Multi wire branch circuit handle ties

[hornetd]

It has been suggested a number of times in this forum and eleswere that all multi wire branch circuits should have handle ties installed on the breakers in order to protect harry and harriet hoemowner from part of the circuit still being live while they are working on it.

I just thought I would point out that cutting off a circuit to a box has never gauranteed that the box does not contain another circuit and there is always a chance that there is power that is controlled by more than one Over Current Protective Device (OCPD) in any box. When there is more than one circuit in a box there is at least a fifty fifty chance that there is 240 volts between the two circuits. The only unique thing about multi wire branch circuits is the use of a common grounded conductor for two or three ungrounded conductors.

So my question is why dont the proponents of banning multi wire branch circuits in order to protect the incompetent and the ignorant from the hazaards of an open neutral also campaign for a ban on having two different circuits of any type in the same junction or outlet box.
--
Tom

 

[iwire]

Re: Multi wire branch circuit handle ties

Originally posted by hornetd:

So my question is why dont the proponents of banning multi wire branch circuits in order to protect the incompetent and the ignorant from the hazaards of an open neutral also campaign for a ban on having two different circuits of any type in the same junction or outlet box.
--
Tom

I would like to see what Panelboards would look like after that.

I think that the opponents of Multi wire branch circuits are not that familiar with them, and forget that all services are multiwire/common neutral set ups.

 

[tom baker]

Re: Multi wire branch circuit handle ties

In the 2002 NEC multiwire branch circuits that terminate to a recptacle on a common yoke require a common trip circuit breaker. I understand your concern on a mulitwire circuit. Its too late for a proposal on the 05 NEC, but you may be able to comment on proposal that has made.

 

[bphgravity]

Re: Multi wire branch circuit handle ties

I agree with Bob, you can properly install multiwire branch circuits, but still lose the grounded conductor from the utility side. It comes to proper training and education for electricians on use of these type of circuits, and good identification and labeling of multiple circuits within boxes for future service workers and Joe-Homeowner. The fact is that every electrical installation has a hazard, keeping this hazard to lowest level as possible is all we can do.

 

[vd_2kil_cm]

Re: Multi wire branch circuit handle ties

Forgive my cynicism, but the reward one receives for protecting fools from their folly is to fill the world full of fools. To continue the plagarism, wiring's no hobby, call an electrician.

 

[roger]

Re: Multi wire branch circuit handle ties

vd, well put. By making things fool proof, (impossible) the fool will bring us to his level and beat us with experience.(plagerism)

We only breed greater ignorance trying to make things fool proof..

Roger

 

[bphgravity]

Re: Multi wire branch circuit handle ties

so i guess we should just give up on trying to do anything correct. everyone can run around doing whatever they want because it doesn't matter anyway. What is wrong with trying to do things a better way, or to maybe prevent someone getting hurt or something being damaged. The whole point of this forum is reducing general ignorance. Everything counts.

 

[hurk27]

Re: Multi wire branch circuit handle ties

I have known a few electrican's that will run a seprate conduit for every circuit in a house just to avoid having multi-wire/multable-wire circuits in the same jb. and I asked them how in the (*^^$^%$) do you make any money? they will just say this is the way they were tought. or they had a bad experance with a multi-wire/multable-wire circuit, and did some damage to someone's appliance's. but like anything else if you dont know how to cook stay out of the kitchen!

 

[iwire]

Re: Multi wire branch circuit handle ties

BPH, I think all of us that come to this forum are interested in doing a safe and quality job.

I am all for improvements in safety I hope the bugs can be worked out with AFCIs if they do what they claim it sounds like a great improvement.

But My own feelings run along with Roger on this. Once Unqualified people break out tools and start opening covers, removing devices, changing splices they should be responsible for them self's. I do my installations to code and if you or Roger came to work on them you would understand how it was done, you are qualified.

Many things in this world will hurt you if you do things without training.

Instead of changing how we wire, how about stopping the unqualified from working on wiring. Stop all these DIY shows and Big box stores from giving the impression that wiring is easy and anyone can do it. I believe in my state right now an apprentice needs 8000 hours in trade 300 hours school. But people watch a 30 minute show on a Saturday and they know it all. :roll:

The NEC made a change about using a white to feed a switch, here in MA it was changed back we can still use a white to feed a switch, the feeling was this worked for years why change now, and if a handyman does not know this stay out of the boxs.

