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Old 11-14-2008, 11:13 AM   #16
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Conduit Fill and Derating


I'm not going to go into my dislike for a bunch of junction boxes so that is your call. Also I'm not sure what your budget is but some of the manufacturers make renovation panels that allow you to get those short neutrals, grounds , hot conductors and service entrance to reach their appropriate termination points in a very workman like manner. I'll give you a link to the cutler hammer one I always liked and hey they have improved it since I last installed one......

http://www.salesmanagementplus.com/C...Renovation.pdf

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Old 11-14-2008, 11:39 PM   #17
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Conduit Fill and Derating


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Originally Posted by InPhase277 View Post
Jamie, don't forget about box fill when you are putting all these circuits in. You have more or less got the gist of the pipe fill and derating, but you must keep in mind the volume of the boxes too. Since you are going with the pipe method, you might consider a 24 x 6 x 6 wireway as your junction. The only draw back is you have to drill your own holes in it, but it will likely have more than enough volume. Just keep good track of the circuits and don't mix things up.
No mix -up's nice and organize.
Conduit Fill and Derating-img_4482.jpg

Since I was only putting 4 in each conduit, and after I do some re-wiring, I think I may only end up with 12 circuits, so that will only be 3 boxes, not too bad. My neutrals were just long enough once clamped into the box.

I used 4"x4" boxes, based on the chart I saw in the NEC, I am fine with 4 circuits in it.

Conduit Fill and Derating-img_4480.jpg

Thanks
Jamie
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Old 11-14-2008, 11:43 PM   #18
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Conduit Fill and Derating


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Originally Posted by jamiedolan View Post
No mix -up's nice and organize.
Attachment 6036

Since I was only putting 4 in each conduit, and after I do some re-wiring, I think I may only end up with 12 circuits, so that will only be 3 boxes, not too bad. My neutrals were just long enough once clamped into the box.

I used 4"x4" boxes, based on the chart I saw in the NEC, I am fine with 4 circuits in it.

Attachment 6037

Thanks
Jamie

Looks nice, great work!
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Old 11-14-2008, 11:45 PM   #19
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Conduit Fill and Derating


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Looks nice, great work!
Thanks :-) Hopefully I can finish up the old connections tommrow, then I am going to start running some new circuits.

Jamie
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Old 11-14-2008, 11:57 PM   #20
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Conduit Fill and Derating


Quote:
Originally Posted by Stubbie View Post
I'm not going to go into my dislike for a bunch of junction boxes so that is your call. Also I'm not sure what your budget is but some of the manufacturers make renovation panels that allow you to get those short neutrals, grounds , hot conductors and service entrance to reach their appropriate termination points in a very workman like manner. I'll give you a link to the cutler hammer one I always liked and hey they have improved it since I last installed one......

http://www.salesmanagementplus.com/C...Renovation.pdf
They do look pretty slick. I will keep them in mind if I ever have to do one of these again.

I should have had the meter pulled today, it would have be so much faster. In the pushmatic panels, the mains are in such a bad position, your right next to them when you are taking out the neutrals / grounds. My main is AL and it is covered in some old coating that looks like cheap waxed paper. I was kind of afraid I was going to end up making contact with the main with my pliers or a ground wire and cause a fault. I wondered what happens if you cause a fault on your main prior to your breaker, does the meter have some type of overcurrent / fault protection?

I used live tools and handeled everything properly, just in case the mains energized somethig they shouldn't have.

I am keeping my junction boxes nice and neat, and up in between the joists.

Thanks
Jamie
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Old 11-15-2008, 12:03 AM   #21
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Conduit Fill and Derating


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Originally Posted by jamiedolan View Post
does the meter have some type of overcurrent / fault protection?
No, the meter does not have any protection other than being able to be pulled. I do not think there is overcurrent/fault protection after the xformer. I know there is one before it. If any person who has worked with poco lines want to fill me in here, Id appriciate it...


xformer diagram (split-phase aka 120/240)
Attached Thumbnails
Conduit Fill and Derating-xformer.jpg  

Last edited by rgsgww; 11-15-2008 at 12:18 AM. Reason: added diagram
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Old 11-15-2008, 07:47 AM   #22
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Conduit Fill and Derating


Why didn't you just run two neutrals up and make them multi wire branch circuits? just curious thats all.
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Old 11-15-2008, 11:27 AM   #23
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Conduit Fill and Derating


I know what you mean about close quarters, I once had to replace/move an old split buss pushmatic 100 amp panel that had a new 4" main plumbing drain installed by the homeowner....which he ran vertically about 12 inches in front of the panel. He removed the hinged door of the panel since he couldn't open it with the drain pipe in the way. Why do people do this?? Sounds like you needed to move yours too.

It would do you some good (learning curve..) to draw out what Chris was saying about the two multiwires. This would have had some advantages that I think you would have appreciated... to get you started... draw 2 multiwires from the panel to that junction box then split the 4 nm cables between them. Then think of things in terms of how many conductors you used compared to what you have now and also box and conduit fill plus conductor deration. Doesn't make either way any better but it is a good way to see a different approach to what you have now.
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Old 11-15-2008, 01:49 PM   #24
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Conduit Fill and Derating


Quote:
Originally Posted by rgsgww View Post
No, the meter does not have any protection other than being able to be pulled. I do not think there is overcurrent/fault protection after the xformer. I know there is one before it. If any person who has worked with poco lines want to fill me in here, Id appriciate it...


xformer diagram (split-phase aka 120/240)
I will be glad to due I work on high voltage system from time to time but I will keep it simple here

The only protection you will get this from the transfomer is the primary side { high voltage } and there is no protection on secondary side { low voltage } due pretty good percetage of the overhead cans { transfomer(s)} secondary side do feed few home they can go anywhere from one home to many as 10 homes depending on the grid size and setup.

