electrical box on compressor

[Vinko]

I forgot what this is call but I had it replaced a few years ago. The one before that lasted (as far as I can remember) since the original install of the compressor about 25 years ago.

Do you know what make this is? Where I can find them online?

Current problem is that the compressor isn't kicking in when it's getting low on air. And something happening because the Baldor engine's running hot. Maybe it's something simple? I haven't had a chance to really look at it. But last time this happened, we had to replace the box.

Compressor itself is a 120 gallon vertical Saylor Beal 755 Total workhorse so far!

Motor seems to run OK though and I took a video and will upload it if I can figure how

 

[Norcal]

IInside the box is a magnetic starter, try pushing the black bar on the lower part to reset the overload relay that is part of the starter if it has tripped.

 

[Dagny]

The purpose of the box is to protect the motor as well as turn it on and off. If the motor is running hotter then normal there might be something wrong with it. If it's single phase per haps a run capacitor. Three phase bearings or something binding in compressor. If it's not tripping then your pressure switch is probably sticking.

 

[Stuart in MN]

The manufacturer is Square D.

 

[justsam]

Look for a small box that has a small airline going to it and wiring (flex conduit) going into the box you have shown. Confirm that it is getting air pressure, nothing clogged, etc.

Make sure the electrical contacts in it are clean. (Turn off power first of course)

 

[Vinko]

IInside the box is a magnetic starter, try pushing the black bar on the lower part to reset the overload relay that is part of the starter if it has tripped.

Yes, black bar keeps getting tripped.

 

[Vinko]

The purpose of the box is to protect the motor as well as turn it on and off. If the motor is running hotter then normal there might be something wrong with it. If it's single phase per haps a run capacitor. Three phase bearings or something binding in compresso

Thanks dagney, stuart and justsam will check it out.

 

[wyliesdiesels]

If the overload is tripping then that means the motor is drawing too much current. U also indicated this is the case because u said the motor is getting hot. Is it tripping while starting or after it runs for awhile?

 

[Vinko]

If the overload is tripping then that means the motor is drawing too much current. U also indicated this is the case because u said the motor is getting hot. Is it tripping while starting or after it runs for awhile?

I'll have to check. I believe after it runs a while. I assumed the motor was getting hot at first because it kept trying to run to build up pressure. Maybe there's a communication problem somewhere where one thing doesn't know what the other is doing.

digression:

That said, out of curiosity I took at look at how much the Square D magnetic starter was: I see it's retail for $385 or so. And selling on Amazon for $168.00 -- I wonder how wholesale places are doing with stuff being discounted this much online? I guess if you're installing it -- fair play to you -- you've got to make a profit somewhere. But I wonder if this is hurting the trade at all.

 

[Norcal]

That starter prob. has a definite purpose contactor which is a cheap throwaway item, they are a lot cheaper then a starter w/ a proper contactor which is why compressor manufacturers use them.

 

[nehog]

I'll have to check. I believe after it runs a while. I assumed the motor was getting hot at first because it kept trying to run to build up pressure...

I'd venture a guess the problem is not the 'box' but the motor. I would not spend money replacing the box until you do proper diagnostics to determine where the problem is.

 

[wyliesdiesels]

I'll have to check. I believe after it runs a while. I assumed the motor was getting hot at first because it kept trying to run to build up pressure. Maybe there's a communication problem somewhere where one thing doesn't know what the other is doing.

digression:

That said, out of curiosity I took at look at how much the Square D magnetic starter was: I see it's retail for $385 or so. And selling on Amazon for $168.00 -- I wonder how wholesale places are doing with stuff being discounted this much online? I guess if you're installing it -- fair play to you -- you've got to make a profit somewhere. But I wonder if this is hurting the trade at all.

A starter simply starts and stops a motor and has an overload relay that protects the motor and wiring. Your starter and overload relay are functioning.

I would check the voltage at the motor starter. If youre not getting 240v minus about 5% then u have a voltage drop issue. A motor that is ran at reduced voltage will draw higher current and WILL run hotter than normal! This will cause the overload to trip.

Also, check that the fan on the motor is operating, if it has one.

If youre voltage is good, then u may have an issue with the pump putting too much load on the motor. Or an issue with the motor such as a bearing going out.

 

[Vinko]

A starter simply starts and stops a motor and has an overload relay that protects the motor and wiring. Your starter and overload relay are functioning.

I would check the voltage at the motor starter. If youre not getting 240v minus about 5% then u have a voltage drop issue. A motor that is ran at reduced voltage will draw higher current and WILL run hotter than normal! This will cause the overload to trip.

Also, check that the fan on the motor is operating, if it has one.

If youre voltage is good, then u may have an issue with the pump putting too much load on the motor. Or an issue with the motor such as a bearing going out.

Thanks. I'm going to check this. I've had sporadic problems since then.

Unfortunately I didn't "hear" about the problem until 3 months in (that pisses me off -- because one should report equipment probs right away, and given how much there is to do, you can't be everywhere and notice everything).

Anyway, the motor is apparently running at the temp it's supposed to (I thought it was getting hot but tech said it's within range of normal). One of three heaters is getting tripped (after running a while).

