# Clarke compressor won't shut off



## William Higgs (Mar 10, 2021)

I have a Clarke 2HP/ Twin Tank air compressor that will not shut off. It keeps pumping air into the tanks until it exceeds the max safe pressure and then the escape vlave opens up and it releases all the pressure in the tanks. Can you tell me what is going on? What part do you think I need to replace? 
Thanks


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## stevon (Mar 5, 2019)

Will,

Your electric pressure switch contacts have welded "on" and won't release when they should "open" at peak set pressure.
This is a maintenance item to replace like a check valve or air filter in store quality compressors. That's why most commercial units over 2 HP have a magnetic starter to avoid this problem. When an electric motor starts from 0 rpm, and especially under a load, up to ten times the FLA current is needed to make the rotor turn or start turning. This is what is meant by the term LRA "locked Rotor Amps". So if your Full load amps listed on the motor is say 12 amps, it will take up to 120 amps for a second or more for the compressor to start up. This load is put through the contacts of a pressure switch, and all pressure switches will eventually weld shut (get stuck on) without out the use of a magnetic starter. This is also why a pressure switch is rated in HP along with maximum load. Example 15 amp contact load rating is listed for 3/4 HP motor or less.

Stephen

Stephen


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## stevon (Mar 5, 2019)

Will, 

You are lucky and I am glad that your safety valve worked like it should otherwise you would have had a bomb go off in your house!










Stephen


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