sections each with its own TEV (no liquid line solenoid
valves) but handling the same load, two methods may be used
to avoid operating interference between sections:
1. Use a separate discharge bypass valve for each evaporator
section.
2. Use one discharge bypass valve to feed two bypass lines
each with a check valve between the bypass valve and the
evaporator section inlet. The check valves will prevent
interaction between the expansion valves when the bypass
valve is closed.
CAUTION - Introduction of the bypassed gas
between the thermostatic expansion valve and
the distributor is not generally recommended.
Hot gas flowing through the distributor nozzle
and circuit tubes, that were sized for normal cool-
ing flow rates, causes excessive pressure drop.
Careful evaluation and testing should precede
any application where hot gas is bypassed
between the TEV and the distributor.
BYPASS TO EVAPORATOR INLET
WITHOUT DISTRIBUTOR
Many refrigeration systems and water chillers do not use
refrigerant distributors, but may require some method of com-
pressor capacity control. This type of application provides the
same advantages as bypassing hot gas to the evaporator inlet
with a distributor. All information relating to bypassing hot
gas to the evaporator inlet with a distributor, except that con-
cerning distributors or ASC’s, also applies to bypassing to the
evaporator inlet without a distributor.
BYPASS TO SUCTION LINE
On many applications, it may be necessary to bypass directly
into the suction line (fig. 2). This is generally true of systems
with multi-evaporators or remote condensing units, as well as
on existing systems where it is easier to connect to the suction
line than the evaporator inlet. When hot gas is introduced
directly into the suction line, the danger of overheating the
compressor and trapping the oil in the evaporator exists. As
the suction temperatures rise, the discharge temperature like-
wise starts to increase. This can cause breakdown of the oil
and refrigerant with the possible result being a compressor
burnout. This method offers added flexibility for multi-evap-
orator systems or remote systems because the hot gas bypass
components can be located at the condensing unit. However,
to insure oil return, special care must be taken in the system
piping.
DESUPERHEATING THERMOSTATIC
EXPANSION VALVE
On those applications where the hot gas must be bypassed
directly into the suction line downstream of the main expan-
sion valve’s bulb, an auxiliary thermostatic expansion valve
(commonly called a desuperheating TEV or a liquid injection
valve) is required. The purpose of this valve is to supply
enough liquid refrigerant to cool the hot discharge gas to the
recommended suction temperature. Most compressor manu-
facturers specify a maximum suction gas temperature of 65°F.
For these requirements, special desuperheating thermostatic
charges are available which will control at the proper super-
heat to maintain the suction gas at or below 65°F. For appli-
cations requiring suction gas temperatures appreciably below
65°F, contact Sporlan Valve Company or the compressor man-
ufacturer for assistance. In all cases the maximum per-
missible suction gas temperature published by the
compressor manufacturer must be followed.
INSTALLATION INSTRUCTIONS
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