NEC Table 450.3 Grouped Fuse Locations

[eeee]

Table 450.3(A) of the NEC states that fuses from the secondary of a transformer must be in the same location. I interpret this to mean the same mechanical room I guess??.

I plan to put my secondary fuses of my transformer in two separate mechanical rooms located 150 feet away from each other servicing two separate circuit breaker panels (that service two separate functionally different areas of my building).

Is this a violation of the NEC Table 450.3(A), note 2 as I fear?

I know I have seen this done in other facilities, but those facilites were built in 1945 most likely before this table in the NEC was produced.

 

[jim dungar]

Re: NEC Table 450.3 Grouped Fuse Locations

The basic intent is to treat the secondary of a transformer (with primary >600V) similar to a service entrance.

This rule is similar to (and has the same confusion as) the requirements of 230.71.

 

[charlie b]

Re: NEC Table 450.3 Grouped Fuse Locations

Originally posted by eeee: Is this a violation of the NEC Table 450.3(A), note 2 as I fear?

Yep.

I believe the rule cannot be met unless the two sets of fuses must be "within sight" of each other, meaning no more than 50 feet apart and no walls between them. I suspect that some AsHJ might require them to be within a hands reach of each other.

You could install a small panel with two sets of fuses right next to the transformer. From that panel, you run two sets of conductors to your two rooms. That way, it does not matter how far apart the rooms are.

 

[steve66]

Re: NEC Table 450.3 Grouped Fuse Locations

In addition, the secondary conductors might be taps. So you have to consider the rules for protecting conductors in addition to the transformer protection requirements. For example, see 240.4(F) and 240.21(C).

Steve