FORM 201.19-CL2 (309)
4
JOHNSON CONTROLS
Economizer Superheat
(Not all models are equipped with economizers)
Check economizer superheat at steady full compres-
sor load only, under conditions when the economizer
solenoid is energized. Measure gas temperature on
the economizer outlet pipe next to the expansion valve
bulb. Measure gas pressure at the back seat port of the
economizer service valve. Superheat as measured should
be 10°F to 12°F (5.6°C to 6.7°C).
Subcooling
Check liquid subcooling at steady full compressor load
only. It is important that all fans are running for the
system. Measure liquid line temperature on the copper
line beside the main liquid line service valve. Measure
liquid pressure at the liquid line service valve. Sub-
cooling should be 12°F to 15°F (6.7°C to 8.3°C). No
bubbles should show in the sight glass. If subcooling
is out of range add or remove refrigerant as required.
Do not overcharge the unit. The liquid flow to the main
evaporator TXV is subcooled further by the economizer,
increasing subcooling to between 22°F and 28°F (12°C
and 15°C) at ambients above 90ºF.
General Operation
After completion of the above checks for System 1, stop
the unit, switch “OFF” the
“
SYS 1
”
switch on the main
panel microprocessor board and repeat the process for
each subsequent system. When all run correctly, stop the
unit, switch all applicable switches to the
“
ON
”
position
and restart the unit.
