5hp 240 Volt Air compressor Install

[AllThingsOld]

I purchased a 60 gallon 5hp compressor recently. I was about to wire it up when I ran in to a small issue. The panel has room for the double pole 240, but I cannot access any of the terminals for the neutral wire. I am using 10/2 flexible conduit whips. I ran the first whip from the pressure switch to the disconnect box using both hots and the ground. Would I be able to run the next whip from the 240 double pole in the panel to the disconnect using only both hots, no neutral in the panel for this circuit ? Here is a photo of the panel. Thanks

 

[Ilikeike]

Not sure I'm following correctly, you just need to hit the ground buss on the left,correct ? along with your dbl pole breaker.

 

[pattenp]

There is no need for a neutral. 240V for the compressor is just the 2 hots and a ground.

 

[Kaizen]

Me either. Are you using premade whips of some sort? Or do you mean there is no more open screws on ground bar?


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[AllThingsOld]

Yes, you are correct, but I cannot access any of the terminals to install the neutral and do I need the neutral in this case ? If I am running a dedicated circuit just for the compressor, do I need a neutral for the double pole ? Or can I install both hot wires in to the breaker, no neutral and run just those 2 hots to my disconnect ?

 

[AllThingsOld]

There are no more open screws on the ground bar, I’m an idiot and kept saying neutral, geez

 

[AllThingsOld]

Sorry about that, every time I said neutral, I should have said ground.

 

[AllThingsOld]

What can I do for the ground with an open screw for it ?

 

[Ilikeike]

You can add another short ground buss, remove a ground from the existing buss up size the wire and feed the added ground buss..?

 

[pattenp]

Two grounds can be under one screw. Neutrals are only allowed to be one to a screw.

 

[AllThingsOld]

You can add another short ground buss, remove a ground from the existing buss up size the wire and feed the added ground buss..?

There are some open terminals on the top left side under the cable, but that would require me removing that cable. Can I remove that cable on the left, install my compressor ground and just tighten that cable back down ?

 

[AllThingsOld]

Two grounds can be under one screw. Neutrals are only allowed to be one to a screw.

Oh, well that would be super easy then.

 

[wyliesdiesels]

I purchased a 60 gallon 5hp compressor recently. I was about to wire it up when I ran in to a small issue. The panel has room for the double pole 240, but I cannot access any of the terminals for the neutral wire. I am using 10/2 flexible conduit whips. I ran the first whip from the pressure switch to the disconnect box using both hots and the ground. Would I be able to run the next whip from the 240 double pole in the panel to the disconnect using only both hots, no neutral in the panel for this circuit ? Here is a photo of the panel. Thanks

A 240v motor does not need a neutral wire. It needs a ground wire.

your panel appears to be a subpanel with an isolated neutral bar.

the ground wire from your motor circuit needs to go to the ground bar on the left hand side not the neutral bar on the right hand side

 

[AllThingsOld]

Thank you, that is what I needed to know. Now the cable that is covering my ground bar has open terminals at the top, can I loosen that cable, add my ground, then tighten down that cable again ?

 

[BillK]

Thank you, that is what I needed to know. Now the cable that is covering my ground bar has open terminals at the top, can I loosen that cable, add my ground, then tighten down that cable again ?

The cable you are talking about appears to be the ground cable for the entire panel. If you are going to disconnect it at the top I would personally shut off power to the entire panel which might mean pulling the meter unless there is a cutoff between the meter and the panel.

If it was mine I would shut the power off and then see if the neutral buss can be turned upside down or if the connection can be moved to the bottom. That is a crappy way of attaching it and having it cover all of the attaching screws. If the buss cant be turned up side down they should have run the neutral up to the top and looped it downwards so it came into the clamp from above.

Same with the neutral on the right.

Who does this kind of stuff ???

 

[pattenp]

This is being made more complicated than needed. The big bare aluminum wire on the left side can be detached as you asked so to have access to the open ground bar spaces to install the new ground wire for the compressor. It is advisable to turn off the main breaker.

