how would you proceed?

[Jon Prouty]

Hi guys,

I got my recently purchased lathe to the new house. It is a PB3520b. I had the house built with a couple 220 / 30A circuits in the garage for my tools. The builder installed dryer outlets (NEMA 14-30). Since the 14-30 receptacle is already installed, the cord on my lathe has a NEMA 6-20 plug already installed. Obviously I have an incompatibility issue... I can't find just a plug at the BORG that goes to the NEMA 14-30 receptacle - only pigtailed built up assemblies. Do I change out the power cord on my lathe or change out the receptacle in the wall? If I change over the receptacle in the wall, I guess I just wire nut the neutral line and tuck it back into the box. Right?

Help - want to get this ironed out soon... been waiting forever to get moved in and fire up my new lathe. I finished painting the garage and am in the process of moving all my junk in from the other house. Here is a pic.

Thanks,
Jon
273702

[Dale Gillaspy]

I'm thinking the simplest thing to do would be to change out the plug on the end of the PM cord. Disclaimer. My electrical knowledge is only good if the wires are compatible. If there is a mis-wiring issue, the Risk Manager in me says to consult a qualified electrician.

[Jamie Donaldson]

Dang, that shop space looks more like a home theatre set-up!

[Thomas Canfield]

You should also consider changing the breaker in the distribution panel from 30 amp to 20 amp when you change the plug to provide a little protection for the equipment and the components in the circuit (outlet, plug, wire to lathe).

[Ryan Mooney]

Personally, and I am not an electrician, but I would change the outlet to nema 6-20 and swap the breaker for a 20a as Thomas suggested.

My reasoning is thus:

You should change the breaker to 20a anyway because over that you don't have as much protection on the lathe side (whatever that's worth).
If you change the breaker the outlet isn't the correct "size" so it would be correct to change it to reflect the breaker
I prefer the locking plugs anyway (and would personally do it just for that reason).


edit: capping the neutral should be fine.

[Thom Sturgill]

I believe it may be a code violation to change the plug to a lower amperage without also changing the breaker. The breaker is supposed to protect the wall wiring and outlet (not the equipment plugged into it). A 20 amp outlet could be overloaded and the breaker would not prevent it. The wire being oversized is fine. Ask over in workshops, there are several electrician types that hang out there.

[Mike Cruz]

If I understand correctly, the electrician put in a 4 wire outlet. Your PM has only a 3 wire plug. First of all, I'm no electrician. So, take this for what it is. Pass it by your electrician, check, recheck, and triple check with others...but I'm just saying that this is what I would do because it makes sense to me and I can go to the Borg to get the parts. Anyway, here it goes: I'd change the breaker to a 20 amp breaker. I'd change the outlet to a 4 prong 20 amp twist lock (connecting the wires just as the electrician did). I'd put a 4 prong plug on my PM cord. I'd connect the two hot wires and the ground where they are supposed to go on the plug (leaving the neutral wire spot empty since there is no wire to go there...just make sure that the two hot wires correspond with the two hots on the outlet in the wall). That way, you aren't capping something off in the wall box, leaving the next home owner thinking there is only a 3 wire run to that receptacle.

When my shop was built, to be up to code, all the 220 outlets were run with 4 wire (2 hots, 1 neutral, and a ground). But NONE of my machines are wired with 4 wires. So, I did as above and put 4 wire plugs on the ends of the cords. Everything works as it should.

[Dan Hintz]

I would change the outlet to something more common for equipment like this. Leave the breaker as a 30A... you're protecting the wiring in the wall, not the lathe wiring (there are separate, smaller fuses on the lathe for protection) or the outlet itself. The outlet is designed to only allow equipment of a specific amperage to be plugged in... a 15A outlet on a 20A breaker/line is perfectly fine as you can only plug in items that pull 15A max, same with a 20A outlet, same with a 30A outlet.

[Mike Cruz]

You may be correct, Dan, but if an inspector saw a 20 amp receptacle on a 30 amp circuit, he might scratch his head...leading him to start questioning other stuff in the panel, leading him to asking who did this, leading him to site you for not pulling a permit (if one was required). I know that there is an electrical inspector in my area that would POUNCE on a situation like this... Just sayin'...that's why I would mate the receptacle and the breaker.

[Scott Hackler]

Not to mention the fact that 30amp is super overkill for a lathe. I would NOT run a lathe that has an amp draw of 10-12amps on a 30 amp breaker/circuit. The breaker is there to protect against over draw or short of the devices plugged in. For design and code, a breaker should be spec'd for 80% max draw. Same goes for the actual wiring. If the electrician installed 30amp capacity, you will NEVER have a problem with hot wires. So if you have a 20amp breaker, you should never exceed 16amps. That lathe shouldn't be over 12 so that would work fine. I would change the breaker, receptacle and plug on the lathe cord and have fun!

