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Evacuate the System
NOTICE
Compressor Damage!
A proper vacuum must be drawn on the refrigerant
system to remove moisture prior to charging. If this is
not done, the refrigerant charge will combine with
moisture in the pipes to form an acid that will
eventually lead to compressor failure. A triple
evacuation procedure with dry nitrogen is
recommended, especially for systems with newly
installed refrigerant piping.
Notes:
•
A vacuum pump should be used that is capable of
evacuating the entire volume of the A/C system,
including newly installed or existing piping. It is
essential to use a well maintained pump that is in good
operating condition. Always ensure it contains clean,
fresh oil. You may need to change vacuum pump oil
more than once during the procedure.
•
Use high quality hoses, ensuring they are free of
defects and don't leak. It is recommended to use
copper tubing instead of hoses if possible due to the
low vacuum that must be attained when evacuating
the system. The use of short, large diameter hoses
helps reduce evacuation time.
3. After ensuring there are no leaks, relieve pressure and
evacuate the entire system while maintaining all the
solenoids (and hot gas reheat valve) open. Pull an
initial vacuum of 150 microns or lower using the
suction and discharge service ports and the service
port of the receiver (if applicable).
Note: When pulling a vacuum, the Schrader valves will
unnecessarily restrict the openings, increasing the
evacuation time. During the evacuation process it
is recommended to remove the Schrader valve
cores with a Schrader valve removal tool and draw
the vacuum through the port on the removal tool.
4. If you cannot evacuate the system below 150 microns,
close the vacuum pump isolation valve and perform a
rate-of-rise test by observing the standing pressure
over time. If the pressure rises slowly (up to 200
microns in 15 minutes), moisture is in the system that
still needs to be boiled off. Proceed to
pressure rises rapidly up to atmospheric pressure
(more than 50 microns per minute), there is a leak that
wasn't detected during
shoot the entire system for leaks and repair them. Then
begin the initial evacuation process again starting at
Step
1.
5. If no leaks are detected after the initial vacuum, release
the vacuum and pressurize the system with 2-3 lb of
dry nitrogen. Allow the system to stand for two hours
with the dry nitrogen charge. This gives time for the
AH-SVX008C-EN
Step
5. If the
Step
2. In this case trouble-
nitrogen molecules to disperse in the system
absorbing moisture.
6. After two hours, release the pressure. Then turn on the
vacuum pump and evacuate the system a second time
down to 150 microns or less. Close the vacuum pump
isolation valve and pressurize the system again with
dry nitrogen and allow the system to stand for two
hours as in
Step
5.
7. After two hours release the pressure. Turn on the
vacuum pump and complete the process of evacuating
the system, this time with a goal of achieving a 500
micron vacuum or less. Close the vacuum pump
isolation valve. When you can hold the vacuum at 500
microns or lower for at least 2 hours with no significant
rise in pressure, the system is ready to charge.
8. Replace the Schrader valve cores if you removed them
during the evacuation steps. You may now introduce
the refrigerant charge through the Schrader valves.
Refrigerant Charging Procedures
R407C refrigerant must be weighed in when performing
the charge.
When charging a system with a blended refrigerant,
maintaining the composition of the refrigerant is essential.
To ensure correct composition, introduce the refrigerant
(R407C) into the system in liquid form rather than vapor
form. Cylinders which are not provided with dip tubes
should be inverted to allow only liquid refrigerant to
charge the system. Keeping the temperature of the
cylinder below 85°F will help maintain the correct
refrigerant composition while the cylinder is emptied.
WARNING
Confined Space Hazards!
Failure to follow instructions below could result in
death or serious injury. Do not work in confined spaces
where refrigerant or other hazardous, toxic or
flammable gas may be leaking. Refrigerant or other
gases could displace available oxygen to breathe,
causing possible asphyxiation or other serious health
risks. Some gases may be flammable and or explosive.
If a leak in such spaces is detected, evacuate the area
immediately and contact the proper rescue or response
authority.
Initial System Charge
Follow the step-by-step instructions below to charge
systems using R407C refrigerant. The initial charge will be
performed by introducing liquid refrigerant (R407C) to the
discharge side of the compressor or an available liquid line
port with the A/C unit turned Off.
Break the vacuum by supplying liquid refrigerant to the
discharge port near the compressor until the pressure is
equalized. This holding charge allows the low pressure
switch to "hold" enabling the compressor to operate
throughout the process of charging the system.
Installation
29
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