York YLUA0248 Series Installation Operation & Maintenance page 93

FORM 150.73-NM2
ISSUE DATE: 09/07/2020
D. CHECKING SUPERHEAT AND SUBCOOLING
The subcooling temperature of each system can be
calculated by recording 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 (liquid line saturation temp. is converted from a
temperature/pressure chart).
Example:
Liquid line pressure =
202 PSIG converted to temp.
minus liquid line temp.
Subcooling =
The subcooling should be adjusted to 15°F at design
conditions.
Record the liquid line pressure and its corresponding
temperature, liquid line temperature and subcooling
below:
Liq Line Press = _______
Saturated Temp = _______
Liq Line Temp = _______
Subcooling = _______
After the subcooling is verified, the suction superheat
should be checked. The superheat should be checked
only after steady state operation of the condensing unit
has been established, the leaving water temperature
has been pulled down to the required leaving water
temperature, and the unit is running in a fully loaded
condition. Correct superheat setting for a system is 10°F -
15°F (5.56°C - 8.33°C) 18" (46 cm) from the cooler.
Superheat should typically be set for no less than 10°F
with only a single compressor running on a circuit. The
superheat is calculated as the difference between the
actual temperature of the returned refrigerant gas in the
suction line entering the compressor and the temperature
corresponding to the suction pressure as shown in a
standard pressure/temperature chart.
P.O. Box 1592, York, Pennsylvania USA 17405-1592
Copyright © by Johnson Controls 2012
Form xxx.xx-xx (xxx)
Issue Date: January xx, 2012
NEW RELEASE
JOHNSON CONTROLS
102°F
- 84°F
18°F
SYS 1 SYS 2
_______ PSIG
_______ °F
_______ °F
_______ °F
800-861-1001
www.johnsoncontrols.com
SECTION 6 – COMMISSIONING
Example:
Suction Temp =
minus Suction Press
60 PSIG converted to Temp - 34°F
Superheat =
When adjusting the expansion valve (TXV only), the
adjusting screw should be turned not more than one
turn at a time, allowing sufficient time (approximately 15
minutes) between adjustments for the system and the
thermal expansion valve to respond and stabilize.
Assure that superheat is set at a minimum of 10°F (5.56°C)
with a single compressor running on each circuit.
Record the suction temperature, suction pressure, suction
saturation temperature, and superheat of each system
below:
SYS 1
Suction Temp = _______ _______ °F
Suction Pressure = _______ _______ PSIG
Saturation Temp = _______ _______ °F
Superheat = _______ _______ °F
E. LEAK CHECKING
Leak check compressors, fittings, and piping to ensure
no leaks. ......................................................................
If the unit is functioning satisfactorily during the initial
operating period, no safeties trip and the compressors
cycle to control water temperature to setpoint, the chiller
is ready to be placed into operation.
Subject to change without notice. Printed in USA
FORM 150.73-CL2
ISSUE DATE: 10/29/2012
46°F
12°F
SYS 2
6
ALL RIGHTS RESERVED
93