RTAD-SVX01F-E4 41
Installation - Mechanical
Freeze Protection
If the unit will remain operational at
subfreezing ambient temperatures,
the chilled water system must be
protected from freezing, following
the steps listed below
1 Heaters are factory-installed on the
packaged unit evaporator and will
protect it from freezing in ambient
temperatures down to -18°C (0°F).
2 Install heat tape on all water
piping, pumps, and other
components that may be damaged
if exposed to freezing
temperatures. Heat tape must be
designed for low ambient
temperature applications. Heat
tape selection should be based on
the lowest expected ambient
temperature.
3 Add a non-freezing, low
temperature, corrosion inhibiting,
heat transfer fluid to the chilled
water system. The solution must
be strong enough to provide
protection against ice formation at
the lowest anticipated ambient
temperature. Refer to Tables 1-22
for evaporator water storage
capacities.
Note: Use of glycol type antifreeze
reduces the cooling capacity of the
unit and must be considered in the
design of the system specifications.
Note: All Free Cooling units must be
freeze protected with 30% Ethylene
Glycol in the cooling loop circuit
which is the most convenient
percentage in order to protect the
unit against freezing.
Protection coverage with 30%
Ethylene Glycol:
- freezing point without burst effect
= - 13°C;
- freezing point with burst effect
= - 50°C.
In ambient temperatures below
-18°C, the water circuit must be
protected against freezing by the
one of the following methods:
- purge the water circuit or add an
an anti-freeze fluid.
- Activate the heat tapes on the unit
and do not shut the unit down.
Freeze protection with hydraulic
module and dual pump
To protect the chiller against freezing,
there are 5 means of protection:
• Using the proper glycol percentage
in the water (no risk of damage due
to power failure)
• Draining the unit during the cold
season. However, be aware of the
corrosion process when drained.
• Using the heat tape protection
(protect the unit down to -18°C)
• Using freeze protection by pump
activation.
• Using pump activation and heat
protection one being a safety for the
other.
CAUTION!
When using the freeze protection by
pump activation during the cold
season, water must be able to
circulate freely. Check that no closure
valve or other device might block
waterflow.
Note:
For dual pump hydraulic model,
activation of the heat tape is not done
through the thermostat but by the
pump controller.
Single pump hydraulic module does
not provide protection by pump
activation and require the thermostat.
Water Pressure Gauges
Install field-supplied pressure
components as shown in
Figure 18-23. Locate pressure
gauges or taps in a straight run of
pipe; avoid placement near elbows,
etc. Be sure to install the gauges at
the same elevation on each shell if
the shells have opposite-end water
connections.
To read manifolded pressure
gauges, open one valve and close
the other (depending upon the
reading desired). This eliminates
errors resulting from differently
calibrated gauges installed at
unmatched elevations.
Water Pressure Relief
Valves
CAUTION! To prevent shell damage,
install pressure relief valves in the
evaporator water system.
Install a water pressure relief valve
in the evaporator inlet piping
between the evaporator and the inlet
shutoff valve, as shown in
Figures 18-23. Water vessels with
close-coupled shutoff valves have a
high potential for hydrostatic
pressure buildup on a water
temperature increase. Refer to
applicable codes for relief valve
installation guidelines.
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