HR's - a few large holes or a bunch of smaller ones?

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bjp_ne_elec

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Curious what approach you take - either drill a few larger holes (1-1/2" or so) or drill a series of smaller holes when routing home runs of NM (or MC for that matter) back through floor joists and vertically through the floors (but you'd be drilling in the horizontal top and bottom plates.

If you do use smaller holes, what size and how close?

Edit - I've just read a few posts that I found by doing a search on "drilling joists" - and now I'm a little confused. First when driling say 7/8" holes in joists, how close can they be. One thing I read was regarding drilling 1-1/2" holes and it indicated there had to be 1-1/2" from edge to edge of the hole. Does this mean 7/8" holes also have to have 7/8" edge to edge? Also is the criteria different if you're talking drilling the top and bottom plate? I don't see how you maintain that spacing when you're trying to bring your HR's down through the first floor space.

Thanks,

Brett
 
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If you drill large holes than you must drerate once you have more than 2 cables in the hole if the holes will be fire caulked-- art. 334.80 last paragraph.

I usually use 7/8" holes close together and I also use stud bays on both sides of the panel.
 
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The stud bay is the area between 2 studs. The panel fits in one stud bay and we have access (sometimes) to stud bays to the right and left of the panel.

If you keep your holes in the middle it wont weaken the wall.

When you have many wires in the panel uses just the top plate is not enough that's is why I go to the left or right of the panel bay. Once I penetrate the top plate I can go horizontal with more wires since it won't be caulked.

In our area they will not allow more than 2 wires in a hole. I have not had that issue yet but I plan on challenging it.

Sometimes I use the other bays to go down to the bottom of the panel esp. If I am in the basement where you can't go through the floor.
 
bjp_ne_elec said:
Curious what approach you take - either drill a few larger holes (1-1/2" or so) or drill a series of smaller holes when routing home runs of NM........
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If I have enough HRs to fill several large holes in each joist, I start thinking about installing a subpanel instead. :)
 
I use a 7/8" auger bit for the majority of my drilling, vertical or horizontal. At times I will use a 1/2" bit so I can use a more manageable drill, it depends on the circuit and/or house. If I have a solid joist house inbetween floors, I will use an 1 1/4" so to cut down on the # of holes. The rule I know as far as solid joist and certain beams (some you cannot drill at all, now that is fun:rolleyes: ), is to stay away from the inner 1/3 of the beam. It is off limits to boring. Or so I have been told by GCs. For HRs I use large holes with a coule of small ones if necessary.
 
360Youth - what do you consider the "inner 1/3"? You're talking about joists - do you mean the upper third (closest to the side the upstairs flooring is nailed to) or the lower 1/3 (where the sheet rock would be screwed to?

Thanks
 
bjp_ne_elec said:
360Youth - what do you consider the "inner 1/3"? You're talking about joists - do you mean the upper third (closest to the side the upstairs flooring is nailed to) or the lower 1/3 (where the sheet rock would be screwed to?

Thanks
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The middle third.... In between the two outside thirds...:smile:
 
Stickboy - that's why I questioned it - he is indicating you have to "stay away from the inner 1/3" - I'm thinking you only want to be in the "middle third". See my point?
 
The MA building code states that holes shall not be in the middle third of a span, shall not be within 2" of the top or bottom of a joist, and shall not be within 2" of another hole, and diameter of the hole shall not exceed 1/3 the depth of the joist. This is for dimensional lumber. For engineered lumber, you must follow the manufacturers instructions.

With regard to drilling top and bottom plates for HR's: I try to have my panels located in the basement directly below the stud bay where I drop to the basement. So nearly every home run runs overhead therough the first or second floor. In this case, I drill 2 or 3, 1 3/4" holes in the top and bottom plates for all my cables to drop to the cellar. There is no regulation for how close these holes may be to each other, nor how big they can be. Essentially you could cut out the whole top and bottom plate of this stud cavity as long as it were firestopped afterward. Every other hole that I drill for running wires is 7/8". Except for some alarm wires which get 3/8" holes.

edit: So I'd say 360 was trying to say what I just quoted above. Note that with engineered joists, the middle third of the span is where you can cut your largest holes. Just opposite of dimensional lumber.
 
ceknight said:
If I have enough HRs to fill several large holes in each joist, I start thinking about installing a subpanel instead. :)
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This is going to become quite an issue when 80 circuit panels become the norm...
 
j_erickson said:
edit: So I'd say 360 was trying to say what I just quoted above. Note that with engineered joists, the middle third of the span is where you can cut your largest holes. Just opposite of dimensional lumber.
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That about sums it up:grin:

LawnGuyLandSparky said:
This is going to become quite an issue when 80 circuit panels become the norm...
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Ewww. Can you imagine one of those with a dozen AFCI and GFCI breakers. Talk about a nest. What would an 80 circuit panel be rated at??
 
This is why you try and plan your house with sub panels. Less drilling and shorter runs. I rarely have just a main panel. If it is a two story house I always put one up there to serve that space. It also gives access to power from the attic above--if there is an attic.

The issue of drilling the joist in the middle versus the outer 1/3 of the joist (length dimension) does not usually apply to a small hole such as a 7/8" .
 
Dennis Alwon said:
This is why you try and plan your house with sub panels. Less drilling and shorter runs. I rarely have just a main panel. If it is a two story house I always put one up there to serve that space. It also gives access to power from the attic above--if there is an attic.
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The only reason I don't do this is because if someone wants to be able to set up circuits for use with a small gen-tran, they basically can't. If I do subpanels in a house, it will usually be a larger house than average. And then I'll usually run a pipe between main panel and subpanels.

The issue of drilling the joist in the middle versus the outer 1/3 of the joist (length dimension) does not usually apply to a small hole such as a 7/8" .
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I agree that a small hole usually is inconsequential. You'll sometimes find knot holes that large. But the building code doesn't address the size of the holes.
 
j_erickson said:
But the building code doesn't address the size of the holes.
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I believe the building code does address the size of the hole. That's way the plummers have to gussett their 3" holes. If you take a certain % of the joist then you have to repair it or gussett it.

I have never had a problem drilling 7/8' holes anywhere in the joist as long as I am in the width center.
 
clayton said:
what doesit mean to gusset the joist?
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It could be a metal plate used to strengthen a joist but it is usually a piece of plywood added to both sides of the joist to reinforce it. This allows you to drill a larger hole. The plywood would be as wide as the joist but about 2' long.
 
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