PC8900A
Control Panel
®
TRADELINE
INSTALLATION INSTRUCTIONS
APPLICATION
SPECIFICATIONS
The PC8900 Control Panel provides 24 Vac energy saving
control for a heating and cooling system, while providing
reliable, precise temperature control, ventilation control,
humidity control, programmable fan control and air filter/
cleaner status information.
Temperature Setting Range:
45°F to 88°F (7°C to 31°C).
Humidity Setting Range:
10% to 80%.
The PC8900 must be used with a W8900 Remote Module.
Operating Relative Humidity:
5% to 90%, noncondensing.
The PC8900 includes a SYSTEM light, which is lit when
the heating or cooling system is running, and a CHECK
light, which lights as a prompt to check messages on the
CHECK list.
Finish:
White
Dimensions in in. (mm):
These models will replace most heating/cooling system
thermostats. Check Table 1 to make sure the thermostat is
compatible with the intended system.
6-3/8 (163) width x 4 (102) height x 1-5/8 (41) depth.
Accessories:
205224A Wall Cover Plate to cover marks left on the
wall by the old thermostat.
C7189A Wall Mount Indoor Air Temperature Sensor.
C7089A Outdoor Sensor.
Table 1. Compatibility Chart.
Compatible
System Type
with PC8900
Gas—Standing Pilot
Gas—Electronic Ignition
Gas-Fired Boilers
Gas—Millivolt
Yes
RECYCLING NOTICE
M3375
Yes
If this control is replacing a control that contains
mercury in a sealed tube, do not place your old
control in the trash.
Yes
See Note a
Yes
Contact your local waste management authority for
instructions regarding recycling and the proper
disposal of any control containing mercury in a
sealed tube.
Oil-Fired Boilers
Oil-Fired Furnace
Electric Furnace
Yes
Yes
Electric Air Conditioning
Yes
If you have any questions, call Honeywell Inc. at
1-800-468-1502, Monday through Friday, 7 AM to
5:30 PM, Central time.
Baseboard Electric
(120/240 Line Volt)
See Note b
Heat Pumps/Multistage Equipment
Yes
a
Use R8222N Relay if installing as part of millivolt
system (see W8900 Remote Module Instructions form
69-0894).
b
Use R8222D Relay if installing as part of a 120/240 Vac
baseboard electric system (see W8900 Remote Module
Instructions, form 69-0894).
U.S. Registered Trademark
Copyright © 1995 Honeywell Inc. •
•
All Rights Reserved
69-0893-1
PC8900A CONTROL PANEL
NOTE: If the old thermostat has left marks on the wall
that are not covered by the PC8900, order part
no. 205224A Wall Cover Plate to mount between
the wall and the PC8900.
CAUTION
Disconnect power supply before connecting wiring
to prevent electrical shock or equipment damage.
All wiring must comply with applicable electrical codes,
ordinances, and regulations.
WALL
1. Loosen the terminal screws and insert one wire
beneath each numbered terminal (1,2,3,4). Note the
color of wire that is attached to each terminal
number to later match the colors with the terminals
on the W8900 Remote Module. See Fig. 3 and 4 for
technique and wiring diagram. Four wires are
required at the thermostat to assure operation.
2. Securely tighten screw terminals.
WIRES
THROUGH WALL
WALL
ANCHORS
(3)
1
3. Push excess wire back into the hole. Plug the hole
with nonhardening caulk, putty or insulation to
prevent drafts from affecting PC8900 operation.
IMPORTANT
In replacement applications, more than four wires
may be available. In these applications, tape off
the unused wires at the PC8900 location and
W8900 location.
MOUNTING
HOLES (4)
1
MOUNTING
SCREWS (3)
1
USE THREE MOUNTING HOLES THAT BEST
FIT APPLICATION
M4466
Fig. 2. Mounting PC8900 Wiring Plate.
WIRING
CAUTION
Keep wiring at least one foot away from large
inductive loads such as motors, line starters,
lightning ballasts and large power distribution
panels. Failure to follow these wiring practices can
introduce electrical interference (noise), which can
cause erratic system operation. Use shielded cable
to reduce interference when rerouting is not
possible. Ground the shielded cable to the GND
terminal on the W8900.
FOR STRAIGHT
INSERTION STRIP
5/16 in. (8mm).
FOR WRAPAROUND
INSERTION STRIP
7/16 in. (11mm).
M7518
IMPORTANT
Fig. 3. Proper Wiring Technique.
Erratic temperature readings can occur as a
result of any of the wiring practices described
below. These practices must be avoided to
assure proper operation. Use shielded cable to
reduce interference when rerouting of wiring is
not possible.
a. Do not route thermostat wiring with building
power wiring, next to control contactors or
near light dimming circuits, electric motors or
welding equipment.
b. Avoid poor wiring connections.
c. Avoid intermittent or missing building earth
ground.
3
69-0893—1
PC8900A CONTROL PANEL
W8900
Mounting the PC8900 on the Wiring Plate
To mount the PC8900 on the wiring plate, engage the tabs
on the wiring plate with the back of the PC8900 and then
press the PC8900 to latch.
OPERATION
1
2
The PC8900 is not a typical thermostat. It senses tempera-
ture and humidity conditions in the living space and
transfers the information to the W8900 Remote Module.
The W8900 activates the proper equipment based on
room conditions and programmed settings.
1
3
2
4
GND
CHECKOUT
WARNING
Do not jumper any PC8900 wires in an attempt to
activate equipment.
See checkout procedures included with W8900 Remote
Module.
To test for 24V at the PC8900, measure between termi-
nals 1 and 4.
3
CALIBRATION
The PC8900 is calibrated at the factory and cannot be
recalibrated in the field.
PROGRAMMING
2
1
See Owner’s Guide, form 69-0891, for programming
instructions.
1
2
3
4
1
2
POWER OUTAGES
The PC8900 requires no backup batteries. In event of
power outage, the time of day and day are retained for
approximately six hours. Program times, temperatures,
and settings will be held indefinitely.
NOTE WHICH COLOR WIRE IS ATTACHED TO EACH TERMINAL.
FOUR WIRES ARE REQUIRED FOR PROPER OPERATION.
IF FEWER THAN FOUR ARE AVAILABLE, ADDITIONAL WIRES
MUST BE RUN TO PC8900 LOCATION. IF MORE THAN FOUR
ARE AVAILABLE, TAPE OFF UNUSED WIRES.
3
IF SHIELDED CABLE IS REQUIRED, GROUND TO GND
TERMINAL ON W8900.
M7519
NOTE: When power is restored, the time and day
information must be re-entered.
Fig. 4. Wiring Diagram for PC8900 to
the W8900 Remote Module.
W8900 REMOTE MODULE
INSTALLATION
To install the W8900 Remote Module, refer to form
69-0894 for instructions packed with the remote module.
Home and Building Control
Honeywell Inc.
1985 Douglas Drive North
Golden Valley, MN 55422
Home and Building Control
Honeywell Limited-Honeywell Limitée
35 Dynamic Drive
Scarborough, Ontario
M1V 4Z9
69-0893—1 J.H. Rev. 5-95
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