Can I plug my 230V compressor (NEMA 6-20P) into a dryer (NEMA 10-30R) receptacle?

I am a certified electrical inspector by the IAEI and the ICBO with 8 years experience performing over 3,000 electrical inspections and finding over

3,000 violations. I already got the egg on my face and served my apprenticeship. I suggest you get some time under your belt before you make an ass out of yourself anymore.

In misc.industry.utilities.electric Jack Sourdough wrote:

|> Are you referring to "40 ampere receptacle" and "20 ampere receptacle" in |> terms of the NEMA configuration of the device, or the ampere rating of the |> device? The NEC says "rating". If the device is _rated_ for 40 amperes, |> even though it only has a pair of NEMA 6-20Rs on it, how do we know that |> the writers of the NEC didn't actually intend that? I'll argue that maybe |> they really did intend that. Such a device could be considered as safe |> when both loads plugged in do not exceed the rating of their own plugs. |> That kind of logic and assumption is already made for NEMA 5-15R and 6-15R |> devices in duplex on a 20 ampere circuit. If the NEC writers _meant_ for |> the device _configuration_ to apply, instead of the current rating, don't |> you think they would have said that? |> |> A lot of interpretations of the NEC do often hinge on the exact word used |> and in some cases even whether a singular or plural form is used. |> |> I personally have no problem with 210.21(B)(3) as written. If they were |> to change it and refer instead to the device configuration, I'd still have |> no problem with it. Those who do one way are the other are the ones who |> should deal with it. If you don't like the fact that it refers to the |> device _rating_ maybe _you_ should be the one to submit a proposal to |> change it. I won't oppose it. |> |> -- | I am a certified electrical inspector by the IAEI and the ICBO with 8 years | experience performing over 3,000 electrical inspections and finding over | 3,000 violations. I already got the egg on my face and served my | apprenticeship. I suggest you get some time under your belt before you make | an ass out of yourself anymore.

Doing something wrong more than once doesn't make it right. Just because you have done all those inspections and found what you claim to be all those violations does NOT mean you have done them right. Inspectors can, AND DO, make incorrection inspections often. I have no idea how many of the 3,000 violations you found were true violations were wrong, but now I suspect at least some of them might well be.

Do you know that a receptacle device can have a configuration for one amperage and a rating for another? Apparently not. But they do. For example receptacle devices for NEMA 5-15R and 6-15R can be had with a

20 amp rating and even a 30 amp rating.

You'd probably fail an inspection just because it has #10 wire protected by 15 amp or 20 amp circuit breakers.

Wait, this is legal, right? Suppose I installed #10 wire with 40+ amp.-rated switches and receptacles but only put a 20-amp breaker in the panel. It seems to me this would be a good way to go. The circuit breaker definitely protects the wiring, so it meets its goal. The only downside is that it may be more expensive than really required.

Thanks, Pete

AFAIC, it's safe ... and legal. But someone (and I've heard that inspectors actually have) could argue that mismatching the ratings could lead to some confusion, possibly resulting in future changes being doing wrong or the inspection being done wrong, where something gets underrated because the breaker was replaced with a higher rating. In your example I don't see much chance of that. But an example where it could be a problem is when there is #10 wire and 20 amp rated 5-20R receptacles. Someone working in the panel might assume the circuit is safe at 30 amps because of the #10 cable coming to the breaker. Of course, anyone doing that would be stupid and any licensed electrician doing that should be investigated and maybe have his license yanked.

The biggest problem, I think, is that there being a shift towards more DIY home wiring, perhaps due to the discounted electrical stuff at the big box stores, there is a fear that many people will be installing things in an usafe way. It's a legitimate fear. And I can understand electricians making the suggestions to use their services instead. However, I have seen some terribly unsafe wiring in my time, and most of it was in fact wired by licensed electricians.

People who are going to be doing the wiring themselves do need to learn the safe way to do it, and how to do it meeting the code. But the attitude I seem to be getting from a number of electricians (and also from an inspector in this thread) is that the NEC is something they are reserving to themselves. Well, if they think that, then I say they should inspect on the basis of whatever it is that they suggest DIY-ers read, instead of the NEC. And I have read some of those books. They have nice pretty pictures for learning techniques and information for avoiding the common mistakes. But they just don't over all the possibilities people might run into. That's where the NEC is really necessary. Mostly it's a good resource. But in some areas it's confusing, in some it's open to wide interpretation, and in a few it's even outright misleading. I have not kept a diary of the problems I have found with it since there is still no documented way for the average guy to work with the NFPA to get things reworded (people have said to submit changes, but until I see the NFPA specify exactly where and how, I have to assume they don't want them and I'll spend my time on other things, instead).

