Please refer to the owner's manual of your old thermostat … Just moved, and new thermostat system has 7 wires: W2 - White Wire. Y1 - Yellow wire. O = Orange wire W2 = White wire E = Black wire R = Red wire Y1 = Yellow wire. Am I compatible with ecobee? R - Red wire. C - Blue Wire. So, EXPAND, if you must, and use one of these free wires as the C wire. OB - X. Rc - X. W1 - White wire. I would say there “appears” to be quite a bit of confusion surrounding how you work out if a thermostat is compatible with your current HVAC system. W2 - … IF YOUR SYSTEM INCLUDES A GAS FURNACE, THE WIRING WILL BE SEPARATE FROM THE 3 OR 7 CONDUCTOR CABLE. The Venstar Add-a-Wire is an inexpensive adapter that turns a four-wire system into a five-wire system.. One more alternative: get a smart thermostat that’s designed to work with systems lacking a C-wire.Check out the ecobee line of thermostats – all ecobees ship with an adapter for C-wireless systems. O - Orange wire. The device is relatively inexpensive, and it’s easy to install. If you have heat and AC, you’ll need 18/5. R - Red Wire. Hi, A little confused. Is My Thermostat Compatible with My HVAC System I suspect a lot of you will be interested in reading this page. G - Green wire. (Heat) • Connect the orange wire from the SZLCD thermostat COMMS terminal to the orange wire that runs from the SZLCD control relay box. Most brands use the O pump, as this connects to a valve used to trigger cooling. ** The common wire could be labeled "C" on your old thermostat, or it could be labeled "B" or "X". my new thermostat Honeywell rth3100c has e aux y g o l r b and c how do I wire … Dark blue wires connect to the B terminal, found in heat pumps, although this may be an orange wire connecting to the O terminal in some makes. (Fan) Y terminal will use the yellow wire. What is the proper wiring for this. Venstar makes their own version of a power extender kit. The thermostat uses the low voltage wires to send an electrical signal to the furnace or boiler, which is a way of providing commands to turn the heat or air conditioning on and off. See (B and O) above: R : RH and RC single power for HEAT and COOL. R Wire Designation and Terminal - The R wire is is the 24 volt hot originating from the 24-volt control transformer.That is the power to energize the control relays and contactors in your system. O/B - Orange Wire. The most common is 18/5 (5 strand, 18 gauge). In most thermostat wiring hookups the red wire is the power source for the system. There is an orange wire in the old thermostat, but not in the new one. Types of Thermostat Wire. tags may be wrong. However, the fact is there IS a lot of confusion. Installing Common Wire Maker Kit If there is not an extra unused wire running from the thermostat to the furnace, and using the g-wire as a common wire is not an option, in most cases, installing a Common Wire Maker Kit is the best solution. * If the old thermostat has separate RC and RH wires coming out of the wall, clip the RC/RH jumper on the back of the thermostat above the battery compartment. Again, the W2/E etc. Thermostat Wiring and Wire Color Chart. There are 4 wires coming out of the wall – Green, White, Orange and Blue. For the old thermostat, the blue wire went to “RH” and there was a red jumper from RH to RC. THEREFORE … Choose an 18/5 C wire for the installation, irrespective of whether you have a HVAC system or just a heating unit. If you really want to skip the C wire installation, a smart thermostat without the common wire (ecobee3 is a good example) is your best bet. Each wire in the thermostat cable serves a different purpose. However, the wiring is a bit different. 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