Welder & Air Comp Breaker Requirements?

[REPO]

Just thinking about my future shob build and making a list of things I will need next spring when I start construction. I plan on running 100 amp service and was unsure of what the requirements are for a welding plug, as well as a 220 air compressor plug? 40s? 50s?

Also, I plan on installing a varsol washing station, should that be on its own plug that is a GFI? Or maybe it would be ran in the same system as the outdoor plugs that are GFI?

Any other things you guys recommend for shop wiring, things you wish you had done, or any tips, etc?

Thanks!

 

[BC1]

A mig or modern tig welder (garage/light fab style) will most likely never trip a 30 amp breaker unless its over a 200amp model. A compressor (unless it's huge) should never trip a 20 amp breaker. That being said, at home I have 30amp breakers for these things and at my shop they're 40 amp. Look at the manufactures literature for the power consumption of your device then do some calculations, it should be fairly straightforward.

 

[Falcon67]

What size compressor? at 240V, 3.5 HP can run on 12-2 with a 20A breaker, 5HP should use 10-2 with a 30A. Read the welder manuals for the units you like and that will tell you the type of socket you need. 10 gage/30A is probably plenty for most hobby 240V welders. Check the manual.

Every plug (and therefor every piece of equipment) in my shop is on the load side of a GFCI except for the 240V electric heater and the big compressor.

 

[Gary S]

Installing wiring and receptacles for equipment you don't own yet makes about the same sense as buying new tires for a car you might buy someday.
Wait until you have the equipment, and then get it wired correctly.

 

[trbomax]

Installing wiring and receptacles for equipment you don't own yet makes about the same sense as buying new tires for a car you might buy someday.
Wait until you have the equipment, and then get it wired correctly.

2
This^, sort of. I personally think 100a is a bit light for a shop,a 2 car garage maybe,but not any kind of working shop. I have a 400a service and a 100a subpanel that is dedicated to a 5hp and a 7.5 hp comp,a miller 210 mig,a lincoln 175 mig,and a miller 180 tig. It is entirely possible that both compressors will be running if the cabinet blaster has or will be being used,and one welder. This would account forabout a 70a load. Doesnt leave much for lights,fridge, heat,fans,and anything else that someone working with you may be useing. In my case,all that stuff is on another 100a sub so it wouldnt matter.You can never have too much electric capacity,and if you are building new,you should provide for the most rediculous situation that will ever occur.

 

[wyliesdiesels]

Just thinking about my future shob build and making a list of things I will need next spring when I start construction. I plan on running 100 amp service and was unsure of what the requirements are for a welding plug, as well as a 220 air compressor plug? 40s? 50s?

Also, I plan on installing a varsol washing station, should that be on its own plug that is a GFI? Or maybe it would be ran in the same system as the outdoor plugs that are GFI?

Any other things you guys recommend for shop wiring, things you wish you had done, or any tips, etc?

Thanks!

The requirements are entirely up to what your machine requires. Check the manuals for or stickers on, the welder and compressor

As far as the washing station, I would put it on its own circuit, that way if there is a fault, it won't cause other stuff to loose power!

 

[REPO]

Installing wiring and receptacles for equipment you don't own yet makes about the same sense as buying new tires for a car you might buy someday.
Wait until you have the equipment, and then get it wired correctly.

I understand what you are saying, but unfortunatly, I do not own either of these at this time. My wiring is planned to be inside the walls, so adding it later on would not be pretty. Hence why I thought I would check around to see what most people are currently putting in their own shops, to hopefully avoid issue down the road.

Neither the welder or air compressor will be huge, this is just for my hobby shop, and being I am only going to have 100 amp service, these items are not going to be huge.

 

[PT Doc]

Quincy recommends 50a breaker for a 5hp, 80 gal, 2 stage, 18 cfm. A Hobart Ironman 230(?) requires a 50a breaker per Hobart.

 

[Gary S]

I understand what you are saying, but unfortunatly, I do not own either of these at this time. My wiring is planned to be inside the walls, so adding it later on would not be pretty. .

Adding on wire externally to the walls later is a much better way to go over putting the wrong wire inside the walls now and then still adding the right wire outside the walls. Buy the device first, and then wire it right the first time.
It is just like buying new tires now for that Honda Accord you might buy someday only to find you bought a Ford SUV instead and the tires are wrong and you have to spend the money twice.

 

[trbomax]

I put the 110 in the walls.When I figured out what I wanted and where, I ran the 220 in pipe. Another advantage of doing it this way is that you can add or upsize wires as reqd. My new machine tool room will be the same way.When all the machines are set,I will run the electric from the 60a subpanel on the wall.It actually looks quite nice that way,kind of "industrial"!

