostat wires connect and this might have the letters printed on it. Trace them back and connect them appropriately.
If you have a furnace that is like mine (a single-stage natural gas one), chances are that R is +24V, C is common, W is heat call, and G is the blower. Y is generally cooling. The furnace could be turned on by connecting R, W, and G together, I suppose, if the above doesn't work... but it won't shut off automatically.
Go to the hunter web site. They will have the proper wiring diagrams on the site. If you cannot do that pick up a basic wiring book at your local electric parts supplier. the place you got the thermostat would be a good start. I do know that menards has some books in the electric area that would be a great help to you. You also will need to be sure that the thermostat is able to handle both air and heat. many only do heat. If this does not help let me know and I will try and get more information to you
On the back of most t-stats is a dip switch that is marked E or G that is changes the stat to work with either Electric heat or Gas heat just make sure you set it for the appropriate type of heat source your house has. Usually when we speak of Furnaces we are talking about gas, if that is so just change the switch to G. Good luck
Here is a link that will have wiring diagram it is for a similar model hunter. Also check your dip switch on the back of the stat to ensure it is set for gas (HG) or electric heat (HE) depending on your type of unit. Good Luck. Rule of thumb for most four wire systems is RED (power to stat) Yellow (Cooling) Green (Fan) White (heat)