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Electric Service Panel Splices

Home inspectors often see splices of branch circuits in service panels. Our reporting system ( has two places where inspectors could note the presence of splices in a service panel (Satisfactory or Further Evaluation Required). So, are splices in a service panel acceptable? If so, how many splices are allowed? How should you advise your client if there are splices in the service panel? These questions are the subject of many discussions among home inspectors. First we will look at the proper requirements regarding splices in a service panel. The National Electric Code states that enclosures for over current devices shall not be used as a junction box, auxiliary gutters, or raceways for conductors feeding through or being tapped to other switches or over current devices, unless adequate space is provided. Conductors inside a service panel shall not fill the wiring space to more than 40%, & splices and taps shall not fill the wiring space at any cross section to more than 75%.

An example of this using a service panel with a total wiring space of 64 square inches. The total fill should be no more than 40% of the 64 square inches of available space. That would equal 25.6 square inches. Any splices & taps should not fill any cross section wiring space by more than 75%. The detail at the beginning of the newsletter shows 4 cross sections. If the bottom section is 15 inches wide by 3 inches high that would be 45 square inches. So the total amount of space allowed for splices (including feed through conductors) in this section of the panel would be 33.75 square inches (45 x .75 = 33.75).

Making these calculations in the field for a home inspector is not necessary, however, as you can see, quite a few splices could be present in this panel. Whenever I see multiple splices, I try to determine why they are there. It could be conductors were cut short, or the panel was updated from a smaller box. Proper splicing is the subject for another newsletter.

Although splices are acceptable, if an excessive number of splices are observed, and the section appears crowded, a home inspector should make a note in the inspection report for the client to follow up with a qualified electrician.

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