 

[brewchief]

I would run a 50 amp circuit for the welder, even though the smaller hobby 240v welders may only need a 30 amp circuit all of them I have seen have the 50 amp plug, it's also nice to be able to plug in a decent size stick welder if needed.

 

[Falcon67]

I have a lot of machines in my 960 sq/ft and have not yet come close to tripping the 70A breaker. I'm wired for 90A but the 70A was cheap and in stock. If you are guessing on sizes, then make a plan and run the cable, then hope it all works out like you wanted. For me, I put fixed outlets along one wall only. In the work areas, I ran home runs to a 4" box, then out from there on the wall surface with MC cable or conduit. If'n I don't like it, I can change it up quick. Or add on, real easy.

When I move up from a 120V MIG to a 240V, I will run a drop to the wall separating the tool room and the work room and socket both sides and use a short extension from there if required.

 

[Aceman]

If a customer asked me to run circuits not knowing what they're getting, I'd run 8-2 for the compressor and 6-2 for the welder. The washing station would get a dedicated 12-2. Sure, the customer may spend a little extra on wire that may be a size or two too big(after they buy the equipment), but I'd feel confident any scenario was covered.

If they want to spend a little less money on wire, then they can give me a cut sheet for the equipment they're gettting and I'll install exactly what's required, no more, no less!!

 

[PT Doc]

If a customer asked me to run circuits not knowing what they're getting, I'd run 8-2 for the compressor and 6-2 for the welder. The washing station would get a dedicated 12-2. Sure, the customer may spend a little extra on wire that may be a size or two too big(after they buy the equipment), but I'd feel confident any scenario was covered.

If they want to spend a little less money on wire, then they can give me a cut sheet for the equipment they're gettting and I'll install exactly what's required, no more, no less!!

Doing the above is easy and clean. Put the wire in the walls now. If you need a lower amp breaker then you can change that out at the subpanel. You can't increase the wire size later so do it now and adjust the breaker later if needed.

 

[Norcal]

If a customer asked me to run circuits not knowing what they're getting, I'd run 8-2 for the compressor and 6-2 for the welder. The washing station would get a dedicated 12-2. Sure, the customer may spend a little extra on wire that may be a size or two too big(after they buy the equipment), but I'd feel confident any scenario was covered.

If they want to spend a little less money on wire, then they can give me a cut sheet for the equipment they're gettting and I'll install exactly what's required, no more, no less!!

Doing the above is easy and clean. Put the wire in the walls now. If you need a lower amp breaker then you can change that out at the subpanel. You can't increase the wire size later so do it now and adjust the breaker later if needed.

There is a problem w/ oversizing the wire & using NM cable as no good deed goes unpunished, you run afoul of 250.122(B). NM cable w/ 6 & 8 AWG conductors only has a 10 AWG grounding conductors, use a metallic conduit w/o a grounding conductor & all would be well.


(B) Increased in Size. Where ungrounded conductors are
increased in size, equipment grounding conductors, where
installed, shall be increased in size proportionately according
to the circular mil area of the ungrounded conductors.

Bold/ italics by me.

Copied & pasted from the 2011 NEC


Edit:A number of NEC editions back, 250.122(B) only applied when the ungrounded conductors were increased in size for voltage drop, it now applies to everything.

 

[wyliesdiesels]

There is a problem w/ oversizing the wire & using NM cable as no good deed goes unpunished, you run afoul of 250.122(B). NM cable w/ 6 & 8 AWG conductors only has a 10 AWG grounding conductors, use a metallic conduit w/o a grounding conductor & all would be well.


(B) Increased in Size. Where ungrounded conductors are
increased in size, equipment grounding conductors, where
installed, shall be increased in size proportionately according
to the circular mil area of the ungrounded conductors.

Bold/ italics by me.

Copied & pasted from the 2011 NEC


Edit:A number of NEC editions back, 250.122(B) only applied when the ungrounded conductors were increased in size for voltage drop, it now applies to everything.

So in the proposed scenario, what size should the egc be to stay in compliance of 250.122(B)? #10 would not still be correct?

 

[pattenp]

So in the proposed scenario, what size should the egc be to stay in compliance of 250.122(B)? #10 would not still be correct?

I believe the application of 250.122(B) as Norcal cites is a misapplication of the section and does not apply to a manufactured cable such as NM. The code section says grounding conductors in multiconductor cable is to comply with Table 250.122, which makes #10 the minimum size grounding conductor for #6 NM @ 55A or #8 NM @ 40A.

