Improper multi-wire circuit??

[Terry Beck]

This is an old Bulldog Pushmatic panel. There are a couple of issues with the panel wiring, but I am asking about multi-wire circuits. See the picture. If I understand correctly, the two breakers that feed the multi-wire circuit should be on different busses. Correct? If I understand the bus design of a Pushmatic panel, then this circuit is on the same bus. Correct?? What happens if is is wired wrong?

1-IMG_5439-2.jpg

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[ROBERT YOUNG]

Pushmatic & Bulldog circuit breakers use a thermal breaker design with no magnetic trip mechanism. Breakers have been known to stick. Possible Safety & Operating Concerns. Recommend upgrade or replacement.

[Jerry Peck]

I don't know the wiring schematic design of those panels, but - do you carry a multimeter with you?

The best way to confirm suspicions of many things is with a multimeter (or a Wiggy), including what you are asking.

Use the multimeter or Wiggy and measure the voltage between the two conductors and between each conductor and neutral.

You should get 120 volts between each conductor and neutral.

You should get 240 volts between the two conductors.

If you get 120 volts between conductors - then it is wired wrong.

240 volts between conductors means the neutral conductor of the multiwire branch circuit only carries the off-balanced current on the multiwire circuit.

120 volts between conductors means the neutral is carrying the full current of each leg of the circuit (this is Part A of the answer to your question).

That means the neutral could be overloaded, could overheat, could cause a fire (this is Part B of the answer).

[John Kogel]

I believe you are correct. The red and black appear to be on the same buss, which means the neutral carries current from both 120 v circuits. Wrong.

The 240 v breaker at the top of the pic shows the black wire connected on the left side and the red wire going around to the terminal on the right side, correct.

[Gunnar Alquist]

... If you get 120 volts between conductors - then it is wired wrong...

120 volts between conductors means the neutral is carrying the full current of each leg of the circuit (this is Part A of the answer to your question).

Uhhh... Jerry?

If checking a multi-wire circuit at the two breaker terminals, correct is 240v. Incorrect is 0 volts, not 120v. Since you are essentially checking the difference at the same buss bar, there would be no voltage potential.

But, you know that.

[Jerry Peck]

Uhhh... Jerry?

If checking a multi-wire circuit at the two breaker terminals, correct is 240v. Incorrect is 0 volts, not 120v. Since you are essentially checking the difference at the same buss bar, there would be no voltage potential.

But, you know that.

Guess I was doing my typing without thinking ... you are correct sir , there will be 240 volts or 0 volts between the conductors ... and here I was being so careful about specifying the 120 volts to neutral ...
(I would blame on that I was typing that on my phone - I was - but that wasn't the cause, not thinking about what I was typing was the cause.)

[Gunnar Alquist]

Jerry,

I do that verbally a lot. The best part are the looks that I get when I say it. They start off with a blank look, then the brow furrows (while the individual is running what I said back through their head) and then puzzlement. It's usually about the time the brow furrows that I realize what I just said and start making my correction.

[Jerry Peck]

Jerry,

I do that verbally a lot. The best part are the looks that I get when I say it. They start off with a blank look, then the brow furrows (while the individual is running what I said back through their head) and then puzzlement. It's usually about the time the brow furrows that I realize what I just said and start making my correction.

Gunnar,

Yep, when they look puzzled ... we need to revisit what we just said.

[Terry Beck]

Thanks guys.

[Vern Heiler]

Sorry for coming in late but don't MWC's require a handle tie? Found NEC 240.15(B)(1). Probably pre 2008.

[Jim Port]

Sorry for coming in late but don't MWC's require a handle tie?

Previously the code only required the simultaneous disconnect if both legs landed on one device strap in residential or all commercial application. The code added the requirement for all usages only in the last few cycles.

[Vern Heiler]

Previously the code only required the simultaneous disconnect if both legs landed on one device strap in residential or all commercial application. The code added the requirement for all usages only in the last few cycles.

Thanks Jim. What is "one device strap"?

[Jerry Peck]

Sorry for coming in late but don't MWC's require a handle tie? Found NEC 240.15(B)(1). Probably pre 2008.

That requirement came into the NEC in 2008 ... I suspect that panel is older than that.

[Jim Port]

A device strap holds the device to the box. A standard duplex is mounted on one strap.

[Jerry Peck]

Thanks Jim. What is "one device strap"?

Two receptacle outlets on one strap, such as for a dishwasher and a garbage disposer.

[ROBERT YOUNG]

Thanks Jim. What is "one device strap"?

I as yourself am unformalized to the term, "one device strap"
This is what I found under patente; W. DRAPKIN Sept. 24, 1968 MOUNTING MEANS FOR ELECTRICAL WIRING DEVICES.

[Jerry Peck]

I as yourself am unformalized to the term, "one device strap"
This is what I found under patente; W. DRAPKIN Sept. 24, 1968 MOUNTING MEANS FOR ELECTRICAL WIRING DEVICES.

Robert,

Device straps have been around for much longer than that patent ... presuming that patent is for what a quick glance indicated it was for.

