Refrigerant Charge Adjustment Mode - Mitsubishi Electric HP120TNU-A Service Handbook

[6-3 Evaluating and Adjusting Refrigerant Charge ]
6-3-4

Refrigerant Charge Adjustment Mode

When the function switch (SW4 (922)) on the main board on the outdoor unit (OC only) is turned to ON, the unit goes into the
refrigerant amount adjust mode, and operation <A> below is followed.
The unit will not go into the refrigerant amount adjust mode when the switch on the OS is set to ON.
Operation <A>
When the unit is in the refrigerant amount adjust mode, the LEV on the indoor unit does not open as fully as it nor-
mally does during cooling operation to secure subcooling.
1) Adjust the refrigerant amount using TH4, TH3, Tc, SC11 (on the BC), and SC16 (on the BC) according to the flowchart on the
next page. Check the TH4, TH3, Tc, SC11 (on the BC), and SC16 (on the BC) values according to the flowchart. The TH4,
TH3, Tc, SC11 (on the BC), and SC16 (on the BC) values can be displayed by setting the self-diagnosis switch (SW4 (SW6-
10): OFF)) on the control board of the OC or OS.
2) There may be cases when the refrigerant amount may seem adequate for a short while after starting the unit in the refrigerant
amount adjust mode but turn out to be inadequate later on (when the refrigerant system stabilizes).
When the amount of refrigerant is truly adequate.
All the following formulas are true:
3°C [5.4°F] SC11 (on the BC) on the outdoor unit
10°C [18°F] SC16 (on the BC) on the outdoor unit
5°C [9°F] SH on the indoor unit
The refrigerant amount may seem adequate at the moment, but may turn out to be inadequate later on.
Any of the following formulas is true:
SC11 (on the BC) on the outdoor unit < 3°C [5.4°F]
SC11 (on the BC) on the outdoor unit > 10°C [18°F]
SC16 (on the BC) on the outdoor unit < 10°C [18°F]
SH on the indoor unit < 5°C [9°F]
In this case, check the refrigerant amount after all the following formulas become true:
3°C [5.4°F] SC11 (on the BC) on the outdoor unit
10°C [18°F] SC16 (on the BC) on the outdoor unit
5°C [9°F] SH on the indoor unit
3) If the high pressure is not at least 2.0 MPa [290 psi], a correct judgment will not be possible for refrigerant adjustment. Perform
the adjustment when the outdoor air temperature is at least 20°C.
4) Refrigerant amount adjust mode automatically ends 90 minutes after beginning. When this happens, by turning off the SW4
(922) and turning them back on, the unit will go back into the refrigerant amount adjust mode.
Self-diagnosis swithes on TH4
Self-diagnosis swithes on TH3
ON
1 2 3 4 5 6 7 8 9 10
4 -
chapter 6
10°C [18°F]
15°C [27°F]
10°C [18°F]
15°C [27°F]
ON
1 2 3 4 5 6 7 8 9 10
ON
1 2 3 4 5 6 7 8 9 10
Self-diagnosis swithes on Tc
ON
1 2 3 4 5 6 7 8 9 10
The figure at left shows that the switches 1 through 5 are set to ON and 6 through 10 are set to OFF.
Self-diagnosis switch on SC11 (on the BC)
ON
1 2 3 4 5 6 7 8 9 10
Self-diagnosis switch on SC16 (on the BC)
ON
1 2 3 4 5 6 7 8 9 10
HWE18220_GB