Pressure Testing Of The Refrigeration System - Fisher & Paykel 790 Active Smart Service Manual

7.16

Pressure Testing Of The Refrigeration System

The use of the in-line pressure gauge can speed up and eliminate the incorrect diagnosis of a leak within a
refrigeration system. In some cases it has been found to be the service manifold that was being used that
was leaking and not the system. There are very few parts on the in-line pressure gauge that can leak.
Rule one:
In pressure testing any cabinet, before disconnecting any joint please be 100% sure that it is not the joint
that is at fault, otherwise a lot of time can be lost looking for a joint/leak that doesn't exist.
Rule two:
NEVER
Only use dry nitrogen to pressure test a system, NOT REFRIGERANT OR COMPRESSED AIR.
OXYGEN
Rule three:
Don't over pressurise the system. It could be dangerous.
How to use the In-line Pressure Gauge
Step 1:
Cut and connect the pipe circuit to be tested to the in-line pressure gauge and braze this joint.
Step 2:
At the other end of the pipe circuit being tested, crimp off the pipe with crimp off pliers and braze this end off
to totally seal the circuit.
Step 3:
Connect a nitrogen bottle to the in-line pressure gauge by means of a hose with a Schrader valve-
depressing key in the hose coupling.
Step 4:
Open the nitrogen bottle fully with the regulator backed off.
Step 5:
Increase the regulator pressure in the circuit being tested to 150 psi.
Step 6:
Close nitrogen bottle valve, back off pressure regulator.
Step 7:
Disconnect the hose coupling to the Schrader valve fitting.
Step 8:
Seal the Schrader valve with its sealing cap.
Step 9:
Use a bit of masking tape to mark the face of the pressure gauge at the set pressure. Record date and time
also.
Step 10:
Check all exposed brazed joints with soap bubbles including the joints on the in-line pressure gauge.
Step 11:
Allow pipe circuit under test to sit on drop off test. This could take a number of days for a result.
NOTE: In some cases a leak may not be found by pressurising the circuit whereas a vacuum pulled on the
same circuit will find it. Keep this in mind as oil within the circuit can block a hole.
In some cases, if the brazed joint is warmed while under pressure, this can thin the oil and help to expose
the leak. A heat gun or hair drier is useful.
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