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6.6 - Refrigerant line connections (30hZV)
6.6.1 - Recommendations for the installation of liquid
chillers with remote condensers
To guarantee optimum and reliable performance of the
30HZV units (split units for connection to condensers) it is
necessary to comply with the regulations described below,
when these units are connected to remote condensers.
1. Install a valve in the discharge piping (valves are
factory-installed in sizes 043-063, and supplied non-
installed in sizes 091-280).
2. Size the discharge and liquid line piping according to
the recommendations in the following paragraphs (if
necessary, install a double riser to ensure correct oil
circulation in the refrigerant circuit).
3. Depending on the layout and the routing of the dis-
charge piping it may be necessary to install additional
silencers (to reduce pulsations and noise emission)
between the liquid chiller and the condenser.
4. Select a condenser with an integrated subcooler to
obtain a minimum of 3 K subcooling at the inlet to the
expansion device.
5. Keep the condensing pressure as stable as possible
(pressostat staging or fan control via Pro-Dialog Plus).
A speed controller may be required for the first fan
stage for operation at low ambient temperature and
partial load.
6. If the system can have several operating modes (sum-
mer/winter, dual set point etc.), it is necessary to install
a tank (or receiver) to absorb the variations in charge.
6.6.2 - General
Refrigerant pipe sizing must be carried out, taking account
of the following constraints:
Oil return to the compressor must be ensured for the majo-
rity of applications. Oil return is ensured by entrainment. A
minimum refrigerant velocity is required to ensure entrain-
ment. This velocity depends on the pipe diameter, the refri-
gerant and oil temperature (these are treated as being the
same in most cases). A reduction of the pipe diameter per-
mits an increase of the refrigerant velocity. The problem of
a minimum entrainment velocity does not exist for the pipes
that carry liquid refrigerant as the oil is fully miscible here.
The pressure drop at the compressor discharge (pipes
linking the compressor outlet with the condenser inlet)
must be limited to avoid system performance losses (the
compressor power input inceases, and the cooling capacity
decreases).
As a first estimate and for standard air conditioning appli-
cations, a one degree Celsius pressure drop on the discharge
side decreases the cooling capacity 2% and increases the
compressor power input by 3%. Increasing the pipe diameter
permits limiting the pressure drops.
The pressure drop in the liquid line (linking the condenser
outlet to the expansion device) must not result in a change
in phase. The estimate of these pressure drops must include
those for the possible accessories, such as solenoid valves,
filters, filter drier, etc.
6.4.2 - Pipe connections
After welding the pipes to the flanges previously removed
from the water boxes:
1. Reinstall the pipes and tighten lightly to a torque at
the low end of the range.
2. Fill the system with water.
3. Wait for 10 minutes and check for minor leaks
-
at the water box joints
-
at the flange joints
4. Drain the system.
5. Disconnect the pipework.
6. Tighten the head bolts to their final torque (middle of
the range) in the sequence illustrated.
7. Reconnect the water pipes, tightening the flange bolts
to the mid-range torque value.
8. Refill the system with water.
9. Pressurize the system.
6.5 - Frost protection
The 30HZ and 30HZV units are designed to be installed
under cover at outside temperatures b5°C and
+40°C. Therefore they do not include anti-freeze protection,
as standard.
If the water piping is in an area where the ambient tempera-
ture can fall below 0°C it is recommended to install a trace
heater on the piping and to add an antifreeze solution to
protect the unit and the water piping to a temperature of
10 K below the lowest temperature likely to be reached at
the installation site.
Use only antifreeze solutions, approved for heat exchanger
duty. If the system is not protected by an antifreeze solution
and will not be used during the freezing weather conditions,
draining of the cooler and outdoor piping is mandatory.
Damage due to freezing is not covered by the warranty.
IMPORTANT: Depending on the climatic conditions in
your area you must:
•
Add ethylene glycol with an adequate concentration to
protect the installation up to a temperature of 10 K
below the lowest temperature likely to occur at the
installation site.
•
If the unit is not used for an extended period, it is
recommended to drain it, and as a safety precaution
add ethylene glycol to the heat exchanger, using the
water entering purge valve connection. At the start of
the next season, refill the unit with water and add an
inhibitor.
•
for the installation of auxiliary equipment, the instal-
ler must comply with basic regulations, especially for
minimum and maximum flow rates, which must be
between the values listed in the operating limit table
(application data).
