Breaker box & breaker type help
 

New shop breaker box, what can you tell me about it?

30A breaker is too small for my compressor. Also why does the one outlined have the neutral going into the breaker? In my old building, neutral went to a buss bar.

Compressor is 7.5 hp motor so I would need a 60A.

Hoping to prevent a service call tomorrow.

http://forums.pelicanparts.com/uploa...1729537181.jpg


http://forums.pelicanparts.com/uploa...1729537181.jpg

I'll preface with "I'm not an electrician." Looks like a 3 phase breaker. If I had to guess, someone cut some corners when they wired it up. But before you do anything, wait for someone who stayed in a Holiday Inn Express last night to comment.

Well, that's a 3 phase box, so you're going to get about 208v going across a pair.

Why is there a white wire going into a breaker? Because it wasn't run by an electrician would be my answer. If you've got a regular single phase outlet on the other end of that run, you're in for a surprise when you plug something in.

LOL!
First thing that came to mind when I read your post.
https://www.memesmonkey.com/images/m...3bf3b524b.jpeg

The second thing that popped into my head.
http://forums.pelicanparts.com/uploa...1729539020.jpg

The secondary box across the shop that this breaker goes to has an on/off lever, the white wire is not connected at the ON side which feeds an outlet for a single phase lift.

We have 3 phase square d panels like that, but there is a main disconnect in the box. We do not have neutrals on 3 phase equipment. Just 3 hots and a ground are what we have and that white wire is probably be the high leg of the 3 phase.

After looking at the panel you probably don't have a high leg, every third breaker slot would have the higher voltage.

The cost of a service call will soon be forgotten when you can use any plug without worry of electrocution.

Did I tell you guys the story of my cousin who was fishing in an aluminum boat on a private lake that had a bridge over it?
He reached up and touched the bridge and was electrocuted. Someone didn't wire the lights on the bridge correctly.
He was only 10 years old.
Part of the reason I don't mess with electrical stuff like this. It can and will kill ya if given the chance.

Will start with I'm not an electrician. But thinking somebody possibly ran out of #12 blue wire or they needed 3 phase power where that ends up and just reused the white. Pretty dangerous if somebody assumes that white is a neutral wire at the other end. At least put blue tape on it to identify it.

60A for 7.5hp? Sounds high, is that motor single phase?

This more or less. Someone didn't have correctly colored wire for 3 phase and used standard 12/3 intended for 2 phase use. Yeah, blue tape on it, both ends.

Probably used 10/3 romex, or some type of cable for that 30A 3-phase circuit. That being the case, you have to use the white wire for one of the 3 "hot" conductors. That's allowed, but the white wire should have been marked with tape or paint on both ends.

If your compressor motor is single phase you have a snag, unless you have a 3 phase to single phase transformer. But a 3 phase motor would be a better choice.

On a more positive note (http://forums.pelicanparts.com/support/smileys/wat3.gif) three phase is good. It's expensive to get put in so great that someone else paid for it. And it all looks very tidy too.

This. Here it would pass inspection if both ends were taped to identify it as one of three phases.
60 amps isn't all that high to handle the inrush at startup on a single phase compressor.
If three phase is available, I would change the motor to three phase if it the original were to fail.
The wire size would need to be sized to the breaker. #6 for 60 amps I think.

It's a basic 5 wire 3-phase box. Allows for the standard 3-phase power, plus 120V single phase by combining one of the legs with a neutral and a ground. Let's you have 120V outlets without any extra transformers. Also allows 208/3 and 120/1 and 240/1 all in the same machine without a transformer.

Skinny wire for 30A, isn’t it?

So much to digest here, thank you. I'll put together a more inclusive description of details a little later on.

I can say now the compressor is 1.5 years old, an Atlas Copco screw, single phase 230V that I have a buck boost transformer for. I can ask how much a 3 phase motor is. The compressor was 5 figures so I need to keep it.

I was told this place is single phase 208V.

208V would indicate a 3 phase service. 120V between each hot leg and neutral, 208V between the hot legs. If you take a voltmeter and measure 208V from A>B, A>C, and B>C, I would say you've got 3 phase. Is this the same service that you were jacking around with the loose connection outside?

Someone either lied or was confused.

Shaun, where’s the main three phase disconnect for that box? Is it a blade lever box next to or is it disconnected only by a main breaker in a main panel elsewhere? You need to know the service limit feeding your box as well.

I'm going with confused. He was very nice, I don't think any malice or trickery was intended.

Here's testing on the main box. Main shut-off. And how the single phase 2-pole lift is wired against the 30A breaker. The metal tube on the left goes to a standard 3-prong dryer plug for lift.

http://forums.pelicanparts.com/uploa...1729612684.jpg




http://forums.pelicanparts.com/uploa...1729612684.jpg




http://forums.pelicanparts.com/uploa...1729612684.jpg

Prior to pricing the motor from Atlas take a look at the existing motor contactor (relay) and see if it has a free electrical terminal, if not will also need a different contactor and overload protection.

You can order and install a generic 7.5hp motor but there are a few different frame types and sizes, and mounting specs between manufacturers can be different, so just need to measure carefully.

Thank you. I have sent an email to Atlas Copco. And will research the relay.

How is the single phase lift working?