I just talked to my dad, a licenced electrician in Ontario. The Ontario Electrical code is loosely based on the NEC, but has some differences. Some things that are forbidden by the NEC are OK according to the Ontario code, and some things accepted by the NEC are not approved in Ontario.

Anyway, according to him, there is one simple legal way to connect that 20 amp compressor to the 30 amp drier connector.

Take a 30 amp drier cord, and using an approved strain relief chassis connector connect that cord to either a breaker or a fuse block in an approved disconnect box fastened to a 2 foot square 3/4" plywood panel.

Mount a 20 amp receptacle to the panel and wire it to the protected side of the disconnect.

Plug the disconnect into the 30 amp drier receptacle, and plug the 20 amp compressor into the 20 amp receptacle.

That way you are connecting a 30 amp device to the 30 amp circuit (you effectively have a 20 amp sub panel) and plugging a 20 amp device into a 20 amp circuit. In the disconnect the neutral must go straight through, and the ground must go straight through - only hitch is the drie plug must be a 4 connector plug.

The Ontario Electrical Code is based on CSA standard C22.1. "Based loosely on the NEC" is not really true; the CSA code was largely developed independently. Though, since the physics is the same on both sides of the border, the results are not fundamentally different. And in order to not unduly burden the far-off manufacturers of wiring devices that fill our lumberyards and home improvement stores, harmonization efforts on both sides of the border have resulted in substantial agreement.

I'd like to find a really authoritative examination of the differences between NEC and CEC.

Bill

Canadian regulations would never allow 15 ampere devices on a 20 ampere circuit.

| Canadian regulations would never allow 15 ampere devices on a 20 ampere | circuit.

But what is it that makes it a "15 ampere device"? Is it the maximum current rating, or the blade configuration according to NEMA?

And how many words does it take for these guys to make that definition?

The answer to my question could be given in 1 or 2 answers. I'm not looking for who has authority or not to say. I'm looking for a clear well written and concise answer. Given that NEC has numerous poorly written parts, and the wordings of other standards and such can get lengthy, they are of no interest to the issue of resolving exactly what is the formal answer.

I do know the answer, but I want to see it from other people to see if they really know, and to use that for a point of debate (I'll argue the wrong answer is right to see if they are even confindent of their answer if they do get the right one).

Exactly! There is always some info troll that will debate the stated rules for a loophole somewhere. That is why the code is stated with so many words. people that cannot read shouldn't be wiring homes or businesses where people can die in fire because of bad techniques or ignorance.

Wir>

| Exactly! There is always some info troll that will debate the stated rules | for a loophole somewhere. That is why the code is stated with so many words. | people that cannot read shouldn't be wiring homes or businesses where people | can die in fire because of bad techniques or ignorance.

But there is wording in the NEC that if taken literally is wrong. That wording depends on one having experience as an electrician, or having at least done a lot of wiring and/or studied electricity. The problem is that people really do read the NEC (because it is the "final authority") and as a result can come away with the wrong idea. That would be the reader's fault if the wording was literally correct. But it states "rating" instead of "configuration". In this case it is the writers that have it wrong. It's not wrong to those with experience because they can draw on that experience and know what is meant. But some people who don't have that experience will be using the NEC because they have to.

| Wiring is not a hobby.

But it is something that DIY-ers are doing a lot more of, and the NEC needs to be able to guide them precisely. If that comes in the form of a separate document just for DIY usage, that might be better. But one of the existing "home wiring done easy" type books is not it because it is not, by itself in any way, authoritative. What I am referring to is a separate book that can entirely stand on its own such that being in compliance with that book is being in compliance, and the primary NEC document will never need to be consulted. It would not allow anything the NEC would not allow, but might not allow some things the NEC does.

One problem NEC does face is having to handle both extremes from DIY home wiring to industrial electricians doing major work site wiring. It's not easy. But be separating things, I think it could be made to work by relaxing the need to handle any commercial situations in the new document. I'll even suggest the name "NEC @ Home" to give it the cool modern sounding name. And again, it is not a how-to do wiring book ... it is a rule book. It supplements a wiring book (and may be licensed by NFPA, if they ever develop this, to be included in such books if they wish).

So there are DIY people with insufficient experience to install electrical wiring/equipment properly. Imagine that! And you want to "fix" that by dividing the NEC into two portions - one for those with sufficient experience and one for those with insufficient experience?

| So there are DIY people with insufficient experience to install electrical | wiring/equipment properly. Imagine that! And you want to "fix" that by | dividing the NEC into two portions - one for those with sufficient | experience and one for those with insufficient experience?

I didn't say that. I said they have insufficient experience to INTERPRET THE NEC as intended. Lots of people have plenty experience wiring basic things in their own home. But when they run across something a little bit different, and their "home wiring for dummies" book doesn't cover it, they might just try to get an answer from the authority ... the NEC. Of course the NEC is NOT a "how to" book. But it is often treated as a "what to" book. There needs to be such a book, written for the DIY market that will not go away no matter how much you wish it would, which ALSO is sufficiently complete that it can serve AS THE CODE for all the situations a home will have. One would simply choose whether to use the NEC or the "NEC-EZ"; the latter would not permit anything it does not cover, which generally won't been needed in 99.99% of homes.

