Table of Contents
Advertisement
DESCRIPTION OF THE DEFROSTING SYSTEM
The defrosting process is activated during heating mode in heat pump units, when the outside temperature is low
and the outdoor coil could become frozen.
To melt the ice the defrosting function will switch the unit to cooling operation for a short period.
During defrosting mode the low pressure is at minimum level, consequently the pressure switch is disabled in this
mode.
The manufacturer uses default control settings which apply to most installations. The set parameters determine
the following:
INITIAL DEFROSTING TEMPERATURE
The defrosting cycle begins when outdoor probe temperature is below -1ºC.
END DEFROSTING CYCLE
The defrosting cycle ends when:
For one circuit units, when outdoor probe temperature of the refrigerating pipe reaches 25ºC.
For two circuits units, when end defrosting pressure switch detects 24 bar.
DELAY BETWEEN TWO DEFROSTING REQUESTS
Time between two defrosting cycles is calculated from the end of one to the beginning of next, and it is 30 minutes.
This defines the time during which the initial defrosting temperature (-1ºC) must be maintained. When this time
has elapsed, the unit starts to defrost. If the initial defrosting temperature (-1ºC) increases before this time has
elapsed, the timer would block and it would only start to count when the temperature returns below the starting
defrosting temperature. This pausing prevents the unit from carrying out continual defrosting patterns.
MAXIMUM DEFROSTING DURATION
It is the maximum defrosting time.
This defines the maximum period if the temperature has not exceeded a set value.
This timing prevents too long defrosting cycles.
The maximum defrosting time will be 5 minutes.
DEFROSTING CYCLE SEQUENCE:
When a probe located in the outside exchanger detects -1ºC, the compressor stops, the four-way valve reverses
30 seconds and after 30 seconds, the compressor starts. This cycle ends when the outside exchanger probe detects
the final defrosting temperature or exceeds a safety interval. When the defrosting cycle has finished, the compressor
stops for 30 seconds. Then the four-way valve reverses and 30 seconds later, the compressor starts again in
heating mode generating again warm water more efficiently due to the absence of frost.
19
Hide quick links:
Advertisement
Table of Contents
