Got a quick electrical question I’m sure someone here can answer. I’ve run 12-2 cable for the set of outlets I’m running in my basement. I’ve run one set of 15 AMP outlets (its only 6 outlets)on one 15 amp breaker. According to previous posts I read here this is OK.
Question I have is, the second breaker I plan to run on a 20 AMP breaker (possibly overkill) but it will be for all future TV and Entertainment equipment so I figured why not (just to be safe). Anyway can I put any 15 AMP outlets on this circuit and if I do would they have to be before or after the the 20 AMP outlets? I had planned to only use the 20 AMP outlets in a few select locations. Is this safe or do I have to run everything as 20 AMP once I put in a single 20 AMP outlet?
Thanks
Tom
Edited 4/30/2005 9:08 pm ET by Ribs
Replies
On your 20 amp branch circuit you can use either 15 or 20 amp receptacles, as long as you're feeding at least two or more receptacles. So, you should be OK. If anyone asks, this is called out in section 210-21(b)(3) of the 1999 NEC.
Sure some of the real electricians will chime in but for now I will repeat what I have been told/read. There is no problem putting 15amp rated outlets on a 20 amp 12ga circuit. As I remember the code you can put a single 15 amp as long it is a duplex (two holer)(don't recall ever seing a simplex 15amp). Anything (more outlets) after that is fine. I believe most 15 amp recptacles are rated 20 amp pass through (at least the gfci versions I have seen are).
I would pigtail passthroughs and not look back. Using the side terminals is ok but will be regreted when replacing recptacles later.
Hope this helps and is not contrary to anything :-).
Bob
The in floor outlets are often 15 amp simplex for some reason. Like the ones sold at the big box places, but the brand escapes me at the moment.
There are also clock hanger receptacles that are simplex.But it took me some looking to find some general purpose ones.http://www.passandseymour.com/products/product.html?s=89&mkt=3Note we hav implied 120 volt circuits, but the same thing holds for both 120 & 240.A 240 singles are commmon. They have both here in 15 and 20 amp devices.And they also have these, which consist of a single 120 recptecle and a 240 one on the same yoke, but electrically separate.http://www.passandseymour.com/products/product.html?s=86&mkt=3And combo devices (recptacle and switch/pilot/etc) are also single.As is the common duplex if you break the bridge.Note it is the really the number of "live" devices, not the number on the yoke. But in 96.37% of the cases (excluding Canadian kitchens) they are one in the same.
Edited 5/2/2005 11:59 am ET by Bill Hartmann
The 125/250 combo device, is that something that can be used for, say a washer and a dryer? I need to re-wire the washer and dryer in the carriage house (surface mount) and I was thinking of seeing if it was possible to mount both outlets in one large box, with two circuits feeding it through conduit (provided the right cover plate exists). But I only see, I guess, two hots and a ground on the lower outlet? That wouldn't work for a dryer anymore would it? Plus I think a dryer needs 30 amp, but I have to check that.
The only combo devices that I ahve seen are limited to 15 & 20 amp devices.The 30 amp are two big and in fact require a two gang box just for the 240/30 amp receptacle.And you are right. New dryer circuits require a 4 wire connection. @ hots,neutral and ground.
Is it ok to use a triple gang box, and put a simplex 20 amp in one gang, and the dryer outlet in the other two? This was my original thought, mainly to avoid running two pieces of conduit. Just use one conduit of the correct size, 10 ga red, black, white, green for the dryer and white, black, green 12 ga for the washer.But I don't know if a cover plate exists. I presume I could join two boxes with a second piece of conduit.
Yes, you can run all of those into one box. And you can get by with just runing one ground, the biggest one, and pigtailling it for the 2 receptacles.And if you can't find a matching coverplate there is nothing wrong with using a 2nd box connected with conduit and feeding the appropriate wires through.There are "make a plate" cover plates which consists of individual snap together plates with snap on ends. But I suspect that they are for all for groupings of single gang devices, but you can look.Another option is if you can find a tripple blank metal plate and then drill it out.
Guess my memory is failing. I have seen those, I have a floor one in my living room and have seen the clock versions. I should have said they are not common. Thanks.
