JOHNSON CONTROLS
125
SECTION 6 – COMMISSIONING
FORM 150.67-NM2
ISSUE DATE: 01/31/2019
6
FORM 150.67-CL1
ISSUE DATE: 1/21/2015
P.O. Box 1592, York, Pennsylvania USA 17405-1592 800-861-1001 Subject to change without notice. Printed in USA
Copyright © by Johnson Controls 2015 www.johnsoncontrols.com ALL RIGHTS RESERVED
Form 150.67-CL1 (115)
Issue Date: January 21, 2015
Supersedes: 150.67-CL1 (309)
D. CHECKING SUPERHEAT AND SUBCOOLING
The subcooling temperature of each system can be
calculated by recording the temperature of the liq-
uid line at the outlet of the condenser and subtract-
ing 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 =
325 PSIG converted to temp. 101 °F
Minus liquid line temp. -86 °F
Subcooling = 15 °F
The subcooling should be adjusted to 15 °F at
design conditions.
1. Record the liquid line pressure and its corre-
sponding temperature, liquid line temperature
and subcooling below: .......................................
SYS 1 SYS 2
Liq Line Press = ––––––– ––––––– PSIG
Saturated Temp = ––––––– ––––––– °F
Liq Line Temp = ––––––– ––––––– °F
Subcooling = ––––––– ––––––– °F
After the subcooling is veried, the suction superheat
should be checked. The superheat should be checked
only after steady state operation of the chiller has
been established, the 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 heat exchanger.
Superheat should typically be set for not 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 refriger-
ant 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), the
adjusting screw should be turned not more than one
turn at a time, allowing sufcient 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.
2. Record the suction temperature, suc-
tion pressure, suction saturation tempera-
ture, and superheat of each system below:
SYS 1 SYS 2
Suction Temp = ––––––– ––––––– PSIG
Suction Pressure = ––––––– ––––––– °F
Saturation Temp = ––––––– ––––––– °F
Superheat = ––––––– ––––––– °F
E. LEAK CHECKING
Leak check compressors, ttings, and piping to en-
sure no leaks. ..........................................................
If the unit is functioning satisfactorily during the initial
operating period, no safeties trip and the compres-
sors cycle to control water temperature to setpoint,
the chiller is ready to be placed into operation.
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