If you are asking me about the single phase lift, just using two of the three phase wires will give voltage, the waveform being 120 deg vs 180 deg and not really opposite. Not sure what happens running a motor continuous on it, likely less power more heat would be a concern. I have not tried it, up here most 3 phase in industry is 575v so need a transformer to bring it down to 240v anyways.

If you also need single phase for the lift possibly a transformer is a better solution?

Hopefully I am wrong and you can just use the two phases of three to run your compressor with no issues, does not sound right though.

Is it possible that the 3 prong single phase dryer receptacle used to be a 3 phase receptacle, and when someone changed it to the single phase receptacle they reused the wiring and disconnected the white wire on both ends? The fact that you've got a 3 pole breaker and disconnect switch would seem to indicate that at some point in time it was feeding a 3 phase load. Is the existing 7-1/2HP single phase motor fed from this panel or somewhere else? What are the bottom two 3 pole breakers feeding? If you're getting a 3 phase motor, make sure that it can run on 208V. It would be specified something like this: 208-230/460/3/60.

Anything is possible. That said, I am 99% sure the white wire hadn't been crimped with the grub screw. It is in the pic because I had put it in. But I found out this switch box and outlet were feeding a large compressor years ago.

I used this box to "test" connect my compressor before putting it in place. I used the wiring I installed in my old shop to make an extension cord.

I have a single phase to 3 phase converter I got for my 3hp buffer. I wish I could make it go in reverse.

Mike, can you expand on how to get 240/1 out of this box?

breaker just arrived. Why the two clips on the back vs. the one for teh 30?


http://forums.pelicanparts.com/uploa...1729628039.jpg


http://forums.pelicanparts.com/uploa...1729628039.jpg

No!


I was mistaken...

ok thanks.

if there's a possible bright spot, the motor runs for only a few minutes at a time, 10+ times a day.

I'm waiting to hear back from Atlas.

Googling a little, I get stuff like this:

Yes you can run the 1-phase, 220V motor from a line-line connection on a 3-phase, 220V delta. You would still need the start capacitor. Also, make sure case grounding is properly maintained as applicable (detailed wiring drawing will show).

If you are asking if you can supply the start capacitor leg with one of the other line-line delta voltages (for out-of-phase voltage) IN PLACE of the start capacitor then you will have to ask the manufacturer. Using another line-line would provide a full ±120°
shift whereas using the start capacitor and the same line-line voltage would be something less (e.g. −90°<��<+90°).

Is the start capacitor something I can wire inline AFTER the buck boost transformer?

The single phase motor will already have the start capacitor.

This is worth watching: https://www.youtube.com/watch?v=r3hSaiIt8-Y

Thanks. I'm puzzled about him talking about seeing higher voltages, I was measuring 203-204V at the panel and at the switch box in the other room.

I have a 208V to 230V buck boost transformer.

So my question becomes, and I hope this scenario works:

I put in the new 60A breaker
The switch set up for the car lift uses only Black, Red and Green, white wasn't connected

Can I just use the Black and Red into my transformer in the same way or is there a different/better way to wire it?

Secondary to this, because I essentially made an extension cord out of my old wiring (metal clad), it's only grounded at the switch box. Is that ok?

In my old shop, white was neutral at the buss bar and center mounted to the outlet, green grounded at the box and to the metal box in the wall in the compressor room.

I greatly appreciate all the help on this. The last 6 weeks have truly been hellish and I'm not surprised at all about this latest twist. In fact I would be surprised if this hadn't happened.

With all the talk about car lift, air compressor, buffer, buck/boost transformer, phase converter, single phase, three phase, I've actually lost track of exactly what you're trying to do.

Sorry, I’m trying to connect my single phase air compressor into a 3 phase system.

Assuming your 7-1/2HP single phase motor is rated to run on 208V, you should be able to install a 60A 2-pole breaker (not sure why you got a 3-pole) and run a couple of #6 copper wires (not white) along with a #6/8/10 ground conductor (green). There should also be a 60A lockable disconnect switch at the compressor. If you are using metal conduit, that can serve as the grounding conductor and you wouldn't need the green wire. But, if you use flexible metal conduit or flexible non-metallic conduit between the disconnect and air compressor, that would need to use the green ground wire.

As you saw in the video, you can get 240v from 2 legs of residential power. I stupidly got in my head that they were two PHASES, but in fact they're two legs that are 180 out, not 2 phases that are 120 out. So, no 240V for you! :)


Well, except for using your existing transformer.

Honestly, your 208 to 240 transformer is kinda weird, when you could get (or build!) a single phase, 120V to 240V transformer that would probably be smaller and cheaper. a 120V to 240V single phase transformer is just a couple coils of wire, while the 208 2-phase to 240 1-phase probably needs some sort of rectifier circuit.



This is all coming from someone who had to cobble together all sorts of power feeds for all sorts of old, used, decrepit heavy machines from many countries, power standards and eras. NEVER take my electrical advice as code, or legal or safe, but it usually worked.

Thank you. I got the three wire because that's what was in the cabinet. I have to get stitches out this morning but will install the 3 pole breaker leaving the white out of the circuit, just for testing.

Thanks Mike. I got the 208-230 9 years ago for at my old single phase 208 shop.