Don't know why they are 15 amp though, those floor plugs. Seems like they could be 20 amp, but maybe the box would have to have more volume. I didn't even notice until the electricians pointed it out. I had to install about 9 of them because there were all these cut-outs in the floor for all sorts of weird outlets. One of them had, like six, all in a column (ungrounded of course).I think the clock and floor ones are the same thing, but with a slightly different box. The clock ones don't have a flush cover - it's recessed too.
Sturart & other poster are correct. As long as it's a duplex 15A receptacle, it's fine on a 20A circuit. There are single 15A receptacles, but they are not common.
But, why would you want to put a 20A outlet in a house?
I've never seen a household tool, appliance, or other utilitzation equipment that needs a 20 amp receptacle.
If all you want is a beefy outlet, get a commercial grade duplex 15A receptacle. It'll be just as difficult to remove the plug from, as a 20A recep!
Cliff
sometimes if its raining and everything is wet, my skill saw likes a 20 amp better
our temp power is 20 amp including the gfci's
but then again, if its raing real hard , we dont plug it in.......read .......go home
20 amp circuit breaker, 20 amp wire (12 ga) 15 amp outlet= legal
20 amp circuit breaker. 15 amp wire(14 ga) 15 amp outlet= illegal
15 amp circuit breaker 20 amp wire(12 ga) 15 amp outlet= legal
15 amp circuit breaker, 15 amp wire(14 ga) 20 amp outlet= illegal
20 amp circuit breaker, 20 amp wire(12 ga) 20 amp wire= only legal
<<"15 amp circuit breaker, 15 amp wire(14 ga) 20 amp outlet= illegal">>Can you explain why this is so?I know the 20 amp outlet has a horizontal slash opening (coming out of the verticals).Is that just to "identify" circuits that are 20 Amps, or are there appliances with this kind of plug configuration?"I would never die for my beliefs because I might be wrong."
-- Bertrand Russell
"<<"15 amp circuit breaker, 15 amp wire(14 ga) 20 amp outlet= illegal">>Can you explain why this is so?"Code only cover safety by also practicality. 20 amp outlet on a 15 amp circuit would be safe, However IF you had a 20 amp load it would trip the breaker and not be very practical."Is that just to "identify" circuits that are 20 Amps, or are there appliances with this kind of plug configuration?"There are 20 amp plugs, but I have never seen them on anything include things like my table saw which is rated for 18 amps. But I have "heard rummors" of commercial device, one of whcih was a margarita machine, that came with 20 amp plugs.And some one also told me that they picked up a heavy duty extension cord at one of the home horror stores that had a 20 amp plug.
Slightly of subject, but hinted at in this discussion.Many people make the comment that 20 amp receptacles are much better quality than 15 amp receptacles. That is not true as long as you are comparing like devices.The residential grade receptacles, 33 cents, 10 @ $2.99 are only available in 15 amp versions.At the spec grade level (about $2) and commercial ($3-4) they come in 4 flavors.15 amp
15 amp, backwired **
20 amp
20 amp, backwired.They all have the same quality and basic design. ** Backwired is system that uses pressure plates that are tightened down by the side screws. They are quality connection and is similar to what is used on some circuit breakers and industrail teminal systems.Completely different from the backstab connections are are used on some of the residential grade devices.
<<"** Backwired is system that uses pressure plates that are tightened down by the side screws. They are quality connection and is similar to what is used on some circuit breakers and industrail teminal systems.Completely different from the backstab connections are are used on some of the residential grade devices.">>****************I installed some GFI's with this back wired system (pressure plates). Have you ever seen regular outlets that use these type of pressure plates? I haven't -- at least from the home centers."I would never die for my beliefs because I might be wrong."
-- Bertrand Russell
"Have you ever seen regular outlets that use these type of pressure plates? I haven't -- at least from the home centers."Yes, I get them all the time.They often have a confusing mix so you need to look carefully to see which is which.There are 4 different flavors for sepc grade and then there are different colors so they don't have all of the variations. But I have alway found 15 amp backwired at my local Lowes. And I know HD has some backwires, but I don't remember with grade or current rating.
Thanks --- I appreciate your info."I would never die for my beliefs because I might be wrong."
