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The handle ties would be a major problem in commercial work, many typical office cubes (modular office partitions) are designed to be fed multiwire (3 hots 1 Neutral).
It would basically put a whole section out when one person plugs in a heater for their feet.
LK I am sorry for your friend that lost someone, but I still do not agree with handle ties.
Would you also have the NEC say you can only have one circuit in a box?
As in two or more two wire circuits.
My views may be bias as I install and maintain multiwire circuits almost daily, and I do not see any more problems with these than 2 wire circuits.
It is difficult to actually get 208 or 240 volts when the neutral is lost, this would require a dead short on one side of the multiwire circuit and the loss of the neutral.(I will admit I have seen surge protectors taken out by lost neutrals)
It is not unusually for us to have an entire 42 circuit panel wired with multiwire circuits (42 hots 14 neutrals) as that is what the office furniture requires.
JMO, Bob
Bob Badger Construction & Maintenance Electrician Massachusetts
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Bob,
You have a good point. Personally I don't see the same benefit to Handle Ties in Commercial work and wouldn't recommend that.
It does tick me a little to 'dumb down' things with a 2 pole breaker, but the fact is that many people that do Electrical work in homes are less than qualified to do so, and tie handles or common-trip breakers might help save someone.
I wouldn't oppose a code requirement for tie handles on multi-wire circuits in Residential occupancies.
JMO, Bill
[This message has been edited by Bill Addiss (edited 09-16-2003).]
Bill
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Why single this out? Why not leave wiring diagrams around the house for any intrepid homeowners looking to play Thomas Edison. Do you think the average handyman would know what an afci breaker is? What about a couple of threeways and fourways? A gfci breaker? Nevermind a multiwire circuit. Read the posts on the diy websites. A two pole breaker is not going to make one bit of difference. These nuts are flying blind and clearly don't have a clue. The fact is the NEC does not require this in the scenario above.
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As an ex-commercial electrician I think Bob nailed it on the head. I don't think a multi-wire branch circuit is any more dangerous than a two wire circuit...if worked on by qualified personnel. If I'm not mistaken, certian members of the IBEW have been trying to push a code into the NEC that would ban multiwire branch circuits altogether. The justification used is the danger in working on them.
Ryan Jackson, Salt Lake City
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Ryan, Not only is there a danger working on a mulitwire bracnh circuit with only one hot locked out, it is also an OSHA violation. Part of the push for the common disconnect from the IBEW is beacause the OSHA hot work rules are being taught by the IBEW to their members and compliance with these rules would require that all of the hots for a multiwire branch circuit be locked out if you are working on the grounded conductor of that circuit. The use of common trip breakers or handle ties on the breakers feeding a multiwire branch circuit would make the OSHA required lockout of all of the hots on that circuit automatic. Don
[This message has been edited by resqcapt19 (edited 09-17-2003).]
Don(resqcapt19)
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It is borderline insanity not to use an AC non-contact voltage tester when reworking any wiring, much less for a multiwire circuit. A critical part of qualified use is knowing when the tester may give "false positive" (like with “floating conductors” ) or "false negative?" (wet romex) indications.
Their use to check conductors after a neutral has been broken should be part of the routine, if there is any question of the circuit status. Like has been mentioned earlier, noncontact AC testers are used daily on up to 765kV circuits.
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Don, this is very disturbing to me. The use of common trip breakers or handle ties on the breakers feeding a multiwire branch circuit would make the OSHA required lockout of all of the hots on that circuit automatic. So now we are saying IBEW trained (or otherwise trained) electricians need the protection to be automatic. This is truly a sad state of affairs if electricians can not be properly trained. Lets just install shunt trips on all circuits, activated by micro switches in every box, that when you take the cover of the box it would trip all associated breakers. Bob
Bob Badger Construction & Maintenance Electrician Massachusetts
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Bill: Your solution is one that I use sometimes to expedite matters.
Guys, I remember a few times that someone got "bit" by an open neutral that was part of a multi-wire. They learned real fast!
Some of the cubicle jobs that we have done had a spec for 3 pole common trip cb's. I have to agree with Don about the OSHA reg, as that is the reasoning the architect/engineer wanted the 3 pole cb's. The heater problem was/is controlled by the office managers, as they have to answer to the bean counters "why" the electrician had to come in, and what was the cause. That's not the case at all sites, but it's becoming more prevelant. "Who's responsible"??
John
John
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Bob, I'm just saying that handle ties would let you use one lock in place of 2 or 3. These locks are required any time you are working on a grounded conductor of a multiwire branch circuit. If you are called in on a service call to work on a receptacle, how would you know if it is part of a multiwire branch circuit without doing a physical trace of the circuit? There is no code requirement that multiwire branch circuits and their grounded conductors be identifed as such. There isn't even a requiment that the breakers be installed next to each other. You can use circuits 1, 9, and 17 as a multiwire branch circuit just like you use circuits 1, 3, and 5. Don
Don(resqcapt19)
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