Modified service upgrade


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Old 05-06-09, 11:42 PM
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Modified service upgrade

I enjoy electrical work and have always prided myself on doing it right. I have rewired the circuits in a couple of my houses, then hired an electrician to install the panels.
I am in a bit of a pickle now.

I hope I explain this properly.

My property has two houses on one lot, each with it's own service, both of which come in on the front corner of the the front house then split through two separate meters, and two separate mains.

The 400 sq ft. rear cottage was built in 1946. The main has two 30A switches linked together, which, as I understand it is two legs of 30A power. The service leaves the main, and travels about 40' underneath the front house via two #8 wires to a junction box at the rear of this house, where it goes underground through conduit, up the side of the cottage, through the attic, and into a two fuse panel in the bedroom (about another 45' total).
In short, this whole house is run on two 15A circuits.
The intention of the upgrade is to provide a couple of designated circuits, and to provide some relief to existing K & T circuits by splitting them up a (bit and replacing the K & T).

In short, 40' of #8 from the main, about 45' of #8 to the two circuit fuse box.

I consulted with an electrician, and I believe this was the plan-
Replace the initial 40' run from the main with #6/3 romex.
Run three #8 to a new surface mounted six circuit panel.
Run separate wire for each circuit from the panel to a 6" junction box in the attic where each circuit can be linked up to it's respective breaker.

In short, 40' of #6 to the first box, about 25' of #8 to the new panel, then a bunch of individual circuit wires running from the panel, up into the attic junction box.

I have started running the circuits, but the electrician isn't answering my calls.
Does my memory of his plan sound correct (codes)? I need to keep working, and I need to locate this 6" attic junction box.

If not what am I missing?

If so, here are my specific questions-

Assuming there are five or six circuits coming from the new panel. Since there will be this intermediate 6" junction box, are two wires required for each circuit, or would two #8 neutral wires do the trick, with each circuit tied into the appropriate neutral leg?
In short, five or six black #12 wires, plus either two #8 white wires or fie or six #12 white wires.


What about grounding?
Should there be a continuous ground all the way from the front main through the underground to the new panel?
The electrician indicated that the new panel should be grounded at it's location, so is it necessary to have a ground in that first run of #6 and underground run of #8?
Does each circuit leg need to have a ground running from the panel to the 6" attic box, or will a #8 ground wire work?

If each circuit requires a separate wire for each function, there will be 18 wires running up to that 6" box in the attic. What diameter conduit would be necessary for this?

I know I am long winded. Thanks in advance for your patience (and your answers).
 
  #2  
Old 05-08-09, 06:08 AM
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In the future, you may want to try to shorten your posts so you'll get more readers and likely more answers.

I can't comment on your entire plan, but a few comments do come to mind...

You're going to run into problems with that one 6" junction box. Actually, it's not the box which will be the problem, but the conduit leading up to it. You can have a maximum of 9 current carrying conductors in one conduit before you have to start derating the wiring. This basically equates of 4 circuits (4 hots + 4 neutrals = 8 current carrying conductors). If you run more, you'll have to use 12ga wire for 15A, 10ga for 20A etc. It's sort of a pain.

To get around this, you can run a couple conduits and limit the number of circuits in each, or you can run individual NM-B into one (or multiple) junction boxes. I did something similar recently, and found that using NM was actually cheaper than conduit + THHN wire since I only needed a couple short rolls in different colors.

As far as I understand, you can't combine neutrals as you're planning. Two 15A circuits can't use one 10ga wire as a neutral. (You can use a MWBC, but that's a different discussion). Each hot needs its own corresponding neutral.

Grounds on the other hand can be combined. Since they just carry fault current, one ground is required in each raceway/conduit, sized for the largest circuit. For example, if in one conduit you have two 20A circ and one 15A circ, you can use one 12ga ground wire for all three.

It sounds like you may have more questions... feel free to ask!
 
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Old 05-08-09, 07:00 AM
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I am not sure why you are not going from the meters right into the new panels. Why are you splicing the #6 to the #8?
 
 

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