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.
FOR ELECTRIC HEAT APPLICATIONS (AUTO FAN OPERATES WITH W1
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
THERMOSTAT OPERATION.
DENOTES THERMOSTAT TO SUBBASE INTERCONNECTION.
M1016C
HEATING
TRANSFORMER
R
C
W1
W2
B
STAGE 1
HEAT RELAY
STAGE 2
HEAT RELAY
HEATING DAMPER OR
CHANGEOVER RELAY
COOLING
TRANSFORMER
O
Y2
Y1
G
RC
STAGE 1
COOLING RELAY
STAGE 2
COOLING RELAY
COOLING DAMPER OR
CHANGEOVER RELAY
FAN RELAY
HEAT 2
HEAT 1
HIGH
LIMIT
HIGH
LIMIT
L1
(HOT)
L2
HEAT
OFF
COOL
SYSTEM
SWITCH
COOL 1
COOL 2
AUTO
ON
FAN
SWITCH
L1
(HOT)
L2
NON-ELECTRIC
ELECTRIC
FAN
OPERATION
SWITCH
3
2
4
1
3
1
SUBBASE
LOGIC/
CONTROL
CIRCUIT
5
1
2
3
4
5
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD
PROTECTION AS REQUIRED.
FOR GAS OR OIL APPLICATIONS OR ELECTRIC HEAT APPLICATIONS
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.
POWER
SUPPLY
THERMOSTAT
LOGIC CIRCUIT
