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5 69-0580—2
Fig. 8—Typical hookup for MABS II and MABS II-L Control Panels with T874D Thermostat/Q674B,D
Subbases in multistage heating-cooling zone system. MABS II Control Panel shown; MABS II-L Control
Panel hookup is the same.
M1393A
Y2
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
JUMPER RC, RH TOGETHER AND WIRE AS SINGLE R TERMINAL.
ZONE 1 O AND B TERMINALS MUST BE CONNECTED FOR PROPER SYSTEM OPERATION.
IF SINGLE-STAGE COOLING, DO NOT CONNECT Y2; IF SINGLE-STAGE HEATING, DO NOT CONNECT W2.
Y1
O
G2
G1
RC
RH
B
W2
W1
E
ADD-A-ZONE
EM. HEAT
RELAY
SECOND
STAGE
RELAY
FAN
RELAY
HEAT
RELAY
COOL
RELAY
CAC
RELAY
ZONE 1
RELAY
ZONE 2
RELAY
ZONE 3
RELAY
A4
A3
A2
A1
T8
T7
T6
T5
T4
M6
M4
M1
ZONE 3
T8
T7
T6
T5
T4
M6
M4
M1
ZONE 2
T8
T7
T6
T5
T4
M6
M4
M1
ZONE 1
O1
G1
B1
E1
2
1
CHANGEOVER
CONTROL
COOL
FAN
HEAT
EM. HEAT
24 V, 40 VA
TRANSFORMER
456Z
DAMPER
ACTUATOR
1
23X
456Z
DAMPER
ACTUATOR
123X
456Z
DAMPER
ACTUATOR
123X
L1
(HOT)
L2
1
MABS II
CONTROL PANEL
RC
Y2 W2 Y1
RH W1
2
2
T874D THERMOSTAT/
Q674D SUBBASE
RC
Y2 W2 Y1
RH W1
2
T874D THERMOSTAT/
Q674D SUBBASE
BY2W2Y1RH W1
3
T874D THERMOSTAT/Q674B SUBBASE
RC
OG
TO SINGLE-
STAGE
HEATING/
COOLING
EQUIPMENT
2
3
4
444