Frozen Steam Coils

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Frozen Steam Coils

Slow down for a few minutes and try to figure out why the steam coil froze. Because if it happened once, chances are it’s going to happen again.

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bill_brooks

i used to have this problem with steam coils (preheat) on the ground floor air handlers. the
freeze stats were always affected and consequently shutting down the air handlers.
not wanting this to happen, we drained the coils and quit using them. a rather poor solution, but it prevented those coils from freezing. the return air was used to supplant.
turns out the older parts of the bldg. had their coils well inside the bldg. and with return air
dumping AHEAD of the coils thus keeping them from freezing.
the newer coils had their freezestats jumpered-out to keep the ahus from shutting down.

had the newer design called for a similar placement, this problem would not have occurred.
the difference between 1975 design philosophy and 1985. naturally the later ASHRAE
standards required more OAT forcing the newer steam coils nearer the outside.

EBEBRATT-Ed

Also, what should happen is the coils need a manual reset freeze stat. If the freeze stat trips it should close any outdoor air dampers, kill the fan motor and put the control valve wide open to save the coil

You can have 1 freeze stats with a manual reset. and also a low limit (set slightly higher) to put the steam valve wide open.

Also if you read the instructions for installing a freeze stat the capillary tube should be zig zagged horizontal. Every one usually zig zags it vertically

Always a battle with the "control" people over this