 

[AllThingsOld]

Thank you. I’m not looking to reinvent the wheel, just looking to do this with the least amount of difficulty

 

[Kaizen]

Op....see these screw holes on the back of the panel? Those are for an additional ground bar. Go to Home Depot and get one off the shelf. Easy peasy. Yes you always need a ground with a 240v circuit.




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[AllThingsOld]

Op....see these screw holes on the back of the panel? Those are for an additional ground bar. Go to Home Depot and get one off the shelf. Easy peasy. Yes you always need a ground with a 240v circuit.




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That is what I am going to do. I’m sure this is another dumb question, but I’m asking it anyway. When I mount the new ground bar, the only thing I need to do is mount it using those 2 holes. Once the bar is installed, it’s grounded and ready, correct ?

 

[Kaizen]

That is what I am going to do. I’m sure this is another dumb question, but I’m asking it anyway. When I mount the new ground bar, the only thing I need to do is mount it using those 2 holes. Once the bar is installed, it’s grounded and ready, correct ?

Right. The top bar grounds the whole case so no need to run ground wire between new and old


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[AllThingsOld]

I really appreciate the simple solution. Thanks for taking the time to reply.

 

[AllThingsOld]

Right. The top bar grounds the whole case so no need to run ground wire between new and old


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Ok, part 2. On the junction box, what is the wiring configuration, I believe I am wrong, but right now on the left side, I have both hots from the compressor and then the ground. I was initially thinking I would just wire the opposite side with the power from the panel. But now I’m thinking I should be using the tip half for the compressor side and the bottom half for the power from panel. I have tried to look this up, but can’t find it anywhere. I would appreciate anyone who can tell me how to properly wire this box

 

[Bert_]

Ok, part 2. On the junction box, what is the wiring configuration, I believe I am wrong, but right now on the left side, I have both hots from the compressor and then the ground. I was initially thinking I would just wire the opposite side with the power from the panel. But now I’m thinking I should be using the tip half for the compressor side and the bottom half for the power from panel. I have tried to look this up, but can’t find it anywhere. I would appreciate anyone who can tell me how to properly wire this box

Line wires go on top.

That's the least of the problems though. That 30A switch is only going to be rated for a 3hp motor. Also looks like 10/2 Romex which is also not quite enough for 5 hp. Originally sounded like you where using a flexible whip with #10thhn which would be ok.

 

[AllThingsOld]

Line wires go on top.

That's the least of the problems though. That 30A switch is only going to be rated for a 3hp motor. Also looks like 10/2 Romex which is also not quite enough for 5 hp. Originally sounded like you where using a flexible whip with #10thhn which would be ok.

From the compressor to the junction, I am using a whip. From the panel to the box, I am using 10/2 romex.. Says the motor draws 22amps

 

[Kaizen]

I used 10 on my 3hp lift. For my compressor I used way heavier as I had it. You should run heavier gauge and learn to use flexible conduit. Way easier then using what you have. This was mine I did. Used emt and flex. You’re playing in the big league now.




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[wyliesdiesels]

From the compressor to the junction, I am using a whip. From the panel to the box, I am using 10/2 romex.. Says the motor draws 22amps

Thats where you went off the road.

Motor circuits are sized by HP rating in NEC FLC T430.248 NOT the amp rating on the nameplate.

A 5HP motor needs 35a rated wire. NM-b is limited to 60* c ampacity which is 30a.

So you need #8/2 NM-b or use #10 THWN in pipe.

 

[AllThingsOld]

Thats where you went off the road.

Motor circuits are sized by HP rating in NEC FLC T430.248 NOT the amp rating on the nameplate.

A 5HP motor needs 35a rated wire. NM-b is limited to 60* c ampacity which is 30a.

So you need #8/2 NM-b or use #10 THWN in pipe.

I have learned a lot, thanks guys. If not for this forum, I would have never been able to get this done. I can pull the romex and run the 8/2 NM. Thanks for the help guys, really appreciate it

 

[Bert_]

30A fused disconnect in the pic is to small also as I noted earlier. None of the 30A disconnects are rated over 3hp on 240V single phase. 5hp single phase takes a 60A disconnect.

 

[AllThingsOld]

30A fused disconnect in the pic is to small also as I noted earlier. None of the 30A disconnects are rated over 3hp on 240V single phase. 5hp single phase takes a 60A disconnect.

