Coil Freeze Protection - BAC HXV Operation & Maintenance Manual

Coil Freeze Protection

For protection against coil freeze-up, recommended coil fluid solutions are an industrial
grade inhibited ethylene glycol or propylene glycol solution. When the use of glycol is
not practical, the system must be designed to meet both minimum flow and minimum
temperature requirements.
Minimum Operation
When a glycol solution is not utilized, operate the system to meet the following conditions.
• Maintain the minimum recommended flow through the unit coils at all times.
• Maintain a minimum heat load on the circulating fluid so that the temperature of the
fluid leaving the prime surface coil (wet coil) is not less than 50°F (10°C). To maintain
the leaving fluid temperature at 50°F (10°C) when the process load is extremely light
or shut off, apply an auxiliary heat load to the circulating fluid and adjust the flow
to ensure that fluid leaving the prime surface coil (wet coil) maintains the minimum
required temperature.
HXV-1212x-xxxxTx-x, HXV-1218x-xxxxTx-x
HXV-1212x-xxxxQx-x, HXV-1218x-xxxxQx-x
HXV-1212x-xxxxHx-x, HXV-1218x-xxxxHx-x
Table 4. Minimum Coil Flow
Emergency Coil Drain
Do not drain the coils as a normal method of freeze protection. Frequent draining promotes
corrosion inside the coil tubes. However, draining is acceptable as an emergency method
of freeze protection if the coils are not protected by a glycol solution. If the coils are not
protected, automatic drain valves and vacuum breakers are recommended to drain both
the prime surface coil (wet coil) and the finned coils (dry coils) if flow stops or the fluid
temperature drops below 50°F (10°C) when the ambient temperature is below freezing.
Further protection against coil freeze-up is possible with the installation of an alarm to
alert personnel when the temperature of the fluid leaving the prime surface coil (wet coil)
falls below 50°F (10°C). Contact your local BAC Representative for guidelines on the
installation of an emergency coil drain system.
Model Number
Minimum Coil Flow
(USGPM)
175
220
350
Cold Weather Operation
Fan Section Icing Protection
Fan Control
Dry Operation
Basin Water and Internal Piping
Freeze Protection
Cold Water Basin Protection
Coil Freeze Protection
Minimum Operation
Emergency Coil Drain
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