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Wiring Examples and Instructions How-To-Wire-It.com Basic or Common Connection Points TerminalColourSignal-TypeDescription
24 Vac Common
Common side of 24 Vac Transformer See Diagram below
R or V
24 Vac Transformer Power
Power side of 24 Vac Transformer See diagram below
RH or 4
24 Vac for heat
24 Vac power before heat switch see diagram below
24 Vac for cool
24 Vac power before cool switch see diagram below
switched power (cooling)
Signal to turn on cooling system see diagram below
Switched power (heating)
Signal to turn on heating system see diagram below
Switched power for fan
Signal to turn on fan (forced air) see diagram below
Heat Pumps/Multi-Stage Units TerminalColourSignal-typeDescription
Switched power (2nd stage cooling)
2nd stage cooling signal to compressor
Switched power (2nd stage heating)
2nd stage heating/ sometimes used as emergency heat
Emergency heat enable
Dedicated emergency heat
Reversing dynamics of the heat pump
The best way is to write down how the old t-stat was wired. If that's not available, the only way to determine for certain where each wire goes, is to check what the installer did at the terminals in your home comfort system. Please note the there is high voltage electric in each piece of equipment so if you decide to open up panels, there is always the risk of damaging the equipment or worse, injury or death if you are not a qualified service technician. However, typical color assignments are as follows:
R= (24v from heating appliance) Red
RC= (24v from cooling appliance) Red
These two are only separated when you have two different appliances providing seasonal comfort, like a boiler and an air handler. If you have a warm air furnace with an air conditioner or a heat pump attached then R+RC will have a jumper across them and only one RED wire will be landed there
W= (heat) White
Y= (cool) Yellow
G= (fan) Green
Those colors are pretty standard
The rest of the colors depend on availability in the jacket and are really up to the installer. You mentioned 7 wires but 8 conductors is more likely so I'm assuming the remaining colors are black, brown, blue, and orange.
I always use the following:
C= (common) Black
O/B= (reversing valve for a heat pump) Orange if the valve is energized for heat and Blue if the valve is energized for a/c.
Aux/E= (auxiliary or electric heat) Brown
L= I believe this is a diagnostic terminal for some systems with feedback data and is not used frequently.
After wiring there is some programing to do to set up your new thermostat to your type of system.
These are color codes wires for terminals that control fan relay,start,stop, temp-up/down ect. Also you can trace out those wires, Where they are going and what terminal on the wiring schematic they control.
On the Protectorelay Oil Burner Control R8184G4009, you connect the two thermostat wires @ "T" and the other "T". On the ACE Smart Temp Universal programable therostat, connect one wire to "Rh" and the other wire to " "W". Be careful if you are using this thermostat for A/C. In that case, make sure there is no jumper between "Rh" to "Rc".
yea you should be able to just when you remove the old one mark witch wire went to witch connection by marking it some how i personaly take one wire at a time wrap it with a small piece of white tape and write the letters on the piece of tape then when i replace with the new one i cant mess it up also look for any of the wire connections to see if any have to be or have been jumped out