Bringing Zs value down

onions1066 · Dec 22, 2013

Just a quick question, need to add some lighting to an existing circuit, during Pre tests found zs value exceeds maximum permitted, it is a long circuit to be fair around 200m, it is 1.5mm twin. It is on a 10amp type b at the minute cant drop it to a 6A due to the amount of fittings on the circuit. There is a sub board half way round the building in the lift motor room I have the choice of re feeding the second half from this board which is possible but the other problem is it has a 110v emergency back up supply to each fitting which is the same length. Would it be deemed acceptable to pick up a 4mm earth from the sub board half way round into the circuit to bring the zs down? I really can't think of another way around this unless anyone has an idea?

Plonker 3 · Dec 24, 2013

Nic Owen has a new alias on here too

spark 68 · Dec 24, 2013

Which one was Lofty ?, there has been quite a few dipsh*ts on lately I cannot keep track

malcolmsanford · Dec 24, 2013

And hopefully some tasty remedials as well.

Funny enough I have done a few remedials for my lasses nursing homes, most were the dreaded BS 3036 semi enclosed boards that over the years have had MCB conversions one and the covers cuts exposing the copper bus.

Not sure what our thinking was in the good ole days but you go in and find about 4 or 5 8 way boards all on different phases, so I've been stripping them out and fitting Merin TP & N Boards and also installing EM lighting for the homes has a few have fire audits and the photoluminescent signs were deemed inadequate................never realised what a minefield EM lighting is now a days

Gone are the days of sticking a few bulkheads up in corridors and escape boxes over doors

GLENNSPARK · Dec 24, 2013

spark 68 said:
Which one was Lofty ?, there has been quite a few dipsh*ts on lately I cannot keep track

he was the one that used to ask really stupid dumb questions about the most basic stuff.....like really basic....

should never be let loose on the tools.....never..

spark 68 · Dec 24, 2013

Regs was the one I thought you meant, reckoned he was a Plod the To$$er, lol

malcolmsanford · Dec 24, 2013

GLENNSPARK said:
he was the one that used to ask really stupid dumb questions about the most basic stuff.....like really basic....

should never be let loose on the tools.....never..

I remember my old deputy engineer saying something similar to me

GLENNSPARK · Dec 24, 2013

malcolmsanford said:
And hopefully some tasty remedials as well.

Funny enough I have done a few remedials for my lasses nursing homes, most were the dreaded BS 3036 semi enclosed boards that over the years have had MCB conversions one and the covers cuts exposing the copper bus.

Not sure what our thinking was in the good ole days but you go in and find about 4 or 5 8 way boards all on different phases, so I've been stripping them out and fitting Merin TP & N Boards and also installing EM lighting for the homes has a few have fire audits and the photoluminescent signs were deemed inadequate................never realised what a minefield EM lighting is now a days

Gone are the days of sticking a few bulkheads up in corridors and escape boxes over doors

thing is though Malcolm is you cant really fail em for that as if you look at that gap that i know your on about around the plug ins....less than 13mm so it still meets IP4X....

i carried out some condition reporting on several stalls in Leeds city markets where the council had sent someone round from ARUPs....this guy had been instructed to fail stuff when carrying out his visual reports....several highlights included his fail given to some pVC trunking with damaged lid....containing twin....should`v been no code

another one was no RCD...which he failed....in my world thats a 3

the question of the IP rating on metal clad 4 way wylex boards using a mixture of BS3871s and BSEN60898s plug ins was again given a fail by this man who (according to the stallholders) spent all of 2 mins standing at the edge of the stall....then failed it..

well...to give you an example the lowest global IR i got was 77 Meg...

Ok there were a few things like a bonding cable piggy backing (tie wrapped) to a pipe...a non-conformance...but hardly anything to start flapping about is it...

cables behind wooden cladding without any earthed mettallic protection..and no RCD....a 3

stuff like that really....
anyway...the council have my reports now for the stalls i did...

general condition: satisfactory for all 5 of em...

GLENNSPARK · Dec 24, 2013

spark 68 said:
Regs was the one I thought you meant, reckoned he was a Plod the To$$er, lol

oh `im...

came in here and openly addmitted he wasn`t an electrician....but visited forums in order to gain info on how to do this, that and`t other.....

worst thing is though is there were folk just handing it out....

malcolmsanford · Dec 24, 2013

I would agree with you glen but to be honest this was one of the CUs and I agreed with the lad that changing it was the best option in this case, that is bare copper on the right

[ElectriciansForums.net] Bringing Zs value down

GLENNSPARK · Dec 24, 2013

malcolmsanford said:
I would agree with you glen but to be honest this was one of the CUs and I agreed with the lad that changing it was the best option in this case, that is bare copper on the right

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yep..thats `em malc....

thing is i looked at them in the market...i didn`t like the fact that 2 of the stalls were clothes shops...with metal clothes hangers....

i constructed a small wooden cupboard around one of them...put a hasp on it so it was lockable...just in case the council officials came round....

i mean it didn`t fail if you apply BS7671 to it....but as you suggest theres also the common sense thing as well as those likely to use the install...unskilled/uninstructed person/s not under supervision n all that lot...

i agree those old enclosures are a bit dicey arn`t they....

i suppose this is what happens when the lid is just done away with rather than an effort made to cut it to allow the breakers to come through...

i always keep them plastic lids off these boards whenever i do a board change and i come across them...

Engineer54 · Dec 24, 2013

Wylex actually made retro fit covers for those rewirable 3036 boards that were converted to HRC fuses and MCB's, but only ever saw one or two instances where they had been provided by the electrician making the conversions....

GLENNSPARK · Dec 24, 2013

Engineer54 said:
Wylex actually made retro fit covers for those rewirable 3036 boards that were converted to HRC fuses and MCB's, but only ever saw one or two instances where they had been provided by the electrician making the conversions....

its because they see it as an unnecessary expense eng....

Engineer54 · Dec 24, 2013

GLENNSPARK said:
its because they see it as an unnecessary expense eng....

Maybe, but most of the electricians that i've spoken too, didn't even know they existed!! lol!!
Hense why you see original covers that have been cut out to accommodate the extra depth of the retrofitted OCPD's...Better than nowt i suppose!! lol!!

GLENNSPARK · Dec 24, 2013

Engineer54 said:
Maybe, but most of the electricians that i've spoken too, didn't even know they existed!! lol!!
Hense why you see original covers that have been cut out to accommodate the extra depth of the retrofitted OCPD's...Better than nowt i suppose!! lol!!

i`v come across a few of them what your on about eng..

now, i wouldn`t have a problem adapting the existing cover to suit.....but would not do it `rough`...as most of em i have come across are.....nothing wrong with getting a file around it is there after you have created the exits for the MCBs to come through...is there...