Your argument is specious. It nets out to them having insufficient experience to do the wiring properly, if they are forced to rely on their misinterpretation of the NEC as you stipulate in the scenario you created.

But what the hey - if you can write a book that addresses the DIY problem you have in mind, go for it!

There are lots of guys out there who know enough about wiring and electricity to do a safe wiring job who could never, in a hundred years, understand or interpret the NEC.

They know what size wire is needed in what circumstances, and how to connect the wires. They know what receptacles and switches to use, and how many wires are allowed in a box. They know how much wire to strip, and how to bend the ends so they fit properly under the screw, and how tight to make the connection.

Some of them cannot read.Others just can't read english.

Yet they will very often do a better job of wiring a building than some highly educated electrical engineer type who can interpret the NEC day in and day out.

Some of them are even licenced electricians. Some are even union members.

Since today was a "holiday" for us union people, I was sitting here reading this thread. I don't have ANY idea of what people do up in the NE section of the US but here in Miami,FL it would be done the usual rat way and someone would just snip of the compressor plug and put in a new plug that matched the dryer receptacle and use it until it burned up or burned the house down. The "Hialeah" way. Now, while everyone has just posted a lot of data the refers to this issue, I (personally, not to DIS anyone) have a problem with giving advice on electrical needs to anyone because it is just cutting someone (preferably a IBEW guy) out of making money doing the work. The NEC code book is NOT an instruction guide for anyone, it is the basis for which state/count/local inspectors go from. As for the dryer, older houses used 2hot/1gound plugs and new constriction is for 2hot/1nuet/1ground outlet. Did anyone ever think that the dryer has the NEUT bonded (what a word...poor choice of words) to the ground inside the dryer itself where the power cord plugs in or has anyone not ever worked on appliances before where this happens? I do new construction, some side work but not really much, and all new construction is 4wire receptacle BUT the dryers being installed in a new high rise condo I am @ do say on the back that

3wire is for OLDER and/or mobile homes only and to use a 4wire plug if NOT used in one of those situations. If your house was built in the 1960-70's, is it piped in or is it romex. If it's piped, just pull new wire (4 wire), change the dryer (un bond) the nuetral-ground, replace the power cord for that end of the circuit. Make a sub panel out of the old dryer outlet box (use X rings) and make one recept. for the dryer and one for the compressor. For me, the simple answer is usually the right answer. Just make sure the BREAKERS are turned off....you know, no one ever mentioned that. What if this guy goes and touches 2 hot wires.....? The volts will not kill you..the amps will...so he would be getting 60 AMPS...only takes 50 milliampere to stop your heart. I mean, to sum up my post on this interesting topic. He should just call a licensed electrician, preferably 3 of them, to compare quotes, and just get the job done with out trying to work with hot circuits that may or may not explode or burn up anything. 120/208 hurts...277/480 hurts a lot more. The neutral is to carry back what amps are not used by the appliance. So using a ground on 3wire as a neutral is NOT a good idea. It will carry a load. Just my 2 cents worth........it does not in anyway imply I "know it all" or I am omniscient. Just after reading all the posts over and over, all of them...hey, I wanted to jump on the band wagon too. phil

| The NEC code book is NOT an instruction guide for anyone, it is the | basis for which state/count/local inspectors go from.

By that logic, the law is not a guide for how to live your life, it is the basis for which police arrest you when you do break the law you didn't know about.

| The volts will not kill you..the amps will...so he would be getting 60 | AMPS...only takes 50 milliampere to stop your heart.

Move volts -> more amps ... in same impedance.

Otherwise we can all feel safe using 2400 volts as long as we keep the amps low.

| He should just call a licensed electrician, preferably 3 of them, to | compare quotes, and just get the job done with out trying to work with | hot circuits that may or may not explode or burn up anything.

With no advice, he is likely to have found a random solution. Maybe it would be safe. Maybe not. I don't think he needs an electrician until he has to deal with wiring in the walls. And some solutions do not involved that. The ideal solution is to wire up 4-wire circuits for each dedicated load. But not everyone has the money for it.

| 120/208 hurts...277/480 hurts a lot more. The neutral is to carry back | what amps are not used by the appliance. So using a ground on 3wire as | a neutral is NOT a good idea. It will carry a load.

All those dryers are unsafe, right?

It is not a question of logic - it is a question of intent, and it is stated in the NEC in article 90-1 (c) (2002 code): "(c) Intention. This Code is not intended as a design specification nor an instruction manual for untrained persons."