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-   -   Making holes in junction boxes (http://www.diychatroom.com/f18/making-holes-junction-boxes-105642/)

WillK 05-26-2011 10:36 AM

Making holes in junction boxes
 
6x6 junction boxes don't come with 2" or 1-1/2" knockouts, so I need to make my own holes. What is the best way to do this, with a strong preference for keeping tooling costs low... I know that a hole saw is one of my inspectors suggestion (the other being a punch) but if I buy a hole saw, I want to be sure that my need for low cost doesn't end up being a waste because I get something where the teeth are gone before the first hole is done.

Multiple smaller holes connected by saber saw is one option I'm considering, but if I can get something that isn't going to cost $30 per hole that will come out cleaner that's the kind of suggestion I'm looking for.

jbfan 05-26-2011 10:47 AM

Will you have need for the hole saws after you finish this project?

Invest in a hole saw kit with the needed sizes.

A good kit should last you a very long time.

WillK 05-26-2011 10:58 AM

In a seperate project, I was going to use hole saws to cut the holes in my wood boards from inside the side attic to vent my soffits, but the hole saw I had bought for that lasted 3 holes. It was using a d-shaped hole to drive the saw off the arbor, and the D rounded out.

gregzoll 05-26-2011 11:49 AM

Punch & Die set will work. What do you mean that you need to make your own holes? If the 6x6 will not work, you will have to move up to a larger box then.

WillK 05-26-2011 11:59 AM

6x6 has 3/4" and 1" knockouts. Same with 8x8, it just has more knockouts. 10 x 10 has 1-1/2"knockouts, but no 2" knockouts and no knockouts in the back. Plus it's $48 to the 6x6's $15. Nothing is even getting spliced in any of these boxes, just making a turn so the garage feeder goes to the left and the 3-way switch loop goes up.

Buda556 05-26-2011 12:12 PM

These work well.
http://www.lowes.com/pd_291471-72068...0051&langId=-1
Little pricey but it should last for quite awhile.

These work good as well but not sure if it goes up to the size you need though.
http://www.lowes.com/pd_158038-72068...bit&facetInfo=

J. V. 05-26-2011 12:13 PM

The preferred method is a KO punch. But they are expensive. I would buy "Lennox" hole saws in the sizes required. Or get a set. When drilling metal, hole saws get super hot. Some oil will assist in saving the teeth. Taking it easy also is a great help.

I had an old electrician show me how to pack some fire stop into the hole saw about half way up. This also helps keep the hole saw cool. I have had one 1-1/8" hole saw for over 20 years and it still cuts. Not like new but it does cut.

powerfactor 05-26-2011 12:21 PM

the reason a 6x6 box doesn't have 2" knockouts in it is because it is not large enough to have a 2" pipe enter and exit it. for an angle pull like you describe the pipes have to be 6 times the largest size away from each other. I wouldn't gamble on the inspector not knowing that. :no:

WillK 05-26-2011 12:36 PM

It's not making any more of a turn than it would be inside an LB pull elbow. If I wasn't needing to have 14 gage THHN go up while the 1/0 XHWN goes to the side, I'd be using an LH fitting.

The old coot is the one that suggested cutting the larger holes in a 6x6 when I asked him for suggestions because the available boxes don't have knockouts larger than 1".

powerfactor 05-26-2011 01:21 PM

I am not on any of the code making panels,(meaning I don't write the code) just informing you that you are planning to violate the NEC. The lb you reference is another place many people go wrong as the 2" lb is not large enough for all wire sizes that 2" conduit is rated for. it is not unheard of to have to use a 3" lb on 2" conduit to pull in larger conductors, legally that is. :whistling2:

HouseHelper 05-26-2011 01:24 PM

Quote:

Originally Posted by WillK (Post 655377)
It's not making any more of a turn than it would be inside an LB pull elbow. If I wasn't needing to have 14 gage THHN go up while the 1/0 XHWN goes to the side, I'd be using an LH fitting.

The old coot is the one that suggested cutting the larger holes in a 6x6 when I asked him for suggestions because the available boxes don't have knockouts larger than 1".

You need a bigger box to have 2" pipe enter/leave... there needs to be a minimum of 12" between the two knockouts.

