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Operation
Defrost pressure switch (PHE version)
In winter mode, frost occurs in the return air side of the exchanger increasing pressure drop.
The defrost pressure switch setting should be setup so that it does not switch in free cooling
mode (100% exhaust air flow).
During the free cooling test mode, adjust the pressure switch setting to reach the threshold
point. This value of pressure drop is the maximum non frosted pressure drop. Increase this
setting by +50% to set up the frosted pressure drop.
ERM defrost mode is active when the timer relay light is activated.
The defrost pressure switch activates a timer relay that opens the bypass damper for a
duration of 5 minutes (default setting).
During defrost operation, the mixing damper stays in the minimum position.
Figure 13 - Air circulation in defrost operation
PHE
125-155-175-200-250-265-290-340
0%
Min%
Min%
100%
Min%
Min%
By-pass
100%
PHE
275-300-350-400-500-600
Min%
Min%
Min%
Min%
Min%
By-pass
Defrost operation
14
RT-SVX42B-E4
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