430.32

[Pinnie]

Where does the code say you cant round up a fuse for motor overload protection?

 

[augie47]

There is noting in 430.32(A)(1) that allows "next size up" so you would need to round down however 430.21(C) does provide for situations where (A) is not sufficient.

 

[don_resqcapt19]

Where does the code say you cant round up a fuse for motor overload protection?

When the code language says;

This device shall be selected to trip or shall be rated at no more than the following percent of the motor nameplate full-load current rating:

When the code says something like that, without an exception, that calculated value is an absolute maximum value. When using a fuse, you must select a fuse that has a rating equal to, or less than the maximum permitted rating. While the next lower standard size would be 15 amps, fuses are available in non-standard sizes and in this case you could us a FRN-R-17-1/2 fuse to get closer to the maximum permitted overload trip point.

 

[Pinnie]

So unless there’s an exception point you to 240.4(b) you cant round up?

 

[don_resqcapt19]

So unless there’s an exception point you to 240.4(b) you cant round up?

You can never round up where the code language says "not greater than" or "not more than", or something similar unless there is an exception that says you can. For example the language in 430.52(C)(1)(a), or Note 1 to Table 450.23(B). There are even examples in 240.21(B) and 240.21(C) that say, "Section 240.4(B) shall not be permitted".

 

[Pinnie]

You can never round up where the code language says "not greater than" or "not more than", or something similar unless there is an exception that says you can. For example the language in 430.52(C)(1)(a), or Note 1 to Table 450.23(B). There are even examples in 240.21(B) and 240.21(C) that say, "Section 240.4(B) shall not be permitted".

Ah I see. Thank you