Evacuation; Charging; Line Piercing Valves; Operating Test - Amana PTAC Service Instructions Manual

SERVICING
SILVER SOLDER (Alloy of 30% silver, 38% copper, 32% zinc.)
is used with fluoride base flux on copper to steel, brass to
copper, steel to steel, brass to steel. Recommended heat
is approximately 1200°F.

Evacuation

WARNING
TO PREVENT SEVERE BURNS. DO NOT ALLOW THE
SLUDGE OR OIL TO CONTACT THE SKIN.
This is the most important part of the entire service proce-
dure. The life and efficiency of the equipment is depen-
dent upon the thoroughness exercised by the serviceman
when evacuating air (non-condensables) and moisture from
the system.
Air in the system causes high condensing temperature and
pressure, resulting in increased power input and reduced
performance.
Moisture chemically reacts with the refrigerant and oil to
form corrosive hydrofluoric and hydrochloric acids. These
attack motor windings and parts, causing breakdown.
The equipment required to thoroughly evacuate the system
is a high vacuum pump, capable of producing a vacuum
equivalent to 50 microns, and a thermocouple vacuum gauge
to give a true reading of the vacuum in the system.
NOTE: Never use the system compressor as a vacuum pump
or run when under a high vacuum. Motor damage could
occur.
1. Connect the vacuum pump, vacuum tight manifold set
with high vacuum hoses, thermocouple vacuum gauge
and charging cylinder.
2. Connect the low side line to the process tube of the
compressor.
3. Connect the high side line to the process tube of liquid
line strainer.
NOTE: If either process tube is not long enough to receive
the compression or flare fitting and still leave room for a
pinch-off, swag the tube and braze in an extra length of
tubing.
4. Start the vacuum pump and open shut off valve to the
high vacuum gauge manifold only. After the compound
gauge (low side) has dropped to approximately 29 inches
of vacuum open the valve to the vacuum thermocouple
gauge. See that the vacuum pump will bank-off to a
minimum of 50 microns. A high vacuum pump can only
produce a good vacuum if its oil is not contaminated.
5. If the vacuum pump is working properly, close the valve
to the vacuum thermocouple gauge and open the high
and low side valves or the high vacuum manifold set.
With the valve on the charging cylinder closed, open
the manifold valve to the cylinder.
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6. Evacuate the system to at least 29 inches gauge before
opening valve to thermocouple vacuum gauge.
7. Continue to evacuate to a minimum of 250 microns.
Close valve pump and watch rate of rise. If vacuum
does not rise above 1500 microns in three minutes,
system can be considered properly evacuated.
8. If thermocouple vacuum gauge continues to rise and
levels off at about 5000 microns, moisture and non-
condensables are still present. If gauge continues to
rise a leak is present. Repair and re-evacuate.
9. Close valve to thermocouple vacuum gauge and vacuum
pump. Shut off pump and prepare to charge.

Charging

Charge the system with the exact amount of refrigerant.
Refer to the unit nameplate for the correct refrigerant
charge. An inaccurately charged system will cause future
problems.
1. When using an ambient compensated calibrated charg-
ing cylinder, allow liquid refrigerant only to enter the
high side.
2. After the system will take all it will take, close the valve
on the high side of the manifold.
3. Start the system and charge the balance of the refrig-
erant though the low side. Do not charge in a liquid
form.
4. Close the low side valve on the manifold and pinch-off
both process tubes. Remove the manifold set, crimp
shut the open ends of the process tubes and braze.
5. Recheck for refrigerant leaks.
NOTE: Do not use a refrigerant other than that shown on
the serial number identification plate.
All precautionary measures recommended by the refriger-
ant manufacturers and suppliers should be observed.

Line Piercing Valves

Line piercing valves may be used for diagnosis but are not
suitable for evacuating or charging due to the minute holes
pierced in the tubing.
Line piercing valves must not be left on the refrigerant sys-
tem. The connection between the valve and the refrigerant
tubing is not hermetically sealed and will eventually leak.
Open Lines
During any processing of the refrigeration system the lines
should never be left open to atmosphere since water vapor
will enter and add to the problem of proper evacuation.

Operating Test

The final step in a successful repair is an accurate operat-
ing test. Follow the Cooling and Heating Performance tests
provided to make sure the product is again performing to
design standards.