But the breaker did trip after all

[mbrooke]

Mag Trip levels aren't as studied in the US , as elsewhere for residential protection.

The best it gets is explaining why the main OCPD tripped , and not the branch OCPD

Where this different, we'd have a much longer debate for you in this thread about the proper choices, as well as their incendiary expectations

That the Insurance industry has not delved into these specifics astounds me , given GC's will still be the major culprit if we installed AFD from 13.2KV all the way down to 120V circuitry


~RJ~

What is your opinion on mag trip btw? I notice you mention this a lot in relation to AFCIs and as you may know from my postings it is that very concept which has been of major interests to those who created the AFCI. If anything this could either prove scientific concept of marketing gimmick.

 

[kwired]

What is your opinion on mag trip btw? I notice you mention this a lot in relation to AFCIs and as you may know from my postings it is that very concept which has been of major interests to those who created the AFCI. If anything this could either prove scientific concept of marketing gimmick.

They are a big deal IMO. Long before they made us use AFCI's Square D QO breakers had (AFAIK) the lowest mag trip settings on their single pole 15 and 20 amp breakers of anyone, and they would trip in many situations where other breakers wouldn't, or at least a lot faster.

I still remember a demonstration unit they used to have for trade shows or other similar places that they could connect a short wire link creating a short circuit and it had a means to connect their QO breaker as well as other competitor breakers in series with the short circuit. The QO breakers always tripped leaving the wire link intact, all competitor breakers held while the wire link burned in half.

Sure seems to me like a big step in the right direction for protection from parallel arc faults, and we had this before we ever heard of the term AFCI.