Simple (I Hope) 240V AC Electrical Code Question

[Art Mann]

Art, to the best of my knowledge, you cannot use 20-amp receptacles on a 30-amp circuit. So you are correct in standing ground there. I haven't researched it, but I am pretty sure that not even the motor sections of the NEC sway on this part as it pertains to any receptacles.

My apologies if I missed where you backpedaled on the 15-amp receptacles. The original statement was pretty strong, and I hadn't noticed anything correcting it later on.

As for the $0.59 bulk-pack receptacles, they are what they are. However, they are still required to carry the full 20 amps of the circuit for which they can be legally connected to. The issue is that they are just plain super-cheap, not that they are not rated for the amperage. Any heating you observed on those outlets was due to poor connections, whether it was loose lugs or sloppy fitting prong compressions. The cross sectional area of the internal bus components must still meet minimum requirements.

In order to understand what I am saying you need to read all my posts instead of just picking out one. My point is that it is a bad idea, and a violation of the NEC, to replace a 30A receptacle with a 20A receptacle regardless of what you plan to plug into it. The reason is there is no guarantee some future owner of the shop will not install a 20A plug onto a 30A machine or appliance and the plug it into that same outlet. In this case, he will be drawing 30A through a 20A receptacle and that receptacle is going to get hot.

My original advice to the OP was to simply cut the 20A plug off and install a 30A one on his saw. The reason is purely mechanical. If he had a 20A 240V outlet available, I would have suggested he just plug it in and use it regardless of what the manual says.

As far as the cheapo 15A receptacles are concerned, they probably do well enough with 20A until a few years go by and the contact and wires start corroding. Then they will start getting hot under heavier loads. As I have already said, I have replaced the receptacles in my shop because I saw one fail. I have fixed this same type of failure in houses owned by other people and I know of at least one case where someone on this forum had the same problem. That is not an NEC issue but a UL issue.

[Art Mann]

A 15a outlet is the same as a 20a outlet of the same manufacturer and the same grade; except for the slots.
It doesn't really need to be said that if they are different grades they will be different. What don't you get?

Your comment stated that 15A and 20A plugs are identical. That is just simply wrong and anybody who doesn't believe that can go down to Home Depot and see for himself. The vast majority of 15A receptacles sold are of the contractor special variety and are obviously of lesser quality than the 20A ones, which cost 3 times as much.You made a blanket statement that is not true and you ought to admit it.




You didn't make a mistake on the side of safety. Using 20a outlets is no safer than using using 15a outlets. You simply erred on the side of not understanding electrical work.

Let it rest!

15A and 20A ratings on some outlets don't make any difference but for the vast majority of 15A outlets sold, there is a huge difference between them and 20A outlets. Once again, I would invite anyone to go to their local hardware store and see for themselves. By the way, are you a licensed electrician? Have you wired and repaired the defective wiring in enough houses to presume to judge my understanding of electrical work? I don't claim to be an electrician because I have not made it my profession nor studied all aspects of the discipline. However, as I told you in a private message, I have done enough installation and repair work to have seen the disastrous results of bad wiring many times.

[Andy Shearon]

Actually, it is.
It can answered with a single phone call to his building inspector, regardless of any positions stated here. Including mine.

:-) I thought the question would be an easy one. :-)

I'll try to call the inspector tomorrow, and see what he says. The first working day after the weekend is usually crazy-busy down there, as all the G.C.s start new projects, so I might not be able to get him on the line. I'll let everyone know what he says if I can get hold of him.

FWIW, I did a little quick searching for 6-30P to 6-20R adapter and found a whole lot of nothing (actually, a found the locking plugs to straight receptacles, but I don't have the locking receptacle). Looks like I'll have to make one. Plug is ~$15, connector is ~15, and some SJOOW wire is maybe $2 for a foot or so. $32 for the pigtail versus $5.50 for the 20A receptacle, oh well...


Since this topic seems to have fanned the flames of debate, let me add a little fuel to the fire. :-) While looking for the two ends of my do-it-yourself adapter, I found the following at the Home Depot:

http://www.homedepot.com/c/electrica...tlets_HT_BG_EL

"Because 15-amp receptacles can be used with 20-amp circuits, most of the receptacles you see in homes are the standard 15-amp variety, with two slots and a u-shaped grounding hole."