What will be the next requirement, shunt trip main breaker so if Joe homeowner removes the cover of his panel the panel trips out?

 

[charlie]

Re: Multi wire branch circuit handle ties

making things fool proof, (impossible)

Of course you can make things fool proof . . . you just can't make things damn fool proof.

The handle tie issue is upon us again in Article 240. Proposal 10-38 will delete 240.20(B)(2) & (3). After the ROP is published, contact the NFPA to get a free copy and make a comment if you feel strongly about the issue (for that matter, get one and comment on any issue you feel strongly about but use a technical argument). The intent is to require the more expensive common trip type breakers instead of allowing handle tied two pole breakers to be used. The only exception will be for multi-wire branch circuits.

If you haven't made a proposal, you can still be a part of the process by making comments. Your comments and the panel comments will be published in the ROC.

ROP = Report on Proposals
ROC = Report on Comments

 

[bphgravity]

Re: Multi wire branch circuit handle ties

I agree Bob, I made these same statements on another post "Licensed in New Jersey" or something like that and got my head chewed off for daring to say hardware stores and cosumers purchases need to be regulated to prevent unqualified and untrained for work from happening. I am a realist, I know this will never happen. So when it is my job or my students, my way is to do whatever possible and teach to do all that can be doneto protect if someone untrained comes in later.

 

[scott thompson]

Re: Multi wire branch circuit handle ties

With the exception of a Multiwire Branch Circuit terminating on a Single Device (Single Yoke / Mounting Strap Device), I would hate to see all Multiwire Branch Circuits to be derived from a Multipole Breaker / Common Trip Breaker / Multipole Handle Tie.

If one Branch Circuit trips due to an Overload / Overcurrent, this takes out the other one or two.

Not really in the best designing references for the client, is it?

Since I do so little Residential work (more than 95% Commercial Installations and Designs), I do not deal with the typical "DIY Electrical Hobbiest" that is mentioned here alot!
Also, if the Electricians on my jobs are unfamiliar with Multiwire Circuits, I want to know this so I can teach them what to do!
If any Electrician(s) do cr@ppy installations, they get to hear me babble on about Workmanship, Integrety, Pride in work, Circuit / Component / Equipment Failure, Theory, Fires, Proper Design and Installs, Liability, and Clients' Best Interests. If this doesn't make an impact or the person does not care, off my job they must go!

This is not something I have to deal with often! Almost every experienced Commercial Electrician knows what's up with the common "Full Boat" Multiwire Circuit (at least the ones I have seen).

Leaving my Soapbox.

Scott35 S.E.T.

 

[hornetd]

Re: Multi wire branch circuit handle ties

Originally posted by bphgravity:
So i guess we should just give up on trying to do anything correct. everyone can run around doing whatever they want because it doesn't matter anyway. What is wrong with trying to do things a better way, or to maybe prevent someone getting hurt or something being damaged. The whole point of this forum is reducing general ignorance. Everything counts.

I'm not sure who you are aiming at with that but what you suggest is not what others here are saying.

What I think many of us are saying is that discontinuing tried and true techniques in order to dumb down electrical work to a safer level for unqualified persons has a logical consequence. That is a massive increase in cost and far less convenience. We could convert all receptacle outlets to pin and sleeve connections because pin and sleeve connector parts are never energized when exposed to the slightest degree. We could use Canadian style panels that have a separate dead front over the supply terminals and do not allow branch circuits or feeders supplied form the panel to pass through the dead fronted area in all homes. We could out do the Canadians and require shunt trips in main breakers to open the breaker if the cover is removed or physically interlock the cover and main breaker handle to force the breaker to be thrown to the off position in order to remove it. The possible "improvements" to electrical safety are nearly endless and could also be endlessly expensive.

As I tried to point out in my original posting it does not take a multi wire branch circuit to introduce two sources of current into a box. So to the people who want to ban multi wire circuits I ask if they would also forbid using an undivided box to hold multiple switches unless they are supplied from the same circuit.

