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#57740 - 10/19/05 10:37 PM external means for disconnect  
lamplighter  Offline
Member
Joined: Oct 2005
Posts: 101
Clawson,Michigan,USA
When I was living in Fl., I used to have to adhere to the N.E.C. as well as the S.F.B.C.(south florida building code).
S.F.B.C. is in place due to hurricane ratings and the like.
On any service, you had to leave an external means of disconnect and the meter did not qualify as such.
This meant a main breaker mounted usually to the side of the meter can with an offset nipple before going on to the distribution panel inside.
In Michigan, I ran into something I had never seen in Fl., i.e. buss riser system.
The problem is that a buss riser system has no external means for disconnect unless you mount a shunt-trip which is never called for by the architect up here.
My father-in-law is a fireman for over 35 years and he says that in case of fire, the firemen sever the service drop near the pole. The main problem I see with this is that when it comes to an industrial fire in a small manufacturing facility, the fireman on the ladder might be cutting a 5000 amp service or even bigger while there is a load on it, with water spraying everywhere, in the dark, and trying to see through a possibly soot covered face shield while doing it.
Does this sound unsafe to anyone else?


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#57741 - 10/19/05 11:00 PM Re: external means for disconnect  
resqcapt19  Offline
Member
Joined: Nov 2000
Posts: 2,148
IL
First very few firefighers are qualified to cut energized serivce conductors, and then most likely don't have the correct PPE to do it safely. Second, it might not be very wise to cut the power at the pole because it could be feeding the building fire pump. Third, the building "pre-plan" that should be done by the fire department for commerical and industrial building will show the locations of all of the building utility service disconnects. This makes it easy to use the normal building disconnect to kill the power in the building, while waiting for the utility to kill the service drop.
Don


Don(resqcapt19)

#57742 - 10/20/05 12:58 AM Re: external means for disconnect  
gfretwell  Online Content


Member
Joined: Jul 2004
Posts: 9,103
Estero,Fl,usa
Alas the SFBC is long gone. The UFBC is the NEC (2002 right now) unaltered, statewide.


Greg Fretwell

#57743 - 10/20/05 11:55 AM Re: external means for disconnect  
lamplighter  Offline
Member
Joined: Oct 2005
Posts: 101
Clawson,Michigan,USA
---"This makes it easy to use the normal building disconnect to kill the power in the building, while waiting for the utility to kill the service drop."---

The problem I see with this is that the fire may very well prohibit the firemen from getting to the disconnect without having to spray large amounts of water on the energized switchgear, bussrails, etc.
The main building disconnect could very well be the source of the fire and I wouldn't want to be the one to have to spray water on an energized 5000 amp main.
I simple little shunt trip could solve some of the problems here but still wouldn't kill the power on the line side of the main.
I think that for once in Fl.'s life, they actually had it right.
An external means for disconnect sounds like a good idea to me.


#57744 - 10/20/05 12:30 PM Re: external means for disconnect  
macmikeman  Offline
Member
Joined: Jul 2002
Posts: 717
Honolulu, Hawaii
I am taking a wild guess , but perhaps the reason that exterior disconecting means are not so popular on buildings in plenty of area's in the country is because the fire crew might also need to shovel a bunch of snow away in order to acess the thing.


#57745 - 10/20/05 01:02 PM Re: external means for disconnect  
gfretwell  Online Content


Member
Joined: Jul 2004
Posts: 9,103
Estero,Fl,usa
I suppose all fire fighters are not created equal but the guy I saw pull a meter (with his axe) did it quickly and was pretty far away from the arc. It came out in one fluid motion with his back to it and moving away.
A fireman in his running gear is fairly well protected anyway, at least as far as a typical dwelling load is concerned.


Greg Fretwell

#57746 - 10/20/05 01:23 PM Re: external means for disconnect  
resqcapt19  Offline
Member
Joined: Nov 2000
Posts: 2,148
IL
Quote
A fireman in his running gear is fairly well protected anyway, at least as far as a typical dwelling load is concerned.

The face protection, and even the normal fire gear does not provide suitable protection for arc flash conditions.
Don


Don(resqcapt19)

#57747 - 10/20/05 01:55 PM Re: external means for disconnect  
resqcapt19  Offline
Member
Joined: Nov 2000
Posts: 2,148
IL
It is not uncommon to use water fog on energized electrical equipment. Look here


Don(resqcapt19)

#57748 - 10/20/05 02:04 PM Re: external means for disconnect  
gfretwell  Online Content


Member
Joined: Jul 2004
Posts: 9,103
Estero,Fl,usa
Way back in the olden days when I was a sailor (65-71) they had us using low velocity fog on just about everything. The principle is you are cooling the fire off to below ignition temp.


Greg Fretwell

#57749 - 10/20/05 02:50 PM Re: external means for disconnect  
lamplighter  Offline
Member
Joined: Oct 2005
Posts: 101
Clawson,Michigan,USA
I'm not really concerned with the dangers of a dwelling load as much as a wharehouse or manufacturing facility.
A dwelling has an external means even if it's not considered so by local codes. (the meter)
It's those building with a bussriser system or equivalant that I'm mainly talking about here.
Would anyone here want to be the one to sever a 5000 amp, 480v. service drop with an axe or bolt cutters while there is a possible load on it?
I'm sorry, but, an axe handle or fiberglass handles on a pair of bunny guns just wouldn't give me much confidence when there's a possibility of a 4000 amp load or even greater on the service drop conductors.


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