 

[Norcal]

250.122(B) overrides other sections, there is no exception for any cable assemblies listed in there, in fact there are no exceptions listed.

 

[BDT/NWMN]

I have a commercial rated compressor with a 5 HP motor.... Rated at about 22 amps, so a 30 amp breaker and 10 gauge wire should be ok???..............................no--no--no............... Reading the manual,, It stated that the motor, with it's magnetic starter switch, should be properly wired for 60 amps; which I did.. Takes some power to start my compressor,,, Double check the manual for YOUR compressor before you hard wire it...


If your compressor came with a cord and plug factory installed, much more simple,, just plug it into the PROPER outlet..

 

[KinzeMech]

I've got a 3hp compressor that takes 15 amps. It's got a 220V 50A plug on it, because that is what's there. It works just fine.

A 50 amp plug will be enough for any single phase compressor motor you are realistically likely to find in any home hobby shop. Likewise for the welder. The one you have today may not need 50 amps, but if you put in a 50 amp outlet, you haven't limited your upgrade options down the road.

 

[pattenp]

250.122(B) overrides other sections, there is no exception for any cable assemblies listed in there, in fact there are no exceptions listed.

Yes per 250.122(B) when ungrounded conductors are increased in size you need to also keep the grounding conductor proportionately sized. An example would be if you have a 20 amp breaker supplying individual THHN #12 with a #12 ground and because of voltage drop you decided to use #10. The #12 ground would also need to be increase to #10. Potentially someone could come back and put a 30A breaker on that circuit and then the #12 ground would be undersized. My understanding is this is why 250.122(B) exists. The point I’m trying to make is that it’s a mute point when NM is used because the ground size is increased as the ungrounded conductors are increased in size. It makes no logical sense that NM would become noncompliant because of the ground being undersized. So please show me an example where using NM that the ground would not be sized correctly to meet 250.122(B).

 

[oleguy]

Yes per 250.122(B) when ungrounded conductors are increased in size you need to also keep the grounding conductor proportionately sized. An example would be if you have a 20 amp breaker supplying individual THHN #12 with a #12 ground and because of voltage drop you decided to use #10. The #12 ground would also need to be increase to #10. Potentially someone could come back and put a 30A breaker on that circuit and then the #12 ground would be undersized. My understanding is this is why 250.122(B) exists. The point I’m trying to make is that it’s a mute point when NM is used because the ground size is increased as the ungrounded conductors are increased in size. It makes no logical sense that NM would become noncompliant because of the ground being undersized. So please show me an example where using NM that the ground would not be sized correctly to meet 250.122(B).

i agree.also no ckt exists yet.op wants opinions on what ckt size wire would be recomended.sience this is the case 250.122(b) playes no part.also nm cable bieng a factory assymbly,no upsizeing is required.also see table 250.122.i say this because going from #8 to #6 romex,you still have a #10 ground conductor.

 

[Norcal]

8 & 6 AWG NM has a 10 AWG EGC, if they are used in place of a 30A conductor for example, the EGC is too small, because the ungrounded conductors have been increased in size, it is a case of no good deed going unpunished as I wrote in a earlier post in this thread.


1999 NEC: 250.122(b)

Adjustment for Voltage Drop. Where conductors are adjusted in size to compensate for voltage drop,equipment grounding conductors ,where installed, shall be adjusted proportionately according to circular mil area.

This was new in the 1999 edition.

The only other change was slight, 250.122(b) in the '99 to 250.122(B) in the '02.

The change occurred in the 2002 NEC with this:

250.122(B)
(B) Increased in Size. Where ungrounded conductors are
increased in size, equipment grounding conductors, where
installed, shall be increased in size proportionately according
to the circular mil area of the ungrounded conductors.

This is unchanged in the 2005,2008, & 2011 editions.

 

[Aceman]

There is a problem w/ oversizing the wire & using NM cable as no good deed goes unpunished, you run afoul of 250.122(B). NM cable w/ 6 & 8 AWG conductors only has a 10 AWG grounding conductors, use a metallic conduit w/o a grounding conductor & all would be well.

(B) Increased in Size. Where ungrounded conductors are
increased in size, equipment grounding conductors, where
installed, shall be increased in size proportionately according
to the circular mil area of the ungrounded conductors.

Bold/ italics by me.

Copied & pasted from the 2011 NEC


Edit:A number of NEC editions back, 250.122(B) only applied when the ungrounded conductors were increased in size for voltage drop, it now applies to everything.

Personally, I would rather take my chances and run NM in the wall before it's sheeted. I'll worry about possible 250.122(B) issues later if it comes up.