-- Bertrand Russell
Thanks Everyone glad to see this. I'm also glad to see you guys think the backwired systems with the pressure plates are OK. I got the commercial grade Levitron 15 amp receptacles at HD and they do have these. I haven't been using them because I didn't think most people approved of them. This will make the rest of the plugs a bit easier (getting the 12-2 on the side posts was a PIA yesterday).
if you are backwiring those receptacles, remember that although there are four screws on the back you cannot "feed through" the device, this is a dangerous situation, the device MUST not be part of the circuit feeding anything "downstream. A heavy load at any outlet will cause the "upstream" outlets to overheat. All of the terminations must be pigtailed, unless you only have a hot and neut. to terminate. Backwiring is fine but you cannot use the method to make things easier to land some stiff wires. I hope that you did not interpret what was explained by others as ####way around your problem. Again , the receptacle must NOT carry the load through it.
Thanks, I think. I don't understand why the pigtailing is necessary (I know what you mean by pigtailing). I thought the main danger with not pigtailing was that if you blow one receptacle it takes out everything down the line from that one. To be honest I've never pulled an outlet out of the wall that was pigtailed. Not that that means a lot of outlets but in every apartment I've ever lived in, my parents house, my house or jobs for/with friends I've never come across one that was a pig tailed outlet. As for the pig tailing I started doing this but after about an hour minutes of frustration on a single outlet I switched to wiring through the outlets (granted to the side terminals). Even the directions on the GFI only show the ground being pigtailed. I was really wishing for 14 Gauge wire (even a little bit thinner would have been easier) trying to pigtail the 12 was a b%$#h never mind trying to get all the wires in the box (which is also supposed to be dangerous) I know everyone doesn't uses oversized boxes on everything and I can't imagine fitting all those wires in a standard box (and these were not shallow boxes).
backwiring was a way for the trim guys to make better time on a house way back in the ' 70's, ..that, combined with Aluminum wire caused many problems. ......I don't know if this was the reason for the code changes,..... but, to wire receptacles in a series path is just inviting disaster, to say nothing of opening a neutral when you change out a device. Anybody who has seen the lights get bright in a house knows what I mean. .....so long computer, .......goodbye TV , As for the GFI, you will see that there is a different rating for feeding through that device.
If you can't get the wires in the box ,the box is too small ! the multiplier for #12 is x 2.5
as in cu. in. per wire. Count the # of wires entering the box ,add the wires needed for the pigtails ,then compare that number to the one for the particular box you are using, the wires should have the smaller # the capacity for the boxes is found in the Code tables , or probably on the web. Be Careful !
maddog,You've certainly got some opinions about wiring in receptacle outlets. Given that you're a "skilled trade worker" (what does that mean, exactly?) based on your profile info, some people might believe your opinions to be fact, or Code.For instance, you say connections to receptacles "MUST" be pigtailed. Well, there isn't any Code requirement to do so, except in the case of the neutral of a multiwire circuit, as Bill H. explained. Most professional electricians use the pressure-plate back wiring terminals for outlets if they can, including in commercial buildings and industrial settings. As Bill said, the device is tested and listed for 20 amp feedthrough. And yes, it's quicker to use the pressure plate terminals than to pigtail.Sure, a properly done splice and a pigtail, with properly done screw terminations at the receptacle, gives a better connection than a poorly done connection with the pressure-plate backwire terminals. But a properly done pressure-plate connection eliminates one connection. So with a pigtail, if the installer does not properly make the wirenut splice, well, there's another possible point of failure. I've seen a lot of pooly done wire nut splices, both by pros and DIYs--move or even touch the splice, and it falls apart. As a skilled trade worker, you've probably run into the same thing.Should we go back to wrapped and soldered splices, as in the days of knob-and-tube, to make the pigtail splice? That'd probably give us a slightly more reliable pigtail connection than a wirenut... Keep in mind that a pressure plate terminal is the same or very similar to the terminal connection used in circuit breakers and lugs. Virtually all molded-case circuit breakers now have terminals where the wire is clamped by a pressure plate (or directly by a screw). This is a pretty good sign that the connection method is sound, it's the application (or misapplication) of the method that causes any problem.If someone wants to pigtail for a receptacle, and if they know how to do it right, more power to 'em. But, on occasion, I've wired some residential branch circuits with pigtails, and others using pressure-plate backwire terminals, and done voltage drop testing. Sometimes the pigtailed circuit had lower voltage drop, and sometimes the pressure-plate backwired one did, but the difference (either way) was small.best regards,Cliff
Edited 5/2/2005 12:24 pm ET by CAP
I agree with what you say, I have done the same things..... But,
none of the AHJ around Chicago / suburbs that I had the joy of knowing will allow feed thru wiring on receptacles.
