Hussmann Proto-Aire Installation Manual page 91

Protocol™ Installation and
Service Manual
will re-energize the solenoid when the condensing temperature reaches 65 °F. Consult
Engineering representative if adjustment of the T-STAT control is required.
FIELD PIPING & TXV SIZING
Besides standard discharge lines, the liquid return line from the condenser must also be
piped back to the unit when remote air-cooled units are used with low temp cases.
If the unit has low and medium temp suction groups, the protocol unit will have TWO
liquid lines leaving the unit- one for medium temp cases and one for low temp cases.
Only the liquid to the low temp cases will be subcooled to 50 °F. The liquid to the
medium temp cases will be at the condensing temperature.
Units with low temp ZFKV compressors must insulate the liquid line to the low temp
cases/walk-ins coolers since the refrigerant is at a subcooled temperature. Also, suction
line sizing should take into account the lower liquid temperature.
When expansion valves are selected for the cases, they should be sized for a liquid
temperature of 50 °F due to subcooling.
SERVICE
There is a shut off valve before the TXV for service of solenoids, the TXV, or the EPR in
the Low Temp economizer loop. Shut off valves are also present at each compressor
injection port.
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