Page 29 mrcool.com
Air Evacuation
Note on Adding Refrigerant
Some systems require additional charging depending on pipe lengths. The standard pipe length varies
according to local regulations. For example, in North America, the standard pipe length is 25 ft (7.5 m). In
other areas, the standard pipe length is 16 ft (5 m). The refrigerant should be charged from the service port
on the outdoor unit’s low pressure valve. The additional refrigerant to be charged can be calculated using the
following formula:
Flare nut
Cap
Valve body
Valve stem
Fig. 7.2
11. Remove the charge hose from the service port.
12. Using hexagon wrench, fully open both the
high-pressure and low-pressure valves.
13. Tighten valve caps on all three valves (service
port, high-pressure, low-pressure) by hand. You
may tighten it further using a torque wrench if
needed.
OPEN VALVE STEMS GENTLY
When opening valve stems, turn the hexagonal
wrench until it hits against the stopper.
DO NOT try to force the valve to open further.
ADDITIONAL REFRIGERANT PER PIPE LENGTH
Connective
Pipe Length (m)
Air Purging
Method
Additional Refrigerant
≤ Standard pipe length
N/A N/A
> Standard pipe length Vacuum Pump
Inverter R410A:
(Pipe length – standard length) x 15 g/m
(Pipe length – standard length) x 0.16 oZ/ft
Fixed-frequency R410A:
(Pipe length – standard length) x 20 g/m
(Pipe length – standard length) x 0.21 oZ/ft
Inverter R410A:
(Pipe length – standard length) x 30 g/m
(Pipe length – standard length) x 0.32 oZ/ft
Fixed-frequency R410A:
(Pipe length – standard length) x 40 g/m
(Pipe length – standard length) x 0.42 oZ/ft
CAUTION
DO NOT mix refrigerant types.
Vacuum Pump
Liquid Side: Ø 0.25” (ø 6.35)
Liquid Side: Ø 0.375” (ø 9.52)
3. Open the low-pressure side of the manifold
gauge. Keep the high-pressure side closed.
4. Turn on the vacuum pump to evacuate the
system.
5. Run the vacuum for at least 15 minutes, or until
the Compound Meter reads -76 cmHG (-10
5
Pa).
6. Close the low-pressure side of the manifold
gauge, and turn off the vacuum pump.
7. Wait for 5 minutes, then check that there has
been no change in system pressure.
8. If there is a change in system pressure, refer to
Gas Leak Check section for information on how
to check for leaks. If there is no change in
system pressure, unscrew the cap from the
packed valve (high-pressure valve).
9. Insert hexagon wrench into the packed valve
(high-pressure valve) and open the valve by
turning the wrench in a 1/4 counter clockwise
turn. Listen for gas to exit the system, then close
the valve after 5 seconds.
10. Watch the Pressure Gauge for one minute to
make sure that there is no change in pressure.
The Pressure Gauge should read slightly higher
than atmospheric pressure.
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