[Jon Prouty]

Not to mention the fact that 30amp is super overkill for a lathe. I would NOT run a lathe that has an amp draw of 10-12amps on a 30 amp breaker/circuit. The breaker is there to protect against over draw or short of the devices plugged in. For design and code, a breaker should be spec'd for 80% max draw. Same goes for the actual wiring. If the electrician installed 30amp capacity, you will NEVER have a problem with hot wires. So if you have a 20amp breaker, you should never exceed 16amps. That lathe shouldn't be over 12 so that would work fine. I would change the breaker, receptacle and plug on the lathe cord and have fun!
I had the option of 20 or 30 amp outlets. I went overkill on the wiring so as to future proof my shop. I'm not interested today in welding or flat work so I probably won't "need" a 30amp outlet.


I would change the outlet to something more common for equipment like this. Leave the breaker as a 30A... you're protecting the wiring in the wall, not the lathe wiring (there are separate, smaller fuses on the lathe for protection) or the outlet itself. The outlet is designed to only allow equipment of a specific amperage to be plugged in... a 15A outlet on a 20A breaker/line is perfectly fine as you can only plug in items that pull 15A max, same with a 20A outlet, same with a 30A outlet.
I think this is the direction I am leaning toward... a 30A twist lock receptacle and wire up the lathe with a twist lock plug. I am leaning toward leaving the breaker as 30A. The lathe would probably internally fault before tripping a 20A breaker thus a 30A breaker wouldn't provide any additional protection to the lathe? A 30A breaker, wiring and twist lock receptacle seems to keep everything happy with regard to code.


If I understand correctly, the electrician put in a 4 wire outlet. Your PM has only a 3 wire plug. First of all, I'm no electrician. So, take this for what it is. Pass it by your electrician, check, recheck, and triple check with others...but I'm just saying that this is what I would do because it makes sense to me and I can go to the Borg to get the parts. Anyway, here it goes: I'd change the breaker to a 20 amp breaker. I'd change the outlet to a 4 prong 20 amp twist lock (connecting the wires just as the electrician did). I'd put a 4 prong plug on my PM cord. I'd connect the two hot wires and the ground where they are supposed to go on the plug (leaving the neutral wire spot empty since there is no wire to go there...just make sure that the two hot wires correspond with the two hots on the outlet in the wall). That way, you aren't capping something off in the wall box, leaving the next home owner thinking there is only a 3 wire run to that receptacle.
This is my plan on the lathe wire plug... leaving the neutral wire spot empty.

When my shop was built, to be up to code, all the 220 outlets were run with 4 wire (2 hots, 1 neutral, and a ground). But NONE of my machines are wired with 4 wires. So, I did as above and put 4 wire plugs on the ends of the cords. Everything works as it should.
thanks - glad to hear that I'm not in a unique situation.


Dang, that shop space looks more like a home theatre set-up!
Thanks Jamie - I've spent three weeks working every evening painting the entire house before we moved in. I couldn't stand the builder base white paint... had to get it looking good before moving in all the stuff. I wanted to do something special in my man cave so I went a little crazy in the garage with the paint. I love it!

[Pat Scott]

I wired my shop with a 20a breaker and 20a 3-prong plug on my PM3520b and have never tripped the breaker. In fact all of my big tools are wired the same as the lathe (table saw, 15" thickness planar, 20" bandsaw, 8" jointer), and I can't remember when or if I've ever tripped the 20a breaker.

[Thom Sturgill]

I would change the outlet to something more common for equipment like this. Leave the breaker as a 30A... you're protecting the wiring in the wall, not the lathe wiring (there are separate, smaller fuses on the lathe for protection) or the outlet itself. The outlet is designed to only allow equipment of a specific amperage to be plugged in... a 15A outlet on a 20A breaker/line is perfectly fine as you can only plug in items that pull 15A max, same with a 20A outlet, same with a 30A outlet.

My concern above was that a 20amp outlet on a 30amp breaker (changing out ONLY the outlet) would leave the possibility of a short burning out the receptacle before the breaker tripped. Reverse of that - 30 amp receptacle on a 20 amp breaker and the breaker should trip before the receptacle is damaged. Mike's suggestion makes the most sense to me.

[kevin nee]

How about a dryer plug with the pigtail to some type of safety switch then the lathe cord.
That way you could shut off the power to the lathe.

[Dan Hintz]

My concern above was that a 20amp outlet on a 30amp breaker (changing out ONLY the outlet) would leave the possibility of a short burning out the receptacle before the breaker tripped. Reverse of that - 30 amp receptacle on a 20 amp breaker and the breaker should trip before the receptacle is damaged. Mike's suggestion makes the most sense to me.

Sure, but you could make the same statement about the plug itself, or the lathe's wire, or... etc. In the end, it doesn't much matter which of our suggestions he takes, I think they're all reasonable on one level or another.

