Install Instructions

69-0990—14
ST74A1053 DEFROST CONTROLLER
Home and Building Control
Honeywell Limited
155 Gordon Baker Road
North York, Ontario
M2H 2C9
69-0990—1 J.S. Rev. 5-96 Printed in Mexico
Home and Building Control
Honeywell Inc.
1985 Douglas Drive North
Golden Valley, MN 55422
POWER
UP
SETS ALL TIMERS TO ZERO
WALL
THERMOSTAT
CONTACTS
CLOSED
WALL
THERMOSTAT
CONTACTS
OPEN
NO
NO
NO
STARTS OFF-CYCLE TIMER
ACCUMULATES OFF-CYCLE TIME
OFF-CYCLE
COMPLETE
HOLDS
OFF-CYCLE TIMER
HOLDS
ON-CYCLE TIMER
STARTS ON-CYCLE TIMER
COIL
THERMOSTAT
CONTACTS
CLOSED
COIL
THERMOSTAT
CONTACTS
OPEN
WALL
THERMOSTAT
CONTACTS
CLOSED
ACCUMULATES
ON-CYCLE TIME
ON-CYCLE
COMPLETE
PULLS IN
DEFROST
RELAY
DROPS OUT
DEFROST
RELAY
DEFROST
TERMINATED
YES
YES
YES
YES
YES
YES
YES
NO
NO
NO
NO
DEFROST
INITIATED
OFF-CYCLE
HOLD MODE
ON-CYCLE
HOLD MODE
OFF-CYCLE
TIMING MODE
(SELECTABLE
TIME)
ON-CYCLE
TIMING MODE
(10 MIN)
M7827
Fig. 2. Typical operation sequence of ST74A time/temperature defrost control.