Technical data

7.6.3 Vacuum Testing
Vacuum testing should be conducted as follows:
1. Connect a high capacity vacuum pump, with
indicator, to the system charging valve and start the
pump.
2. Open wide all system valves. Be sure all valves to
the atmosphere are closed.
3. Operate the vacuum pump until a wet bulb
temperature of 0°C or a pressure of 5 mm Hg
(absolute) is reached.
4. To improve evacuation circulate warm water (not to
exceed 50°C) through the evaporator and
condenser tubes to thoroughly dehydrate the
shells. If a source of hot water is not readily
available, a portable water heater should be
employed. DO NOT USE STEAM. A suggested
method is to connect a hose between the source of
hot water under pressure and the evaporator head
drain connection, out the evaporator vent
connection, into the condenser head drain and out
the condenser vent. To avoid the possibility of
causing leaks, the temperature should be brought
up slowly so that the tubes and shell are heated
evenly.
5. Close the system charging valve and the stop valve
between the vacuum indicator and the vacuum
pump. Then disconnect the vacuum pump leaving
the vacuum indicator in place.
6. Hold the vacuum in the system for 8 hours; the
slightest rise in pressure indicates a leak or the
presence of moisture, or both. If, after 8 hours the
wet bulb temperature in the vacuum indicator has
not risen above 4.4°C or a pressure of 6.3 mm Hg,
the system may be considered tight.
Be sure the vacuum indicator is valved off while holding
the system vacuum and be sure to open the valve
between the vacuum indicator and the system when
checking the vacuum after the 8 hour period.
7. If the vacuum does not hold for 8 hours within the
limits specified, the leak must be found and
repaired.
7.6.4 Refrigerant Charging
When opening any part of the refrigerant
system for repairs, the refrigerant charge
must be removed. If the chiller is equipped
with optional valves, the refrigerant can be
isolated in either the condenser or evaporator
/ compressor while making repairs.
To prevent liquid freezing within the evaporator tubes
when charging an evacuated system, only refrigerant
vapour must be added to the system until the system
pressure is raised above the point corresponding to the
freezing point of the evaporator liquid. For water, the
pressure corresponding to the freezing point is 58.9 kPa
for R134a (at sea level).
While charging, care must be taken to prevent
moisture laden air from entering the system.
Make up a suitable charging connection from new
copper tubing to fit between the system charging valve
and the fitting on the charging drum. This connection
should be as short as possible but long enough to permit
sufficient flexibility for changing drums. The charging
connection should be purged each time a new container
of refrigerant is connected and changing containers
should be done as quickly as possible to minimise the
loss of refrigerant.
7.7 Evaporator and Condenser
Maintenance of condenser and evaporator shells is
important to provide trouble free operation of the chiller.
The water side of the tubes in the shell must be kept
clean and free from scale. The following
recommendation should be followed in determining the
condition of the water side of the condenser and
evaporator tubes.
1. The condenser tubes should be cleaned annually
or earlier if conditions warrant. If the temperature
difference between the water off the condenser
and the condenser liquid temperature is more than
4° greater than the difference recorded on a new
unit, it is a good indication that the condenser tubes
require cleaning.
2. The evaporator tubes under normal circumstances
will not require cleaning. If however the
temperature difference between the refrigerant
and the chilled water increases slowly over the
operating season, it is an indication that the
evaporator tubes may be fouling or that there may
be a water by-pass in the water box requiring
gasket replacement or refrigerant may have leaked
from the chiller.
7-6 160.81-ICOM-GB0 (01/02)