wiring up a compressor.

ceilingwall · #1 (**permalink**) 09-23-2006, 02:53 PM

Hi, I am having problems getting a Ingersoll-rand compressor wired up to the power so that the pressure switch works, I know the switch works as you can see it trip when it get to the pressure required, but the problem I have is no-one know where the two black wires that come from the pressure switch go to in the star-delta switch, they must go to the star-delta switch as all the wires go down a flexy armour cover, the machine is 3 phase two stage 60 gal, I have wired it up with the two black wires going nowhere and it runs perfectly but with the two black wires not being connected to some point the pressure switch will not click in to stop it, as I have said you can see and hear it click in as the required pressure is reached but will not stop the compressor, I have tried electricians to on joy, so can anybody help out with this problem.

Three Peaks · #2 (**permalink**) 09-23-2006, 03:13 PM

With a 3 phase compressor, you will require a magnetic starter with an on/off switch . The pressure switch control wires go in series between the switch and the hot side of the coil power so it will operate when the switch is in the on position and won't come on automatically when it is supposed to be turned off.
If you need more help, e-mail me at bsfx(at)aol.com and I'll talk you through it. I'm an electrician/electrical contractor and I specialize in commercial/industrial work.

BTW, it is very dangerous to run your compressor without the pressure switch hooked up. The sound you are hearing isn't the switch, it is the blowoff valve letting off the excess pressure when it gets to the limit. If that fails you can damage the compressor tank or compressor head or get seriously injured.

Bob

rblong · #3 (**permalink**) 09-23-2006, 03:17 PM

Being three phase you will have starter that actually applies power to the motor. The starter will have a coil on it that is powered to make it close power. If yours is two stage I assume you mean you have two motors/compressors? You may have two starters. Depending on whether your compressor system was designed run the compressors simultaneously, staged or alternating will make a difference how they are wired. Tell me what components you have on th system.

Excaliber · #4 (**permalink**) 09-23-2006, 03:48 PM

A typical two stage compressor is simply a single TWO cylinder compressor. First stage pumps into second stage and then into the storage tank.

The bulk of my work is to follow someone like Three Peaks around and wire that LOW voltage contactor that supplies HIGH voltage to the compressor motor, to a computer. "Industrial Controls"

trularin · #5 (**permalink**) 09-23-2006, 06:18 PM

Bob is correct, you will need a contactor or motor starter 'relay' in a box with Flex line going between the motor and the box.

Allen Bradley is probably the most widely used where you can find parts and service. There are parts on ebay just about every week.

May I suggest you visit ebay and find a 110 VAC coil, three contact motor starter.

All three of the incoming wires get connected to it, and then three more wires go to the motor. One leg can be tapped for the coil voltage. it will go to your pressure switch, then the other side goes to the contactor or motor starter. The other side of the contactor coil goes to neutral.

Hope this helps.