Additional Refrigerant Charge; Calculation Of Additional Refrigerant Charge - Mitsubishi Electric City Multi PQHY-P-YLM-A series Installationshandbuch

Precautions for heat source unit combinations
Refer to [Fig. 9.2.3] for the positioning of twinning pipes.
[Fig. 9.2.3] (P.8)
<A> When the piping (from the twinning pipe) exceeds 2 m [6 ft], include a trap
(gas pipe only) within 2 m [6 ft]. Make sure the height of the trap is 200 mm
[7-7/8 in] or more.
If there is no trap, oil can accumulate inside the pipe, causing a shortage of
oil damaging the compressor. (for PQHY-P·YSLM-A)
<B> Example of piping connection (for PQHY-P·YSLM-A)
Indoor unit
A
Within 2 m [6 ft]
C
Field-supplied piping
E
Straight pipe length that is 500 mm [19-11/16 in] or more
G
Precautions for heat source unit combinations
Refer to [Fig. 9.2.4] for the positioning of twinning pipes.
[Fig. 9.2.4] (P.8 - 9)
<A> Install the piping so that oil will not accumulate in the stopped heat source
unit. (both the liquid and the gas side for PQHY-P·YSLM-A, the high-
pressure side only for PQRY-P·YSLM-A)
1. The NG example shows that oil accumulates because the units are installed
on a reverse gradient while unit 1 is in operation, and unit 2 is stopped.
2. The NG example shows that oil accumulates into unit 1 while unit 2 is in
operation, and unit 1 is stopped. Vertical pipe height (h) should be 0.2 m
(7-7/8 in) or below.
3. The NG example shows that oil accumulates into unit 1 while unit 2 is in
operation, and unit 1 is stopped. Vertical pipe height (h) should be 0.2 m
(7-7/8 in) or below.
4. The NG example shows that oil accumulates into unit 2 while unit 1 is in
operation, and unit 2 is stopped. Vertical pipe height (h) should be 0.2 m
(7-7/8 in) or below.
<B> Slope of twinning pipes (for PQHY-P·YSLM-A)
Make sure the slope of the twinning pipes are at an angle within ±15° to the
horizontal plane.
If the slope exceeds the angle specified, the unit may be damaged.
<C> Example of piping connection (for PQRY-P·YSLM-A)
Slope downward
A
BC controller (standard or main)
C
Slope of the twinning pipe is at an angle within ±15° to the earth
E
Twinning pipe (low-pressure side)
F
Field-supplied piping (low-pressure connecting pipe: between heat source
H
units)
Field-supplied piping (low-pressure main pipe: to BC controller)
I
Field-supplied piping (high-pressure main pipe: to BC controller)
J
Caution:
• Do not install traps to prevent oil backflow and compressor start-up
failure.
• Do not install solenoid valves to prevent oil backflow and compressor
start-up failure.
• Do not install a sight glass because it may show improper refrigerant
flow.
If a sight glass is installed, inexperienced technicians that use the
glass may overcharge the refrigerant.

10. Additional refrigerant charge

At the time of shipping, the heat source unit is charged with refrigerant.
This charge does not include the total amount necessary for extended piping
lengths, so an additional charge of each refrigerant line will be required on
site. Always keep a record of the size and length of each refrigerant line and
the amount of additional charge by writing it in the space provided on the heat
source unit for future reference.
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Trap (gas pipe only)
B
Twinning pipe
D
Twinning kit
F
Slope upward
B
Twinning pipe
D
Twinning pipe (high-pressure side)
G
10.1. Calculation of additional refrigerant
charge
• Calculate the amount of additional charge based on extended piping lengths
and the refrigerant line size.
• Use the table below as a guide for calculating the amount of additional
charge and then charge the system accordingly.
• If the calculation results in a fraction of less than 0.1 kg [4 oz], round up to
the next 0.1 kg [4 oz]. For example, if the result of the calculation was 28.73
kg [1014 oz], round the result up to 28.8 kg [1016 oz].