Switches and receptacles have been mounted as straps, fixed in place or interchangeable, since before the 1920s (I think before the 1920s as I have seen 1920s houses with switches and receptacles on straps which looked original to the houses).

I'm not sure when standardization started for electrical components (I didn't do a search for it), but it was likely early on in electrical wiring history.

[ROBERT YOUNG]

Robert,

Device straps have been around for much longer than that patent ... presuming that patent is for what a quick glance indicated it was for.

I understand Bonding straps, bonding jumpers, but I have never heard the term used in conjunction with a device;a thing made for a particular purpose.

As for the PDF, I went looking for a PDF or image on Google to get a better understanding.

Switches and receptacles have been mounted as straps, fixed in place or interchangeable, since before the 1920s (I think before the 1920s as I have seen 1920s houses with switches and receptacles on straps which looked original to the houses).

Yes, I understand somewhat. I was looking for an image or link to define the types of straps I may/will run into while during an electrical survey.
The lack there of, defective, or disconnected being my point.

I'm not sure when standardization started for electrical components (I didn't do a search for it), but it was likely early on in electrical wiring history.

When you find some information please post it. I would be greatfull.

Pst...Jerry. Just between me and you, shh... I do not want Claude to listen in, "any shortcuts?"

[Gunnar Alquist]

My recollection was the word "yoke" rather than "strap". Is "strap" used in the IRC? I found this in the 2005 and 2011 NEC (Actually, the 2007 and 2013 California Electric Code). CA uses the NEC as its model code for residential and commercial, not the electrical part of the IRC.

210.7 Multiple Branch Circuits. Where two or more branch circuits supply devices or equipment on the same yoke, a means to simultaneously disconnect the ungrounded conductors supplying those device shall be provided at the point at which the branch circuits originate.

[ROBERT YOUNG]

Could you put yoke or strap in a sentence please.

[Jerry Peck]

When you find some information please post it. I would be greatfull.

http://www.kyleswitchplates.com/desp...tches-outlets/

Pst...Jerry. Just between me and you, shh... I do not want Claude to listen in, "any shortcuts?"

(I think he heard you ... )

Could you put yoke or strap in a sentence please.

Sure ... Strap that yoke on them oxen over there.

Receptacles and switches are "devices", "devices" are attached to, and supported by, a mounting strap, which is also referred to as a yoke (not yoking ).

The link above, which references the old interchangeable device line (used to sell those as replacements at an electrical contractor's place I worked at way back when) shows the "strap"/"yoke" into which those devices would fit, each being interchangeable with another, allowing any combination of of up to three devices on a single strap, and the devices could be installed horizontally or vertically, depending on the strap and the size of the box.

Anyhoo, help that solves your disconnection issue.

[ROBERT YOUNG]

Stop for a moment...Let me get this straight.
So when my boss and I (strapped) in his team of horses , Clyde and Jim, during winter freeze up we were practising electrical procedures attaching the 1" inch hemp rope and end chains to Clyde and Jim's (yoke) to pull out selectively fallen trees we had cut in the fall from his homestead in the laurentians and not performing land management and solid fuel storage?

Wow, you learn something new everyday.

Thanks for the link.

PS: Just having fun Claude. You are an ambassador and good sport.

[Jerry Peck]

Stop for a moment...Let me get this straight.
So when my boss and I (strapped) in his team of horses , Clyde and Jim, during winter freeze up we were practising electrical procedures attaching the 1" inch hemp rope and end chains to Clyde and Jim's (yoke) to pull out selectively fallen trees we had cut in the fall from his homestead in the laurentians and not performing land management and solid fuel storage?

Wow, you learn something new everyday.

That 1" hemp rope was for electrical bonding - you didn't already know that? (Bonds the everything together to form an equipotential plane for that darn static electricity.)

[David Bertrams]

The splices seem unusual.

[david shapiro]

That 1" hemp rope was for electrical bonding - you didn't already know that? (Bonds the everything together to form an equipotential plane for that darn static electricity.)

Only during or after precipitation, or after it's gotten soaked with sweat (or with a liquid that once was used in tanning).

- - - Updated - - -

http://www.kyleswitchplates.com/desp...tches-outlets/

.

You'll find Despard-type receptacles, if not also switches (I don't recall) not only as interchangeable electrical devices for switch-box yokes but also as inserts into medicine cabinets.

[david shapiro]

It's not in NEC Article 100, Definitions, but in the NEC "device" is used not alone, in the dictionary sense, but as part of "wiring device," meaning switch, receptacle, indicator light &c.

[ROBERT YOUNG]

That 1" hemp rope was for electrical bonding - you didn't already know that? (Bonds the everything together to form an equipotential plane for that darn static electricity.)

Well,in away, I guess.
I use to get a real charge out of doing it but was never shocked when performed correctly.

[Derek Guridi]

It's not in NEC Article 100, Definitions, but in the NEC "device" is used not alone, in the dictionary sense, but as part of "wiring device," meaning switch, receptacle, indicator light &c.

Wanna bet? 2014 NEC

Device.
A unit of an electrical system, other than a conduc-
tor, that carries or controls electric energy as its principal function.

Also an indicator light is not a device.