Personally, I wasn't expecting 40+ responses. Next, let's talk about locking plugs versus straight plugs. I have a fundamental aversion to locking plugs from the standpoint that all my machines are on movable bases, and lord knows I'm going to forget unplugging one once. :-)


Andy

[Mike Cutler]

Andy

Here's a solution.
http://www.quail.com/P-WS-112/Nema-6...ter-Black.aspx

Don't sweat the debate. This always happens when electrical code questions arise. It's good because it forces folks to think about the things they're doing, or might have done, and ask themselves if they did it as well as it could be done. The code is not as black and white as we would like it to be, and it is far from simple to interpret.

While I disagree with some of Art's argument points, as long as it's a conservative safety approach, I have to respect his position. Like Art, Ive done a lot of home remediations to wiring through the years. Some of the stuff I've seen was pretty scary.

[Wade Lippman]

In order to understand what I am saying you need to read all my posts instead of just picking out one. My point is that it is a bad idea, and a violation of the NEC, to replace a 30A receptacle with a 20A receptacle regardless of what you plan to plug into it. The reason is there is no guarantee some future owner of the shop will not install a 20A plug onto a 30A machine or appliance and the plug it into that same outlet. In this case, he will be drawing 30A through a 20A receptacle and that receptacle is going to get hot.

I don't think anyone takes issue with that. A couple people suggested that code might possibly allow the use of a 20a outlet in this limited circumstance (and contrary to what you have said, I disagreed with that suggestion); but nobody thought it was safe in general.

It is your outright errors and your inability to read, that you refused to let go of them even after code to the contrary was pointed out to you, that are being objected to.

As far as the cheapo 15A receptacles are concerned, they probably do well enough with 20A until a few years go by and the contact and wires start corroding. Then they will start getting hot under heavier loads.

And here is a good example of the problem I referred to above. Yes, cheapo 15a outlets tend to fail and could cause a fire when they do; but cheapo 20a outlets will fail and cause a fire in precisely the same manner because there is no difference between the two. In fact 20a outlets are MORE dangerous because you can plug a 20a device into them, but you can't into a 15a outlet. That might be a small thing, but if one is more dangerous, it is the 20a outlet.

But you won't let this go; you will come up with some nonsense about how 15a outlets encourage users to plug more load into them, or something else silly.
Let it go and try to learn from what people tell you.

Moderators, how about locking this? There is nothing else constructive to be said on the subject.

[Wade Lippman]

Andy

Here's a solution.
http://www.quail.com/P-WS-112/Nema-6...ter-Black.aspx

Is it? The input is approved to 20a. Can you use it in a circuit with a 30a breaker? I guess you could argue that it isn't part of the wiring, so the fact that it is no safer than a 20a outlet doesn't matter; but the fact that it is no safer should matter. Just like the OP could use a 20a outlet for something else, or leave it there when he moves, he could do those things with this adapter also.

[Steve Milito]

I don't understand the big deal about replacing the cord or plug. It's a simple $5.00 and 5 minute fix.

[Mike Cutler]

Is it? The input is approved to 20a. Can you use it in a circuit with a 30a breaker? I guess you could argue that it isn't part of the wiring, so the fact that it is no safer than a 20a outlet doesn't matter; but the fact that it is no safer should matter. Just like the OP could use a 20a outlet for something else, or leave it there when he moves, he could do those things with this adapter also.

Wade

Yes you can use it. You can use it for the same reason you can plug a 240/15 amp plug into a 240/20 amp receptacle. What you would not want to do is what Art asserted. That being, wire a 30 amp load to a 20 amp plug and use it. The code essentially ends at the receptacle, and there is very little beyond that point to prevent someone from being intentionally, or unintentionally, stupid.
My dryer plugs into the 240/30 amp plug in the wall. Inside the dryer the the wiring parallels off a terminal strip and goes to a 240/20 amp receptacle on the back of the dryer for the washer, which plugs into the back of the dryer (My washer has an on demand how water heater built into it.) You would be correct in thinking this caused the electrical inspector fits in 1993. All he saw was potentially 50 amps plugged into a single 30 amp connector. Nothing stop you from running the washer and dryer at the same time. But this is the manufacturers required installation. Now it is more normal, but in '93 it was a bit out of the box. We were both kind of thinking, was this right? at the time.
Art's position on the safety aspect concerned leaving a 20 amp receptacle in the wall and having someone else down the line wire a 30 amp device to a 20 amp plug and use it in the now existing installation. Anyone can be stupid and wire a plug/receptacle for any voltage they want. I can wire 240/50 amps to a 115 plug/ receptacle if I want too. Pretty stupid, but electrically it will work. If I'm not mistaken, it is that person that Art is trying to protect from themselves.

