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4
2
HVAC
BEFORE
Thermostat
1
Home
Installation Guide
customer.honeywell.com
C WIRE ADAPTER
Online Guides and Support
OFF
Turn the power off at the
breaker box or control
switch for your HVAC*
system.
Remove your old thermostat
from the wall plate.
*Heating, ventilation, and air conditioning
Overview
This product provides a C wire (common wire) to power a
thermostat. Only install if you do not have a C wire available to
connect to your thermostat.
5
Open HVAC system’s cover
to reveal the control board.
6
Take a picture of the wires
on the control board.
Ensure the terminal labels
and wires are in the image.
You may need to reference
the picture later.
*
O or B terminal may also be used.
CONTINUE
7
Use the provided stickers to
label the following
connected wires:
8
Disconnect ONLY the wires
that you just labelled:
AFTER
HVAC
C Wire
Adapter
Thermostat
C
OFF
ON
Breaker box Switch
Do not remove any wires
at this time!
ZONING CONTROL PANEL CHECK
For zoned systems, install the C Wire Adapter
between the thermostat and the zoning panel, NOT
between the zoning panel and HVAC equipment.
3
Take a picture of the wiring.
Ensure the terminal labels
and wires are in the image.
You may need to reference
the picture later.
Confirm that you do not have
a wire in the C terminal. If
you have a wire in the
C terminal, then you do not
need this product.
Look for an unused wire. If
you have an unused wire,
then you do not need this
product. Connect one end of
that wire to C terminal at the
HVAC and the other to C
terminal at new thermostat.
*
The C wire (common) might be
labeled as B rather than C on certain
thermostats.
Go to your HVAC system. It may be located in your
attic, crawl space or basement.
C terminal
*
EXAMPLE
*
R
C
W or W1
Y or Y1
R or Rc
G
G
Y
W
W2
**
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Terminal Labels
Wires
G
C
R
W
W2
Y
G
R or Rc
•
•
*
**
EXAMPLE
*
C
Y or Y1
R or Rc
G
W2
R
G
W
Y
W or W1
W or W1
Y or Y1
•
•
*
Not all systems will have a
W or W1-wire. On a heat pump
application, the wire coming from
O/B on the old thermostat would
match to either O or B at equipment
rather than W.
**
If multiple wires are connected
to a terminal, only label the the wire
running to your thermostat.
G
R or Rc
•
•
W or W1
Y or Y1
•
•
*
Do NOT disconnect wires that you
did not label.
**
If multiple wires are connected
to a terminal, only remove the the
wire running to your thermostat.
***
On a heat pump application,
the wire coming from O/B on the old
thermostat would match to either O
or B at equipment rather than W.
***
33-00342-06