4 Cold Weather Operations
4 Cold Weather Operations
W W W . B A L T I M O R E A I R C O I L . E U
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COLD WEATHER OPERATIONS
About cold weather operation
BAC cooling equipment can be operated in sub freezing ambient conditions provided the proper measures are
taken. Listed below are general guidelines which should be followed to minimize the possibility of coil freeze-up.
As these guidelines may not include all aspects of the anticipated operation scheme, system designer and
operator must thoroughly review the system, location of the equipment, controls and accessories to ensure reliable
operation at all times.
Protection against sump water freezing
To prevent sump water from freezing, either sump heaters or a remote sump located in a heated indoor area must
be installed. For a seasonal shut down during the cold weather period, it is recommended to drain the sump.
Thermostats for electrical sump heaters for this equipment are set to maintain a sump water temperature of 4°C.
CAUTION
Switch off heaters when the sump is drained.
Capacity control
In addition to protecting the sump water, all exposed water piping, in particular make-up water lines should be heat
traced and insulated.
It is necessary to prevent the recirculating water from approaching freezing conditions when the system is
operating under load. The most « critical » situation occurs, if operation at subfreezing conditions coincides with
light load conditions. The key to protecting the recirculating water is capacity control by adjustment of air flow to
maintain the temperature of the recirculating water minimal above freezing point. As a rule of thumb this minimum
temperature is 5°C, but there are applications, where even lower temperatures can be accepted. (Contact your
local BAC Balticare representative for advice.)
The desired method to match the cooling capacity to load and weather conditions is to adjust the air flow by the
use of modulating controls (variable speed drives).
Alternatively, multi speed fan motors or fan cycling can be applied, but fans operating on a common heat exchange
section should always be operated simultaneously.
Whenever two speed motors are used for capacity control, a time delay of at least 15 seconds is required when
switching form high to low speed. Sudden switch over might damage the drive system or the motor.
When operating with VFD drives above nominal frequency be aware of the potential risk for motor overload
or mechanical damages.
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VT1
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