Refrigerant Recovery Control; Backup Control; Water Pump Protection Control - Mitsubishi Electric PUHY-M200YNW-A1 Service Handbook

[5-3 Hydro Unit Control ]
5-3-5

Refrigerant Recovery Control

The refrigerant recovery control function controls the refrigerant flow at the Hydro unit during heating operation to keep the
refrigerant from collecting inside the Hydro unit.
It is also performed during cooling operation to prevent an excessive amount of refrigerant from accumulating in the outdoor
heat exchanger.
Starting criteria for the refrigerant recovery cycle (during Cooling or Heating mode)
The refrigerant recovery mode starts when all of the following conditions are met:
1) When 5 minutes have passed in the Heating mode or 30 seconds have passed in the Cooling mode since the completion of
the previous refrigerant recovery cycle AND the when following conditions are met.
Outdoor unit TH4 > 105°C [221°F]
2) When the port is not in the 4-minute restart delay mode
Starting criteria for the refrigerant recovery cycle (during Cooling or Heating mode)
The opening of LEV1 on the Hydro unit is increased.
5-3-6

Backup Control

The following backup control is started on the Hydro unit as necessary.
(1) Backup mode for plate heat exchanger protection
The following control is performed depending on the outlet pipe temperature of the plate heat exchanger for freeze-up pro-
tection.
1) Outdoor unit (Heat source unit)
Cooling Thermo-off
2) Hydro unit
Outdoor unit
(Heat source unit)
Hydro unit
Indoor unit
(2) Heating water temperature backup mode
When the heating operation can be continued without receiving heat from the refrigerant due to water temperature rise during
heating operation (the outlet pipe temperature of the plate heat exchanger is 50ºC or above), the outdoor unit goes into the
Thermo-OFF mode, and the heating operation is performed only by circulating the hot water by the water pump. When the
water temperature decreases to a certain level (the outlet temperature of the plate heat exchanger is 45ºC or below), the out-
door unit starts up.
5-3-7

Water Pump Protection Control

When the circuit is clogged or air enters the water circuit, the protection control starts on the Hydro unit to protect the water
pump and the system is stopped depending on the situation.
(1) When the internal temperature of the water pump increases
When the detection temperature of the water pump outlet pipe is above a certain level, the water pump is stopped to protect
it from the heat.
(2) When the revolutions of the water pump increases
When the revolutions of the water pump is above a certain level (The value changes depending on the specified voltage.),
the water pump is stopped to reduce the risk of air infiltration and water leaks.
BS_05_E
Operation
mode
LEV1
SV1
WP1
FCV The opening depending on the indoor unit operation mode
Control mode
Cooling
Cooling Thermo-OFF
Opening during Cooling Thermo-OFF
Open
Continues the cooling-only operation
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chapter 5 -