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3
JOHNSON CONTROLS
FORM 100.50-NOM6 (1207)
Example:
The suction pressure is 130 PSIG and the
suction line temperature is 57 °F
Suction Line Temperature = 57°F
Saturation Temperature for 130 PSIG = 45°F
Evaporator Superheat = 12°F
When adjusting the expansion valve, the adjusting
screw should be turned not more than one turn at a time,
al low ing suf fi cient time (ap prox i mate ly 15 min utes)
be tween ad just ments for the system and the ther mal
ex pan sion valve to re spond and stabilize.
The superheat setting should be adjusted to 12°F at
design conditions.
Leak Checking
Leak check compressors, fi ttings and piping to assure
no leaks. Verify the evaporator distributor tubes do not
have bare copper touching each other or are against a
sheet metal edge. If you are leak checking a unit charged
with R-410A make sure the leak test device is capable
of sensing refrigerant R-410A.
If the unit is functioning satisfactorily dur ing the
ini tial op er at ing period, no safeties trip and the unit
controls are functioning prop er ly, the roof top unit is
ready to be placed into operation.