Rules and Guidelines
Want to participate in the discussions? Please read our Community Rules and Guidelines. Need some help? Visit Support and Answers.

  • State Suggested Helpful Answer
  • Replies 36 replies
  • Answers 1 answer
  • Subscribers 38 subscribers
  • Views 4404 views
  • Users 0 members are here
Options
You may also be interested in

is a discontinuous CPC, where all accessory points are Zs good, on a RFC, with no RCD protection, potentially dangerous or just needing improvement ?

psychicwarrior

as time moves on and opinions shift - especially via pressure from changes in Regs, H&S, CP Scheme influencers;   what was once safe is now not safe and all that !

e.g some now may consider the lack of RCD additional protection to skts  (even if everything else is ok)  is a potentially dangerous situation, where as previously that may not have been the case; same goes for lack of RCD to lighting circuits and even more so if circuit serve/pass a bathroom .

therefore, to the subject question as written ...  what's the consideration 'today'  please ?

and then, same question but where RCD protection on the RFC is present ?

and best wishes to all for a lovely day

Habs

Parents
  • 0

    I recall back when I did inspections that such a circuit would not comply if it was protected by a BS3036 fuse but would comply if protected by a BS3871 or BS60898 mcb. Since when has this changed?

    I think there was a very common attitude that only Zs was important when using MCBs - and c.s.a. could be ignored (nothing in BS 7671 itself supported that, but a lot of guidance seemed to make that assumption). Even today saying 1.5mm² c.p.c. is OK on a B32 is a bit dodgy - as the generic energy let-through numbers from BS EN 60898 only seem to agree with that for devices rated braking capacity up to 3kA. For higher fault currents (remember than for the general case we might be looking at anything up to 16kA at the intake) or on paper even sub 3kA fault currents but with higher rated MCBs, there's nothing general on paper to say it's OK. Individual manufacturers of MCBs might well quote lower figures for their products, but that's not something that can really be relied up on in the likes of the OSG unless you can show that it's true for all BS EN 60898 devices.

    No doubt many years of UK practice suggest the actual problem is small, but that doesn't really demonstrate BS 7671 compliance.

       - Andy.

Reply
  • 0

    I recall back when I did inspections that such a circuit would not comply if it was protected by a BS3036 fuse but would comply if protected by a BS3871 or BS60898 mcb. Since when has this changed?

    I think there was a very common attitude that only Zs was important when using MCBs - and c.s.a. could be ignored (nothing in BS 7671 itself supported that, but a lot of guidance seemed to make that assumption). Even today saying 1.5mm² c.p.c. is OK on a B32 is a bit dodgy - as the generic energy let-through numbers from BS EN 60898 only seem to agree with that for devices rated braking capacity up to 3kA. For higher fault currents (remember than for the general case we might be looking at anything up to 16kA at the intake) or on paper even sub 3kA fault currents but with higher rated MCBs, there's nothing general on paper to say it's OK. Individual manufacturers of MCBs might well quote lower figures for their products, but that's not something that can really be relied up on in the likes of the OSG unless you can show that it's true for all BS EN 60898 devices.

    No doubt many years of UK practice suggest the actual problem is small, but that doesn't really demonstrate BS 7671 compliance.

       - Andy.

Children
No Data

Join us to get the best from IET EngX.

Joining EngX lets you personalise your experience so you stay up to date on the topics that interest you, plus you’ll be able to make connections who are looking to collaborate, exchange ideas and more.

Join us Not now

Community Rules & Guidelines