kawaikfx400

So im still a new guy here in the electricial field, only been in 10 months but, a buddy of mine has an air compressor with a pressure switch. Its 240 into the motor,then it has a whip off of it to the pressure switch off the tank to shut it down when it reaches operatering pressure. But its not shutting down so i took off the switch. Replace it? And i dont understand how its 240 into the motor from the plug, then a whip to the switch. How does the switch tell it to shut off the motor? Is is low voltage sending back to the motor? and it was only 2 wires on one side of the pressure switch. I've wired some wells with the boss with these switches before, just never an air compressor.

randomkiller

The pressure switch is just breaking one leg of the 240v, just like switches in many appliances, one side is often hot.

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kawaikfx400

So it was wired correctly then? Being just 2 wires from the motor down thru some carflex into the pressure switch and landing on one side of the switch? I'm just trying to make sure everything was wired correctly before i purchase a new switch. Im asking the boss in the morning about this but im just confused right now and its driving me crazy.

micromind

It's very common, and completely legal to break only one leg of a 240 volt circuit like this. Almost all stoves and ranges do so, and heater thermostats that are wall mounted and two pole only break one leg unless they're turned all the way off.

As a side note, it's also legal, but not as common, to break 2 legs of a 3 phase motor circuit for control of the motor.

Rob

randomkiller

I see that all to often in cheap a/c equipment for the compressor circuits.

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A Veteran - whether active duty, retired, guard or reserve - is someone who, at one point in his life, wrote a blank check made payable to "The United States of America," for an amount of "up to and including my life."

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kawaikfx400

on another note, What would make a pressure switch not work? Can i adjust it at all? Doesnt seem like theres much to it.

randomkiller

If there are holes in the diaphram from moisture in the air the switch will not make. Some are and some are not adjustable.

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A Veteran - whether active duty, retired, guard or reserve - is someone who, at one point in his life, wrote a blank check made payable to "The United States of America," for an amount of "up to and including my life."

"One Nation Under God"