Yes, I am looking at disconnects right now actually. Do I need a fusible disconnect or can I go with the non fusible ?

 

[Bert_]

Yes, I am looking at disconnects right now actually. Do I need a fusible disconnect or can I go with the non fusible ?

Usually no. You do need some sort of overload protection for the motor and the breaker doesn't work for that. Most of the time the motor will have the red reset button or the compressor will have a starter with overload.

If it has none of those then a time delay fuse would be one way to provide overload protection.

An A/C disconnect of a cheap and good motor disconnect. Most are rated 60A and 10hp.

 

[AllThingsOld]

Usually no. You do need some sort of overload protection for the motor and the breaker doesn't work for that. Most of the time the motor will have the red reset button or the compressor will have a starter with overload.

If it has none of those then a time delay fuse would be one way to provide overload protection.

An A/C disconnect of a cheap and good motor disconnect. Most are rated 60A and 10hp.

I was looking at a/c disconnects. My motor does have a reset, so I will pick up a cheap a/c disconnect. I hopefully will be up and running after the wire upgrade and disconnect.

 

[Terry D]

Back to the problem of not having a open spot to land the equipment ground in the panel. I personally would add another ground bar. I would not put 2 under one screw. And i dont want to open up a whole new discussion here, but it is not allowed everywhere to do that, i know for a fact its not allowed here. Not saying its not allowed in your area. That groind wire is just as important, if not more, than the other wires in that circuit. Just my opinion.

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[sberry]

I will agree it is an opinion. It's not a current carry conductor under operation, not sublet to loading and thermal.

 

[pattenp]

Most panels are listed for 2 grounds per lug, some even allow 3. The NEC allows what the listing calls for. NEC only allows one current carrying conductor to a lug. I can't imagine a local amendment only allowing one ground per lug, must be the inspectors personal thing.

 

[wyliesdiesels]

Back to the problem of not having a open spot to land the equipment ground in the panel. I personally would add another ground bar. I would not put 2 under one screw. And i dont want to open up a whole new discussion here, but it is not allowed everywhere to do that, i know for a fact its not allowed here. Not saying its not allowed in your area. That groind wire is just as important, if not more, than the other wires in that circuit. Just my opinion.

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Ok does your AHJ have a local WRITTEN amendment for that? If not then the inspector is blowing smoke up your ***. His personal interpretation and urban myth codes are not gospel (aka NEC)...

 

[Norcal]

Most panels are listed for 2 grounds per lug, some even allow 3. The NEC allows what the listing calls for. NEC only allows one current carrying conductor to a lug. I can't imagine a local amendment only allowing one ground per lug, must be the inspectors personal thing.

One note, when putting multiple grounding conductors under one screw they need to be the same size and material cannot mix them. It is governed by the listing and manufacturers instructions.

 

[Terry D]

Ok does your AHJ have a local WRITTEN amendment for that? If not then the inspector is blowing smoke up your ***. His personal interpretation and urban myth codes are not gospel (aka NEC)...

I understand what your saying, i have been called out on it before. Might have been just that one inspector. No i dont have a written amendment. Its just easier for me to put a $ 6.00 ground bar in the panel

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[AllThingsOld]

I added an additional ground bar, so I should be fine. I also pulled the 10/2 romex and 30 am disconnect. I purchased a 60 amp disconnect, flexible conduit and I’m about to purchase Red, green and black 6 gauge THHN. Is the 6 THHN overkill ? If so I’m good to go

 

[Terry D]

I added an additional ground bar, so I should be fine. I also pulled the 10/2 romex and 30 am disconnect. I purchased a 60 amp disconnect, flexible conduit and I’m about to purchase Red, green and black 6 gauge THHN. Is the 6 THHN overkill ? If so I’m good to go

You only need a # 10 if you your using THWN

 

[sberry]

I have put 2 bars in. You don't got to but I oft run a 10 between them when I do it. Low impede pathway and instead of using 2 sets of screws and the can it ties it to the one with the wire from the main.
5 hp needs 3 number 10 and breaker from 30 to 60 with a 40 being somewhat ideal. Hard wired.