Page 6 of 16
Drawing : - TPC142
Issue : - 4
Date : - 24/11/16
DEFROST OPERATION
If the ambient temperature of the room, or space in which the dehumidifier
unit is conditioning falls below 25ºC, ice will form on the evaporator coil as the
air is passed over it, after a time this build up of ice on the evaporator coil will
effect the efficiency of the dehumidifier unit, on its ability to maintain the
required conditions for the room.
The BD12 is therefore fitted with a defrost control device. This defrost control
device is timed to operate every 50 minutes, at which time, for approximately
4 minutes the high pressure gas is diverted by means of a by-pass valve to
enter the evaporator coil. The effect of this high pressure gas entering the
evaporator coil is to melt any build up of ice on this coil; this melted ice is
collected and disposed of by means of the condensate tube.
When the temperature falls below 15ºC, even with the defrost operation, it is
possible that some ice will remain on the evaporator coil. To ensure that all
the ice is removed from the evaporator coil during the defrost mode, the BD12
dehumidifier unit is fitted with a temperature sensitive device (thermo-stat).
When the dehumidifier unit, is required to go into the defrost mode by the
timing device and the temperature has fallen below 15ºC, the fan motor will
stop. With the fan motor stopped the refrigeration gas temperature will
increase because of the rise in pressures.
Because the heat now within the refrigeration circuit is not being removed
from the condenser coil, this heat will ensure that all the ice is removed from
the evaporator coil.
WARNING
•Due to high pressures that are within the sealed refrigeration circuit, under
no circumstance must direct heat be applied to the evaporator coil in an
attempt to remove the build up of ice.
•Neither should any attempt be made to cut open, any part of the
refrigeration circuit for the same reason.
HIGH TEMPERATURE CUT OUT
The BD12 dehumidifier unit has been designed to work in ambient conditions
of between 0ºC and +35ºC. Should the temperature in the room or space
become excessive a thermo-stat (winding protector) within the compressor
casing will open and dehumidifying will stop until such time as the thermo-stat
automatically resets.
WARNING
If the dehumidifier unit is switched off at the mains power supply for any
reason, it must be allowed to stand and rest for at least three minutes before
restarting. Failure to do this may cause the unit to blow the fuses owing to the
compressor starting current occasioned by the imbalance of the refrigerant
pressures.
