Tecumseh AH5540E, Service Handbook

Page: 93 / 120

85
WARNING! Never use a compressor to evacuate a system. Instead, use a high vacu-
um pump specifically designed for that purpose.
Never start the compressor while it is under deep vacuum. Always break a vacuum with
refrigerant charge before energizing the compressor.
Failure to follow these instructions can damage the hermetic terminal and may result in
terminal venting. As always, to reduce the risk of serious injury or death from fire due
to terminal venting, never energize the compressor unless the protective terminal cover
is securely fastened.
Charge the System and Check the Pressure Drop
Charge the system and place in operation. Follow the safety precautions outlined in “Sys-
tem Charging” on pages 5-6. Immediately after startup, check the pressure drop across
the suction line filter-drier. This will serve two purposes:
» Verify that the filter-drier selection was properly sized.
» Serve as a base point to which subsequent pressure checks can be compared.
Because the permissible pressure drop across the drier is relatively small, it is suggested
that a differential pressure gauge be used for the measurement.
Measure the Pressure Drop
After the system has been operating for an hour or so, measure the pressure drop across
the suction line filter-drier.
In the case of Compressor Housing Contamination, little change should be noted. The
pressure drop will, in most instances, be below that tolerable for a permanent installation
(see Table 5-7).
On the other hand, where System Contamination occurred, an increased pressure drop
will be measured. Change the suction filter-drier and the liquid line filter-drier whenever
the pressure drop approaches or exceeds that allowed for temporary operation during
cleanup (see Table 5-8).
Keep changing both the suction and liquid line filter-driers until the pressure drop stabilizes
at a figure equal to or below that permitted for permanent operation in a system (see Table
5-7). At this point, it is the service person’s option as to whether to leave the suction drier
in the system or remove it from operation.
If the system is to be opened to permit the permanent removal of the suction filter-drier, the
liquid line filter-drier should be changed once more.
Table 5-7: Suggested Maximum Pressure Drop (psi) for
Permanent Suction Filter-Drier Installation
Application Air Cond High Medium Low
Evaporator
Range, °F
+55 to +32 +55 to +20 +30 to -10 +10 to -20 -20 to -40
R-12, R-134a 2 2 1 1/2 1/2 1/2
R-22,
R-404A, R-
407C, R-502,
R-507
3 3 2 1 1/2