# Design Limitations of an Electrical Engineer



## jar546 (Dec 2, 2018)

This is a good one for commercial electrical plan reviewers.  Where do you draw the line?  Where does the code draw the line?

You are reviewing a set of prints and associated documentation for the installation of an 800A standby generator for an assisted living facility which means no critical care systems.  Of note you see that the engineer specifies that the electrical contractor utilize the tap rule to provide 3 120v 20Acircuits from the ATS to the generator, 1 for the battery charger, one for lighting and a receptacle and one for a block heater.  There are no specifics for how or exactly where the ATS is to be tapped other than the tap goes to a safety switch to be mounted outside the enclosure where the conduit feeds to the generator.

Upon looking at the ATS provided documentation you don't see any integral hardware or fittings that are listed for tapping and again, no specifics from the engineer specifying changing of lugs adding P-Taps in order to complete the design.  When questioned, the engineer states that there is a note on the page directing the electrician to tap in accordance with local code requirements.

How would you handle this situation?  Are you OK with an electrician modifying a UL listed ATS  used as a service disconnect in order to to this without specs from an engineer?  Would you require that the engineer provide more detailed documentation on how to do this?

OR are you not OK with an engineer modifying a UL listed ATS without info or approval from the manufacturer?

What say thee?


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## steveray (Dec 3, 2018)

The engineer can't over rule the listing of an appliance/ piece of equipment......If you allow the engineer to do it, you allow the electrician to do it....


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## ICE (Dec 8, 2018)

They will need a field evaluation by a NRTL.  That's to modify it or to return it to the original condition.


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## jar546 (Dec 8, 2018)

OK, now that I steered this into the current direction, let me ask you these:

1) Is P-Tapping a conductor inside a panel a modification of a UL listed product?
2) Is changing the lugs of the main OCPD, ground or neutral bar modifying a UL listed product when the product itself has a listing of lugs for different wire sizes on the label?
3) Is mounting a safety switch/disconnect on the outside of UL listed equipment such as an ATS considered modifying it?  If so, do you hold AC condensing units to the same standard?


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