Matching wires to replacement thermostat?

Question

I'm replacing a mercury thermostat with a digital one, and my wire options are not matching up to my new one.

The wires that were on the old thermostat are:
G (green wire), R (red wire), Y2 (blue wire), W1 (white wire), W2 (red wire), (Y1 had no wire)

On the new one the options are:
G, RH, RC, W, Y, B, O, C

I've looked around and haven't been able to find directions with W1 & W2 wirings - any help matching these up would be appreciated. Thanks!

Answer 1

Keep in mind that more than one disconnect may be required to remove all power from a piece of equipment. If your unit has service switches find them first. Or turn off the circuit breakers or pull the fuses, then check with a meter or test lamp to be sure the circuit is dead.
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With all that said lets get to the terminal designations and colors. 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 to activate electric heat and turn on the AUX. heat lamp).
(G), Green, furnace blower fan. (needed for air conditioning, heat pumps and some electric furnaces). NOTE: on most thermostats the "G" and "Y" are connected together at all times when the fan switch is in the "Auto" mode, If you sully R to G then you will most likely energize the outdoor unit contactor!
(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 (energize to heat) above. York and Trane like to use (B) as common.
(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. Also used as indicator lamp or misc. contacts on other systems.

Answer 2

American Standard Thermostat Wiring

Answer 3

This Site Might Help You.

RE:
Matching wires to replacement thermostat?
I'm replacing a mercury thermostat with a digital one, and my wire options are not matching up to my new one.

The wires that were on the old thermostat are:
G (green wire), R (red wire), Y2 (blue wire), W1 (white wire), W2 (red wire), (Y1 had no wire)

On the new one the options are:
G,...

Answer 4

While the first long answer is nice, I think you have a problem because the digital needs a complete circuit and while you have the red, you don't have the black. You may have to pull another wire or another cable (6 wire) to get it.

Answer 5

rh,rc power ,connect together for one transformer..g-fan,,y first stage cooling..w-first stage heat..w2 second stage heat only used in some elect furnaces..b, reversing valve powered in heating mode..o.. reversing valve powered in cooling mode.t stat could be used for heat pump with no back up heat strips.no idea y red on w2. see if equipment has wiring diagram on it .dont know y y2 had wire usually used for 2 compressor large systems. y2 turns onsecond compressor 2 degrees later than y1