M thermal Mono
202004 81
Notes:
1. Discharge pipe temperature sensor connection is port CN8 on the MHA-V4(6,8,10)W/D2N8-B outdoor unit refrigerant system main PCB (labeled 15 in
Figure 4-2.2 in Part4, 2.3 "Main PCB for Refrigerant System, Inverter Module"). port CN8 on the MHA-V12(14,16)W/D2N8-B outdoor unit refrigerant
system main PCB (labeled 15 in Figure 4-2.3 in Part 4, 2. 3 "Main PCB for Refrigerant System, Inverter Module"), port CN4 on the
MHA-V12(14,16)W/D2RN8-B outdoor unit refrigerant system main PCB (labeled 15 in Figure 4-2.4 in Part 4, 2. 3 "Main PCB for Refrigerant System, Inverter
Module").
2. Final outlet water temperature sensor and water side heat exchanger water outlet temperature sensor connections are port CN6 on the hydronic box main
PCB (labeled 10 in Figure 4-2.1 in Part4, 2.2 "Main PCB for Hydronic System"). Domestic hot water tank temperature sensor connection is port CN13 on
hydronic box main PCB (labeled 13 in Figure 4-2.1 in Part4, 2.2 "Main PCB for Hydronic System").
3. Measure sensor resistance. If the resistance is too low, the sensor has short-circuited. If the resistance is not consistent with the sensor’s resistance
characteristics table, the sensor has failed. Refer to Part 2, 1 “Layout of Functional Components” and to Table 5-5.1 or 5-5.2 in Part 5, 5.1 “Temperature
Sensor Resistance Characteristics”.
4. High pressure switch connection is port CN13 on the MHA-V4(6,8,10)W/D2N8-B outdoor unit refrigerant system main PCB (labeled 16 in Figure 4-2.2 in
Part4, 2.3 "Main PCB for Refrigerant System, Inverter Module"). port CN13 on the MHA-V12(14,16)W/D2N8-B outdoor unit refrigerant system main PCB
(labeled 16 in Figure 4-2.3 in Part 4, 2. 3 "Main PCB for Refrigerant System, Inverter Module"), port CN31 on the MHA-V12(14,16)W/D2RN8-B outdoor unit
refrigerant system main PCB (labeled 20 in Figure 4-2.4 in Part 4, 2. 3 "Main PCB for Refrigerant System, Inverter Module").
5. Measure the resistance among the three terminals of the pressure sensor. If the resistance is of the order of mega Ohms or infinite, the pressure sensor
has failed.
6. High pressure side blockage causes discharge temperature to be higher than normal, discharge pressure to be higher than normal and suction pressure to
be lower than normal.
7. Check air side heat exchanger, fan and air outlets for dirt/blockages.
8. Check the water side heat exchanger, water piping, circulator pumps and water flow switch for dirt/blockages.
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