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Old 08-15-2010, 05:35 PM   #1
8ntsane
 
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Default Air Compressor wiring hookup?

Hello everyone
I have a buddys air compressor to hook up, and have a question regarding the wiring to to pressure switch. This is a 5hp , 575v 3-phase job. He picked this up used, and when I got over to his place, I found all the wiring removed from the unit. all it had was the wires hanging out of the motor. Kinda made me step back and have another look.

The pressure switch is a Furnas 69HA U1 , now this is the part that puzzles me? The Pressure switch has 4-terminals on it. The two outside ones are maked (line, L1 & L2) and the two middle ones are marked (Motor)

The inside of the cover says 2-pole rating, for 1-phase , 3-phase , and DC. The listing for 3-Phase says 240-600v -5hp. I,m not used to any of this compressor hook up, so shouldn,t this have 6-terminals L1-L2-L3 for line in, and T1- T2-T3 to the Motor? This just seems weird to me that it only has provision for what appears to be single phase hook-up.

Maybe compressors have there own way of wiring these pressue switches, I don,t know. After installing the disconnect, and running the wiring over to the compressor, I didnt go any farther with the job, because of this.
I did temporary hook the motor up direct, too see if it was ok,it started and ran, so that works.
If any one knows how to hook up this pressure switch , or let me know if there is a site that shows how they are normally wired, would be most helpfull.

Thanks guys

Paul



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Old 08-15-2010, 06:42 PM   #2
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Default Re: Air Compressor wiring hookup?

A 5 HP motor has to have a magnetic starter connected between the breaker panel and the motor. The pressure switch you have is just used in pilot duty to operate the magnetic starter.

This is probably a case where your friend should get an electrician to do the hookup.



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Old 08-15-2010, 07:15 PM   #3
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Default Re: Air Compressor wiring hookup?

Maybe one of the electricians here may be able to answer. Not something I would want to guess on. Your buddy should probably talk with or hire a local pro. 3 phase high voltage in not something to take lightly and a 5 hp motor is an industrial size.
this question is a bit outside the hobby realm of this board. so do not be disappointed if you do not get a lot of feedback.
Tin

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Old 08-15-2010, 07:18 PM   #4
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Default Re: Air Compressor wiring hookup?

Opening two phases of a three phase motor makes it stop. No where for the electricity in the phase still connected to go. Shouldn't matter which two you hook up.


After thought - that is for delta connected three phase. Wye connected uses four wires, three hot and a neutral.

I found a wiring hook-up that shows the contactor opening and closing two of the three phases, maybe it'll give you the info you need. search google too!

Kermit

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Old 08-15-2010, 07:34 PM   #5
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Default Re: Air Compressor wiring hookup?

Hi Paul,
Electrical advice is trickey with out the location of the device as things like color codes might not be the same for all parts of the world.

Photos might help but, I think that an electrician to do the hook up is the best answer.

Dan

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Old 08-15-2010, 08:06 PM   #6
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Default Re: Air Compressor wiring hookup?

Hi just to put my 'ore' in


As the other chaps suggest this is a job for a professional ,

I've worked for a company that makes controlgear for them. for a number of years.


apart from a pressure switch you may have to wire a unloader valve as a lot of are electrical on 5 hp systems ..
under 1 -5 hp they are generally built into the pressure switch.

The other chaps are also correct in stating you will need a 'starter' ie contactor,or star-delta starter which is controlled bu the pressure switch

so same advice I'm afraid at least talk to a spark's

Steve


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Old 08-15-2010, 08:15 PM   #7
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Default Re: Air Compressor wiring hookup?

Kermit-

With all due respect, I would definitely not recommend your wiring diagram for the 3-phase situation described.

Pardon my criticism of you feedback, but I think it should be different.

SteamNut

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Old 08-15-2010, 08:49 PM   #8
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Default Re: Air Compressor wiring hookup?

Quote:
Originally Posted by steamnut2010
Be sure to verify anything on this forum with a licensed electrician
I agree 100% bad advice could be a costly mistake. A licensed electrician should be used for the job if you or your buddy do not have the proper qualifications.

Dan
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Old 08-15-2010, 09:05 PM   #9
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Default Re: Air Compressor wiring hookup?

Quote:
Originally Posted by steamnut2010
Kermit-

With all due respect, I would definitely not recommend your wiring diagram for the 3-phase situation described.

Pardon my criticism of you feedback, but I think it should be different.

SteamNut


I NEVER said to hook it up that way, I NEVER said it was a diagram of HIS situation. It was a diagram I found that illustrated the 'basic concept' of using two legs of a three phase circuit to stop or start a motor.

Forgive me of my criticism of YOUR feedback, but try a little harder to read what was written and keep in mind that I offered the diagram as an illustration of a relay that breaks two of the three phases for a three phase motor. Nothing more, nothing less.


Getting tired of the jump to a conclusion, hammer you over the head attitude of certain members here. READ what was written is all I ask. It's a written word forum for god's sake. Written words are all anyone here have to go by.

If I was going to make a diagram of his situation, I would have started by asking for a whole hell of alot more information than what he gave. Even then I doubt I would try to make any suggestions other than the very reasonable one given by yourself. "Get an electrician to do it".

The original poster described his contactor and that it was only labeled for two wires L1 and L2, then described his motor as a three phase motor labeled with 220-500 V three phase. I offered some insight into how that might be 'correct' for the equipment he had. Then I found a diagram that showed such a setup as drawn for a different purpose, not stated or written on the diagram.

The desire to see some other nefarious purpose behind it simply is not needed or called for. If you ask for help, I offer up what I know. If you want to know how to do a SPECIFIC task and I don't know how to that SPECIFIC task then I stay silent.

He didn't ask for specifics and I didn't give any.




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Old 08-15-2010, 09:09 PM   #10
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Default Re: Air Compressor wiring hookup?

Kermit-

My humblest apologies.
I will try and pay more attention and be a better forum contributor.

No offense meant in any way, so please don't take it that way.
Just trying to help.

SteamNut



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