And I am not trying to tell Ribs not to use the pressure connection, just not the way it seemed to be explained earlier in the discussion. OK?
Bro,Well, those City Fathers in Cook County go overboard in a lot of other ways, too--namely, I'm given to understand that Chicago codes require any and all electrical wiring, low-voltage like doorbell and telephone included, to be run in metallic conduit (EMT). This for all occupancies, including single-family homes. Is that still true (or was it ever)? Given your experience, I completely understand where you're coming from. But based on my experience, using the "device as splice" (if it's done right) doesn't lead to any more problems than pigtailing.About pigtailing a neutral or not: I can't imagine a case in a properly wired system where a problem would arise from taking a device out of a circuit and so opening the neutral, even inn a multi-wire set up, as long as the connections were restored before the circuit is re-energized. Now if there is a miswire, where a neutral is shared between circuits, the second circuit would go dead (due to the loss of the return conductor). I don't see this as a problem or dangerous per se; a real problem (resulting on damage to equipment) would arise only if the shared neutral circuit was a multi-wire circuit. But your point about neutrals being shared improperly between circuit is a good point; I've seen it in old K&T systems plenty, and with newer but badly modified and maintained systems as well. It's just one of the lurking hazards that a person qualified to do electrical work will be aware of.Best regards,Cliff
yep , you are right about the " more is better" code in Chi , I guess we may have been on the right page just different books,
and yes , a tradesman would know of the dangers , but I did not think that Ribs is an electrician, I apologize Ribs if I'm wrong! But I have to disagree with you about the second circuit going dead because of no return path,............ with out a neut. , phase to phase voltage could end up on those circuits that just had the neutral opened
Edited 5/2/2005 4:05 pm ET by maddog
Cliff,
I don't remember your position on the "one circuit/one neutral" debate,but it seems to me if three wire Romex homeruns are used,with shared neutrals,the NEC requires pigtailing.
For those who don't have a code book handy:" 300.13 Mechanical and Electrical Continuity-Conductors (B) Device Removal : In multiwire branch circuits,the continuity of a grounded conductor shall not depend on device connections such as lampholders,receptacles,and so forth,where the removal of such devices would interrupt the continuity."
If you wire a house with all two wire NM cable circuits I can see in and outs on devices being allowed.But if you take a 12/3 to the first kitchen receptacle, for example ,and then run 12/2's out for the small appliance circuits,you do have a multiwire circuit and I think you do have to pigtail at least the neutral connections at receptacles.I know it's faster to use the receptacle for joints but the Code to me seems pretty clear,if you remove the device, continuity is lost.
My work is 95% 3 phase commercial buildings where all of our circuits are multiwire and all receptacles are pigtailed,hots and neutrals.It's the way our apprentices learn to make joints on the rough in,so it isn't just Chicago.
So,do you use three wire homeruns?Or just disagree with how other AHJ's enforce the Code?
You really are quite the diplomat in your responses by the way.
Barry
Barry,
Hey, thanks for the kind words. I'm getting more mellow as I get older...
Anyway, on a multiwire circuit--the way I read it, the Code only requires an independent splice (by that I mean a connection independent of a device) for the neutral at the point where the two halves of the multiwire circuit diverge or separate. The requirement of the Code (the way I read it) is that removal of any device shall not interrupt the continuity of the multiwire circuit grounded conductor (as you said, 2002 Code, 300.13). That section also explicity states that this requirement does not apply to two-wire circuits.
My point is, once the multiwire circuit diverges into two-wire circuits, the neutrals in those two-wire circuits can be spliced by the device. That's because the loss of a neutral in a two-wire circuit (even if it originates from a multi-wired circuit) will not cause a problem. It's only the loss of the grounded conductor connection at the point of transition from multi-wire to two wire that will cause the loads on the two-wires circuits to become series-connected across the phase-to-phase voltage (240v for a residential multiwire circuit). I sketched a schematic to verify this, just to be sure. I'm sure. (Famous last words, eh?)
I do three-phase work (about 30 percent of my business is commercial). Once the circuits fed by the three phases diverge, they are two-wire circuits. I've seen a lot of 120v receptacles in commercial buildings where the device serves as splice (for both phase and grounded conductors), and installed a few myself. Using the pressure-plate terminals when you're working with stranded wire (in pipe) is a real good way to go.
