Quantech
127
Section 6: Commissioning
Form QTC3-NM1
Issue date: 12/19/2023
6
Quantech
3
Form QTC3-CL1 (1123)
Issue date: 11/10/2023
Checking the superheat and subcooling
Calculate the subcooling temperature of each system by re-
cording the temperature of the liquid line at the outlet of the
condenser and subtracting it from the liquid line saturation
temperature at the liquid stop valve. The liquid line satura-
tion temperature is converted from a temperature-pressure
chart.
Example:
Liquid line pressure =
325 psig converted to temp. 101°F
minus liquid line temp. - 83°F
Subcooling = 18°F
Adjust the subcooling to 18°F (10°C) at design conditions.
1. Record the liquid line pressure and its saturated
temperature, liquid line temperature, and subcooling
below ........................................................................
SYS. 1 SYS. 2
Liquid line pressure = _______ _______psig
Saturated temp. = _______ _______ °F
Liquid line temp. = _______ _______ °F
Subcooling = _______ _______ °F
After verifying the subcooling, check the suction superheat.
Only check the superheat after establishing steady state
operation of the chiller, the leaving water temperature has
reached the required leaving water temperature, and the unit
is running in a fully loaded condition. The correct superheat
setting for a system is 10°F to 15°F (5.56°C to 8.33°C) 18 in.
(46 cm) from the heat exchanger.
Set the superheat for no less than 10°F with only a single
compressor running on a circuit. The superheat is the dif-
ference between the actual temperature of the returned re-
frigerant gas in the suction line entering the compressor and
the temperature corresponding to the suction pressure as
shown in a standard pressure-temperature chart.
Example:
Suction temp. = 46°F
minus suction press.
105 psig converted to temp. - 34°F
Superheat = 12°F
When adjusting the expansion valve, TXV only, turn the ad-
justing screw no more than one turn at a time, allowing suf-
cient time, approximately 15 min, between adjustments for
the system and the thermal expansion valve to respond and
stabilize.
Ensure that superheat is set at a minimum of 10°F (5.56°C)
with a single compressor running on each circuit.
2.
Record the suction temperature, suction pressure,
saturation temperature, and superheat of each sys-
tem below: ..................................................................
SYS. 1 SYS. 2
Suction temp. = _______ _______ °F
Suction pressure = _______ _______ psig
Saturation temp. = _______ _______ °F
Superheat = _______ _______ °F
Checking for leaks
Leak check compressors, ttings, and piping to en-
sure no leaks. ...............................................................
If the unit is functioning correctly during the initial operat-
ing period, with no safeties tripped and the compressors
cycle to control water temperature to the setpoint, the
chiller is ready for operation.
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