Recommended Interconnecting Pipe Sizing; Max Vertical Pipe Run; Correction Factors: Vapour Line Sizing Vs. Cooling Capacity; Pipe-Work Connection - Rinnai DO-SC18Z91 Operation & Installation Manual

6.2

RECOMMENDED INTERCONNECTING PIPE SIZING

Table 3. Recommended Pipe Sizing
Recommended Pipe Size (mm)
For Equivalent Length (m)
Model
Liquid
1-10
DO-SC18Z91 9.52
DO-SC22Z91 12.7
Both units' liquid line connection sizes are 12.7mm. For pipe work less than 10m equivalent
length, the DO-SC18Z91 system can be run with 9.52mm liquid line.
NOTE
Therefore, two 12.7 to 9.52mm copper bushes are included (one with the indoor DI-XU18Z and
one with the DO-SC18Z91 outdoor unit). For pipe work more than 10m equivalent length, a
12.7mm liquid line is needed.
6.3

MAX VERTICAL PIPE RUN

The height difference between indoor and outdoor units must not exceed 8 meters.
If the indoor unit is located more than 5 metres above the outdoor unit, then a solenoid valve should be installed in
the liquid line at the indoor unit, to prevent liquid refrigerant migrating back to the compressor in the off cycle. The
solenoid shall be interlocked with the compressor.
6.4

CORRECTION FACTORS: VAPOUR LINE SIZING VS. COOLING CAPACITY

The total equivalent length of the interconnecting refrigeration lines will affect the cooling capacity of the system.
Table 4 shows the percentage change in cooling capacity versus the equivalent pipe lengths for different suction
line sizes, using the recommended liquid line sizes.
Table 4. Cooling Capacity Correction Factors
Model Size (mm)
Suction line
28.6
DO-SC18Z91
22.2
19.1
Suction line
DO-SC22Z91 28.6
22.2
6.5

PIPE-WORK CONNECTION

•
Locate the suction & liquid pipe service valves in the compressor compartment by removing the service access
panel
•
Check that the service valves are tightly closed (Service Ball valves have been provided for suction and liquid
lines)
•
Wrap each valve in turn with a wet cloth prior to sweating off its associated blanking plate
•
Braze the interconnecting liquid and suction pipes from the indoor unit
•
Pressurise the indoor unit & pipe-work again with dry nitrogen and check for any brazed joint leaks. Repair as
necessary but ensure the system is not under pressure prior to brazing
•
With the indoor unit pressure again released, evacuate to a vacuum pressure of 100 microns minimum
•
Disconnect the vacuum pump whilst retaining the system vacuum
•
Open the liquid line valve fully first, and then the suction line valve
Brivis
Suction
10-30 1-10 10-30
12.7 22.2 28.6
12.7 28.6 28.6
5 7.5
9.52mm Liquid Line
1.10% 0.80%
0.00% 0.90%
-2.50% -4.60%
0.00% -0.43%
-1.83% -3.23%
Maximum
Pre Charge
Equivalent
for 15m
Pipe
Pipe Length
Length(m)
(kg)
[Minimum Pipe
Length is 3m]
30 3.60
30 3.71
Equivalent Pipe Length (m)
10 15
0.50% 0.0%
-1.70% -3.4%
-6.50% -10.80%
12.7mm Liquid Line
-0.83% -1.63%
-4.63% -7.23%
47
Additional
Charge For Indoor
>15m Pipe Coil Piston
Length Orifice Size
(grams/m)
90 0.084"
90 0.074"
20 25
12.7mm Liquid Line
-0.50% -0.96%
-5.10% -6.80%
-15.10% -19.40% -23.90%
-2.43% -3.23%
-10.03% -12.83% -15.63%
ICE Fixed Speed OIM
30
-1.40%
-8.60%
-4.03%