[Mike Cruz]

Jon, you've gotten a lot of advice. Just about any of them would work. I think the BEST option is to change everything out form breaker to receptacle to plug so that you have no "loose ends". You "can" shortcut any of these and have it "work". But why?

One question that "might" answer the question is this... Are all your 220's wired "inline"? Meaning do you have only one breaker for all your outlets? If so, and I'm not an electrician...so I don't know the actual answer, it might be an argument for keeping the breaker 30 amp, the receptacles 30 amp, and just changing your plug. But you are solely relying on your equipment's fuses to protect your equipment because the breaker and outlet will allow WAY more power than your equipment "needs". BUT you might need a 30 amp breaker and outlet for a 5 hp TS, dust collector, or large compressor. Though, arguably, the compressor and DC should be on their own circuits anyway...

[John Lifer]

Give me a break! Per any code, you can have a higher breaker and rated wire than the outlets. The breaker protects the wiring Not the object plugged in. YOU HAVE NOTHING IN YOUR HOUSE THAT IS RUNNING AT RATED AMPS, everything is lower. Otherwise you trip. Change plug and outlet to match saw, or no higher rated than wiring and breaker. That is code.

[Mike Cruz]

Well, John, I gave you a break. Before responding, I did a bunch of research (instead of blindly telling you that you were wrong). My findings are that NEC says your breaker and receptacle (and of course, wire...but oversized wire isn't bad unless you have to altar the wire to get it to fit into an undersized receptacle) should match. I WAS going to link my evidence, but since you made ME look it up, I figure I'll let YOU do the same.

Do you HAVE to do it? No. But you don't HAVE to pull permits, either. You are SUPPOSED to, though. Ergo my comment...the OP "should" change the breaker, receptacle, and plug so that they all match. Enjoy.

[Len Mullin]

Hire a qualified electrician, that lathe looks to be worth 2-3g's at least and your venturing into territory that you know little or nothing about. For me, it would be worth the money, just to know that it's done right and that there's no chance of damaging your lathe or burning down your house.

[Mike Cruz]

Oh, and just spoke with my electrician today. He said NO inspector would allow a 30 amp breaker and 20 amp receptacle combination. The breaker is not only to protect the wire, but the receptacle as well. If the breaker doesn't trip, you could over heat the receptacle (in theory)...melting it or catching it on fire.

His suggestion (go figure) is to keep them the same. Though he strongly suggested going with twist lock receptacles and plugs. Mainly because if an inspector DID see that you were using the receptacle for machines, that is what he would want to see in the wall.

My electrician DID say that you might be able to get away with a 25 amp breaker with a 20 amp receptacle (arguably, at least) because you could, in theory have a piece of equipment that used 18 amps (thus the 20 amp receptacle would be appropriate) but the start up amps might be higher than 20, and therefore you need the extra amps in the panel to allow for that surge. But in all honesty, if you've got a piece of equipment that is pulling 18 amps, it should be on a 30 amp circuit anyway.

So, no more "breaks" given... ALL code (per NEC) says they should match (with some very few exceptions which this case does not fit any).

[Dan Hintz]

Oh, and just spoke with my electrician today. He said NO inspector would allow a 30 amp breaker and 20 amp receptacle combination.

You're right... here it is in black and white:

210.21(B) A single receptacle shall have a rating not less than the branch circuit (OCP)

with the exception of a 15A receptacle being allowed on a 20A circuit.

[Jon Prouty]

Thanks all for such an interesting debate. When we were sitting in the design office at the home builder picking carpet, tile, cabinets, etc I had my list of requirements for the garage. I wanted a couple 220 outlets run and a few extra 110 outlets - I hate that they only have one or two outlets in a three car garage (usually on a house circuit that is loaded up well anyway). I had the option of 220 20 amp or pay a little more for 30 amp. Well, since I was doing it may as well go for the 30 amp dedicated outlets. I have two 220 30 amp outlets in the shop portion of the garage - both are home runs to the the box. I picked up the 220 30 Amp twist lock plug and receptacles from the borg and will be wiring it up soon (last night I was able to finish moving out of the old house so I have been crazy busy). I'll take some pics of what I chose and let you know how it goes - hopefully this weekend or next. :)

I figured this would be a simple question with an easy simple answer... seems to have sparked multiple opinions on what to do. I would have thought that this was a very common issue folks have but perhaps not so much. I suppose if you are wiring up from scratch you have already made decisions on which way to go.

For those interested - my electrical service box is on the opposite side of the house as my garage so the electricians had to run the wire a LONG way rather than a simple punch through on the garage side. I am really glad I had it done during construction rather than doing it later. Since the run was so long, I feel in this case to have not over paid for my upgrade. :)

Thanks everyone for your help - it really is awesome to get such support.
Jon

[Mike Cruz]

That was a good call, Jon. Yeah, 20s on everything may be more appropriate, but as long as you are consistent, I think that is the more important thing. Have fun!

