Amendment 2 and AFDD's

Dave Appleby · Oct 25, 2021

Hi.

Been reading the but around 427.1.7.

Does anyone have any idea on retrospective application?

Is this going to apply to every board change or just adapted to new builds and then as a C3 recommendation for everything else?

Given prices it's going to be a massive cost change on a board swop. Plus, I know for certain I'm going to have space issues with anything over 30 years old here in Fife.

Thoughts?

pc1966 · Nov 10, 2021

Aaron b said:
Perhaps we should install all power circuits with parallel conductors. For another amendment/edition, all accessories could include another live terminal for high integrity supplies.

Or return to the old Wylex board style of double screw terminals?

The Wago style of spring loaded ones were something I looked at with deep suspicion when they first came out, but it turns out they (with clean cable, etc) give a good reliable connection and no need for someone to have either proper experience and training, or to have and use a torque screwdriver to get reliable connections.

Dave Appleby · Nov 11, 2021

And nothing protects against THIS!

Big shout out to SPN who were brilliant yesterday. Onsite in under 90 minutes. Fixed in 30 more.

stevethesparks · Nov 11, 2021

pc1966 said:
Or return to the old Wylex board style of double screw terminals?

I'm a big supporter of that, particularly on the main switch terminals.

newfutile · Nov 11, 2021

the new Wylex boards have double screw terminals on them , which was a pleasant surprise

brianmoooore · Nov 11, 2021

Dave Appleby said:
And nothing protects against THIS!

Big shout out to SPN who were brilliant yesterday. Onsite in under 90 minutes. Fixed in 30 more.

Wouldn't any downstream AFDD that was loaded detect this and switch off. The current passing through the AFDD will be varying with an arc's signature whether the arc is before or after it.
If all loads were AFDD protected, the current through the cut out would fall to zero and the resistive heating would stop.

pc1966 · Nov 11, 2021

brianmoooore said:
Wouldn't any downstream AFDD that was loaded detect this and switch off. The current passing through the AFDD will be varying with an arc's signature whether the arc is before or after it.

That assumes it was arcing, and not just a few tens of mOhm resistance heating.

LastManOnline · Nov 12, 2021

pc1966 said:
That assumes it was arcing, and not just a few tens of mOhm resistance heating.

Yes. And not even a few tens of ohms is required. A half ohm (poorly tightened main fuse) will produce 30 Watts of heat in a fuse enclosure under full load. . Added to the heat produced by the fuse under normal working circumstances.

pc1966 · Nov 12, 2021

LastManOnline said:
Yes. And not even a few tens of ohms is required. A half ohm (poorly tightened main fuse) will produce 30 Watts of heat in a fuse enclosure under full load. . Added to the heat produced by the fuse under normal working circumstances.

I was talking of milli-ohms.

Say 50A (shower and/or cooker) & 0.05 ohm = 125W