Function Setting; Operation Characteristics In Relation To The Refrigerant Charge - Mitsubishi Electric CITY MULTI PUHY-P-YKB-A1 Installation Manual

11-2. Function setting

Make function settings by setting the dipswitches SW4, SW6, and SWP1 on the main board.
Write down the switch settings on the electrical wiring diagram label on the control box front panel for future reference
when the control box needs to be replaced.
・Take the following steps to make snow sensor settings. (Snow sensor control will not function when the outdoor
temperature sensor (TH7) reading is 6ºC (43ºF) or above.)
① Set the 10th bit of SW6 to ON.
② Set SW4 as shown in the table below to select the setting item No.933 or 934. (The setting item No. will be
displayed on LED1.)
③ Press SWP1 for two seconds or longer to change the settings. (The settings can be checked on LED3.)
Setting item
No.
933
Snow sensor
setting
934
*1 Make the SW4 setting after the unit is energized.
*2 This will blink while the system is starting up.
・Make various function settings by setting SW6, referring to the table below.
Setting content
SW6-1
SW6-2
SW6-3
SW6-4 Static pressure setting
SW6-5 High static pressure setting
SW6-6
SW6-7 Low-noise mode selection
SW6-8 Selection of Low-noise or Demand
SW6-9
Selection of Diagnostic display or
SW6-10
Function detail setting
* Do not change the factory settings of SW5-3 through SW5-8.
* Unless otherwise specified, leave the switch to OFF where indicated by "–," which may be set to OFF for a reason.

11-3. Operation characteristics in relation to the refrigerant charge

It is important to have a clear understanding of the characteristics of refrigerant and the operation characteristics of air
conditioners before attempting to adjust the refrigerant charge in a given system.
・During cooling operation, the amount of refrigerant in the accumulator is the smallest when all indoor units are in
operation.
・During heating operation, the amount of refrigerant in the accumulator is the largest when all indoor units are in
operation.
・Refrigerant undercharge creates a tendency for the discharge temperature to rise.
・Changing the amount of refrigerant in the system while there is refrigerant in the accumulator has little effect on the
discharge temperature.
・The higher the high pressure level, the more likely it is for the discharge temperature to rise.
・The lower the low pressure level, the more likely it is for the discharge temperature to rise.
・When the amount of refrigerant in the system is adequate, the compressor shell temperature is 10 to 60ºC (50 to
140ºF) higher than the low-pressure saturation temperature. If the temperature difference between the compressor
shell temperature and low-pressure saturation temperature is 5ºC (41ºF) or less, refrigerant overcharge is
suspected.
KD79S703H01
SW4 0: OFF, 1: ON *
1 2 3 4 5 6
1 0 1 0 0 1
0 1 1 0 0 1
–
–
–
Standard static pressure
60 Pa
–
Performance priority
Low-noise (Night)
–
Diagnostic display
1
7 8 9 10
0 1 1 1 No. 934 ineffective
0 1 1 1 Continuous fan operation
Setting
OFF ON
– –
– –
– –
High static pressure
30 Pa
– –
Low-noise priority
Demand
– –
Function detail setting
GB-45
Setting (LED3 display) * 2
Unlit Lit
No. 934 effective
Intermittent fan operation
Switch setting timing
–
–
–
Before being energized
Before being energized
–
Any time after being energized
Before being energized
–
Any time after being energized