Glycol Chillers : BC Series with MG Control Instrument
Page: 47
ADVANTAGE ENGINEERING, INC.
525 East Stop 18 Road Greenwood, Indiana 46142
317-887-0729 Fax: 317-881-1277
Service Department Fax: 317-885-8683
Email: service@AdvantageEngineering.com
adjustments are required, turn the adjusting nut on the top of the valve counter
clockwise to raise the refrigerant pressure and clockwise to lower the pressure.
Adjustments should be made only when the chiller is running at full load.
3.
Insufficient condenser water flow. Check condenser water pumping system.
4.
Condenser water temperature too high. Check cooling tower for proper
operation if used and the city water temperature if city water is used.
5.
Condenser water tubes scaled. Clean with brushes and chemicals approved by
the Advantage Service Department.
C.
Improperly set high pressure control. Have refrigeration serviceman reset or replace
the control if defective. Contact the Advantage service department for the proper settings.
Adjust on chiller control instrument.
4.4 SHUTS OFF ON LOW PRESSURE CONTROL
Note: Refrigerant low pressure limits are set on and monitored by the MG control instrument. If
the set low pressure limit is reached the refrigeration system is turned off by the control.
The low pressure limit automatically resets when the pressure rises above the cut-in
pressure value after a pre-set time delay to avoid short cycling. If the low pressure does
not reset contact the manufacturer’s service department for instructions.
If the unit low pressure limit is activated three (3) consecutive times during start-up the
unit will lock out and will not be allowed to start. When the chiller control locks out due to
low pressure after three (3) attempts, there is a problem that must be resolved before the
unit should be restarted. To re-start, the unit must be powered down and back on. This
should only be attempted after the cause of the low pressure condition has been found
and the issue has been resolved. Repeatedly re-starting the unit will cause damage to
the unit often including freezing and rupture of the chiller evaporator.
The low pressure switch is set to cut-out at 32°F and cut-in at 36°F - 39°F*. If a
low pressure condition exists for more than five seconds the compressor will
stop and a fault occurs.
After the refrigerant pressure rises above the cut-in pressure, a three minute time delay
will occur before the compressor restarts. This will protect the evaporator and compressor
from damage should a problem occur in the refrigeration system or if the chiller is
operated under circumstances which could cause damage to the refrigeration system.
A.
Low or no water flow through the evaporator. Adjust the flow per section 3.2.C.
B.
Air-cooled units:
Head pressure too low. Check that the entering air temperature is above 60°F.
If below 60°F, find out reason why.
C.
Water-cooled units:
Head pressure too low. Adjust condenser water regulating valve to
maintain 100°F - 105°F refrigerant condensing temperature*. Have a
refrigeration serviceman repair the valve or replace if defective.
* See Temperature-Pressure
chart in Section 8.2 for
refrigerant pressure.
* See Temperature-Pressure
chart in Section 8.2 for
refrigerant pressure.