If in case you wondering why there is no protection on secondary side.,,, the secondory side what the term we called short circuit amparage avablitity that mean the X amout of amparage for short cirucit is avable from the transfomer and the X amout of short circuit will varies a bit due so many factors and type of transfomer.

However typically shortcircuit avabilty useally over 8,000 amp or higher depending on the transfomer size the bigger it go the more short circuit capitcy go up.

Myself I ran into few service cable shorted out and they do pretty good damage there { it don't matter if single phase resdentail or triphase large commercal/industrail user } the last one I work on not too long ago it did actally melt the steel riser{ pipe } on the commercal building sorta like out of control welder.

Yeah for the fuse on transfomer ? they useally are oversized and super long delay before they blow normally they sized to either blow the heck out of the transfomer or hevey shortcircircuit kick the fuse out.
That why you useally don't see the fuse blow on light to pretty good overload sistuation.

IF more question either myself or other electricians can expain more if you like to.

Merci,Marc
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Old 11-15-2008, 02:30 PM   #25
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Conduit Fill and Derating


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Originally Posted by chris75 View Post
Why didn't you just run two neutrals up and make them multi wire branch circuits? just curious thats all.
The only drawback is that with MWBCs you have to use double pole breakers. You have to turn off two circuits just to work on one. Depending on what circuits those are, that can suck.
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Old 11-15-2008, 02:35 PM   #26
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Conduit Fill and Derating


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Originally Posted by InPhase277 View Post
The only drawback is that with MWBCs you have to use double pole breakers. You have to turn off two circuits just to work on one. Depending on what circuits those are, that can suck.
Depends on what code cycle your on, CT is not adopting the 2008, full speed ahead!
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Old 11-15-2008, 02:58 PM   #27
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Conduit Fill and Derating


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Depends on what code cycle your on, CT is not adopting the 2008, full speed ahead!
Wisconsin is on 2005.

Jamie
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Old 11-15-2008, 03:01 PM   #28
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Conduit Fill and Derating


Quote:
Originally Posted by InPhase277 View Post
The only drawback is that with MWBCs you have to use double pole breakers. You have to turn off two circuits just to work on one. Depending on what circuits those are, that can suck.
Just regular double pole breakers that take up 2 slot positions - because you have to make sure each circuit draws power from each phase?

So they trip in common as well, correct? So a lighting circuit, and your outlet circuit on a branch with a shared neutral will both trip at once if the outlets cause a fault/overdraw, correct?

Jamie
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Old 11-15-2008, 03:05 PM   #29
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Conduit Fill and Derating


Quote:
Originally Posted by Stubbie View Post
I know what you mean about close quarters, I once had to replace/move an old split buss pushmatic 100 amp panel that had a new 4" main plumbing drain installed by the homeowner....which he ran vertically about 12 inches in front of the panel. He removed the hinged door of the panel since he couldn't open it with the drain pipe in the way. Why do people do this?? Sounds like you needed to move yours too.

It would do you some good (learning curve..) to draw out what Chris was saying about the two multiwires. This would have had some advantages that I think you would have appreciated... to get you started... draw 2 multiwires from the panel to that junction box then split the 4 nm cables between them. Then think of things in terms of how many conductors you used compared to what you have now and also box and conduit fill plus conductor deration. Doesn't make either way any better but it is a good way to see a different approach to what you have now.
Thanks guys for pointing this out. I have not had a lot of experiance with MWBC before and maybe I didn't give it enough consideration...

My understanding of a MWBC is that you use a double pole breaker, that has both poles connected so it is a common trip. Then you just share the same neutral with 2 circuits. Is this correct?

Also it sounds like I could put 6 circuits in a conduit with MWBC and only have to derate to 70% still.

The only thing I have a question about is what if these circuits need ground fault or ARC fault protection in the panel?

Are MWBC compatiable with ground fault or arc fault breakers?

Thanks
Jamie
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Old 11-15-2008, 04:23 PM   #30
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Conduit Fill and Derating


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Originally Posted by jamiedolan View Post
The only thing I have a question about is what if these circuits need ground fault or ARC fault protection in the panel?

Are MWBC compatiable with ground fault or arc fault breakers?

Thanks
Jamie
I have seen double pole arc fault and gfci breakers, so yes, they are.

Depends on the circuit. If the conduit goes to a bedroom for instance, yes you need afci protection.

MWBC will not work with single pole afcis, but your not allowed to use single poles with MWBC, only common trip dble poles.

Multi wire circuits share the neutral, but MUST use both legs of the panel, not just one. Its all about balance. The neutral is the center-tap of the xformer. The output is called the "secendary" of the xformer.

Split-phase tranformer (xformer) used to power most homes.
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Conduit Fill and Derating-xformer-copy.jpg  


Last edited by rgsgww; 11-15-2008 at 04:31 PM.
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