YORK INTERNATIONAL
126
INITIAL START-UP
After the control panel has been programmed and the
compressor heater has been on for 24 hours prior to
start-up, the chiller may be placed into operation.
q
1. Place the System Switches on the Microproces-
sor Board to the ON position.
q
2. The compressor will start and a flow of refriger-
ant will be noted in the sight glass. After several
minutes of operation, the bubbles in the sight
glass will disappear and there will be a solid col-
umn of liquid when the TXV stabilizes. After the
water temperature stabilizes at desired operat-
ing conditions, the oil should be clear.
q
3. Allow the compressor to run a short time, being
ready to stop it immediately if any unusual noise
or adverse conditions develop. Immediately at
start-up, the compressor will make sounds dif-
ferent from its normal high pitched sound. This
is due to the compressor coming up to speed
and lubrication changing from liquid refrigerant
to oil. This should be of no concern and lasts for
only a short time.
q
4. Check the system operating parameters. Do this
by selecting various displays such as pressures
and temperatures. Compare these to test gauge
readings.
CHECKING SUPERHEAT AND SUBCOOLING
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 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 then normal. (Normal discharge/con-
densing pressure can be found in the refrigerant tem-
perature/pressure chart; use entering air tempera-
ture +30°F for normal condensing temperature.
b.
The temperature of the liquid refrigerant out of the
condenser should be not be more than 15°F less
than the condensing temperature (The temperature
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, con-
verted to temperature from the temperature/pressure
chart.
Example:
Liquid line pressure =
202 PSIG converted to
102°F
minus liquid line temp.
- 87°F
SUBCOOLING =
15°F
The subcooling should be adjusted to 10 - 15°F.
q
1. Record the liquid line pressure and its corre-
sponding temperature, liquid line temperature
and subcooling below:
SYS1 SYS 2 SYS 3 SYS 4
Liq Line Press = _____ _____ _____ _____ °F
Temp = _____ _____ _____ _____ PSIG
Liq Line Temp = _____ _____ _____ _____ °F
Subcooling = _____ _____ _____ _____ °F
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 super-
heat setting for a system is 10 - 15°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 =
46°F
minus Suction Press
60 PSIG converted
to Temp
- 34°F
12°F
The suction temperature should be taken 6" before the
compressor suction service valve, and the suction pres-
sure 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 10 - 15°F.
Содержание Millennium YDAS 410
Страница 135: ...FORM 201 10 NM4 135 YORK INTERNATIONAL ...
