Odd Compressor Problem

[boneyard]

Having a tough time figuring out what is going on here. I'm in the middle of a garage renovation project and going about it completely the wrong way: instead of starting with an empty building, I'm forced to work around multiple cars, machines, etc. As I'm working, it's like playing a full scale game of Tetris.

Anyway, I got to a point where I was able to put my compressor back where it is going to go and try to test out the new outlet that I put in. Here is the problem: As soon as I plug in the compressor, the motor fires right up. This is with the switch on (what I believe is) the pressure switch/starter set to "off". I tried switching to 'auto', but the switch doesn't want to move. Everything was fine 2 weeks ago when I was last able to use the compressor.

If it matters, the compressor is a couple year old Eaton 80 gallon upright with a 7.5hp motor and a Condor MDR3 pressure switch/starter assembly.

 

[jahcure]

You should Open the box to inspect contacts and switching mechanism and take it from there.

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[jkwilson]

New wiring?

 

[boneyard]

Not sure what you mean jk? I didn't change any wiring on the compressor, only installed a new wall outlet.

Jah: I did open the box, but didn't really see anything in the way of exposed contacts or anything like that

 

[LS6 Tommy]

Sounds like the pressure switch is stuck or its contacts welded. Can you post a picture of the pressure switch with the cover off, possibly showing the contacts?

Tommy

 

[boneyard]

Sounds like the pressure switch is stuck or its contacts welded. Can you post a picture of the pressure switch with the cover off, possibly showing the contacts?

Tommy

That makes sense I guess, but what would cause that while the compressor was just sitting there? If there was a problem with the outlet that I added, the breaker should have just tripped, right?

 

[GYPSY400]

Low voltage causes high amperage.. High amperage causes contacts to weld up


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[gregtwojeeps]

Having a tough time figuring out what is going on here. I'm in the middle of a garage renovation project and going about it completely the wrong way: instead of starting with an empty building, I'm forced to work around multiple cars, machines, etc. As I'm working, it's like playing a full scale game of Tetris.

Anyway, I got to a point where I was able to put my compressor back where it is going to go and try to test out the new outlet that I put in. Here is the problem: As soon as I plug in the compressor, the motor fires right up. This is with the switch on (what I believe is) the pressure switch/starter set to "off". I tried switching to 'auto', but the switch doesn't want to move. Everything was fine 2 weeks ago when I was last able to use the compressor.

If it matters, the compressor is a couple year old Eaton 80 gallon upright with a 7.5hp motor and a Condor MDR3 pressure switch/starter assembly.

Sounds like in jostling it around while moving it, something may have moved out of alignment in the mechanical parts on the OFF/AUTO selector switch leaving it in the manual ON position. Hard to tell from where I sit. good luck to you.

 

[LS6 Tommy]

I can't really tell anything from the photo. Sorry!

Tommy

 

[boneyard]

Low voltage causes high amperage.. High amperage causes contacts to weld up


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Admittedly, I know enough about electrical work to be dangerous. Isn't the high amperage condition exactly what a circuit breaker is supposed to prevent?

I'm pretty much certain at this point that I'm just going to have to buy another assembly to fix the problem, but I want to make sure that I don't end up frying the new one as well.

 

[Tim The Tool Man]

try running it from the old location/junction box. Could you have used too small a gauge wire when installing the new box?

 

[larry_g]

Did you run the compressor up to pressure? So you know what the cutoff pressure has been? If the hand switch no longer works then you could have a couple of problems. One the mechanics of the hand switch could have failed and the you can't manually shut it off. second is that the contacts have welded together, not likely. If you run it up to pressure and it cuts off like it should then your contacts are not welded and the pressure switch is working. The hand switch is usually just a mechanical override to prevent the contacts from closing.

My suggestion would be to run it up to pressure keeping a close eye on it to make sure it cuts off correctly and be prepared to pull the plug if necessary. You did say that it runs when plugged in so I am assuming that your wiring is correct in the new receptacle. If it runs and cuts off correctly they your good to go with the inconvenience of not having a hand switch. If the pressure switch works then you have to make the decision if its worth replacing to have the hand switch integrated.

Having a plug on a 7.5 hp pump is another issue to be addressed later.

lg
no neat sig line

 

[boneyard]

try running it from the old location/junction box. Could you have used too small a gauge wire when installing the new box?

A good suggestion, but not really practical at this point. The wire size shouldn't be an issue. I just put the new receptacle in the middle of the old run -- now somewhat closer to the panel.

Did you run the compressor up to pressure? So you know what the cutoff pressure has been? If the hand switch no longer works then you could have a couple of problems. One the mechanics of the hand switch could have failed and the you can't manually shut it off. second is that the contacts have welded together, not likely. If you run it up to pressure and it cuts off like it should then your contacts are not welded and the pressure switch is working. The hand switch is usually just a mechanical override to prevent the contacts from closing.

My suggestion would be to run it up to pressure keeping a close eye on it to make sure it cuts off correctly and be prepared to pull the plug if necessary. You did say that it runs when plugged in so I am assuming that your wiring is correct in the new receptacle. having a plug on a 7.5 hp pump is another issue to be addressed later.

lg
no neat sig line

I didn't run it up to pressure. When I attempted to fire up the compressor for the first time on the new receptacle, I verified that the switch was in the off position, then plugged in the compressor. When I did, it automatically started up, which startled me a bit. I pulled the plug and started to investigate. This was when I noticed that I couldn't move the switch.

Unfortunately, I made the situation worse a few minutes ago. I attempted to pull things apart and locate the contacts and see what was going on there. What I succeeded in doing was cracking the plastic mount for the control box.