For a long time we could run this thing 16 hours a day with an impact and two Dotco grinders.

Now it seems like one impact and one docto and it will trip (though less frequently now).

I've written down run times, air pressure when it trips and a few other stats. I haven't really had time to look into it further but I appreciate all your wise counsel and will keep it as a "checklist" when I can really dig into this thing

Also noticed my auto-drain is kaput. I think it's about 3-4 years old. Need to get another one of those too.

 

[wyliesdiesels]

Thanks. I'm going to check this. I've had sporadic problems since then.

Unfortunately I didn't "hear" about the problem until 3 months in (that pisses me off -- because one should report equipment probs right away, and given how much there is to do, you can't be everywhere and notice everything).

Anyway, the motor is apparently running at the temp it's supposed to (I thought it was getting hot but tech said it's within range of normal). One of three heaters is getting tripped (after running a while).

For a long time we could run this thing 16 hours a day with an impact and two Dotco grinders.

Now it seems like one impact and one docto and it will trip (though less frequently now).

I've written down run times, air pressure when it trips and a few other stats. I haven't really had time to look into it further but I appreciate all your wise counsel and will keep it as a "checklist" when I can really dig into this thing

Also noticed my auto-drain is kaput. I think it's about 3-4 years old. Need to get another one of those too.

so its a 3 phase motor? Have u checked to make sure youre not loosing a leg to the motor? If u loose a leg to a 3 phase motor then the motor will single phase and draw more current.

 

[Vinko]

so its a 3 phase motor? Have u checked to make sure youre not loosing a leg to the motor? If u loose a leg to a 3 phase motor then the motor will single phase and draw more current.

Yes 3 phase.Wouldn't you always want to run a compressor of this size set up?

What is a leg? Sorry, I don't understand that terminology? It's probably basic but

 

[Norcal]

A "leg" is another term referring to a phase, if you lose a leg you, have lost a phase, meaning the motor is single phasing.

 

[wyliesdiesels]

Yes 3 phase.Wouldn't you always want to run a compressor of this size set up?

What is a leg? Sorry, I don't understand that terminology? It's probably basic but

Im not sure what youre asking.

Do u have 3-phase service or single phase?

What is the HP rating of the compressor?

It sounds like your motor is single phasing and overloading...

Have u figured anything out yet?

 

[Vinko]

Im not sure what youre asking.

Do u have 3-phase service or single phase?

What is the HP rating of the compressor?

I'm not sure what I was trying to ask either. I don't recognize my own horrible typos !

That said, yes it's 3 phase. 10 HP.

It's the SB 755 VT 120 / 3 phase.

Bottom model on the Saylor chart:

http://www.saylor-beall.com/air-compressors/tank-mounted-vertical

It sounds like your motor is single phasing and overloading...

Have u figured anything out yet?

I'll check it out.

By the way, I had a Furnas starter (original from about 1990 or 91 that I replaced in early 2013 (I just found some old pics I took at the time) and replaced it with the Square D. Or rather an Air Compressor Service Co. did.

That said, I haven't had a chance to revisit this -- so many other fires to put out and things to fix, that this took a back seat. It hasn't tripped in a month or two. Though to be fair, I'm no longer running 2-3 tools at same time for hours at a time. Though I've had an impact going hours at a time with no problem.

But I definitely need to revisit this, and keep in mind all the useful info on this thread

 

[wyliesdiesels]

Ok well my next question(that i already asked but u missed) is do u have 3 phase service or single phase service?

 

[Vinko]

Ok well my next question(that i already asked but u missed) is do u have 3 phase service or single phase service?

I didn't answer it? I did mention 3 phase above. I do have 3 phase service.

 

[wyliesdiesels]

I didn't answer it? I did mention 3 phase above. I do have 3 phase service.

U said the compressor was 3-phase but didnt answer about your service.

The reason i bring this up is because occasionally someone will have a piece of 3-phase equipment/motor and try to run it on single phase. The motor starter trips because the motor draws too much current only running on 2 legs....

What is the voltage of your service?

Im curious if youre having voltage sag issues which will cause the motor to draw more current than it should and thus cause the overload relay in the starter to trip. Or as i said earlier, youre loosing a leg and thus single phasing the motor which as i already said, will cause the overload relay to trip.

Do u have a digital multi-meter that has 'high low' monitoring capability?

 

[Vinko]

U said the compressor was 3-phase but didnt answer about your service.

The reason i bring this up is because occasionally someone will have a piece of 3-phase equipment/motor and try to run it on single phase. The motor starter trips because the motor draws too much current only running on 2 legs....

What is the voltage of your service?

Im curious if youre having voltage sag issues which will cause the motor to draw more current than it should and thus cause the overload relay in the starter to trip. Or as i said earlier, youre loosing a leg and thus single phasing the motor which as i already said, will cause the overload relay to trip.

Do u have a digital multi-meter that has 'high low' monitoring capability?

I'll find out the voltage for you. This is an area I don't know much about. Do have a decent multimeter and will check. I've got an electrical room that's 10x10x10 and then sub-panels through out. I had asked the electrician (who lucky for me came out of retirement) to make sure it wasn't the electrical in the building. He said it was good.