Two Questions

[securespark]

I am conducting a straw poll, if you like. Please take part, I need many responses!

I believe that RCD protection of a shower circuit is not a requirement of BS7671.

I also believe that MEB's have to return to the MET, not to a local CU fed off a sub-main.

Please say whether you agree or not & why.

The reason I'm asking is that many colleagues disagree on both counts, but cannot state any concrete regulations to back them up!

 

[ELZ4742]

well ill have a go....

I believe that RCD protection of a shower circuit is not a requirement of BS7671.
not now because the good folks on here have put me straight.

I also believe that MEB's have to return to the MET, not to a local CU fed off a sub-main

agree, i think....

reg 542 04 01, although this doesnt say you cant....

not much help, sorry!

 

[luminaire]

I believe it is not a requirement of BS7671 to have a shower on an RCD circuit.

MEBs to go direct to MET

 

[ELZ4742]

I believe it is not a requirement of BS7671 to have a shower on an RCD circuit.

MEBs to go direct to MET

i cant find where it says its a necessity to do this though

 

[scousespark]

RCD protection is not compulsory under current regs, BUT most manufacturers recommend using RCD.

I would say the MEB should return to the MET, but this is agin not in 7671.
When I was training I was taught to keep the MEB continuous and this would be easier if there is a single run to the MET. However, there may be times when it's not practical to do this, so running a separate MEB to a sub may be the better option.

 

[ELZ4742]

i do think theres a lot of grey areas when dealing with electrics, i mean theres things you can do in certain areas on specific installations and others you cant.... contradictary? yip indeedy.

 

[scousespark]

The regs are vague and give a framework to work in. Older versions were more like instruction guides and the IEE took advice to make the 16th the way it is.

Not sure there are things you can do in one installation, but not in others.
Can you give an example ELZ?

 

[ELZ4742]

ok, a 6mm gas bond is fine for tns on old instalation but not on new.

this is an nic-eic thing (checked today) but the regs state that it must be half the diameter of the main bond.

makes sense?

 

[scousespark]

I think this is bacause the regs are not retrospective. If we had to upgrade every installation, we'd not see our families for weeks at a time, or we'd have no customers.

 

[industryspark]

agree that the regs dont specifically require an rcd......but....... isnt there a reg (not got mine to hand) that says manufacturers instructions shall be followed or something like that...... and most manufacturers call for an rcd.

very grey area but i think this ones going to be put to bed by the 17th anyway.

 

[ricicle]

You beat me to it I-spark

 

[ELZ4742]

perhapes the next edition should go from brown to grey!

 

[industryspark]

ricicle wrote

You beat me to it I-spark

its normally me getting pipped to the post

 

[Spark123]

I believe that RCD protection of a shower circuit is not a requirement of BS7671.

Oh no, not again!!!
An electric shower is a water heater hence is not "other fixed current-using equipment" hence RCD protection is not a requirement of BS7671:2001.

I also believe that MEB's have to return to the MET, not to a local CU fed off a sub-main.

In a single building they need to return to the MET. In the case of a separate outbuilding they can run to a BEMT (building earth martialing terminal). The earth rail in a CU can be used as a MET or BEMT. In the case of PME the earthing cable between the MET and the BEMT should not be smaller than that of a MEB cable.

 

[RF Lighting]

I seem to remeber reading somewhere that you can take main bonding to a submain providing the CSA of the earth supply to the submain is greater than or equal to the CSA of the MEB, and the impedance from the main supply the the point of the MEB is low enough.

Personally I still take my MEBs back the the origin, as you have problems such as a submain becoming redundant in the future, and inadvertantly loosing the MEB.