air compresser control

Furnas makes good contactors. The problem might be elsewhere though, I would check the compressor with an amprobe.

I always use a heavy duty relay to switch the motor & just let the regulator operate the pull-in coil of it-(which use very little current.) Try the surplus electronics houses for cheap relays--3Ø relays more popular--just use 2 wires for single Ø .

Richard

Get a bigger contactor. At least twice the HP or more of your compressor. Ebay has lots of them.

Bob AZ

Get a magnetic motor starter to handle the 'heavy lifting' - 5 HP is way too much for a standard pressure switch to handle by itself - I would use a mag starter on anything over 1 HP. And pressure switches don't have that long throw to clear the arc and self cleaning contacts. Change the pressure switch after you install the contactor, and it'll live practically forever at 'pilot duty'.

Motor starter contactors have the contacts mounted in a 45-degree Vee and they self-clean as they are actuated, are much more resistant to welding and sticking closed, and have a nice long arc path and arc chute system when opened to blow out the arc.

If you have a starter with an overload section and the right heaters/settings it'll trip out on a locked rotor overload long before the circuit breaker will - which can make all the difference between the 'Magic Smoke' staying inside the motor or escaping.

And as an extra bonus, with a mag starter it's really simple to rig a night cutoff switch on the compressor right next to the light switch at the door. That way it never starts if the shop is not in use.

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The only one I ever replaced I got from Grainger. I believe it was a Dayton, U.S.-made. That was 10 years ago, still working.

- - Rex Burkheimer Fort Worth TX

I second that. After replacing one years ago, including adaptation for a different design, and at a cost of about $50, my compressor still did not work. That's when I discovered the big red Reset button on the motor. It had been painted over with the green paint that covered everything.

His is apparently working but blowing through contactors. Unless the ones he's using are complete garbage and underrated, they shouldn't be burning up that fast.

I talked to the people at Mastertool and ordered a more heavy duty on/off control and I ordered a two-pole 40 amp per pole relay. This should take care of the problem. The relays that I were getting from Mastertool I believe were copies of Furnace brand. Although they looked the same there was Chinese writing on them.

If you use a relay or contactor to start the motor, you don't need any special or heavy duty pressure switch, you can use any old pressure switch you have that has the right range and deadband. Your pressure switch is only switching the contactor coil, that is around a half-amp inrush and a few milliamps to hold it closed.

You'll get a bit of back-EMF from the contactor coil that will cause a bit of arcing when the pressure switch opens the circuit, but even if you don't install any sort of snubber it's nothing a 30-amp rated pressure switch can't handle.

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Some mighty fine looking cues.

Gunner, who just scored some titanium for a couple ferrules on his Dufferin laminates.

"Pax Americana is a philosophy. Hardly an empire. Making sure other people play nice and dont kill each other (and us) off in job lots is hardly empire building, particularly when you give them self determination under "play nice" rules.

Think of it as having your older brother knock the shit out of you for torturing the cat." Gunner

I needed to get another pressure switch anyway as my present one is sometimes sticking. Wanted to start off fresh and the heavy duty one was only 5.00 more. Dick

Thanks for the compliment. I need to get that web-site up dated as I've put out many better looking cues than most of those. Dick