I have spent a considerable amount of time in coaching home owners to do their own work safely. To those who will not take the time to learn to do it right I say good luck you are going to need it.
--
Tom

[ March 18, 2003, 11:04 AM: Message edited by: hornetd ]

 

[bphgravity]

Re: Multi wire branch circuit handle ties

I like any idea that makes electrical installations safer. So all your examples sound great. I do not believe when something is harder, or less convienent, or more expensive to be the determining point. At one time GFI's were too hard to understand, install, and pay for. Now, no one likes AFCI's for the same reasons. Nearly 100 years ago Edison didn't like Alternating Current. I will never dumb down my work. I will never assume the next guy is as competent as me. I'll never assume the guy before me was a competent as me. I am striving for complete perfection of safety. Anything less is not living up to the responsibilty of the electrician. P.S. my concerns on multiwire-branch circuits has less to do with handle ties and more to do with an open neutral condition. This puts the loads in 240-volt series and develops voltage drops and gains accross the circuits. Can I prevent open neutrals, no. I can prevent multi-wire branch circuits.

 

[roger]

Re: Multi wire branch circuit handle ties

Bph, I don't think you are going to be able to change the three wire installations that supply virtually every 120/240v single phase service, now or future. These installations are multi wire circuits, and have larger consequences when the neutral is lost.

Roger

 

[bphgravity]

Re: Multi wire branch circuit handle ties

Roger, I agree. But this post is talking about branch circuits, not services. There are many more joints, terminals, and opportunities to get an open neutral on a branch circuits than at the service which is only a few connections. These connections are generally much more carefully done, usually by qualified personell, and rarely fooled with by home owners, whereas branch circuits are installed everyday by homeowners.

 

[iwire]

Re: Multi wire branch circuit handle ties

Bph

I can prevent multi-wire branch circuits

I hope you mean you personally will prevent it from your jobs.

I really get tired of the negative comments about multiwire circuits. If they where nearly as bad as some would have us believe I am sure the code would be changed.

The first part of my lay out is seeing how to break the circuits up into 3 phase multiwire circuits. With multiwire circuits I use less copper and when in pipe it cuts down on current carrying conductors.

As an example 40 circuits in a panel with no multiwire circuits will have 80 current carrying conductors if I split these into 2 raceways I will have to derate to 40% which means #8 awg
for 20 amp circuits.

If I do the 40 circuits with multiwire circuits I have a total of 54 conductors only 40 are current carrying split between 2 raceways lets me derate to 50% so I get to use #10s now.

Open neutrals are not any more likely than open hots and just because you lose a neutral on a multiwire circuit does not mean the certain destruction of the connected loads, you will not get a full 208 at `the load on phase A unless one of the loads on phase B or C is a dead short from hot to neutral.

So the Neutral would have to open at the same instant that one of the loads shorted Hot to Neutral, not to likely IMO

I will add in office cubes most of the factory wiring in office furniture is Multiwire and if you bring over 3 two wire circuits how would you connect it, parallel the neutrals from the 3 separate cables or just connect one of the Neutrals?

I will stop ranting now

 

[bphgravity]

Re: Multi wire branch circuit handle ties

Bob, I did mean my jobs. Multiwire-branch circuits are certainly not required, and certainly not a necessity. I am completely aware of the cost benefits and ease of installations these circuits provide. I am not trying to put a negative spin on a generally decent method of wiring. It is simply my opinion on the subject. If I were to promote a dangerous idea or suggest a hazardous installation, I would hope others on this forum would point these out to me. By suggesting not using these type of circuits certainly does not present a hazard or danger. I am only trying to provide a view from the other side. Your comments and suggestions are greatly appreciated!

 

[roger]

Re: Multi wire branch circuit handle ties

Bph, along the lines of Bob's post. Let’s look at the conservation side of this. Natural resources, ie copper and the fuels to generate
electricity, plus $ savings to the customer

Hypothetical situation; A home has (4) 20 amp circuits (loaded to 15 amps each) wired as two wire circuits. We use #12 conductors, at 100’.

The following is not aimed at you, I know you can do the math.

#12 = 1.98 ohms per K’ x .100 = .198

I^2 R heat loss

15 x 15 x .198 x 8 = 356.4 watts

Now if we took the (4) circuits and installed them as multi wire branch circuits, we would reduce the current carrying conductors to 4. (remember hypothetically 15 amps so each grounded conductor is truly neutral.)

15 x 15 x .198 x 4 = 178.2 watts.

Now if we give this a time frame per day, times 365 days, times umpteen million nation or world wide circuits, we have impact on the aforementioned resources.

Roger

[ March 18, 2003, 07:09 PM: Message edited by: roger ]

 

[bphgravity]

Re: Multi wire branch circuit handle ties

Roger, you too may a great point!