Rank: Advanced Member
Groups: Senior Expert
Joined: 10/9/2008(UTC)
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These designations are for 24 volt control wiring used in most residential and light commercial equipment, line voltage stuff can be different. Never assume that a wire color is correct for the function it should perform; check it out first The same goes for high voltage control wiring and motor terminals .
- {Terminal name}, {color}, {function}
- (R), Red, hot side of transformer.
- (C) Common side of transformer (See B)
- (Y), Yellow, Compressor activity (cooling or cooling and heating on a heat pump).
- (W), White, Heat (gas burner, oil burner , electric heat, (auxiliary heat on a heat pump including defrost output from the outdoor unit)
- (G), Green, furnace blower fan. (needed for air conditioning, heat pumps and some electric furnaces).
- (O), Orange , Energize to cool (used for reversing valve on heat pumps)
- (B), Blue or Orange, Energize to heat (used on some systems, Rheem/Ruud is notorious for this).
- (B) or (X), Blue, brown or Black, common side of transformer. Needed on some electronic thermostats or if you have indicator lamps. Do not confuse with (B) Reversing valve above.
- (E), blue, pink, gray or tan, emergency heat relay on a heat pump. Active all the time when selected, usually not used.
- (T), Tan or Gray, outdoor anticipator reset.
Used on GE/Trane/American Standard and some Carrier Products.
- (W2), Pink or other color, second stage of heat (may be same as (W) on heat pump or fossil fuel system). Note: some thermostats require a jumper from W1 to Y for heat pump operation.
- (Y2), Blue or Pink, second compressor stage.
- (L), Blue, brown, tan or gray service indicator lamp.
- Numbers, see manufacture's diagrams but can be stages of electric heat especially on York/Borg Warner/Coleman-Evcon, Frasier Johnson/ Air-pro.
- (X2), Second stage of Electric Heat on GE/Trane/American Standard
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