 

[pattenp]

8 & 6 AWG NM has a 10 AWG EGC, if they are used in place of a 30A conductor for example, the EGC is too small, because the ungrounded conductors have been increased in size, it is a case of no good deed going unpunished as I wrote in a earlier post in this thread.

I can see where you're coming from, but don't agree. If you are correct and #10 is too small in your example; what should it be and how do you calculate the needed increased size?

Edit: I just did a lot of searching and answered my question. First off Norcal you're correct and the calculations can be done by using Chapter 9 Table 8. You get a ratio of increase in size of the ungrounded conductors and multiply that ratio by the required size of the ground from 250.122 Table. So upsizing from #10 to #8 requires the ground to go to an #8. Just seems nutty to me, dumb fuzzy math. See this info.... http://www.cable.alcan.com/NR/rdonl...6DF8AB4023D/0/EquipmentGroundingConductor.pdf

Here's a Mike Holt video if you care to download to watch. At bottom of page. http://www.mikeholt.com/videodisplaynew.php?pageid=4338

*

 

[wyliesdiesels]

I believe the application of 250.122(B) as Norcal cites is a misapplication of the section and does not apply to a manufactured cable such as NM. The code section says grounding conductors in multi-conductor cable is to comply with Table 250.122, which makes #10 the minimum size grounding conductor for #6 NM @ 55A or #8 NM @ 40A.

Yeah, so what he said doesn't make sense and doesn't apply to the suggestion.

What someone suggested, which he was responding to, was to run 6-2 ahead of time, and then if the machine the OP purchases only needs a 30a plug, just change the breaker feeding the #6 from a 50a to a 30a. Norcal then stated there's a problem when over-sizing cable and using NM. Specifically, the #10 EGC in the NM cable would not comply with 250.122. But a #10 EGC with #8 or #6 IS the correct size because of the ampacity of those wire gauges! The NEC code he cited says that when increasing the size of ungrounded conductors, the EGC must also be proportionately increased in size. So Norcal- in THIS exact scenario, if the code you're citing applies, what size SHOULD the EGC be for a #6 cable? #8? That doesn't make sense!! A #8 EGC is for a 100a branch circuit!

What I think that code section has to do with is let's say I'm installing a 50a branch circuit and normally I would run #6 to feed it, but because of distance and possible voltage drop, I had to run #4. To comply with this code, I must also proportionately increase the EGC size because I increased the ungrounded conductor size!

In the suggestion for the OP's situation, cable size is not being increased due to voltage drop, its being re-purposed for a smaller size circuit!

EDIT: I agree with pattenp and oleguy in comments # 21 and 22. But now that pattenp pointed it out, I see what Norcal is saying. It still doesn't make it any more logical that a 30a circuit being fed by #6 requires a #8 ground! Plus, IMHO, that's a contradiction of NEC T250.122!

 

[Norcal]

I agree that it's strange that oversizing causes that situation, but while I do not agree w/ it, just like AFCI's, code is code.

 

[pattenp]

Did anyone watch the Mike Holt video that I posted the link to? The discussion panel talks about the application 250.122 and how it does and doesn't make sense.

 

[REPO]

I've got a 3hp compressor that takes 15 amps. It's got a 220V 50A plug on it, because that is what's there. It works just fine.

A 50 amp plug will be enough for any single phase compressor motor you are realistically likely to find in any home hobby shop. Likewise for the welder. The one you have today may not need 50 amps, but if you put in a 50 amp outlet, you haven't limited your upgrade options down the road.

This is what I am leaning to. I am not a pro, the welder I would like to have would be a Miller 252, air comp would be a regular vertical model found at Home Depot, etc, nothing over the top. I just wasn't sure if I needed 30 or 50 amp plugs for each.

(I just remembered I have an old Lincoln tombstone arc welder hiding in a shed as well, I might have to research it's requirements as well)

 

[wyliesdiesels]

I agree that it's strange that oversizing causes that situation, but while I do not agree w/ it, just like AFCI's, code is code.

I don't follow what your saying about AFCIs!

Did anyone watch the Mike Holt video that I posted the link to? The discussion panel talks about the application 250.122 and how it does and doesn't make sense.

I'm on a '****-berry' so I can't watch it @ the moment!

 

[Norcal]

I don't follow what your saying about AFCIs!

I'm on a '****-berry' so I can't watch it @ the moment!

AFCI's are snake oil, they are code so they have to be used where required, but..................................................

 

[wyliesdiesels]

O ok. So you don't think they work or are necessary? I've only installed a few, as I'm mostly a service electrician, so I haven't heard or read much about their effectiveness or performance!