Mitsubishi Electric MXZ-8A140VA1 Technical & Service Manual page 80

<Table 1>
Total piping length
(b1+ b2 + a1+ a2 + a3 + a4 + a5 + a6 + a7 + a8)
Additional refrigerant charging amount
Reference (for service)
The amount of refilling refrigerant charge
If connecting an indoor unit with 9.52 liquid pipes (model number 71 or more for M-and S-series and model number 60 or more
for P-series), the additional refrigerant charging amount in Table 1 must be corrected (add the following R value from the value
given in Table 1).
Additional refrigerant charging correction amount
R=0.01 [kg/m] 9.52 branch pipe (liquid pipe) total length [m]
Example) b1 = 20m, b2 = 25m
Indoor unit A 9.52 liquid pipe
Indoor unit B 6.35 liquid pipe
Indoor unit C 6.35 liquid pipe
Indoor unit D 9.52 liquid pipe
Total piping length : b1 + b2 + a1 + a2 + a6 + a7 = 95m
According to Table 1, the additional refrigerant charging amount is 3.2kg.
Because indoor units with 9.52 liquid pipes are connected (indoor units A and D in this example), the additional refrigerant
charging amount must be corrected.
Additional refrigerant charging correction amount
R = 0.01 [kg/m] 9.52 branch pipe (liquid pipe) total length (a1 + a7)
= 0.01 (12 + 13m)
= 0.25kg
Therefore, the additional refrigerant charging amount is 3.2kg + 0.25kg = 3.45kg.
Reference
The refilling amount of refrigerant at servicing
Example) 3.45 + 8.5 = 11.95kg
The amount of refrigerant of initial charge (8.5kg) is added.
Refrigerant collection when relocating the indoor and outdoor units (Pump down)
1 Connect gauge manifold valve (pressure gauge included) to the service port near the gas stop valve of the outdoor unit so
that the refrigerant pressure can be measured.
2 Turn on the power supply (circuit breaker).
3 Close the liquid stop valve, and then perform the test run for cooling operation (SW4-1 : ON and SW4-2 : OFF).
NOTE: Be sure to wait at least 3 minutes after turning on the power supply before setting SW4-1and SW4-2.
If the DIP switches are set before 3 minutes has elapsed, the test run may not start.
4 Fully close the gas stop valve when the pressure reading on the gauge drops to 0.05–0.00MPa*(approximately 0.5–0.0 o/f)
* If too much refrigerant has been added to the air conditioner system, the pressure may not drop to 0.5 o/f . If this occurs,
use a refrigerant collecting device to collect all of the refrigerant in the system, and then recharge the system with the correct
amount of refrigerant after the indoor and outdoor units have been relocated.
5 Stop the air conditioner operation (SW4-1 : OFF and SW4-2 : OFF).
6 Turn off the power supply (circuit breaker).
40m or less 41 – 50m
0kg (no need) 0.6kg
8.5kg 9.1kg
(8.5 + 0) (8.5 + 0.6)
a1 = 12m
a2 = 11m
a6 = 14m
a7 = 13m
80
51 – 70m 71 – 90m
1.4kg 2.2kg
9.9kg 10.7kg
(8.5 + 1.4) (8.5 + 2.2)
91 – 115m
3.2kg
11.7kg
(8.5 + 3.2)