Profroid SUPERCOLD SCH - Page 62

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DEFROST CONTROL
 Air D e frost
Sequences:
- Stop compressor, while keeping the fans running by means of the timer or the controller. preferably following a pump down to
drain the air cooler, but without creating a vacuum (the vapour acting as a conductor in a vacuum).
- Keep fans running during the full defrost
- Return to cooling by means of timer or control switch.
 El e ctric a l d e frost
Sequences:
- Stop compressor and the fans by means of the timer or the control switch but preferably after a pump down to drain the air
cooler, but without creating a vacuum (the vapour is conductor in a vacuum). Allow the heaters to warm up.
1) The heaters are controlled by a Defrost Termination Thermostat (when ambient air temperature has been reached).
Cooling is restarted by the position of the thermostat bulb which detects the pre-set temperature which must not exceed 10°C.
The most suitable point on the coil is to be used at frost level. The clock or controller acts as a safety device for restarting
cooling, if this is not done by the thermostat.
2) Theheatersarecontrolledbya Limiter Thermostat(whenambientairtemperaturehasbeenreached).
Cooling is restarted by timer or controller reaching its time limit.
The bulb is positioned a the top of the coil, on the injection side in a free space. Insert the bulb as far as possible. In this case,
the pre-set temperature will be from 7°C to 9°C with a minimum differential (2K)
As the thermostat operates the heaters during defrost, the coil temperature evens out, which allows vapour production to
be reduced.
Restart cooling:
1) Forcoldroomsatpositivetemperatures(forproducewhichmuststaydry)
- Restart cooling (End of Defrost or Limiter) with icing (1 min) to avoid water splashes
- Restart fans.
2) For cold rooms at negative temperatures with wrapped or absorbent produce.
- drainage (3 to 4 min) for the material cooling of heaters.
- restart cooling with fans.
 Water d e frost
Room at positive temperature
Sequences:
- Stop compressor only by pump down and fans
- Open water valve.
- Stop water valve by timer
 drainage or freezing.
- Restart fans. Freezer tunnel
(After removal of produce)
Sequences:
If defrost is initiated:
- Stop compressor only by pump down.
- Keep fans running until positive temperature is reached (initiating thermostat).
- Open timed delay water valve (10 to 15 mins).
- Close and drain water valve (5 mins).
If cycle to be re-started:
- Re-start fans
- Re-start chilling
- MAINTENANCE
RECOMMENDATIONS
If the unit is stopped for long periods of time, the fan motors should be run for at least two hours each week.
A periodic visual check of the following is recommended:
- Blocking and frosting of the coil
-
Fan operation
- Position of axial fans in their collar
- Possible movement of heaters
- State of each axial fan (tightness to shaft, mechanical state of blades etc)
- Water drain (U-bend)