National Electrical Installation Standards

Standards as High as Your Own

Thursday, June 18, 2020


Comments on CQD 06-08-2020


Comment: The disconnect in question may be just a work switch that is non-fused. Often those switches when dislocated from the base look like they have copper bars installed instead of fuses, and in fact they do. They are a work switch and are non-fused. In the  on position the, switch slide, pushes completely into the base , thus making contact. When the slide is withdrawn and turn upside down and reinserted  the switch is in the off position and does not fit completely into the base, thus the switch is in the off position. I suspect this is a non-fused work switch.  Gregory Arvanitis


Comment: Good Day! I read the Code Question of the Day each day and find it a great way to start the day thinking about the Code and how it applies. I believe your response to the CQD from Friday June 5th was not complete and could be misinterpreted. The question asked about copper pipe that had been installed in the fuse holders for the air conditioning unit disconnect at the back of the house. The response would indicate that fuses would always be required to be installed at this location. Article 440, Part II, requires a disconnect to be at the unit, but this disconnect is not required to have overcurrent protection within it. If proper overcurrent protection is being provided from the branch circuit panelboard, then no additional fuses would be required. The one problem I do see with the installation described is using copper pipe which is not in accordance with the listing for the fused disconnect.  Manufacturers do provide solid element, non-fused, units, commonly called "slugs" to install where fuses are not required. These slugs are rated for the full ampere rating of the fused switch. Thank you and keep up this excellent forum for the industry.  Chuck Mello


Comment: A set of fuses might not be required if the circuit is protected by an approved breaker (the big five are all approved) if the condensing unit is approved to be protected by a breaker (they almost all are). Then the question is limited to the fuse holders being listed for the “replacement fuse”. Odds are the copper pipe used has spread the fuse holders beyond their design and won’t hold the correct fuse anyway. Chances are good that’s why the pipe was used in the first place. So, it might be that the only correct solution would be to either replace the fused disconnect with a new fused disconnect and correctly sized fuses or replace the disconnect with a non-fused disconnect and ensure that the breaker is sized correctly.

Matthew Hermanson



Thanks to all our subsequent commenters on the Code Question of the Day and Response for 06-08-2020. The additional information is certain to give the readers other things to consider in this scenario, in addition to copper plumbing pipe not being an acceptable installation. 

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