Surge arresters

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ggunn

PE (Electrical), NABCEP certified
Location
Austin, TX, USA
Occupation
Consulting Electrical Engineer - Photovoltaic Systems
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 said:
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.
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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
 
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.
 
That is kinda what I figured. What about downsizing the neutral per 705.28(C)(2)?
 
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