HVAC Design Engineering Basic Course

A: — that's the most common mistake — assuming the freezestat is a silver bullet. It only reacts after the air side drops cold enough and stops airflow; if the fluid side can still freeze, the metal doesn't care that the fan is off. Tube splitting happens before controls save you.

A: — that's mixing airside chemistry with waterside thinking. The chloride salts plus dissimilar metals set up galvanic cells; you don't need aggressive acids or crazy velocities for fins to disappear in a few seasons.

A: — that's where people drift into wishful compliance. Codes update, but contracts don't magically follow; unless the contract or AHJ adopts the newer edition, you're bound to what's written, even if it's awkward during commissioning.

A: — people overthink this. NC plus a spring is blunt information: remove power and the metal moves where the spring wants it. There's no modulation logic left when the actuator is dead.