am I missing something is 4d2 not also for T+e bs6004 giving 52A in trunking on a wall

I have just this weekend re wired a 10.8KW mira sport rated at 230v. it had been wired in 10mm 6242y, 30 mtrs through 600mm lagging in loft. no clipping. customer used it three times and it tinned the copper from the shower back to the 45A isolator which had a c50 mcb behind it ;-~ and went bang.

Needles to say, the isolator arc'd out, heated live conductor right back through the L side. horrific!

I re wired with 16mm, clipped direct well above lagging, fitted into 50A isolator switch and then terminated quite easy into shower.

Refering to your question, I would suggest looking at your thermal insulation factor and lenght of run.... that will tell you alot about the run you intend to install.

The 10.8 Mira sport is at 240V.
At 230V it is rated 9.9KW

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Regards,
Ebee (M I S P N)

Knotted cables cause Lumpy Lektrik

Sorry, that probably was a bit blunt!

(It just seemed an obvious example of Iz << In, especially for spurs).

- Andy.

LoL - so obvious that most people actually forget it i guess Andy

regards

OMS

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Failure is always an option

I thought Iz had to be greater than In. your right OMS its so obvious ive totally forgotten why it is ok to spur off a ring :s as the 2.5mm of the spur cable is proteacted by a 32A. someone please refresh my memory.

Overload and fault protection can be handled separately.

Provided Zs is low enough, a 32A device will protect 2.5mm2 conductors (indeed, the usual 1.5mm2 c.p.c.) from faults.

We still need to ensure that the cable isn't overloaded though - that can be done in any one of a number of ways:
o Nature of the load - if the load can't draw more than the cable can carry, then there isn't a problem and no further protection is needed (e.g. a known fixed load - say a shower)
o Downstream overload protection - the load could overload (e.g. a motor if mechanically overloaded), but the control equipment at the motor itself will disconnect the motor if it overloads - so the cable is protected overload even though it's on the supply side of the control equipment.

Spurs from rings are protected from overload by the nature of the load - a 13A socket can only be expected to supply a maximum of 13A (usually enforced by the plug fuse) - similarly double sockets are normally rated no more than 20A (even if you had two 13A loads plugged in running continuously - highly unlikely in a domestic environment anyway - the 2.5mm2 would still be fine in most circumstances).

- Andy.

ohhh yeah its all coming back to me. Cheers mate it all makes sense now

10mm on a 50Amp breaker it is.

just wanted to be comfortable in understanding it so i can explain myself if I have to.

Thank you very much all