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Thread: 30A Fusible Disconnect Switch w/ Copper Pipe used as fuses

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    Default 30A Fusible Disconnect Switch w/ Copper Pipe used as fuses

    I found a General Electric 30A/240V single phase fusible disconnect switch that was used as a local service disconnect for a hot water heater. It was fed from a 30A/2P breaker out of a nearby breaker panel. I noticed it had (2) 1/2" pieces of copper pipe installed in place of fuses. I'm sure the National Electric Code book would site this as a code violation. Would they accept dummy fuses ? Do you replace the copper pipe with fuses or replace the switch with a non-fusible type?

  2. #2
    Plumber jimbo's Avatar
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    I don't know if there is such a thing as a dummy fuse. I think it is called "copper pipe"!!

    You can most likely use a non-fused disconnect, but I don't see how it would ever be legal to bypass what is intended to be a fuse.

  3. #3
    Moderator & Master Plumber hj's Avatar
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    Default non fuse

    There have been people here who flatten a copper tube and then put it in the meter socket, after it was pulled for nonpayment of the bill, but I am sure the utility does not consider it a "dummy meter".

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    Electrician Chris75's Avatar
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    Either replace with fuses or dummy fuses, but get rid of the copper pipe.

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    Homeowner Thatguy's Avatar
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    The current to melt a piece of pipe like this was figured out on another forum. The connecting wires and everything else will melt before this does. I guess that makes it an "anti-fuse."

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    At least they used copper.


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    Electrician Johnny C's Avatar
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    Default 30 A fusible disconnect with CU pipe.

    Installing copper pipe in place of proper fuses or fuse blanks is a Code violation of 110-3(B). Use of the disconnect sw with other than a product for which it was tested and listed by the testing laboratory. I will not say I haven't done this in an emergency, but it is a Code violation even though the circuit breaker ahead of the disconnect is rated for the circuit size.

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    Homeowner Thatguy's Avatar
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    And if you want to make it into a slow blow fuse, fill the pipe with water before crimping. That way the water has to boil off before the pipe melts.
    All-in-all this is a very versatile circuit element.

    Just kidding.

  9. #9
    Moderator & Master Plumber hj's Avatar
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    Default fuse

    If the tubing is sealed so the water cannot leak out, neither will the steam. So the water will heat to a "superheated" condition, (not steam), until something ruptures and then there will be a 'mini' explosion as the energy is disipated in a matter of microseconds.

  10. #10

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    Violation NEC 2005 reference standard

    110.3(B)
    110.9
    110.10
    210.20(C)
    240.6(A)
    240.10
    240.60(C)
    240.61


    Take your pick. Remove and replace with the proper sized fuses
    http://www.inspectpa.com/forum/forum.php
    My answers are based mostly on the ICC codes. Advice given is my personal opinion and every person performing work should acquire a permit from his/her jurisdiction and get the work inspected. My opinions are not directions to follow for DIYs or professionals

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    Thanks for your help!

  12. #12
    Homeowner Thatguy's Avatar
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    Quote Originally Posted by hj View Post
    If the tubing is sealed so the water cannot leak out, neither will the steam. So the water will heat to a "superheated" condition, (not steam), until something ruptures and then there will be a 'mini' explosion as the energy is disipated in a matter of microseconds.
    So should I lay off all the employees I have already hired to start building these little gems?


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