As an aside, I do not like the connection I get with two or three stranded conductors with a wirenut. I prefer to use a copper Buchannan sleeve and a C-24 tool (that gives a four-dimple crimp) and a snap on insulator cap. That's usually the way I splice the neutral on multiwire circuits at the point of separation, anyway. It makes it real hard for anyone to inadvertently break that splice. Do you work much with stranded branch circuit conductors? And if you're pigtailing them, do you use a regular wirenut?
Best regards,
Cliff
Cliff,
I'm glad you have inspectors that allow for a little bit of interpretation in reading code sections.The city and county inspectors where I work are "literalists".In the section we're talking about they say the Code doesn't say that you only have to pigtail in the portions of a multiwire circuit where the circuits are actually sharing the grounded conductor.If all it says is "In multiwire branch circuits ..." then the requirement exists for the length of the circuit,from the overcurrent protection to the end of the line device.I do understand what you are saying from an electrical point of view,and that your method avoids the 240v series circuit possibility.I've heard on more than one occasion from our inspectors though "You know,that makes perfect sense and would make a great installation...but that's not what the Code says,so please change it." Another example of literal enforcement is on 8' ground rods.If you leave the connection to the GEC exposed (so that ground moisture doesn't degrade the connection maybe) that's a " no go" also because the Code says the rod shall be in contact with soil for at least 8'.Whatever.
On the stranded wire question,yeah it's almost all stranded conductors and we just use regular wirenuts on them.Two's a yellow,three or four's a red,five's a gray,six.. well...the box isn't going to be big enough anyway.
Hey what is your take on the two wire / three wire homerun issue anyway? Bill H. makes it sound to the H.O's here that it's cornercutting.I think where practical most electricians,both residential and commercial,actually do make use of shared neutrals and it's an accepted safe practice.If you're taking two circuits out to a garage,do you take a 12/3 w/g or two 12/2's ?
TTYL,
Barry
Edited 5/4/2005 8:00 pm ET by IBEW Barry
"Bill H. makes it sound to the H.O's here that it's cornercutting"I am not sure where you got that from. Adk 4lorn1 about them, that might be closer to his comments.I think that my comment is that they are OK, but there are restrictions and many electricians don't like to use them because of the potential confuse to HO and people that work on the circuits in the furture.Personally I am not a fan of them, but would run them for things like kitchens. And places like my side by side furances. But I would also be sure to have the panel clearly marked as beign MW so that it does not get screwed up like my furnaces where they wired both hot to a single switch and then move one hot so that they where on the same leg.However, I don't think that I would run them in your area that does not reconize that it can be split out.BTW, you might want to remind them that the whole service entrance is a MW circuit. But them again you might not, they might want to treat every circuit in the house as being MW.
Barry,
Yea, I hear ya, six #12s, a gray...box too small! I have a friend who's planning to build an office building for his law practice, and I'm going to lobby him to run at least 3/4" EMT out of every loadcenter for branch circuits, and terminate it at a 4-11 box. Not that I mind running new pipe in an old building, the money's good. But it's funny, the law office buildings are interesting, a suprising number of lawyers stop and chat; most have a story they have to tell me about how they almost got electrocuted. A version of the construction site sidewalk superintendant.
Anyway, I think multiwire circuits are great, they offer efficiensy of materials, labor in installation, and actually provide for marginally better electrical efficiency. The last because when there two halves of the circuit are carrying similar loads, there's less voltage drop (less power lost to the resistance of the wire). I run multiwire circuits whenever I can. If some doofus moves a breaker around and burns the neutral, that's his problem--anyone who doesn't know about multiwire circuits shouldn't be playing around in a panel,anyway.
You're right on, for a house with a detached garge, if I I run one multiwire circuit I can provide two 20 amp circuits--and not have to set a subpanel, with its groundng electrode. That's for a spec house; for a custom, the homeowner almost always wants it wired for a shop.
