Main breaker in seperate enclosure

[mbrooke]

Just want to pick some of the best and brightest minds (which are) on this site. What do you think about having the main service conductors and main breaker enclosed in a separate shield like those found in Canadian load centers? Do you believe there are any advantages? That they are worth mandating? Or do you believe such would be of no advantage?


http://www.schneider-electric.ca/images/pictures/news/press/homeline-lr.jpg

 

[don_resqcapt19]

Of course, since I have submitted a number of code proposals to require this, my opinion is biased

My proposals never made it into the code, but the new UL standard for service equipment requires this.

 

[iwire]

I don't see a need for a separate enclosure but certainly substantial barriers between the line and load side of the main breaker would be a great increase in safety.

As it is today you basically are required to have a power company shutdown at most homes. (This does not happen, but it is what is required for most work you would do in a homes service panel)

 

[iwire]

Of course, since I have submitted a number of code proposals to require this, my opinion is biased

My proposals never made it into the code, but the new UL standard for service equipment requires this.

There is no good reason those proposals should not have been accepted.

 

[mbrooke]

There is no good reason those proposals should not have been accepted.

I think, for once, we agree on something


While I am a fanatic for change, this is one where I feel the need to voice my opinion as being a poor one. While I can accept the argument of plastic shields over the main lugs, I do not feel having a metal cover over the service conductors and main breaker providing any advantage. Perhaps it offers protection to clueless homeowners, but in that case a shunt trip pole transformer would be the only wise choice.

 

[mbrooke]

Of course, since I have submitted a number of code proposals to require this, my opinion is biased

My proposals never made it into the code, but the new UL standard for service equipment requires this.

I am humble, and I do not mean to dispute what you probably know more than myself. However, what major advantage does such offer?

 

[ADub]

Holy dejavu, don didn't you have a very similar conversation on this very topic at the other site just yesterday?


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[mbrooke]

Holy dejavu, don didn't you have a very similar conversation on this very topic at the other site just yesterday?


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He did. Which got me thinking. With this being mandated as it seems, what problem is it really trying to solve?

 

[jumper]

Just want to pick some of the best and brightest minds ...

Okay fine, go ahead and not include me.

I am taking my ball and going home........

 

[don_resqcapt19]

He did. Which got me thinking. With this being mandated as it seems, what problem is it really trying to solve?

To make it possible to comply with the electrical safe work rules when working in the enclosure that contains both the service disconnect and additional OCPDs. With out the line side enclosure, the only legal way to do that work is to have the utility kill service and we know that rarely happens.

 

[iwire]

I do not feel having a metal cover over the service conductors and main breaker providing any advantage.

I have no idea how to explain the obvious.:huh:

No live exposed parts to shock or cause an arc flash with the side benefit of giving us compliance with the hot work rules.

Perhaps it offers protection to clueless homeowners, but in that case a shunt trip pole transformer would be the only wise choice.

I hope you are kidding because that is some questionable thinking.

 

[mbrooke]

Okay fine, go ahead and not include me.

I am taking my ball and going home........

No, no, you are a wealth intellect as well

To make it possible to comply with the electrical safe work rules when working in the enclosure that contains both the service disconnect and additional OCPDs. With out the line side enclosure, the only legal way to do that work is to have the utility kill service and we know that rarely happens.

Then why not just shield the lugs? And which electrician turns off the main anyway to add a breaker? I never do. Yes its good work practice, but in most resi panels the arc flash is anywhere anything close to commercial or industrial.

 

[mbrooke]

I have no idea how to explain the obvious.:huh:

No live exposed parts to shock or cause an arc flash with the side benefit of giving us compliance with the hot work rules.

But wouldn't shielded lugs do the same?

I hope you are kidding because that is some questionable thinking.

I'm kidding, but my point is, around untrained personnel idiot proofing is not a solution. In fact it can backfire. No different then handle ties on MWBC.

 

[don_resqcapt19]

But wouldn't shielded lugs do the same?
....

I don't think it is physically possible to completely shield the line side lugs without the use of a complete cover or enclosure. You could make the shield "finger safe" but I don't think you could build a lug shield that prevents any access to the live terminal.

 

[James L]

I haven't been to Canada in a while (ever), but I looked at the picture in the link

The the concept seems somewhat okay from a safety standpoint, I wonder how it works practically.

It lookas as though no branch circuits are able to pass through the main breaker wiring compartment?

What if panel like that is mounted between two studs? Then no wires can enter through either side? Leaving only the bottom?

I think you can "stupid proof" something to the point that it's no longer practical to use

 

[iwire]

It look as as though no branch circuits are able to pass through the main breaker wiring compartment?

Correct

What if panel like that is mounted between two studs? Then no wires can enter through either side? Leaving only the bottom?

That would be one way to deal with it.

The Canadians just mount the panel sideways to deal with it but we really do not have that option due to the 'up is on' requirements for breakers.

I think you can "stupid proof" something to the point that it's no longer practical to use

If an electrician cannot deal with a simple metal cover they may be in the wrong trade.

 

[James L]

If an electrician cannot deal with a simple metal cover they may be in the wrong trade.

I'm not sure what you're getting at.

 

[gadfly56]

Is there a real problem to be solved here? Aside from the technical aspect of working in an enclosure with live conductors, has there been a genuine safety and fire hazard identified through field reports that this solution would "solve"? It strikes me as being only a little more sensible than the whole AFCI breaker fiasco.

I have changed or added a breaker or two in my residential panel and each time I tripped the main before proceeding. Notwithstanding, I confess to a certain uneasiness knowing that the hots at the top of the panel would cheerfully deliver the available fault current if I wasn't careful. I don't believe, however, that my personal trepidation is a good basis for driving the code.

 

[meternerd]

To make it possible to comply with the electrical safe work rules when working in the enclosure that contains both the service disconnect and additional OCPDs. With out the line side enclosure, the only legal way to do that work is to have the utility kill service and we know that rarely happens.

Why does it rarely happen....? Because you don't ask for one? Most, if not all, POCO's will do a service disconnect either at the pole or the meter at no charge, as long as it's done during normal working hours. We, as a utility, would much rather take the time to do a disconnect than have someone get across the line side of a service disconnect. Most transformers have no secondary protection, and it takes a HUGE fault on the secondary to blow a primary fuse. Why risk it? As far as arc fault in a service panel, I guess it could be possible to have an arc fault, but most seem to originate at the meter, and a cover over the main would not make any difference. Seems to me like a solution to a non-problem.

 

[jumper]

Why does it rarely happen....?

In resi? Time, money, convenience, diyers, you name it.