Multiple 240V Outlets On one Circuit

[Ron Natalie]

Twisitng isn't required but not prohibited. There's a lot of argument about whether you should or not but frankly it makes no difference.
As John points out (and I believe you this wasn't your intent), you can't have 30A and 40A receptacles on the same circuit.

[fred klotz]

I'm not sure I agree with the comments about having 30A and 40A receptacles on the same circuit. The breaker for a circuit needs to protect the smallest wire. So you would need to run the 8 gauge wire to the 30 receptacle. A 30A receptacle will not accept a 40A plug. Some 240V receptacles in the 15A and 20A sizes have the blades oriented such that a 15A plug can fit a 20A receptacle, but a 20A plug will not fit a 15A receptacle. The same holds true for 120V receptacles in 15A and 20A configurations. I have a bunch of those sitting on my parts shelf and a few installed. And the vast majority of outlets installed on 20A/120V circuits are rated for 15A. A 20A 120V plug has one blade horizontal, so it cannot be plugged into the 15A outlet. The 20A 120V receptacle has one of the blade sockets in a tee configuration to accept both 15A and 20A plugs. Correct me if I am wrong.

[Steve Meliza]

I'm not sure I agree with the comments about having 30A and 40A receptacles on the same circuit.

It's code, not common sense. A 20A circuit is allowed to have 15A and 20A receptacles and a 40A circuit is allowed 40A or 50A receptacles, but in all other cases the breaker and receptacle(s) must match (2011 NEC 210.21(B)(3)). You are correct that the breaker is there to protect the wire.

[fred klotz]

Thanks for the clarification.

[Richard Jones]

Twisitng isn't required but not prohibited. There's a lot of argument about whether you should or not but frankly it makes no difference.
As John points out (and I believe you this wasn't your intent), you can't have 30A and 40A receptacles on the same circuit.

I've seen several arced connections under wire nuts where the wires were not twisted first. None of these incidents caused the overcurrent device to trip, so a fire could have occurred. I always twist the wires together with my Kleins, then use the wire nut to hold them together (and for protection). So, I'm saying, it DOES make a difference, at least on my watch, and I'm in the code enforcement business. Common sense and experience always gets a priority over the printed word..........

[Ken Fitzgerald]

Folks,

The personal and professional attacks are violations of the Terms Of Service and don't meet the standard behavior expected here at SawMillCreek.

Let's keep it civil and friendly.

[Ron Natalie]

I'll post this again a little more calmly. The manufacturers requirements, UL listing, and hence the National Electrical Code do not require (nor do they prohibit) pretwisting the wires. While there may be a few AHJs that may have opinions on it, I've worked in four states and it has never been an issue and frankly I've never seen an inspector even look to see if the wires were pretwisted or not.

Pretwisting is a convenience thing more than anything else. Twisting does not provide any acceptable amount of mechanical connection. If the pressure fastener (wire nut) fails, you are as likely to get a burned connection even if the wires are twisted (perhaps more likely as if the nut were to come lose on an untwisted connection, the wires would most likely either open or short to something rather than just having a high resistance connection).

This has been hashed out all over the place on the electrical professionals forums so I'll defer all further discussion of this to those.

[Richard Jones]

.....................Pretwisting is a convenience thing more than anything else. You are certainly entitled to your opinion.

Twisting does not provide any acceptable amount of mechanical connection. Why on earth not? Try pulling apart a twisted pair of 12, then try the same thing without being twisted.............wait, that one's already apart, so technically it's not really a connection..............

This has been hashed out all over the place on the electrical professionals forums so I'll defer all further discussion of this to those. You mean Mike Holt's? The one that had the poll where 73% pretwisted? That one? Just want to be clear about what you're referring to

I wasn't ever referring to anything that got inspected, I was discussing what I believe to be the safest manner in which to make a connection.

[Charlie MacGregor]

James, Outside the trist / no twist, and I understand you'd like to use material you have on hand, I don't believe you should run romex in conduit. I may be mistaken.

Regards, Charlie

[Ron Natalie]

Why on earth not? Try pulling apart a twisted pair of 12, then try the same thing without being twisted..

