Thread: Pressure cut off switch
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Unread 17-02-2011, 17:02
Racer26 Racer26 is offline
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Re: Pressure cut off switch
You are correct, it DOES create the case where an error in the code causes the compressor to run continuously. This is however protected by the pressure relief valve (set between 125-130psi). If the compressor over-fills the system because the code didn't shut it off, the relief valve will open and dump the excess to atmosphere.

This rule has been in place since at least 2003.

I agree, the simpler, software-proof solution of series wiring the pressure switch with the relay would make more sense, and be less prone to problems like that, and it will work.

I believe the reasoning for the rule being the way it is, is due to the pressure switch not being rated for the ~25A startup current on the compressor. This means that while it does work, it will dramatically shorten the life of the switch, and one day, the switch will fail, and potentially fail closed.