[Jeff Nicol]

Well, John, I gave you a break. Before responding, I did a bunch of research (instead of blindly telling you that you were wrong). My findings are that NEC says your breaker and receptacle (and of course, wire...but oversized wire isn't bad unless you have to altar the wire to get it to fit into an undersized receptacle) should match. I WAS going to link my evidence, but since you made ME look it up, I figure I'll let YOU do the same.

Do you HAVE to do it? No. But you don't HAVE to pull permits, either. You are SUPPOSED to, though. Ergo my comment...the OP "should" change the breaker, receptacle, and plug so that they all match. Enjoy.

MIke, You are correct and if one would leave the 30 amp breaker in the panel and something failed with the equipment even rated at 20amps, a failure of the VFD, motor, outlet that created a short and the amp draw was at a constant 20amps + that is when the wiring in the wall would begin to heat up and cause a potential fire. The odds of this happening are slim, but best not to take the chance, you never know when a gremlin will mount a 50lb block on the lathe and turn it on full tilt until something gives.

Follow the rules of the NEC or call an electrician if there are ever any questions about electricity, it can kill in a heart beat!

Jeff

[Thom Sturgill]

You're right... here it is in black and white:


with the exception of a 15A receptacle being allowed on a 20A circuit.

I don't have access to a copy of the code, but I knew that was the correct response per code. I drilled my B-I-L when he got his masters permit many moons ago. While some may not like being told what to do, building codes are there to protect the property and those occupying it. The NEC exists to prevent electrical fires - look at the name of the organization that creates it.

[Mike Cruz]

Thom, I found it online. And I would have posted what I found, but I had a bee in my bonnet. I hate when someone replies with "Hogwash!", thus making ME go spend time looking up what I pretty much knew (like you did) was right. So, if he still doubted what I said, HE could go spend the time to look it up.

It is one thing to disagree. I understand that. We can't all agree on things. But, saying 'Give me a break, no code calls for that!' when it does AND might influence someone to do something that would be against code and potentially harmful to their person or property gets my goat...

[Jon Prouty]

Update - I got it all wired up and operational now. Thanks everyone for your help. Here is what I decided to go with (no change to the breaker in the box).
Original configuration:
274348
New Plug and Receptacle:
274349
Installed new parts (I need to find another cover to fit this box and receptacle):
274350
Block mounted up:
274351
Spinning!!!
274352

Thanks again everyone.
Jon

[Mike Cruz]

As long as you are comfortable with your lathe plugged into a 30 amp circuit, that'll do! I suppose it will be fine. I don't know enough to know if it would/could even have a down side...

Oh, and you really ought to cover that receptacle before it gets full of shavings and/or dust...that would NOT be good. ;)

[Scott Hackler]

Jon, I am glad you've got it running. I would strongly suggest lowering that breaker to a 20amp. There is a reason for breaker ratings, SAFETY. Otherwise we would all have our outlets in our homes running off a 100amp main. Your wire is beyond spec for 20 amp so that wont be a problem, but what if the VFD or anything on the lathe motor shorts? It is going to take 30amps to trip that breaker, before the interanl wiring go volcano hot and possibly igniting some wood shavings and such.


I am not the over worrying type, but I wouldn't leave the breaker like that.


.....off my soap box, Happy Turning.....

[Jon Prouty]

Jon, I am glad you've got it running. I would strongly suggest lowering that breaker to a 20amp. There is a reason for breaker ratings, SAFETY. Otherwise we would all have our outlets in our homes running off a 100amp main. Your wire is beyond spec for 20 amp so that wont be a problem, but what if the VFD or anything on the lathe motor shorts? It is going to take 30amps to trip that breaker, before the interanl wiring go volcano hot and possibly igniting some wood shavings and such.


I am not the over worrying type, but I wouldn't leave the breaker like that.


.....off my soap box, Happy Turning.....

Hi Scott - I don't understand. Maybe I am dense. The breaker protects the house wiring and not the appliance plugged into it. My dust collector pulls a lot more current than my desk lamp yet they are both plugged into the same 110 20 amp circuit. Am I supposed to change every breaker to suit the current rating of the device plugged in to that circuit? 20 amps will kill my desk lamp. What is the difference here? 220 vs 110 and now we have different logic? I don't know if a 20 amp breaker will protect my lathe any better than a 30 amp breaker - to my knowledge it isn't supposed to protect my lathe anyway. Anyone pop a 20 amp breaker without the VFD flipping first?

I feel safe with my 30 amp breaker and my lathe plugged into that circuit. If I am wrong I haven't been convinced. If I am wrong here then someone please help.

Jon