WillK 05-26-2011 01:37 PM

1/0 conductor diameter is 0.3249". Section 300.34 defines minimum bending radius for conductors as 8 times the overall diameter for non-shielded conductors. The junction box is 4" deep. So as long as it's less than 1/2" I should be fine. Considering a single 1/0 is can fit inside a 1/2" conduit, I'm pretty sure even if the insulater is included it's under 1/2".

I don't even need the 2" conduit for the underground run, I could've gone smaller and legally met conduit fill, I chose to go larger for my own ease of pulling the wires. Even once I get inside, I'm planning to use 1-1/2" EMT which is larger than the 1-1/4" minimum for the conduit fill requirement.

If there's something else I should be aware of, a code citation would be handy for convincing me.

busman 05-26-2011 02:02 PM

You need to look at the Article on Pull Boxes.

Mark

WillK 05-26-2011 02:19 PM

Quote:

Originally Posted by HouseHelper (Post 655420)
You need a bigger box to have 2" pipe enter/leave... there needs to be a minimum of 12" between the two knockouts.

314.28 reads as follows:

Quote:

314.28 Pull and Junction Boxes and Conduit Bodies.
Boxes and conduit bodies used as pull or junction boxes
shall comply with 314.28(A) through (D).
Exception: Terminal housings supplied with motors shall
comply with the provisions of 430.12.
(A) Minimum Size. For raceways containing conductors
of 4 AWG or larger, and for cables containing conductors of
4 AWG or larger, the minimum dimensions of pull or junction
boxes installed in a raceway or cable run shall comply
with (A)(l) through (A)(3). Where an enclosure dimension
is to be calculated based on the diameter of entering raceways,
the diameter shall be the metric designator (trade
size) expressed in the units of measurement employed.


(1)
Straight Pulls. In straight pulls, the length of the box

shall not be less than eight times the metric designator
(trade size) of the largest raceway.
(2) Angle or U Pulls. Where splices or where angle or U
pulls are made, the distance between each raceway entry
inside the box and the opposite wall of the box shall not be

less than six times the metric designator (trade size) of the

largest raceway in a row. This distance shall be increased
for additional entries by the amount of the sum of the diameters
of all other raceway entries in the same row on the
same wall of the box. Each row shall be calculated individually,
and the single row that provides the maximum
distance shall be used.
Exception: Where a raceway or cable entry is in the wall
of a box or conduit body opposite a removable cover, the
distance from that wall to the cover shall be permitted to
comply with the distance required for one wire per terminal
in Table 312.6(A).
The distance between raceway entries enclosing the
same conductor shall not be less than six times the metric
designator (trade size) of the larger raceway.
When


tran~posing cable size into raceway size in

314.28(A)(l) and (A)(2), the minimum metric designator
(trade size) raceway required for the number and size of
conductors in the cable shall be used.
(3)


Smaller Dimensions. Boxes or conduit bodies of dimensions

less than those required in 314.28(A)(l) and
(A)(2) shall be permitted for installations of combinations
of conductors that are less than the maximum conduit or
tubing fill (of conduits or tubing being used) permitted by
Table 1 of Chapter 9, provided the box or conduit body has
been listed for, and is permanently marked with, the maximum


number and maximum size of conductors permitted.

So first of all, we look at the exception for where it is opposite a removable conductor which points to table 312.6(a) where it says that a 1/0 conductor entering the back of the junction box opposite a removable cover requires 3-1/2" space. The 6x6 and 8x8 boxes I'm considering are 4" deep so that requirement is met.

314.28(a) 2 in the last paragraph talks about transposing cable size into raceway size, and since 3 conductors of 1/0 works out to requiring 1-1/4" raceway, 6x 1-1/4" is 7-1/2" so that sounds like I should be okay with the 8x8 box.

If something larger than 8x8 is really required, I'll just use an LB fitting, run the THHN in and out of the service panel and from there it will go to the switch, but the inspector didn't want that.

If I read anything wrong please explain.

powerfactor 05-26-2011 03:51 PM

Quote:

Originally Posted by WillK (Post 655432)
If there's something else I should be aware of, a code citation would be handy for convincing me.

If you are asking for and receiving help from people, don't act like an ass because I think I can speak for the majority here when I say that we don't give a damn if you are convinced or not. Take the advise or leave it, but just so you know, mine comes with a double your money back guarantee. :laughing:


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