Drilling holes in joists to run cable

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Ian Gills

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Due to the layout of my basement and mostly AC ducts some of my joists are starting to look like Swiss cheese with all of the small holes I am drilling in them to run cable.

I know holes must be drilled at least 2 inches away from the edge of the joists and can be drilled anywhere along the joists (notches have different rules) but am I missing something important here?
 

Ian Gills

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Sorry I did a typo. I meant AC not MC.

In England we very rarely get to buy armored cable. It's normally only used for commercial and security types of work.

So when I saw my house was wired with it in the US, I jumped at the chance to continue using it.

I like the way the sleeve is less susceptible to damage than Romex. I also feel a little more comfortable running it in semi-exposed spaces in my unfinished basement that might otherwise require conduit if I used non-metallic cable e.g. runs up the wall from light switches. The real benefits are when it is behind walls. The sleeve will provide a hint to somebody that may someday inadvertly start drilling into it. Not so with Romex.

Of course, not all gauges of wire are available in AC, and it cannot often be used outside, but 14 gauge and 12 gauge commonly are. I really do not see why professional electricians would use anything else. A little more work with AC brings a lot more benefits than Romex.
 
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Speedy Petey

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I like the way the sleeve is less susceptible to damage than Romex.
Completely valid opinion.


The real benefits are when it is behind walls. The sleeve will provide a hint to somebody that may someday inadvertly start drilling into it. Not so with Romex.
Not so much any more. AC is getting very hard to find. Pretty much everything is MC now with an AL sheathing. You will go through that almost as easily as NM cable with a drill.


Of course, not all gauges of wire are available in AC,
MC cable is available in any configuration you would want.


I really do not see why professional electricians would use anything else. A little more work with AC brings a lot more benefits than Romex.
You really think this, huh?
 

Ian Gills

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I really do think that. The metal sleeve looks so neat!

I have never seen commercial work done in Romex, so there must be something in MC/AC.

So come on Petey, treat your next customer to some nice cable. You'll enjoy it.
 
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hj

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As far as the holes are concerned, just consider them "lightening holes" the same as the ones in the beams of semi trailers. But, "The sleeve will provide a hint to somebody that may someday inadvertly start drilling into it." I would not put even a penny on any bets that it would save the wire. I had a carpenter who was installing shelving in a bedroom. He had a hard time getting the screw to hold, but eventually he drilled a hole in the steel gas pipe which was inside the wall.
 

Cass

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I had a carpenter who was installing shelving in a bedroom. He had a hard time getting the screw to hold, but eventually he drilled a hole in the steel gas pipe which was inside the wall.


Ha Ha Ha Ha...now thats funny...
 

Speedy Petey

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I have never seen commercial work done in Romex, so there must be something in MC/AC.
I see it quite often. Mainly wood framed structures.



So come on Petey, treat your next customer to some nice cable. You'll enjoy it.
No problem. I'll send you the bill for the extra cost.
Have you purchased any lately? It is considerably more than NM cable. And my labor will definitely be more.
I'm sure you won't mind paying.

Of course I use it when I feel it is needed and/or required. Like above a commercial drop ceiling.

You must not have worked with the stuff much. I hate it.
Pulling it sucks.
It takes up MUCH more space.
You have to use metallic boxes.
It does not go around corners nearly as easy.
And the oily finish makes your hands and clothes black and greasy.
 

Ian Gills

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You must not have worked with the stuff much. I hate it.
Pulling it sucks.
It takes up MUCH more space.
You have to use metallic boxes.
It does not go around corners nearly as easy.
And the oily finish makes your hands and clothes black and greasy.

You missed one of my favorites. Using the anti-short bushings and struggling to get the red indicator through the cable clamp.
 

Norcal01

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You missed one of my favorites. Using the anti-short bushings and struggling to get the red indicator through the cable clamp.

Just a FYI: Red heads (anti-short bushings) are not required on MC cable but IMO is a wise practice/cheap insurance, they are required on AC cable by the NEC. Keep it up.:)
 

hj

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The hole in the gas pipe was only funny when he heard the hiss and had to run outside to find the gas meter and turn it off. The gas line was right behind the drywall so we could not use a union, if it were proper to install one inside the wall. So we had to find a 1 1/4" left/right coupling and nipple, then cut and thread both sides of the pipe in the wall, and finally maneuver the left/right into place and tighten it, which anyone who has ever used one will testify is not the easiest thing to do to get both sides tight at the same time.
 

Ian Gills

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Surely you could have used a union and just installed an access panel?
 

Thatguy

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The wood fibers in the center of the joist are not under compression, nor are they under tension, so this is the ideal place to remove wood.
 

Frenchie

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Due to the layout of my basement and mostly AC ducts some of my joists are starting to look like Swiss cheese with all of the small holes I am drilling in them to run cable.

I know holes must be drilled at least 2 inches away from the edge of the joists and can be drilled anywhere along the joists (notches have different rules) but am I missing something important here?

From the "swiss cheese" comment, you might be missing the second part of the 2" rule: all holes should be at least 2" away from the edge of the joist or any other hole.

It sounds like you're definitely missing the basic guideline about boring holes in joists: every time you drill a hole in a joist, you weaken it somewhat; avoid boring unnecessary holes.

If you're using armored anyways, why not just attach it to the bottom of the joists?
 

hj

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The pipe was RIGHT behind the sheetrock, so the union nut would have projected into the room if I had used one. And the access door was not practical, since he still had to install the shelving at that point. Left/right was the only practical solution, even if it had not been required.
 
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