Cheers,
Cliff
"if you are backwiring those receptacles, remember that although there are four screws on the back you cannot "feed through" the device, this is a dangerous situation, the device MUST not be part of the circuit feeding anything "downstream. A heavy load at any outlet will cause the "upstream" outlets to overheat. All of the terminations must be pigtailed, unless you only have a hot and neut. to terminate. Backwiring is fine but you cannot use the method to make things easier to land some stiff wires."Completely wrong.The receptacles are rated for 20 amp feed through. Exactly the same as have 20 amps load on the receptacle. For example ever had a router and shop vac plugged into a duplex receptacle. Problem drew more than 20 amps at peak load.And of course with GFCI's the only way to wire them is feed through if you want them to protected the downstread receptacles. The only type of circuit that you are prohibited from feeding through is the the neutral on a multi-wire circuit. And the reason for that is that if the connection is broken you can end up with 240 on downstream recetpacles.
Bill, how does anyone know how the neutral is spliced in old work? you cannot interrupt the circuit when removing a device !
"Bill, how does anyone know how the neutral is spliced in old work?"Easy, it has to at leave have a 3 wire cable, ie 2 hots. Not there might be some that are not multi wired, such as when you have both a hot and switched not. But if it does not have 3 wire cable then it ain't a multi-wire circuit (at least not at that point)."you cannot interrupt the circuit when removing a device !"I am not sure what you are saying. Do you remove all of the devices with the circuits hot?
no not hot ,but in this area not all jurisdictions use romex. remodeling can wreak havoc on any existing system and sometimes people will add their new circuits to the closest j-box and tie ALL the neutrals together. it also seems as though some folks see nothing wrong with using a receptacle as conductor instead of a terminal point, and I still want someone to say that opening a neutral, even though the circuit is off , can't cause problems.
The tradesman is supposed to know what he is doing , but sometimes people that ask questions will not I am not trying to say that backwiring is bad, only that using as feed-through to speed things up can lead to problems and has to be avoided.
" But,
none of the AHJ around Chicago / suburbs that I had the joy of knowing will allow feed thru wiring on receptacles. "I suspect that got the mindset from backstab receptacles and never bother to look at the difference between that and back wire."no not hot ,but in this area not all jurisdictions use romex."
But AC and MC is still cable. And the same thing hold for conduit. If the each conduit that connects to that box has 1 neutral and 1 hot then it can't be a multi-wire circuit. "remodeling can wreak havoc on any existing system and sometimes people will add their new circuits to the closest j-box and tie ALL the neutrals together. it also seems as though some folks see nothing wrong with using a receptacle as conductor instead of a terminal point, and I still want someone to say that opening a neutral, even though the circuit is off , can't cause problems."Well it depends on what you are doing. If it extending and existing circuit from receptacle then arguement could be made that it would be better to use the receptacle as a feed through rather than have to open up an existing neutral junction or double pigtailing.
well Bill,
I enjoy reading your responses, and it seems that we are speaking the same "language' ......just different ! as far as back stab and backwire , yeah they are two different things , however, I thought that some early explanations would have had someone think they could hook up a receptacle any way they want , as long as it fits in the box. Just MHO hey the whistle just blew , time to go to break !!!!!!
suspect that got the mindset from backstab receptacles and never bother to look at the difference
Have to wonder if they are/were concerned about a wire-through fixture failing, and opening the rest of the circuit. But that's conjecture on my part.Occupational hazard of my occupation not being around (sorry Bubba)
"Have to wonder if they are/were concerned about a wire-through fixture failing, and opening the rest of the circuit. But that's conjecture on my part."Well that is the common failure mode for back stab receptacles. And is is just as likely to be an upstream device as it is the one where a high load is used.But the connections on back wired receptacles just as reliable as those using side terminals.
the connections on back wired receptacles just as reliable as those using side terminals
That's my experience, too. I was thinking maybe the AHJ was not concerned about the connection, per se, but the actual receptacle itself in barring woring-through. A parallel versus series sort of thing, but not as a stated policy that an inspector might actually communicate in the field where it might make an "ah ha" sort of difference.Occupational hazard of my occupation not being around (sorry Bubba)
No guys not a tradesman, just a lowly civil engineer, turned biomedical engineer turned comuter geek (with minimal yet some electrical classes) and DIY fanatic. No offense taken.OK need some clarifications on a number of things."The only type of circuit that you are prohibited from feeding through is the the neutral on a multi-wire circuit. And the reason for that is that if the connection is broken you can end up with 240 on downstream receptacles."What constitutes a multiwire circuit? The previous owner tied a lot of things together in the basement. I've got a junction box where wires go to the bathroom and to a light on the other side of the basement. Is this what you mean by a multiwire circuit? Scary thing about this Junction box is it is part of the 220 line that goes to the dryer. All wires are in metal conduit. There seems to be a second piece of Romex (14 Ga) outside the box running to the box and tied to a second wire going to the basement light. More information there are no neutrals tied together like was mentioned in some other posts. The neutral for the dryer does not tie to the neutral for the romex, they just seem to be sharing the junction box. I'm probably going to take all of this out when I run the new ceiling lights.This one you guys seem to disagree on"to wire receptacles in a series path is just inviting disaster, to say nothing of opening a neutral when you change out a device."These are all backwire connections not back stab.
