As cores padrão podem ser encontradas em vários sites na Web . Aqui está a parte importante desse site (eu fiz o melhor que pude para limpar a formatação, pois acho que não temos suporte para tabelas aqui):
Older systems and base signals on newer ones Code Color Signal Description C Black 24 Vac Common From one side of the 24Vac transformer (Think of this as 24Vac neutral R/V Red 24 Vac Power to be switched From other side of the 24Vac transformer (Think of this as 24Vac L1) Rh/4 Red 24 Vac Heat call switch power Same as R, but dedicated to the Heat call switch Rc Red 24 Vac Cooling call switch power Same as R, but dedicated to the cooling call switch G Green Fan Fan switch on thermostat - is connected to R when Fan /Auto switch is in the fan position W White Heating call Is connected to R or Rh when themostat calls for heat. (Might be jumpered to Y on a heat pump. On others might be second stage heating Y Yellow Cooling call Is connected to R or Rc when themostat calls for cooling. Also Cooling or 1st stage heating on a heat pump. Most often connected to G when Fan switch is set to auto. New signals - for heat pumps and staged systems Code Color Signal Description Y2 Blue/Or 2nd Cooling W2 Varies 2nd Heating First stage Auxiliary heating on a heat Pump E Varies Emg heat Disable the heat pump and turn on first stage Aux heating O Varies Reversing valve Energize to cool (Changes from heat to cool on heat pumps) B Varies Sometimes common side of transformer. Needed on some electronic thermostats or if you have indicator lamps OR Reversing valve (energize to heat) above. York and Trane sometimes use (B) as common. Might be heating changeover or on older stuff common of transformer. X Varies Might be common but sometimes emergency heat relay X2 Varies Second stage heating or indicator lights on some thermostats Might be emergency heat relay T Varies Outdoor anticipator reset Used on GE/Trane/American Standard and some Carrier Products. L Varies Service Light