# Air Compressor wiring hookup?



## 8ntsane (Aug 15, 2010)

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


----------



## Stan (Aug 15, 2010)

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.


----------



## Tin Falcon (Aug 15, 2010)

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


----------



## Kermit (Aug 15, 2010)

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


----------



## Dan Rowe (Aug 15, 2010)

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


----------



## FIXIT (Aug 15, 2010)

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


----------



## steamnut2010 (Aug 15, 2010)

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


----------



## Dan Rowe (Aug 15, 2010)

steamnut2010  said:
			
		

> 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


----------



## Kermit (Aug 15, 2010)

steamnut2010  said:
			
		

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





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.


----------



## steamnut2010 (Aug 15, 2010)

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


----------



## Kermit (Aug 15, 2010)

My apologies as well, I seem to be in a fairly foul mood at the moment, not the result of anything here.

I regretted posting, but not until after I had pressed the post button.

Perhaps I should take some pain meds and get in the jacuzzi for a bit.

 :-\


----------



## steamnut2010 (Aug 15, 2010)

I have had more than a few off days lately, and I know the feeling.
Unfortunately, I have not been as nice to some folks as I should be.

This whole bunch of HMEM folks is really a great group and I think the world of them, also yes, I do get into some rather heated discussions some times when I should just let it go.

I love this board though and all of its members with all of their idiosyncrasies.
No better people out there in my opinion.


----------



## steamnut2010 (Aug 15, 2010)

If you have the unloader valve option, you will want to connect that up so that the motor does not have to start against the tank pressure. The unloader relieves the pressure from the output of the compressor long enough for the compressor to get started. My unloader went bad, and my compresser tried to start, but then locked up and tripped a breaker.

I have had plenty of air compressor woes lately.


----------



## steamnut2010 (Aug 16, 2010)

Here is an interesting note on electrical questions in general.
Due to the internet, anyone in the world can ask anyone else in the world electrical questions, and the answer depends on the respective country in which the two individuals reside.

Due to the transparency of the internet, it is very easy not to know where the person you are conversing with is from, and likewise, I am sure the other person probably does not know where you are.

All wiring advice goes out the window when you cross the border into another electrical system.
Voltages, frequency, etc. can all change, so any answer can be completely wrong.

One should never assume on these boards that the person posting is in the same country that you are.

That applies to this post also.


----------



## dsquire (Aug 16, 2010)

8ntsane  said:
			
		

> 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)
> ...



I would like to suggest that you please read this link. 

http://www.homemodelenginemachinist.com/index.php?topic=10130.0

Cheers 

Don


----------



## dsquire (Aug 16, 2010)

steamnut2010  said:
			
		

> Here is an interesting note on electrical questions in general.
> Due to the internet, anyone in the world can ask anyone else in the world electrical questions, and the answer depends on the respective country in which the two individuals reside.
> 
> Due to the transparency of the internet, it is very easy not to know where the person you are conversing with is from, and likewise, I am sure the other person probably does not know where you are.
> ...



I would like to ask you to please read this link.
http://www.homemodelenginemachinist.com/index.php?topic=10130.0

Cheers 

Don


----------



## steamnut2010 (Aug 16, 2010)

With the transparency of the internet, a safety hazard has been created that I was not aware of.
Solutions to electrical hookups depend on what country you are in, and what electrical system they use in that particular country.

I think one thing is very clear, and that is the fact that most electrical diagrams look very similar, but the seemingly most insignificant change that can be made to the diagram can determine the difference between safe and unsafe circuits. 

The internet is a great communications tool, but does have its safety drawbacks.


----------



## 8ntsane (Aug 16, 2010)

Hey guys
Skip this post
Its not worth some of you getting all excited.
Im suprized some of you guys turn your machines on with out panic.

Paul


----------



## steamnut2010 (Aug 16, 2010)

Paul-

This thread, like many others, is an educational tool, and the guys on the forum range anywhere from the beginner like myself to the very advanced machinists and builders.
Some of the threads come across a bit odd, but they are addressing a wide range of folks and experience, and I feel any thread is a learning experience, and therefore good.


----------



## steamnut2010 (Aug 16, 2010)

A buddy of mine use to say "IT'S ALL GOOD!"


----------



## zeeprogrammer (Aug 16, 2010)

steamnut2010  said:
			
		

> This thread, like many others, is an educational tool, and the guys on the forum range anywhere from the beginner like myself to the very advanced machinists and builders.
> Some of the threads come across a bit odd, but they are addressing a wide range of folks and experience, and I feel any thread is a learning experience, and therefore good.



Hear hear.


----------



## Stan (Aug 17, 2010)

I think I gave the correct advice in the first response. It was technically correct and done very politely.

Now on the third page of responses, I will be more blunt. No inexperienced person should be playing with 575 volt 3ph power.

I won't even get into the electrical code and the liabilities when dealing with industrial power installations. I have been there when the inspector had power turned off to the building when he found an non approved installation.


----------



## steamnut2010 (Aug 17, 2010)

The information I first posted above does not apply to this person's specific situation, so I am going to remove it to prevent confusion and to prevent misapplication.

There are those on the this forum who have 25+ years experience with designing 600V, 4,160V, 12,500V, and 23,000V systems.
The experience is here, it just has to be used carefully and safely, and best done off this forum in my opinion, since there are too many variables to be able to give safe answers on a forum.


----------



## Maryak (Aug 17, 2010)

steamnut2010  said:
			
		

> there are too many variables to be able to give safe answers on a forum.



And on that note gentlemen, the topic is closed

Best Regards
Bob


----------

