How to bring wire from basement to attic


Old 04-26-17, 06:25 PM
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How to bring wire from basement to attic


I have a one-story house with a basement. So in other words, it goes: Basement --> 1st floor --> attic. The electricity comes in from the basement. Both the basement and attic are unfinished.

I am currently remodeling a bedroom and have walls open. What I'd like to do is bring new electricity from the basement, through an open bedroom wall, and into the attic. Then I will close the bedroom walls.

Right now, there is a lot of older romex strewn all over the attic like a big spider web, which is powering receptacles and recessed lights for the rooms below. Later (i.e. next year), I want to re-do (replace) as much of that wiring in the attic as I can, which is why I want to bring up new electricity now.

I originally thought I would just put a subpanel in the attic, so I could tap into it easily by adding breakers as necessary. A little online reading shot that idea down because (1) the attic is considered "inaccessible", (2) headspace less than 6.5 ft, (3) potentially high ambient temperature in the summers, which could degrade performance of the breakers in the subpanel.

So next I thought, well I'll just put a big 2-inch diameter PVC conduit in the bedroom wall, so I could fish up romex from the basement to the attic easily. Again, a little online reading shot that down too, because of heat rating restrictions that limit how many romex runs can be in one conduit.

So I'm out of ideas and asking for advice. How can I take advantage of my current bedroom remodel to bring new electricity from the basement to the attic? Is there a different type of wire besides romex that I can put several (say 6 or 7) runs into a 2-inch PVC conduit? Or is there a better option? I am looking for a flexible option, rather than just bringing up several individual runs of various gauge romex.

Thank you
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Old 04-26-17, 06:38 PM
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Door number 2. Leave the rat maze of wiring alone. It isn't broke, so don't go fixing it. Run your 2" conduit all the way up, but cap it on both ends. It is a chimney and fire code says it must be sealed. So when you pull wires up the pipe, you will need to seal it each time with Fire Caulk (red) to keep air from transferring from floor to floor.
Old 04-26-17, 06:48 PM
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The biggest issue running empty conduits would be that they are a fire chase. In case of a fire that would act as a chimney and make a fire that much worse.

I would recommend not running cables in the conduit, but run individual wires. For derating purposes you need to limit to no more then 9 current carrying conductors. You could run a hot and neutral for each circuit, but I would utilize multi-wire circuits where a 2 hots share one neutral. All you would need to do is protect the multi-wire with a 2 pole breaker. If you were to do that, each conduit could have a total of 6 circuits, 9 wires.

With the above info in hand I would suggest running two or three 3/4" flexible metal conduits from basement to attic. That will give you the possibility of 18 circuits which should cover you very well. Be sure to install large enough boxes in the attic and/or basement (I suggest 4 11/16" square or larger) and to install a ground wire as large as your largest hot conductor. You can also install a string for ease of pulling in new circuits as needed, pulling in a new string until you reach the max number of wires. Remember to terminate both ends of the flex into a box or the electrical panel to prevent the fire chase mentioned above. Keep the conduit to no more then 360 degrees of bends or you will never be able to pull in wires.
Old 04-29-17, 07:31 PM
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Thanks for the information about sealing both ends to prevent a fire chase.

Tolyn, I like your idea of running individual conductors instead. What type of wire should I choose to be inside the conduit. I know that some types of wires are not designed to be inside conduits, so I want to make sure I use the appropriate wire type.

Old 04-29-17, 07:52 PM
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THHN will be fine in the conduit .

Plan how many circuits you will need and run home run cables to the attic. Leave them long.

If the circuits require afci protection you will not be able to use mwbc s .
Old 06-04-17, 09:15 PM
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Originally Posted by pcboss
If the circuits require afci protection you will not be able to use mwbc s
With a little reading about MWBC, I have come to the conclusion that I don't want to use shared neutrals because they can't be AFCI protected (at least not with the breakers available for my panel), and also I would prefer the ability to independently trips each circuit. With MWBC, both circuits sharing the neutral have to trip simultaneously, which is more of an maintenance-time annoyance than savings of a single neutral is worth to me.

However, I have a question: Can I share a ground? I am thinking of running just one 12-gauge green conductor to serve as the sole ground for three 15 amp circuits and one 20 amp circuit. Is that allowable?

EDIT: Does which bus the hots are on matter if they can share a ground?

Thank you
Old 06-04-17, 10:40 PM
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Yes... you can share a single ground wire on those circuits and it can be #12 green. It gets sized to the largest circuit in the conduit which is 20A and #12.

It doesn't make a difference which leg the circuits are on.
Old 06-05-17, 01:17 PM
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Thank you PJmax! One final question because I went to the store today to look at wire, but there was THHN sold as solid copper and also as stranded copper. Does it matter which type I purchase?
Old 06-05-17, 01:25 PM
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Electrically they are the same, but solid wire is usually easier for novices to work with. It's installer's choice of which they prefer to work with.

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