Implications of the term 'recommended' in 7671

David Stone said:

but we must wait for the full report to be sure (or sure-ish).

I think "balance of probabilities" is used in the reports published so far in the public domain.

David Stone said:

It is likely it was caused by ignition of refrigerant (propane),

Ignition of foam insulating the manufacture of which used butane as a "blowing agent" I believe ... foam purported to have been ignited by ... ??

David Stone said:

However an iphone charger is unlikely to sustain a 3A arc

I'm not sure the arc needs to sustain 3 A ... I think the issues is series-arcs in wiring where loads of less than 2.5 A are supplied is at question.

Parallel arc (or, arcing "short" if you will) is another issue.

The OSG is a recommendation of what we might do to conform to BS7671, it is not the only way though.

The Part P approved doc is what we might do in order to comply with Part P (the Law) .

Again not the only way. 

Should we always follow the recommendations? Often yes in practical reality.

Must we always follow it? Well no not quite absolutely always.

When the original Part P approved doc came out it mentioned following BS7671 or an equivalent European Standard. That did not preclude working to Nigeran Standards if it is believed that Nigeria is a civilised safe country. You could work to USA standards if you believed that the USA is a civilised.......................................... Oh hang on , there are only two people in the world who believe USA to be civilised and they are not here today. Ok but you see the point.

We must separate the normative from the informative and make the judgement call.

Spot on Geoff. What a mess we find ourselves in over a definition.

Of course, the simplest option would have been to leave AFDDs off the menu altogether and just leave the decision as to install or not at the discretion of the installer and customer.