Mitsubishi Electric CITY MULTI CMB-WP1016V-GA1, Service Handbook

Page: 87 / 294

[
VI
Control ]
- 78 -
HWE1410A GB
Backup control
-9- Backup control
The following backup control is started on the HBC 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.
[Cooling-main/Heating-main operation]
1) Outdoor unit (Heat source unit)
Cooling-main operation: Continued; Heating-main operation: Continued
2) HBC controller
(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.
Water pump protection control
-10- Water pump protection control
When the circuit is clogged or air enters the water circuit, the protection control starts on the HBC controller 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.
Control mode
Cooling-main/Heating-main Cooling-only
Outdoor unit
(Heat source
unit)
Operation
mode
Continues the current operation Cooling-only Thermo-OFF
HBC controller 21S4Ma Heating side: open (de-energized) Cooling side: open (energized)
21S4Mb Cooling side: open (de-energized) Cooling side: open (de-energized)
LEV1 Maintains the opening that was used in the
previous operation mode
Opening during Cooling-only Thermo-OFF
LEV2 41 pulses: fully closed Opening during Cooling-only Thermo-OFF
LEV3 3000 pulses: fully open Opening during Cooling-only Thermo-OFF
SVM1 Closed Open
PUMP1 Continues the heating operation Continues the cooling-only operation
PUMP2 Continues the cooling operation Continues the cooling-only operation
VB3a~p The opening depending on the indoor unit
operation mode
The opening depending on the indoor unit
operation mode
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