Learn
what the different thermostat wiring colors mean
and
how to service and repair wiring.
On
your gas furnace, oil burner, heat-pump or air-conditioner.
I
get many inquiries about what the different wire colors mean and what they
do and how troubleshoot problems where nothing happens or some parts will
work and others will not.
First I am not into disclaimers because I assume you are smart enough to
know not to mess with stuff that you are not familiar with or competent
at doing. However I must make an exception here.
Control wiring on hvac equipment while harmless looking and 24 volts ac
wont shock you (it will bite) can cause very bad things to happen if connected
incorrectly. You could destroy your equipment at best or burn down your
home or business at worst. Among the control wiring can be high voltages
from 120/240 volts in a residential furnace to 480 or 600 volts in commercial
equipment that can kill you instantly or burn you in a flash.
So if you are unsure of what you are doing or your abilities please leave
it to someone who understands control wiring and electricity.
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.
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).
(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.
(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. See link above.
If you need to see the 24 volt control signal this lamp
is an easy way do it. This 1819 lamp and sockets are available from Radio
Shack. This clamp on ac ammeter is valuable for measuring ac current. The
built in "Non Contact Volts" feature is worth the price. About $80 at Lowes
or The Home Depot.
Link
to White Rodgers that has a good look up table of different manufacturers.
You will notice that Lennox's color codes are TOTALLY WEIRD to put it gently.
Link
to White Rodgers Clip art that has pictures of their different control
products.
Written By: Scott Meenen
N3SJH of: G&S MECHANICAL SERVICES. Specializing in Mechanical, Controls
and Electrical Modifications Of
Heating, air conditioning, Refrigeration,
Cold storage,
Ice Production and Food preservation.
Anything having to do with Heat
and Energy.
Serving MD, DC, and Northern
VA Contact us by pager: 1-877-467-2914
We service and repair the following brands:
American Standard, Amana, Arco, Arco-Air, Bryant, Carrier,
Coleman Evcon, Comfortmaker, Day/Night/Payne, Dunham-Bush, Fedders, Fredrich,
Goodman, General Electric, Hotpoint, Heil, Intertherm, Janitrol, Kenmore,
Lennox (Armstrong, Johnson Air-Ease), Miller, Modine, Nordyne, Rheem/Ruud,
Sears, Stewart Warner, Trane, Williams, White-Westinghouse, Whirlpool,
Weil Mclain, York, (Frasier Johnson/Borg Warner) and others.
