"Point of Connection" To Tap, or Not to Tap" [RE-wrenches]

William Miller wrmiller at charter.net
Fri Sep 15 08:56:15 PDT 2006


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Bruce:

Are you installing a dedicated fused disconnect (which is exactly what the 
section requires)?

When you want to install on the load side, the usual hitch comes with this 
wording: "(2) The sum of the ampere ratings of overcurrent devices in 
circuits supplying power to a busbar or conductor shall not exceed the 
rating of the busbar or conductor."  We would assume that in most cases the 
ampacity of the conductor or busbar matches the ampacity of the service 
OCP, therefore you have no reserve ampacity, unless this is a residential 
installation, in which case you get 20%.  If you violate the section (2) 
above, you must connect to the supply side.  Yes, it is scary, but it is 
what the code requires.

To win a "pissing match" with the AHJ is a consideration of the 
personalities involved.  In many cases, if the inspector recognizes the 
authority of an industry expert, a print out of an e-mail or article by 
Bill Brooks or John Wiles may hold some weight in the argument.  I have 
also convinced inspectors in small municipalities by initiating a three way 
dialog with the main county inspector who was in agreement with my 
interpretation.  There are in some areas professional organizations of 
building inspectors.  If you know a member that has an open mind and can be 
convinced of your point of view, they could also exert some subtle 
influence on your recalcitrant building official.

Good luck and let us know how this works out.

William Miller


At 09:52 PM 9/14/2006, you wrote:

>Hi all.  Has anyone run into Article 690.64 being interpreted as
>prohibiting taps to the load side of the main service breaker?  One
>particular municipality is saying that, even with a fused AC disconnect,
>taps are not allowed because of Item B (1) which says "Each source
>interconnection shall be made at a dedicated circuit breaker or fusible
>disconnecting means."
>
>The only issue that occurs to me is the protection of the section of
>wire between the tap and the fuse in the AC disconnect.  Would it seem
>reasonable to size that section of wire equivalent to the service
>conductors?
>
>Has anybody else run into this?  How have you handled it?
>
>The municipality in question suggests tapping on the supply side of the
>main breaker, but that seems much less safe.  The current on the wire
>between the fused AC disconnect and the tap then only be limited by the
>overcurrent protection on the utility transformer, no?
>
>Thanks for you help.
>
>Bruce


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