Because "pulling apart" is not the issue. In order to have an acceptable connection, it has to be gas tight to keep the resistance from rising to a point which would cause the connection to heat up above acceptable levels. The wire nut is NOT just an insulated cap. IT provides the integrity of the electrical connection.

You mean Mike Holt's? The one that had the poll where 73% pretwisted? That one? Just want to be clear about what you're referring to

That's the one. But whether people prefer pretwisting or not is immaterial.
I didn't say not to pretwist. I didn't say there weren't some reasons why it's convenient to pretwist. However pretwisting is neither NECESSARY nor SUFFICIENT to make an acceptable connection.

Charlie: Short runs of conduit for "physical protection" are acceptable for NM.

[Michael Ginsberg]

I believe Electrical Wholesalers are all over CT. They are open to the public.

I know there are old threads on this topic. But I will not resurrect them.So that there is no confusion and replies to the original posters questions.

I need two 40 amp outlets and two possibly three 30 amp. in my basement shop. What I am planing is to run 10/2 and 8/3 (that's what I have on hand)romex thru my ceiling joists and when I get to the first drop put a junction box in the joist bay and run the romex down in 1/2" metal conduit to the outlet box. Then from the junction box in the joist bay continue to the next drop with romex in the joist bay again till I reach the next drop. Does this sound ok. What is the best way to make the splices in the junction box. Some big honkin wire nuts? Its hard to imagine twisting together two or even three pieces of stranded 8awg wire and capping it with a nut. I don't know of any electrical supply houses near me. So I will need to rely on the blue or orange big box stores for supplies. Unless someone can advise a supply house in CT near 06278 that will deal with the public.

Thank you in advance,
James

[James White]

I believe Electrical Wholesalers are all over CT. They are open to the public.

Thank you. I will keep them in mind for the future. The closest one is 25 miles from me. So that is about average for were I live (the quit corner).

James

[Robert Murphy]

Yes....it's definitely not code or good practice to run multiple 240 receptacles on one breaker unless your wire and breaker upstream are rated for the combined loads. I'm assuming that you're basing this setup on the premise that you would never have both machines running simultaneously... just make sure it is noted or labeled if you ever move! You could do an electrical interlock with a relay, motor contactor, and auxiliary contact that would always prevent the other tool from starting up, but that would lead to way more money and time. As for the wire nuts...I twist multi-strand wire prior to screwing on the wire nut and taping it (I always tape them). However, dealing with single conductor romex...the wire nut does sufficiently bite into the wire as you screw it on. The thing to be cautious of is one of the wires slipping down as you screw on the nut...that can definitely lead to trouble. I always tug them pretty hard and tape them well. Tape is cheap.

[Larry Edgerton]

What other kind of connections would be legal? I just was wondering as I see a lot of loose wires when I am working on remodels due to wirenuts. Seem to be a lousy medium to me. Would you use wire nuts on a car? No.

for example I used to do a bit of off road racing and we used clamped connections that were silver soldered, then covered with shrink tube. Never had a failure.

So say I wanted to do something better in my new shop. What are the options?

Just curious.

Larry

[James White]

Robert,

Could you let us know where in the code that multiple 220 outlets require a breaker large enough to handle the combined load. Is it specific to residential applications? I have seen electricians that stated that it was code compliant and others that have stated it is not. What about 110v circuits. They are not required to handle combined loads. Why is 220v an exception?

James

Yes....it's definitely not code or good practice to run multiple 240 receptacles on one breaker unless your wire and breaker upstream are rated for the combined loads. I'm assuming that you're basing this setup on the premise that you would never have both machines running simultaneously... just make sure it is noted or labeled if you ever move! You could do an electrical interlock with a relay, motor contactor, and auxiliary contact that would always prevent the other tool from starting up, but that would lead to way more money and time. As for the wire nuts...I twist multi-strand wire prior to screwing on the wire nut and taping it (I always tape them). However, dealing with single conductor romex...the wire nut does sufficiently bite into the wire as you screw it on. The thing to be cautious of is one of the wires slipping down as you screw on the nut...that can definitely lead to trouble. I always tug them pretty hard and tape them well. Tape is cheap.