JOHNSON CONTROLS
54
FORM 100.50-NOM6
ISSUE DATE: 8/07/2017
SECTION 3 – START-UP
Example:
On a YPAL 050 the discharge pressure is 388 PSIG and
the liquid temperature is 95 °F.+
Liquid Pressure = Discharge Pressure (388 PSIG)
- 33.0 PSIG
Saturation Temperature for 355 PSIG = 108°F
Minus the liquid line temp
= 95°F
Liquid Line Subcooling of
= 13°F
The subcooling should be 15°F at design conditions.
Superheat (R-410A)
The superheat should be checked only after steady
state operation of the unit has been established, the dis-
charge air temperature has been pulled down to within
the control range, and the unit is running in a fully
loaded condition.
The superheat is calculated as the difference between
the actual temperature of the refrigerant gas in the suc-
tion line and the temperature corresponding to the Suc-
tion Pressure as shown in
.
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, allowing sufficient time (approximately 15 min-
utes) between adjustments for the system and the ther-
mal expansion valve to respond and stabilize.
The superheat setting should be adjusted to 12°F at de-
sign conditions.
Leak Checking
Leak check compressors, fittings 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 during the
initial operating period, no safeties trip and the unit
controls are functioning properly, the rooftop unit
is ready to be placed into operation.
Содержание 050
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