Equipment Spacing

[DavidAVaughan]

I have a situation where a 112.5kva step down transformer sits across the electrical room from the Main Service Switch board. This is a 480/277 volt system. The distance between the outer enclosures of both items is 42" with all covers in place. This is a new construction situation. Does NEC Article 110.26, condition 3 require 48" from cover to cover or does it require 48" from the live parts to the opposing enclosure cover, when one or more than one cover is removed and live parts exposed?

 

[charlie b]

The last sentence of 110.26(A)(1) clarifies that the distance is to be measured from the location of the live parts, if there is no enclosure, and from the face of the enclosure, if there is one.

There is room for debate on the other part of your question. My view is that a transformer does not require live work, and therefore is not considered to have "exposed live parts." That puts you into Condition 2. I anticipate disagreements here. So stand by.

Welcome to the forum.

 

[infinity]

I agree with Charlie.

The transformer enclosure would be considered as a grounded part which for condition #2 would apply. For 480 volts that would be 42" working space.

 

[ron]

There is room for debate on the other part of your question. My view is that a transformer does not require live work, and therefore is not considered to have "exposed live parts." That puts you into Condition 2. I anticipate disagreements here. So stand by.

We have feeder terminations IR scanned while they are energized, because to do them de-energized, would be .... well silly. Many would consider that [FONT=&quot]requiring live work, so 48"[/FONT]