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DEFROST SYSTEM DESCRIPTION (HYDRON B and HYDRON BC UNITS)
For the heat pump units, during the winter (heating) mode, the condenser converts the cooling system into an
evaporator. Consequently, at low outside temperatures frost forms in inside it. The frost prevents the exchanger
from operating efficiently. It is therefore necessary,when in heating mode to activate an automatic defrost function.
This mode operates as follows. When a probe located in the condenser detects low temperatures (-3°C) pausing
takes place (30 minutes) during which the operating mode is reversed, de-energising the return valve without
stopping the compressor. In this way the outside exchanger acting as an evaporator also acts as a condenser.
The outside fan stops in order to prevent the condensation temperature from dropping too low and to reverse all
the condensation heating by melting the frost. This mode ends when the outside exchanger probe detects the final
defrost temperature (13°C) or exceeds a safety interval (5 minutes). At the end of the defrost mode the compressor
stops and begins an anti-cycle pause period (2 minutes). When this is complete, the compressor starts again in
heating mode, generating more warm water at a more efficiently due to the absence of frost.
During defrost mode the low pressure is at minimum level, consequently the manometer is disabled in this mode.
The manufacturer uses default control settings which apply to most installations. The set parameters determine
the following:
Initial defrost temperature
The outside exchanger (condenser) temperature is set so that if the temperature drops below this set point the
defrost mode is validated.
Final defrost temperature
The outside exchanger temperature condenser is set so that if the temperature rises above this point the defrost
mode is invalidated.
Interval between defrost modes
This defines the time during which the initial defrost temperature must be maintained. When this time has elapsed
the unit starts to defrost. If the initial defrost temperature drops before this time has elapsed, pausing is blocked,
and only starts to count when the temperature returns below a set value. This pausing prevents the unit from
carrying out continual defrost patterns.
Max. defrost time
This defines the max. defrost period if the temperature has not exceeded a set limit.
This idling avoids excessive defrost modes.
CONDENSATION CONTROL SYSTEM DESCRIPTION
The purpose of the condensation control system is to avoid excessive low condensing temperatures in the cooling
mode for operation at ambient conditions below 19°C and cooling requirement for internal charges. The control
system achieves this via the probe located in the outside exchanger (condenser). It is important to distinguish
between two control types used depending on the fan system.
AXIAL FANS (HYDRON F and HYDRON B units)
In this case, condensation control is proportional, varying the current entering the fan. The parameters which control
this operation are as follows:
Min. temperature fan speed
Until the exchanger temperature reaches this limit the fan rotates at min. speed or is stopped. Over this temperature
the current supply entering the fan starts to drop.
Max. temperature fan speed
When the exchanger temperature reaches this limit and for higher values, the fan rotates at max. speed.
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