Mounting The Thermostat; Typical Hookup For Mabs Ii And Mabs Ii-L - Honeywell TROL-A-TEMP Q674B Installation Instructions Manual

MOUNTING THE THERMOSTAT

1. Remove the thermostat cover by pulling the bottom
edge of the cover outward away from the base until it snaps
free from the cover clip.
NOTE: The cover is hinged at the top and is removed by
pulling out at the bottom.
2. Carefully remove and discard the polystyrene packing
insert that protects the mercury switches during shipment.
3. Turn over the thermostat base and note the spring
fingers that engage the subbase contacts. Make sure the
Fig. 7—Typical hookup for MABS II and MABS II-L Control Panels with T874A Thermostat/Q674B,D
Subbases in single-stage heating-cooling zone system. MABS II Control Panel shown; MABS II-L Control
Panel hookup is the same.
MABS II
CONTROL PANEL
EM. HEAT
RELAY
Y
2
Y
1
O
G
2
TO SINGLE-
G
STAGE
1
HEATING/
R
COOLING
C
EQUIPMENT
R
H
B
W
2
W
1
E
1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
2 JUMPER RC, RH TOGETHER AND WIRE AS SINGLE R TERMINAL.
3
ZONE 1 O AND B TERMINALS MUST BE CONNECTED FOR PROPER SYSTEM OPERATION.
4
DO NOT CONNECT W2 AND Y2 TERMINALS TO CONTROL PANEL.
T874A THERMOSTAT/Q674B SUBBASE
3
O G B Y1 RC
SECOND
FAN HEAT COOL
STAGE
RELAY RELAY RELAY
RELAY
CHANGEOVER
CONTROL
O
COOL
1
G
FAN
ADD-A-
1
ZONE
A HEAT B
4 1
A E
EM. HEAT
3 1
A 24 V, 40 VA 2
2
A 1
TRANSFORMER
1
1
L2
L1
(HOT)
spring fingers are not bent flat, preventing proper electri-
cal contact with the subbase.
4. Set the heat anticipator indicator(s) to 0.1A for
proper system operation (Fig. 11).
5. Note the two tabs on the top inside edge of the
thermostat base. The tabs fit into the corresponding slots
on the top of the subbase. Mount the thermostat on the
subbase. See Fig. 12.
6. Align the two captive mounting screws in the thermo-
stat base with the posts on the subbase (Fig. 12). Tighten
both screws. Do not overtighten the screws or damage to
the subbase posts can result.
T874A THERMOSTAT/
Q674D SUBBASE
2
4
Y1 Y2 RC RH W2 W1
RH W1 W2 Y2
CAC ZONE 1
RELAY RELAY
ZONE 1
T
8
T
7
T
6
T
5
T
4
M
6
M
4
M
1
4 5 6 Z
DAMPER
ACTUATOR
1 2 3 X
4
T874A THERMOSTAT/
Q674D SUBBASE
2
4
Y1
ZONE 2 ZONE 3
RELAY RELAY
ZONE 2 ZONE 3
T T
8 8
T T
7 7
T T
6 6
T T
5 5
T T
4 4
M M
6 6
M M
4 4
M M
1 1
4 5 6 Z
DAMPER
ACTUATOR
3
1 2 X
2
4
Y2 RC RH W2 W1
4 5 6 Z
DAMPER
ACTUATOR
1 2 3 X
M1634