Honeywell CHRONOTHERM T8621A User Manual page 12

T8621A,C,D
INSTALLATION
Fig. 11—T8621D 2-stage heat/2-stage cool thermostat with HEAT-OFF-COOL system and AUTO-ON fan
switching; auto fan on heat and cool; convertible to auto fan on cool only.
THERMOSTAT
LOGIC CIRCUIT
1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD
PROTECTION AS REQUIRED.
FOR GAS OR OIL APPLICATIONS OR ELECTRIC HEAT APPLICATIONS
2
WHERE THE FAN OPERATION IS CONTROLLED INDEPENDENTLY OF
THE THERMOSTAT (AUTO FAN OPERATES WITH Y1 ONLY), TWO
TRANSFORMERS MAY BE USED. SET SWITCH TO NON-ELECTRIC
POSITION.
5
POWER
SUPPLY
NON-ELECTRIC
HEAT
OFF
COOL
SUBBASE
LOGIC/
CONTROL
CIRCUIT
FOR ELECTRIC HEAT APPLICATIONS (AUTO FAN OPERATES WITH W1
3
AND Y1). USE ONLY ONE TRANSFORMER; JUMPER R AND RC. SET
SWITCH TO ELECTRIC POSITION.
NOMINAL 24 VAC POWER MUST BE PRESENT BETWEEN R AND C FOR
4
THERMOSTAT OPERATION.
5
12
HIGH
LIMIT
HIGH
FAN
LIMIT
OPERATION
SWITCH
3
ELECTRIC
2
SYSTEM
HEAT 2
SWITCH
COOL 1
COOL 2
FAN
SWITCH
AUTO
ON
DENOTES THERMOSTAT TO SUBBASE INTERCONNECTION.
L1
(HOT)
L2
1
HEATING
TRANSFORMER
R
4
C
W1
STAGE 1
HEAT RELAY
HEAT 1
W2
STAGE 2
HEAT RELAY
B
HEATING DAMPER OR
CHANGEOVER RELAY
COOLING DAMPER OR
CHANGEOVER RELAY
O
STAGE 2
COOLING RELAY
Y2
STAGE 1
COOLING RELAY
Y1
FAN RELAY
G
3
RC
COOLING
TRANSFORMER
1
L1
L2
(HOT)
M1016C