[Wade Lippman]

I don't understand the big deal about replacing the cord or plug. It's a simple $5.00 and 5 minute fix.

The OP (or somebody, I am not sure I remember now who, and I'm too lazy to look) was afraid that would void the warranty. But yeah, that was my suggestion also.

[Andy Shearon]

Andy

Here's a solution.
http://www.quail.com/P-WS-112/Nema-6...ter-Black.aspx

Don't sweat the debate. This always happens when electrical code questions arise. It's good because it forces folks to think about the things they're doing, or might have done, and ask themselves if they did it as well as it could be done. The code is not as black and white as we would like it to be, and it is far from simple to interpret.

While I disagree with some of Art's argument points, as long as it's a conservative safety approach, I have to respect his position. Like Art, Ive done a lot of home remediations to wiring through the years. Some of the stuff I've seen was pretty scary.

I found that one. However, the 30A side of that is a locking connector, not a straight plug. I need a 6-20R to 6-30P, not a 6-20R to L6-30p. I guess I could swap out the receptacle. :-)


A.

[Rod Sheridan]

Hi, simply put a 30 ampere cord cap (plug) on the bandsaw cord and plug it in.....................Regards, Rod.

[Jim Neeley]

:-) I thought the question would be an easy one. :-)

I'll try to call the inspector tomorrow, and see what he says. The first working day after the weekend is usually crazy-busy down there, as all the G.C.s start new projects, so I might not be able to get him on the line. I'll let everyone know what he says if I can get hold of him.

Andy

Andy,

A hint I've found handy:

Some electrical inspectors will answer an "Does this meet code?" question while others won't, citing liability. If you get one that won't answer the question, re-word it slightly and ask "Would you find a code violation during an inspection if you saw...?".

This way they're giving their opinion and can't be held liable for it. Those inspectors will tell you that if you that if you want someone to assume liability for it, to hire a Professional Engineer (with E&O insurance) to draw it up and PE Stamp it because they don't want the liability.

Just some hip-pocket info. :-)

Jim

[Chris Friesen]

Rollie, this would imply that one has to hard wire the motor in all cases then, right?

Unless the rules have changed recently you are in fact allowed to oversize the breaker as per section 430 and still use cord-and-plug connections. For an example from this forum, see http://www.sawmillcreek.org/showthre...00#post2128700

However, I personally would hesitate to use the exception in a home shop because most people wouldn't know anything about it and plugging in non-overload-protected devices could theoretically cause a problem.

[Andy Shearon]

Andy,

A hint I've found handy:

Some electrical inspectors will answer an "Does this meet code?" question while others won't, citing liability. If you get one that won't answer the question, re-word it slightly and ask "Would you find a code violation during an inspection if you saw...?".

This way they're giving their opinion and can't be held liable for it. Those inspectors will tell you that if you that if you want someone to assume liability for it, to hire a Professional Engineer (with E&O insurance) to draw it up and PE Stamp it because they don't want the liability.

Just some hip-pocket info. :-)

Jim

Thanks for the advice. Where I live, you can actually e-mail the building inspectors. I shot my tailored original question out to the lead guy yesterday, and he forwarded it on to the electrical plan inspector at the end of the day. We'll see what happens today.

Andy

[Chris Friesen]

This is exactly why I was posting. I just don't understand section 430 of the NEC.

For both of the next cases, this is a dedicated circuit (no other uses):

(Case 1) The collective wisdom (of those who've quoted or referred to 430) is that presuming I have a 20A circuit with 12AWG wire and a 20A receptacle, I could connect an 12.8 FLA inductive load motor with 12AWG in-wall wiring and change the original 20A breaker to a 30A breaker to handle the inrush current (as long as the motor protects itself). In this case, I would have the original 20A receptacle, original 12AWG in-wall wire, and a new 30A circuit breaker.

(Case 2) On the other hand, if I have an existing 30A circuit, with 10AWG wire and a 30A receptacle, and I want to put an 12.8 FLA inductive load motor on the circuit. I cannot take and replace the 30A receptacle with a 20A receptacle, which would leave me with a new 20A receptacle, original 10AWG in-wall wire, and original 30A circuit breaker.

The only end result difference between the two is that I have beefier wire in the second case, which is the non-code compliant one.

As long as the receptacle is rated for #10 wire, I don't see any reason why the second case would be non-code-compliant. You're always allowed to oversize your conductors as long as whatever the conductors are connected to are rated to handle the larger conductor.