Whether you have steam coils or non-freeze coils, any coil is capable of freezing. We often assume steam coils are to blame for a freeze. However, there are several other causes besides steam coils.
What Causes a Coil Freeze?
A freeze will typically occur in an older system. It’s also possible for a freeze to happen in a new system if it’s not correctly installed or maintained. Examples of incorrect installation include open dampers, failing controls, broken freeze stats, etc.
For both a Standard Steam and Steam Distributing Coil, a freeze happens when condensate freezes within the tubes of the steam coil. There are two main factors for frozen steam coils: the steam trap and the vacuum breaker.
The purpose of the steam trap is to remove the condensate once it forms. Condensate typically builds in the lowest part of the coil. If your steam trap is installed incorrectly, the condensate will lay in the coil and freeze as soon as it hits the outside air.
The role of the vacuum breaker is to clear the condensate, minimize water hammers, and help balance temperatures. It is crucial to install the breaker on the control valve and ALWAYS above the steam trap.
Frozen Coil Prevention
Sadly, it is impossible to predict where your steam coil will freeze. Many think that a frozen coil occurs when the condensate turns to ice and expands, causing the coil tubes to burst. In reality, the built-up pressure causes the coils to pop.
At Mainstream, we want to prevent your coils from freezing. Here are a couple of tips about coil design that may help prevent your standard steam and steam distributing coils from freezing:
- Standard steam coils should NEVER be exposed to outside air below 40 degrees.
- ⅝” OD Steam distributing coils over 72” long should have a dual supply
- 1” OD Steam distributing coils over 120” long should have a dual supply
- If it’s possible, make sure your steam coil is pitched. Doing so will angle the condensate to the return connection, which makes it easier to remove the condensate.