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Old 06-26-2010, 04:58 PM   #1
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No knockouts


I want to install a second breaker box but there appear to be no knockouts in the 1st box. What to do?

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Old 06-26-2010, 05:05 PM   #2
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No knockouts


You can make your own with a hole saw.

Drill from the outside and make sure there is nothing in the way on the inside.

This would be perfectly code compliant if this is an indoor panel

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Old 06-26-2010, 07:01 PM   #3
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No knockouts


actually it is code compliant on an outside panel as well as long as a few rules are followed.
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Old 06-26-2010, 07:57 PM   #4
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No knockouts


So, what are the few rules for the outside box. I may be in that situation soon.
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Old 06-26-2010, 08:17 PM   #5
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No knockouts


First, the box must be rated for outside use. 3R is the most common rating for use outside. If you put a knockout in the top of in the side above any internal components, you must use a seal washer or some other means to seal the fitting against leaking water. Typically if you put the KO below any internals, there is no requirement to use a seal washer.

The point is to prevent water from getting onto the internals. If you notice, 3R rated boxes and panels are not weatherproof. They are what is called "rain tight" which simply means that water in the form of rain would simple shed off the box and not enter it where it could get onto the internals.
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Old 06-26-2010, 09:52 PM   #6
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No knockouts


Thanks for the info. Do you have a NEC citation for that?
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Old 06-26-2010, 09:58 PM   #7
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No knockouts


Quote:
Originally Posted by devlp View Post
I want to install a second breaker box but there appear to be no knockouts in the 1st box. What to do?
Step bits do a decent job. Also, with a step bit, you're purchasing a tool that can drill 10 hole sizes or so. Ten hole saws would certainly set you back more money.

I have both, but hole saws cannot easily widen an existing knockout because the pilot bit cannot get purchase on anything. Of course, step bits are typically stepped at around 1/8" of depth, so you usually won't want to use one to drill thick material.

Check these out:
http://www.amazon.com/s/ref=nb_sb_no...words=step+bit
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Old 06-27-2010, 11:14 AM   #8
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No knockouts


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Thanks for the info. Do you have a NEC citation for that?
not offhand but I will try to find something.


as to hole sizes. The hole size is not the "trade" or nominal size of the pipe. Trade size 1/2" would use a 7/8" hole. 3/4 would use a 1 1/8" hole. 1" would use a 1 3/8" hole and so on.

there are many sources on the internet to find the right size hole for any given size of conduit.

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