Operating Theory
133
Defrost
The evaporator coil sensor temperature must be below 18 C (65 F) to initiate a Demand Defrost or
Manual Defrost. The evaporator coil sensor temperature must be below 4 C (39 F) to initiate a Timed
Defrost.
•
Demand Defrost function initiates Defrost immediately when:
•
Temperature difference between the return air sensor and defrost (evaporator coil) sensor is too
large.
•
Temperature difference between the supply sensors and return air sensor is too large.
•
Manual Defrost may be initiated immediately by pressing the
D
EFROST
key or by REFCON Remote
Monitoring Modem (RMM).
•
A Timed Defrost always starts at 1 minute past the hour immediately following a defrost timer request
for defrost. For example, if the defrost timer requests a defrost cycle at 7:35, the defrost cycle will
start at 8:01. The datalogger will record a Defrost event for each log interval in which a Defrost cycle
is pending or active (i.e. both the 8:00 and 9:00 data logs on 1 hour logging interval).
•
On Chill Loads (setpoints at -9.9 C [14.1 F] and above), the conditions for this are:
•
Evaporator Coil Temperature must be below 4 C (41 F) to activate the defrost compressor hour timer.
•
There is an interval set for defrosting, however, the defrost timer is built intelligent - it detects whether or not
there is ice building up on the coil.
•
If there is no ice building up on the coil, it extends the defrost interval, and if there is Ice building up earlier
on the coil it reduces the defrost interval. The maximum interval is 48 hours.
•
On Frozen Loads, the initial time interval is 8 hours. Two (2) hours are added to the time interval each
timed defrost interval. Maximum accumulated time interval is 24 hours.
•
Defrost timer resets if the unit is off more than 12 hours, setpoint is changed more than 5 C (8.9 F) or
PTI (pretrip) test occurs.
NOTE: If unit operating conditions do not allow the unit to enter a defrost cycle, “Defrost Not
Activated” appears on VGA display when the
D
EFROST
key is pressed.
When the Defrost mode is initiated:
•
The controller stops the compressor, condenser fan and evaporator fans.
•
When the compressor stops, the controller turns on the Defrost indicator, Heat indicator and energizes
the solid state, turning on the electric heaters.
The controller terminates the Defrost mode when:
•
Evaporator temperature:
•
Chill mode: Evaporator coil sensor temperature reaches 18 C (65 F).
•
Frozen mode: Evaporator coil sensor temperature reaches 18 C (65 F).
•
Interval timer: Controller terminates defrost after 90 minutes on 60 Hz power (120 on 50 Hz power).
Alarm Code 20 will be generated if this occurs.
•
Power off: Turning
U
NIT
O
N
/O
FF
switch
O
FF
terminates defrost.
Summary of Contents for 098203
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Page 3: ...MAGNUM TK 60275 4 MM Rev 3 08 15 Copyright 2012 Ingersoll Rand EMEIA Printed in Ireland...
Page 193: ...Refrigeration Maintenance 191 Figure 163 Filter Drier...
Page 200: ...Refrigeration Maintenance 198 Figure 169 Receiver Tank Figure 170 Water Cooled Condenser Tank...
Page 257: ...255 Schematic Diagram RELEASED 19 Sep 2013...
Page 258: ...256 Wiring Diagram Page 1 of 2 RELEASED 19 Sep 2013...
Page 259: ...257 Wiring Diagram Page 2 of 2 RELEASED 19 Sep 2013...
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