CG-SVX039C-GB
45
Evaporator Waterside
Freeze Protection
Depending on the ambient temperature the unit may be
exposed to freeze, there are multiple options for freeze
protection. They are listed in order of highest ambient
(least freeze protection) to the lowest ambient (most
freeze protection).
For all chiller running with water under cold ambient
temperature (below 0°C), it is extremely important to
keep full water flow in the evaporator for an extended
time after last compressor stops. This will protect brazed
plate evaporator from freezing by refrigerant migration.
This is why evaporator water pump output relay must
be used to control the chilled water pump. This is not
mandatory if glycol is used with protection down to
lowest ambient expected.
1. Water Pump and Heaters
a. Heaters are factory installed on brazed plates
evaporator. They will protect it from freezing in
ambient temperatures down to -18°C.Heaters are
installed on the water piping and on the pumps of
units equipped with hydraulic module.
b. 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.
c. Tracer™ UC800 controller can start the pump(s) when
freezing conditions are detected. For this option the
pumps must be controlled by the CGAF / CXAF unit
and this function validated on the chiller / Heat pump
controller.
d. Water circuit valves need to stay open at all times.
Note: Water pump control and heater combination
will protect the evaporator down to any ambient
temperature provided power is available to the
pump and the UC800 controller. This option will NOT
protect the evaporator in the event of power failure
to the chiller unless backup power is supplied to the
necessary components.
OR
2. Freeze Inhibitor
a. Freeze protection can be accomplished by adding
sufficient glycol to protect against freezing down to
the lowest ambient expected.
b. See “evaporator glycol requirement” section for
guidance on determining the glycol concentration.
Note: Use of glycol type antifreeze reduces the cooling
capacity of the unit and must be considered in the
design of the system specifications.
CAUTION! When using freeze inhibitor, never fill the
system with pure glycol.
Always fill the system with diluted solution. Maximum
concentration of glycol is 40%. Higher glycol
concentration will damage pump seal.
OR
3. Drain Water Circuit
For ambient temperatures below -20°C and for those
installation not including either option 1 or 2 above
described
a. Shut off power supply to unit and to all heaters.
b. Purge the water circuit
c. Blow out the evaporator to ensure that no liquid is left
inside the evaporator and the water lines. Drain the
pump.
Note: It is not recommended to drain the water circuit
for the following reasons.
1. The water circuit will rust and its lifetime could be
reduced.
2. Water will remain in the bottom of the plate heat
exchangers and freeze damage could occur
CAUTION! Evaporator damage!
If insufficient concentration or no glycol is used, the
evaporator water pumps must be controlled by the
UC800 to avoid severe damage to the evaporator due
to freezing. A power loss of 15 minutes during freezing
can damage the evaporator. It is the responsibility of
the installing contractor and/or the customer to ensure
that a pump will start when called upon by the chiller
controls. Please consult TRANE service for unit setting
and % of glycol required.
With factory-fitted disconnect switch option, evaporator
trace heating is taken from the live side of the isolator.
As a consequence, the heaters are energized as long as
the main switch is closed. Supply voltage to the heating
tapes is 400V.
• Avoid the use of very low or near minimum chilled
fluid flow rates through the chiller. Higher velocity
chilled fluid flow reduces freeze risk in all situations.
• Flow rates below limits have increased freeze potential
and have not been considered by freeze protection
algorithms.
• Avoid applications and situations that result in a
requirement for rapid cycling or repeated starting and
stopping of the chiller. Keep in mind that chiller control
algorithms may prevent a rapid compressor restart
after shutting down when the evaporator has been
operating near or below the LERTC (Low Refrigerant
Temperature Cutout) limit.
• Maintain refrigerant charge at appropriate levels. If
charge is in question, contact Trane service. A reduced
or low level of charge can increase the likelihood of
freezing conditions in the evaporator and/or LERTC
diagnostic shutdowns.
The warranty will be void, in case of freezing due to the
lack of use of either of these protections.
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