Edited 5/3/2005 9:24 am ET by Ribs
A multi-wire circuit consists of 2 (or 3 hots in the case of 3phase) "sharing" a common neutral.For that to not overload the neutral they need to be on different legs of the 240. Thus you will have 120 between each hot and the neutral and 240 between the two hots.If you lose the neutral then you have 2 "120 volt" loads in series. So if one is realatively low resistance then the other one will have near 240 volts across it. Thus the code requires that the neutrals be pigtailed to connect with the receptacle and not feed through. Because if the receptacle was removed it would disrupt the common netural in the multi-wire circuits. In a simple circuit anything down stream would be dead, but with MW you might see 240.MW circuits also require the hot to be on differnt legs, but unless there is a device that has both hots on it there is no requirement for it to be on a 240 breakers.Because of these possible confusions many electricains don't like using MW circuits in residentail applications where the main purpose is only 120 receptacles.Here is an example of a problem that I found in my house. Probably confusion betwen the electricain and the HVAC people. I have 2 furnaces side by side and code requires a separate circuit for each one. So a multi-wire circuit was run.However both hot terminated on single disconnect switch which feed both furnaces. Then at the panel the one hot was moved so that it was on the same leg. Fortunately the loads where small enough that the neutral was not overloaded. BTW, the main service is multiwire. And if you every see lights flickering and some getting BRIGHTER that means that you have a bad connection on the neutral and time to call the power company. While the problem can be on your side with the power co part out in the weather that is the mostly likely point of failure.
Bill - Very timely post. We are in the middle of a major addition (kitchen, bath, laundry addition). The panel was upgraded 5 years ago. There were many MW circuits and more were pulled in for the new addition (GD/DW, Frig/fan, etc). It is near to impossible to assure that the old MW circuits are properly split across phases without tracing the leads into the panel. The new ones are not currently a problem...
I would feel more comfortable if the MW breakers were hard tied (ala 240), and proposed this to an electrician not working on my addition. He stated that he wouldn't do it as it is not common practice and just to keep track. Isn't this a safety issue, as one would want both circuits off should you need to open a receptical/switch box in the future. Of course, I'll clearly label them maybe zip tie them together for future reference.
Dean
"MW circuits also require the hot to be on differnt legs, but unless there is a device that has both hots on it there is no requirement for it to be on a 240 breakers.
Because of these possible confusions many electricains don't like using MW circuits in residentail applications where the main purpose is only 120 receptacles."
Another reason for not using the 240 breakers on MW is that if one side trips you lose both, which might cause more confusion.But you are right in that it would be good to positively ID MW circuits.Maybe something like a piece of red across the 2 120 breakers and red pen vertical "MULTI_WIRE" on the matching 2 circuit legends on the index (they do fill those in RIGHT???).Or a red permanate marker on the cover plate by the 2 breakers.Hopefully that will make some one else think about what those are or ask some questions.In the case of my furnaces I suspect that it was roughed in correctly runing the cable to a single box and on the right breakers. Then when the furnaces where installed the HVAC people connected the two hots to the single switch and then the breakers kept tripping so they moved one until it didn't.Just speculation about how that happened. But maybe, just maybe, if it was flag multi-wire that the guy would have asked what that was and mentioned that the breakers where tripping.Of course the index was never filled out either. That is how I found it when I tried to find the breaker for the furnaces.
Bill - I wanted to thank you for your advise. Labeling and marking the MW circuits is the way I will go.
I understand and agree with your rational for not physically tying the circuits together as in the event of a trip, as it would be hard for a HO to trouble shoot without opening the panel, removing the tie and powering the circuits again, thus repeating the detected fault and increasing the chance of a real problem.
