Harmonics and tripping RCD

Marvo · Jun 3, 2014

I think there's a dislike for them because they tend to be skittish and cause nuisance tripping, especially some of the earlier generation products. I know they're pricey, we had a spec for a panel with arc fault protectors and I was taken back when I saw the suppliers quotes.

davesparks · Jun 3, 2014

What exactly does an arc fault circuit interrupter detect? I should have thought any fault which creates a short circuit is going to create an arc and so your fuse or whatever will operate.
I get that faults can occur which cause an arc but don't cause the OCPD to operate, but how do they detect them?
I am assuming it needs some pretty complex electronics to detect the little fluctuations you get from something like a loose termination? How reliable could that be, bearing in mind how reliable the fairly simple RCD is?

mike the sparky · Jun 3, 2014

There is a 300mA RCD at the main distribution. I've been told a type B RCD may help. The leakage was measured at 200mA + on start up. The pumps are in a lake where fish and birds are present so I think a RCD is required in this situation.

Marvo · Jun 3, 2014

It's only livestock you need to protect with RCD's, the fish and the birds can look after themselves without assistance.

Engineer54 · Jun 3, 2014

Marvo said:
I think there's a dislike for them because they tend to be skittish and cause nuisance tripping, especially some of the earlier generation products. I know they're pricey, we had a spec for a panel with arc fault protectors and I was taken back when I saw the suppliers quotes.

Here's one report worth reading.

AFCI Why I Have a Problem With It

Note, to this day the only ''Approved'' test that can be applied to these AFCI breakers, is to push the test button!! Now i don't know about anyone else here, but that just doesn't instill much confidence, especially when you read observation reports like the one attached here, where they failed miserably to get any of the AFCI breakers to trip!!