How to Prevent Steam Coils from Freezing

How Do You Keep Steam Coils From Freezing?

You can freeze ANY coil, whether it has steam coils or a steam distributing (non-freeze) coil. When a freeze occurs, everyone instantly suspects the steam coil. When, in fact, there are various factors that must be considered prior to the coil.

Freezes are more common in older systems; nevertheless, if your new system is not properly maintained or installed, your steam coil can and will freeze. For example, you'd be shocked how many times dampers are left open, controls fail, freezestats don't work, and so on.

A freeze-up can occur in a standard steam or steam distributing coil when condensate freezes within the tubes of the steam coil. The steam trap and vacuum breaker are the two most prevalent causes of frozen steam coils. The purpose of a steam trap is to remove condensate as soon as it occurs. Condensate frequently gathers at the bottom of the coil. If your steam trap isn't properly installed, condensate will accumulate in the coil and eventually freeze when exposed to outside air. The vacuum breaker also aids in the removal of condensate, reduces water hammering, and compensates for temperature variations. This must be fitted on the control valve and always above the steam trap.

Unfortunately, there are no means to predict where your steam coil may freeze. A common misconception is that the condensate freezes and the expansion causes the tubes of the coil to pop. In reality, it's the pressure that builds up between freeze points.

Here are a few coil design guidelines to keep your regular steam and steam spreading coils from freezing:

Normal steam coils should NEVER be exposed to outdoor air below 40 degrees. If it does, steam distributing is the only way to go!

5/8” OD A dual supply is recommended for steam distributing coils more than 72" in length.

1” OD A dual supply is advised for steam distributing coils that are more than 120" in length.

If feasible, pitch your steam coil. This slopes the condensate to the return connection, making it easier to remove the condensate.

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