Service Valves; Processing The System - Tecumseh AH5540E Service Handbook

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SERVICE HANDBOOK

Service Valves

As shipped with the compressors, the rotolock service valves have a small plastic dust plug inside
the threaded end. Be sure to remove this plug before installing.
Service valves on Tecumseh systems are "front seated" by turning the valve stem clockwise. This
closes the valve and opens the gauge port.
Turning the stem counter-clockwise "back seats" the valve and thus opens the system and closes
the gauge port.
If present, the valve port to the system control (high pressure cutout, low pressure control, fan
control, etc.) is always open regardless of the position of the valve stem.
If the system is to be operated with the service gauge functioning, it is necessary to "crack" the
valve from its back seated position for the gauges to perform. Before removing the gauges, close
the gauge port by returning the valves to their fully open position (back seated).
Remember to check the packing gland nut (if present) on the stem for snugness before leaving the
job. Install the cover nut over the valve stem as a secondary safeguard against leaks at the stem.

Processing the System

The performance and longevity of a refrigeration system is strongly influenced by how the system
was "processed," that is, how the system was prepared for operation at the time of installation.
The procedure is:
1. On split systems, install the liquid and suction line. See "Refrigerant Line Sizes" on
pages 76-81 for recommended line sizes. A properly sized suction line accumulator is
recommended. See "Accumulator Selection" on page 98 for accumulator sizing. Insu-
late the suction line to reduce heat exchange and excessive return gas temperatures
to the compressor.
2. To prevent oxidation and scale forming inside the tubes, it is good practice to flow dry
nitrogen through the tubing during the soldering operations. A light flow of about ¼
cubic feet per minute is sufficient.
3. Install a properly sized filter-drier in the liquid line immediately ahead of the capillary
tube or thermostatic expansion valve (TEV).
4. A properly sized suction line filter-drier is recommended to protect the compressor. A
suction accumulator must be installed on those systems having defrost cycles (heat
pumps, low temperature refrigeration) or the likelihood of periodic floodbacks (bulk
milk coolers, ice machines). See "Accumulator Selection" on page 98 for accumulator
sizing.
5. Pressure test the system for leaks using the safety precautions outlined in "System
Flushing, Purging, and Pressure Testing for Leaks" on pages 4-5. Do not pressurize
the system beyond 150 psig field leak test pressure.
6. Use a vacuum pump (not the compressor) to draw a vacuum of 500 microns or less
from both sides of the system. Entry must be made to both the high and low sides of
the system to properly evacuate that portion of the system. Use a good micron gauge
to measure the vacuum. An accurate reading cannot be made with a refrigeration
gauge.
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 pro-
tective terminal cover is securely fastened.