Box fill refresher

[Jeff Remas]

*This is a box fill calculation question only and nothing else*

While inspecting the unfinished basement for a client you come across a 4" square x 1-1/2" metal box that is fed with one 14/3 NM cable and one 12/2 NM cable. The box has one duplex receptacle and one single pole switch. As you are noting the missing cover for your report you look inside and easily see that the equipment grounds are attached to the box with a ground screw and properly attached to the devices. The NM cables are secured with a single cable clamp.

The client states "There sure are a lot of wires in there." and this gets you wondering if the box fill is compliant with the NEC.

Is it?

[Jerry Peck]

Jeff,

That's not something home inspectors check and calculate out.

Thus, to answer the client, the answer might be: "Yep, sure does look like a lot of wires in there, have the electrician check it out when they are on-site doing all the other things on the report."

Absolutely no need for a home inspector to go further than that.

[Jeff Remas]

Oh my!! Jerry Peck responding to an electrical question..............who would have known! ;)

Anyway Jerry, yep, I agree it is way out of the scope of a HI but that is not the point of the exercise. It is to build knowledge base and understanding.

Any takers?

[Joe Driscoll]

One quick observation ... i have been an electrician for 25 + years and as of today, have never seen a 14/4. As far as the box , trade wise it sounds like a 1900 box, and as such it is permitted to have 11 conductors. However since there are 2 different wire sizees, i would be more concerned that the conductors outide of the grounds having any interconnectons.

[Jeff Remas]

Joe, look again. Something happened during cut and paste and the 14/3 got changed to 14/4. It is back to 14/3 again.

[Roland Miller]

over full by 2.5 cu. in.:)

[Roland Miller]

You can also add the cu in from the plaster ring if it is stamped on it. That is often hard to see or find once they are installed and the sheetrock is on. It probably won't make much of a difference with a 1/2 in ring.