Thanks again... For me, understanding why is as important as understanding how.
240 breakers are sometimes required. If the MW circuit is feeding a split receptacle, or it is feeding both line-to-line and line-to-neutral loads, then the overcurrent protection device is supposed to open all hot leads at once.
Please be careful with the backwire though. I just replaced 42 outlets in my "old house" with the same 15a duplex backwire outlets you mentioned. CHECK EVERY WIRE after you attach it by pulling on it. It is possible to get the wire in the space but not have it be under the plate. Not sure how it happens, but it does. Had this happen 4 times.
Also, make sure the exposed wire stub you insert is STRAIGHT. If it is bent slightly, you will think it is tight, then when wrestling the outlet into the box, that sucker might rotate and become loose. Had this happen 2 times. (went back and rechecked all 42)
Danger of a loose connection is sparks and heat. Both lead to FIRE.
But I have "heard rummors" of commercial device, one of whcih was a margarita machine, that came with 20 amp plugs.
I guess it's commercial kitchen equipment that must use them. The only time I've ever seen one that wasn't field-installed (i.e., actually on a molded-on plug), was one day in Home Depot. A couple had just brought in the cord; they said it was off a commercial hot dog machine (or something like that). The HD kid didn't have a clue, of course. I told them to have a electrician install a 20A, 120V receptacle.
I am guessing stuff that the EQUIPMENT is UL approved. Stuff like my Jet contractors table saw, with a 1 1/2 hp, 18 amp motor is not UL. It has a UL motor, and UL cordset, bu the unit is not approved.(I am use "approved" in a generic sense. UL has several different types of "approval" or "recongnition").
I believe you will find some 110v window A/C units that have that style plug.
Edited 5/1/2005 11:13 pm ET by RASCONC
<<"15 amp circuit breaker, 15 amp wire(14 ga) 20 amp outlet= illegal">>Can you explain why this is so?this was explained to me by the local inspector: They do not like it because if the circuit breaker was change at a later date to a 20 amp because someone saw a 20 amp recepacle thinking they was 20 amp wire in the wall.
Thanks for info.I guess if I were an elec inspector I wouldn't want to rely on the fact that a HO would be smart enough to distinguish between 12Ga and 14 Ga wire at the panel box."I would never die for my beliefs because I might be wrong."
-- Bertrand Russell
BrownBagg,I really appreciated your response, as it just about covers all the bases. With this said, I'm contemplating converting a second kitchen into a landry area with ####dryer.Can I go from a:50 amp circuit breaker, 50 amp wire, 50 amp outlet - stoveto a30 amp circuit breaker, 50 amp wire, 30amp outlet - dryeri.e. just change the circuit breaker and outlet to legally use a dryer???Tark
Yes, you can. The only problem is that the wire might be too big to breaker and receptacle, but probably not for small of difference.One caution. Current requirements for both ranges and dryers is for a 4 wire circuit (2 hots, neutral, and ground). But older ones only used 3 wires (no ground). So if you have a 3 wire range circuit you should not convert it to dryer use." 50 amp wire,"That said there is no such thing as "50 amp wire". The code tables give different ampacity (amps) for different wire sizes, types, and applications. What when you see #14-15 amp, #12-20 amp, etc is just the most common ratings for common applications. For several reasons wires need to be upsided because of degrading or long runs. So the use of larger wire size is not unknown.
Thanks Bill.I've got the 30-amp receptical in, but need to go out and buy the 30 amp breaker. While I know better then to say "50 amp wire", I could not think of the proper gauge (without looking it up) to sound intelligent at that moment. :-)The original 50 amp receptical was only for a 3-wire system which I have replaced with a 30 amp 3-wire receptical. The electrical system does not have a separate ground unfortunately. When I bought the dryer, I ensured that the appropriate 3 prong pigtail was also purchased. I know its not ideal. . .
by the new code the only thing that is legal in 3 wire in the 220 range is the shop welding machine. all dryer and ranges are four wire now. not talking about shop tools but dryer and ranges. 4 lorn will have better infor on this
Cliff brings up a good point - spend a few extra bucks and get the good receptacles. They'll be called commercial grade or specification grade, and they're a LOT nicer than those 49 cheapies in the bin at Home Depot.