Surge arresters

[ggunn]

Do I need to count a surge arrester breaker when I am qualifying a bus under 705.12(B)(3)(3)(3)? Under normal conditions it is neither a source nor a load. Also, when I am sizing a neutral per 705.28(C)(2) can I count a surge arrester as instrumentation?

 

[ggunn]

...can I count a surge arrester as instrumentation?

Or voltage sensing, maybe?

 

[wwhitney]

Do I need to count a surge arrester breaker when I am qualifying a bus under 705.12(B)(3)(3)(3)? Under normal conditions it is neither a source nor a load.

The phrase in 2020 NEC 705.12(B)(3)(3) is "all overcurrent devices on panel boards, both load and supply devices." I take "both load and supply devices" as an amplification of "all," and a contrast to 705.12(B)(3)(1) and (2), which consider only supplies to the bus, rather than a limitation on "all". So I would say unfortunately yes. Although you could try the argument that it is a limitation on "all."

Can you use a plug-on surge arrestor (not an overcurrent device), or piggyback your surge arrestor onto another breaker by splicing the conductors?

Cheers, Wayne

 

[jaggedben]

You should be allowed to ignore it, but the code language doesn't let you. That's my take.

I had the same plug-on thought as Wayne.

 

[ggunn]

That is kinda what I figured. What about downsizing the neutral per 705.28(C)(2)?

 

[jaggedben]

That is kinda what I figured. What about downsizing the neutral per 705.28(C)(2)?

I think you can ignore it as a load, yes.