Indoor Unit Control - Mitsubishi Electric PUHY-P250YNW-A Service Handbook

[5-3 Indoor Unit Control ]

5-3

Indoor Unit Control

<Indoor unit control>
There are two controller circuit boards with two refrigerant circuits inside the indoor unit of 20 HP.
There is one controller circuit board with one refrigerant circuit. Each refrigerant circuit is controlled independently
(in case of one refrigerant circuit, one-to-one control of indoor unit and outdoor unit) in the following method.
-1- Thermostat Functions
(1) Thermostat Functions and Function Selection
·Two control methods are available; suction temperature control and discharge temperature control.
·The suction/discharge temperature control can be switched by the switches (SWC) on the controller circuit board
inside the controller of the indoor unit.
·The discharge temperature control is selected (SWC is set to "Standard") at factory shipment.
·To switch the control, set SWC on two controller circuit boards inside the controller as follows.
To perform suction temperature control: Set SWC to "Option".
To perform discharge temperature control: Set SWC to "Standard".
·The SWC settings made on two controller circuit boards must be equivalent.<20HP only>
(2) Thermostat Reading
A. Discharge temperature control (SWC is set to "Standard".)
(a) Thermo ON Condition
· Three minutes have past since thermo OFF AND
· TH24 - Preset temperature > 1 C [34 F]
· The TH21 value has gone up by 1 C or more compared to its value during Thermo-OFF.
TH24: Discharge thermistor
TH21: Suction thermistor
(b) Thermo OFF Condition
< When Dipsw4-5 on the outdoor unit is ON >
· 30 minutes have past since thermo ON AND
· TH24 - Target Temperature < -1 C [30 F] has been detected fo r 10 minutes
OR TH24 - Target Temperature < -5 C [23 F] was detected
< When Dipsw4-5 on the outdoor unit is OFF >
· Two minutes have past since thermo ON
· TH24 - Target Temperature < -1 C [30 F] has been detected for 5 minute AND F=Fmin
B. Suction Temperature Control (SWC is set to "Option".)
(a) Thermo ON Condition
· Three minutes have past since thermo OFF AND
· TH21 - Target Temperature > 1 C [34 F]
(b) Thermo OFF Condition
<
When Dipsw4-5 on the outdoor unit is ON >
· Thirty minutes have past since thermo ON AND
· TH21 - Target Temperature < -1 C [30 F] has been detected for 10 minutes
OR TH21 - Target Temperature < -5 C [23 F] was detected.
<
When Dipsw4-5 on the outdoor unit is OFF >
· Two minutes have past since thermo ON AND
· TH21 - Target Temperature < -1 C [30 F] has been detected for 5 minute AND F=Fmin
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