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Steam coil on 100% outdoor air
I've installed the controls on a operating room make up air unit. This is 100% outdoor air which goes through a steam coil, and a DX coil. Variable speed blower is controlled to maintain positive room pressure.
This unit is pretty much always calling for cooling, therefore a discharge temp of 50-55 is usually what is called for. This is all done via electronic controls (BMS).
This is a new install I did 2 months ago. Trouble is, the freeze stat keeps tripping now that we have below freezing outdoor temps. Tue steam valve is generally at 15-25% for proper discharge temps. Unit is sized for -30F outdoor temp I'm told.
Would it be best to put the freeze stat up high on the coil? I'd think the would be the hottest. However the bottom part of the coil is where condensate would be that could freeze. Currently I put the capillary for the freeze stat (as per the print) covering the whole coil. Its 15 feet long, coil is roughly 36" x 36".
Serving Northern Maine HVAC & Controls. I burn wood, it smells good!