VC Pro VRF 50/60Hz
153
Part 3 - System Design and Installation
4.3 Permitted Piping Lengths and Level Differences
The piping length and level difference requirements that apply are summarized in Table 3-4.3 and are fully described as
follows (refer to Figure 3-4.2):
1. Requirement 1: The total length of piping in one refrigerant system should not exceed 1000m. When calculating the
total length of piping, the actual length of the indoor main pipes (the piping between the first indoor branch joint and
all other indoor branch joints, L
2
to L
16
) should be doubled.
2. Requirement 2: The piping between the farthest indoor unit (N
11
) and the first outdoor branch joint (L) should not
exceed 175m (actual length) and 200m (equivalent length). (The equivalent length of each branch joint is 0.5m.)
3. Requirement 3: The piping between the farthest indoor unit (N
11
) and first indoor branch joint (A) should not exceed
40m in length (Ʃ{L
9
to L
13
} + k ≤ 40m) unless the following conditions are met and the following measures are taken, in
which case the permitted length is up to 90m:
Conditions:
a) Each indoor auxiliary pipe (from each indoor unit to its nearest branch joint) joint does not exceed 20m in length
(a to q each ≤ 20m).
b) The difference in length between {the piping from first indoor branch joint (A) to the farthest indoor unit (N
11
)}
and {the piping from the first indoor branch joint (A) to the nearest indoor unit (N
1
)} does not exceed 40m. That
is: (Ʃ{L
9
to L
13
} + k) - (Ʃ{L
2
to L
3
} + a) ≤ 40m.
Measures:
a) Increase the diameter of the indoor main pipes (the piping between
the first indoor branch joint and all other indoor branch joints, L
2
to
L
16
) as per Table 3-4.2, except for indoor main pipes which are already
the same size as the main pipe (L
1
), for which no diameter increases
are required.
4. Requirement 4: The largest level difference between indoor unit and
outdoor unit should not exceed 90m (if the outdoor unit is above) or 110m
(if the outdoor unit is below). Additionally: (i) If the outdoor unit is above
and the level difference is greater than 20m, it is recommended that an oil
return bend with dimensions as specified in Figure 3-4.1 is set every 10m
in the gas pipe of the main pipe; and (ii) if the outdoor unit is below and
the level difference is more than 40m, the liquid pipe of the main pipe (L
1
)
should be increased as per Table 3-4.2.
5. Requirement 5: The largest level difference between indoor units should
not exceed 30m.
Table 3-4.2: Diameter increase requirements
Figure 3-4.1: Oil return bend (unit: mm)
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