Hitachi RAS-2-HVNP Service Manual page 89

3. Piping work and refrigerant charge
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Additional refrigerant charge calculation method
Calculate the additional refrigerant charge amount according to the following steps:
Step 1: Additional refrigerant charge calculation for liquid piping (W
Outdoor units have been charged with refrigerant for 30m (20m for RAS-3HVNC) of actual piping length, an additional
refrigerant charged is required in systems with actual piping length longer.
• For all UTOPIA units except RAS-(8-12)HN(P/C)(E)
Use the following formula:
W = (L-30) x P
1
L: Total piping length (m)
P: Additional refrigerant charge (g/m)
N O T E
(*): In case of RAS-(2-2.5)HVNP units installed in 2 indoor units system, the unit is considered to be charged with
refrigerant for 0 m. In these cases, the formula for calculating the additional refrigerant charge is:
W = (L-0) x P
1
In case of RAS-3HVNC, the unit is charged with refrigerant for 20 m. In these cases, the formula for calculating
the additional refrigerant charge is:
W = (L-20) x P
1
Example:
A. 30 m.
B. 8 m.
C. 8 m.
• Chargeless Length ℓ: for RAS-4HVNPE is 30 m according to
the table before.
• Additional Correction Value P : for RAS-4HVNPE, "60" accord-
ing to the table above.
• Additional Charge amount W will be:
W = (L-ℓ) x P
Example: W = (46-30) x 60= 960 (g)
1
• For UTOPIA units RAS-(8-12)HN(P/C)(E)
The additional refrigerant charge for RAS-(8-12)HN(P/C)(E) units must be calculated by multiplying the total piping length
of each diameter per its calculation factor according to the following table. The result is the additional refrigerant charge for
liquid piping. (Fill the table with the values)
Pipe size (mm)
Step 2: Additional refrigerant charge calculation for indoor unit (W
When the outdoor unit is combined with indoor units RPI-(8/10)HP, it´s necessary an additional refrigerant charge (W
kg/unit. For indoor units lower than 8 HP, an additional refrigerant charge it's not needed.
Indoor unit capacity
75
(*)
Ø15.88
Ø12.7
Ø9.52
Ø6.35
≥ 8 HP
< 8 HP
SMGB0079 rev.0 - 01/2013
(kg))
1
Additional refrigerant charge factor (kg/m)
x 0.19
x 0.12
x 0.065
x 0.065
(kg))
2
Additional refrigerant charge (W
1
0
3
) = 1
2
(kg))
2