Trane TRG-TRC014-EN Freeze Protection for Coils, Measures to Prevent Coil Freeze-Up, period five

period five

Application Considerations

notes

Freeze Protection for Coils

RA	80°F
	[26.7°C]
	warm air
OA 10°F	mixed air
[-12.2°C]
	cold air
	cooling
	coil

Figure 98

Freeze Protection for Coils

As mentioned, proper VAV system ventilation often leads to a high percentage of outdoor air at part-load conditions. Streams of air at vastly different temperatures are difficult to mix and may cause the mixed air stream to stratify, resulting in a risk of freezing the water inside the cooling coil.

Air blending devices, mixing baffles, and high-velocity mixing dampers can provide effective mixing, but usually require more space in the air handler and more fan power. As an alternative, preheating the outdoor air before it enters the mixing box decreases this temperature difference, improves mixing and offers freeze protection for cooling coils.

Measures to Prevent Coil Freeze-Up

▲Drain coils during cold weather

▲Keep water in motion

▲Add glycol to the water

▲Use face-and-bypass dampers to limit amount of cold airflow through coil

▲Preheat the outdoor air (heating coil, heat recovery)

Figure 99

Even with effective mixing, the temperature of the mixed air entering the coil may approach that of the outdoor air during cold weather. This may cause water inside the cooling coil to freeze.

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