Table of Contents
Advertisement
System Start-Up
the water temperature stabilizes at desired op-
erating conditions, the oil should be clear.
G
3. Allow the compressor to run a short time, be-
ing ready to stop it immediately if any unusual
noise or adverse conditions develop. Immedi-
ately at start-up, the compressor will make
sounds different from its normal high pitched
sound. This is due to the compressor coming
up to speed and lubrication changing from liq-
uid refrigerant to oil. This should be of no con-
cern and lasts for only a short time.
G
4. Check the system operating parameters. Do this
by selecting various displays such as pressures
and temperatures. Compare these to test gauge
readings.
CHECKING SUBCOOLING AND SUPERHEAT
The subcooling should always be checked when charg-
ing the system with refrigerant and/or before setting the
superheat.
When the refrigerant charge is correct, there will be no
bubbles in the liquid sight glass with the system operat-
ing under full load conditions, and there will be 6 - 8°C
(10 - 15°F) subcooled liquid leaving the condenser.
An overcharged system should be guarded against. Evi-
dences of overcharge are as follows:
a. If a system is overcharged, the discharge pressure
will be higher than normal. (Normal discharge/con-
densing pressure can be found in the refrigerant tem-
perature/pressure chart; use entering air temperature
+17°C (30°F) for normal condensing temperature.
b. The temperature of the liquid refrigerant out of the
condenser should be not be more than 8°C (15°F)
less than the condensing temperature (The tempera-
ture corresponding to the condensing pressure from
the refrigerant temperature/pressure chart).
The subcooling temperature of each system should be
calculated by recording the temperature of the liquid
line at the outlet of the condenser and subtracting it
from the recorded liquid line pressure at the liquid stop
valve, converted to temperature from the temperature/
pressure chart.
Example:
Liquid line pressure =
202 PSIG converted to
minus liquid line temp.
SUBCOOLING =
The subcooling should be adjusted to 7-8°C (12 - 15°F).
98
39°C (102°F)
- 31°C (87°F)
8°C (15°F)
G
1. Record the liquid line pressure and its corre-
sponding temperature, liquid line temperature
and subcooling below:
SYS 1
SYS 2
Liq Line Press = ____
____
Temp = ____
____
Liq Line Temp = ____
____
Subcooling = ____
____
After the subcooling is set, the suction superheat should
be checked. The superheat should be checked only af-
ter steady state operation of the chiller has been estab-
lished, 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 6 - 7°C (10 - 12°F).
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 tem-
perature corresponding to the suction pressure as shown
in a standard pressure/temperature chart.
Example:
Suction Temp =
minus Suction Press
60 PSIG converted
to Temp
The suction temperature should be taken 13 mm (6") be-
fore the compressor suction service valve, and the suc-
tion pressure is taken at the compressor suction service
valve.
Normally, the thermal expansion valve need not be ad-
justed in the field. If, however, adjustment needs to be made,
the expansion valve adjusting screw should be turned not
more than one turn at a time, allowing sufficient time (ap-
proximately 15 minutes) between adjustments for the sys-
tem and the thermal expansion valve to respond and settle
out. Assure that superheat is set at 6 - 8°C (10 - 15°F).
G
2. Record the suction temperature, suction pres-
sure, suction pressure converted to temperature,
and superheat of each system below:
SYS 1 SYS 2
Suction Temp = ____
____
Suction Press = ____
____
Temp = ____
____
Superheat = ____
____
SYS 3
SYS 4
____
____ kPa (PSIG)
____
____ °C
(°F)
____
____ °C
(°F)
____
____ °C
(°F)
8°C (46°F)
- 1°C (34°F)
7°C (12°F)
SYS 3 SYS 4
____
____ kPa
(PSIG)
____
____ °C
(0°F)
____
____ °C
(0°F)
____
____ °C
(0°F)
YORK INTERNATIONAL
Advertisement
Table of Contents
