Control Combinations - Honeywell AUTOMATIC CONTROL Engineering Manual

CONTROL COMBINATIONS

There are many different control combinations for motor
control circuits. Figure 38 illustrates a return fan interlocked
with the supply fan. In this circuit, the supply fan starts when
the START button is pressed energizing starter solenoid 1M.
L1
L2
L3
FUSED
DISCONNECT
F
F
F
TRANSFORMER
F
STOP
PUSH-BUTTON START-STOP
MOTOR CONTROL
FUSED
DISCONNECT
L1
F
L2
F
L3
F
TRANSFORMER
F
SUPPLY FAN
AIRFLOW SWITCH
Fig. 38. Typical Interlock of Supply and Return Fans.
ELECTRIC CONTROL FUNDAMENTALS
The return fan will not start until supply airflow is proven. A
relay can be added to interlock to the temperature control
system. An auxiliary contact on the supply fan starter, when
available, can be used for this same function.
STARTER
OL
1M
T1
OL
1M
T2
OL
1M
T3
START
1M
FS
OL
1M
RELAY
INTERLOCK TO ENERGIZE
TEMPERATURE CONTROLS
STARTER
OL
2M
T1
OL
2M
T2
OL
2M
T3
HAND
OL
OFF
AUTO
HAND/OFF/AUTO SWITCH
MOTOR CONTROL
117 ENGINEERING MANUAL OF AUTOMATION CONTROL
SUPPLY
FAN
MOTOR
RETURN
FAN
MOTOR
2M
C2541-1