7 68-0173—3
IMPORTANT
Be sure to connect the C terminal to transformer
common.
IN NEW INSTALLATION:
1. Locate the terminal strip(s) on the HVAC equipment.
2. Refer to Fig. 11 through 20 for wiring diagrams for spe-
cific equipment applications.
3. Connect all loads to the appropriate W8900A-C wiring
terminal using 18-gauge, color-coded thermostat wire;
see Fig. 10.
4. Use a small screwdriver to connect the loads. Do not
overtighten; device can be damaged.
Fig. 10. Proper wiring technique for
W8900A-C and PC8900A.
Table 2. Conventional Applications (W8900A or C).
aPC8900A/W8900A,C are not compatible with evaporative cooling equipment.
bIn single stage heat pump applications, jumper W1 and Y1 and connect to Y. Configure the system for Auto Fan in Heat.
cDual fuel fan feature configured in installer setup.
dFilter light feature available in PC8900A fan accumulation timer feature.
FOR WRAPAROUND
CONNECTION—
STRIP 7/16 IN. (11 MM)
FOR STRAIGHT
CONNECTION—
STRIP 5/16 IN. (8 MM)
M4464
W8900
W8900A, C Terminal Designation Function Existing Thermostat Designation
1 PC8900A Control Panel —
2 PC8900A Control Panel —
3 PC8900A Control Panel —
4 PC8900A Control Panel —
B Heating, changeove r valve B
C 24 Vac Transformer Common C
CO2Carbon Dioxide Monitor —
VNT VNT Relay —
G Fan Relay G
GND Ground —
HUM Humidity Relay —
OUT Outdoor Air Temperature Sensor —
O Cooling, Changeover Valve O
R 24 Vac System Transformer R
RC 24 Vac Cooling Transformer RC
RH 24 Vac Heating Transformer RH
S, S1 Remote Air Temperature Sensor —
See note a Fan Control—Evaporative Cooling F
See note b Heat Pump Contactor P
T, T1 Discharge Air Temperature Sensor —
W1 Heating Relay W
W1 Stage 1 Heat Relay W1
W2 Stage 2 Heat Relay W2
Y1 Cooling Relay Y
Y1 Stage 1 Cool Relay Y1
Y2 Stage 2 Cool Relay Y2
See note c Fan Control (Honeywell dual fuel thermostat [T834]) 1
See note c Fan Control (Honeywell dual fuel thermostat [T834]) 2
See note d Filter Light X
none Remote Timer Contacts Z