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79
safety is the absolute lowest pressure allowed for
operation. At start-up, the control system ignores
the low refrigerant pressure alarm for a period of 2
minutes to allow the system to build pressure. After
2 minutes, the control system returns to normal
operation and used the higher set point of the
standard low refrigerant pressure alarm.
In most cases, the 2-minute time delay for the low
refrigerant pressure will be sufficient to allow the
compressor(s) to build up the system refrigerant
pressure. In extreme conditions with -10°F
{-12°C}
or
cooler ambient air and/or additional cooling effect
due to wind, the chiller may experience a low
refrigerant pressure alarm after the initial 2-minute
bypass time has expired. Under these conditions,
multiple starts may be required to build the
refrigerant pressure.
Operate the system for approximately 30 minutes.
Check the liquid line sight glasses. The refrigerant
flow past the sight glasses should be clear. Bubbles
in the refrigerant indicate either low refrigerant
charge or excessive pressure drop in the liquid line.
An indication of a shortage of refrigerant is if
operating pressures are low and sub-cooling is low.
Normal sub-cooling ranges from 10°F
{-12°C}
to 20°F
{-6°C}
. If the sub-cooling is not within this range,
check the superheat and adjust if required. The
superheat should be approximately 10°F
{-12°C}
.
Since the unit is factory charged, adding or removing
refrigerant charge should not be necessary. If the
refrigerant pressure, sight glass, superheat, and sub-
cooling readings indicate a refrigerant shortage, gas-
charge refrigerant into each circuit, as required. With
the unit running, add refrigerant vapor by
connecting the charging line to the suction service
valve and slowly charging through the backseat port
until operating conditions become normal.
CAUTION: A clear sight glass alone does not
mean that the system is properly charged. Also,
check system superheat, sub-cooling, and unit
operating pressures. If both suction and
discharge pressures are low but sub-cooling is
normal, a problem other than refrigerant
shortage exists. Do not add refrigerant, as this
may result in overcharging the circuit.
Once proper flow and temperature are achieved,
press the Stop button. The unit is now ready to be
placed into service.
Preventive Maintenance
Once your chiller is in service, follow the
maintenance procedures as closely as possible. The
importance of a properly established preventive
maintenance program cannot be overemphasized.
Taking the time to follow these simple procedures
will result in substantially reduced downtime,
reduced repair costs, and an extended useful lifetime
for the chiller. Any monetary costs of implementing
these procedures will usually more than pay for
itself.
To make this as simple as possible, we recommend
the use of a checklist of the recommended service
operations and the times performed. At the end of
this manual, you will find a checklist to use for this
purpose. Please notice that there are locations for
logging the voltage readings, amperages, etc. With
this information, maintenance personnel may be
able to correct a potential problem before it causes
any downtime. For best results, take all readings with
a full heat load from process, preferably with similar
operating conditions each time. The following is a
list of suggested periodic maintenance.
Once a Week
1.
Check to make sure that the To Process
temperature is reasonably close to the Set Point
temperature. If the temperature stays more than
5°F away from the set point, there may be a
problem with the chiller. If this is the case, refer
to the Troubleshooting Chart or contact our
Customer Service Department.
2.
Check the chiller and/or process pump discharge
pressures. Investigate further if the pressure
starts to stray away from the normal operating
pressure.
3.
Check the suction and discharge refrigerant
pressure at the compressor.
