Where does it say how many cubic inches mud rings are?

[Eddy Current]

In the Mike Holt book it says to count a mud ring as 3.60 cubic inches but where are they getting that and what size mud ring? There are all kinds of different size mud rings?

 

[Hv&Lv]

It should be stamped on it.
Here is one with 7.3 Cu In.
http://www.hubbellcatalog.com/raco/RACO_datasheet.asp?PN=769

 

[jumper]

314.16(A) Box Volume Calculations. The volume of a wiring
enclosure (box) shall be the total volume of the assembled
sections and, where used, the space provided by plaster
rings, domed covers, extension rings, and so forth, that are
marked with their volume or are made from boxes the dimensions
of which are listed in Table 314.16(A).

 

[Eddy Current]

In the Mike Holt book it says to count a mud ring as 3.60 cubic inches but where are they getting that and what size mud ring? There are all kinds of different size mud rings?

But this will be for a test i wont have the physical mud ring in front of me, i thought it might show the different sizes in a table in the NEC.

 

[jumper]

But this will be for a test i wont have the physical mud ring in front of me, i thought it might show the different sizes in a table in the NEC.

No table exists for mud/plaster rings, only for standard extension box rings using Table 314.16(A).

 

[Eddy Current]

No table exists for mud/plaster rings, only for standard extension box rings using Table 314.16(A).

So i hope it is provided in the question.

 

[jumper]

So i hope it is provided in the question.

Yes.

 

[infinity]

If not provided in a test question I would not include it in the calculation.

 

[Hv&Lv]

So i hope it is provided in the question.

I didn't realize it was for a test.

From M. Holt in EC&M:If the cubic inch volume of the mud ring is not stamped on it or given in the problem, we cannot include it in the box volume.
http://ecmweb.com/code-basics/box-fill-calculations