Cable routes

[JamesNorton01]

That's what I'd planned. Although as there's a grannie annex/office at LG floor the incoming will go straight to a switch at gd floor then back down to the annex (say 10 way board); up to a main one on the middle floor (1st) say 15 way then from this up again to the last one at 2nd floor (10 way).

For convenience and spreading everything as close to where needed as possible I had thought about a 5 way switch and putting the alarm and external lights on that as well as the feed to the annex and upper unit(s).

(The subtlety is is that owing to the sloping site the mains comes in at LG level) and preferred the switch at 1st so 3m straight up puts in a reasonable place. There are equal argument to keep it in the basement, all depends on who needs to access it in the eventuality that the flat get let out in the future etc...

RCBOs for the power circuits only perhaps...? (ie the ones that people use and touch regularly...?)

J

 

[riveralt]

I am not trolling and resent the suggestion.

No offence meant but you are asking questions on a DIY forum that you should be discussing with your electrician(s). And as someone has already said, if the electricians cannot answer them then get new electricians.
Furthermore your questions are posed in such a manner that while the answer has been given you seem to insist on continuing the debate.

More relevantly my battens will preferably run horizontal ie counter to the studs and so dropping down will give me head aches galore.

Your socket circuit will just come up from the (wooden) floor, surely?

As far as I can tell what "I" am doing is within the regs because it is a) deeper than 50mm and b) orthogonal with the accessories.
Agreed...? or not ?

Not! Why are you so hung up about the 50mm?
What is total size thickness of your walls?

So putting the quasi offensive stuff to one side the RCBO seems reasonable, but having said that so far I'm up to 30+ ways....

J

In designing this installation have you calculated your maximum demand? Or do you have three phase already planned?

 

[JamesNorton01]

- not sure anything's been answered yet.

- the reason the electrician can't give a straight answer is perhaps that there isn't one, its compliant as far as we can tell (n the absence of any reason why not here other than you saying "No") but just looking for the hidden pitfalls perhaps?

- DIY forum, fine. You don't know either. So why the officious "are you sure you know what your doing sonny?" stuff when I 1st posted? As I say 'am new here.

- Floor not always wood and would prefer to stay out of it as it makes the detailing of the fire resistance and VCL more difficult.

- the regs about safe zones apply where <50mm cover so seemed a good idea to keep to that even if in safe zones, esp. if a bit out of the ordinary...

- wall build up outside to in (mm): 20 cladding, 25 hztl battens, 25 vtl battens, breather membrane, 15 osb, 140 frame w/ insulation, 89 filled cavity, 89 frame w/ insulation, 13 fireline pb, VCL, 38 battens, 13 fireline, 3 skim or 15 clay plaster, paint. (Internal walls 89 studs double boarded each side wiring down centre of studs - but am not on about that condition).

- engineer mate did v. rough and ready calc, no issues with supply/load, many ways more symptom of required and preferred isolation than total load:
4 storey lights and power on each, + kitchen and utility, light and power to front out side and rear, showers, cooker, hob, PV array, ventilation, immersion, alarm, towell rails + spares and interlinks between units

J

 

[ban-all-sheds]

And in each of the paragraphs is a clause which gives permission to use an RCD to protect cables which are not installed in compliance with the other clauses in the paragraph.

No - there's no RCD get-out for 522.6.6

 

[JamesNorton01]

that is my reading also although at 1st glance you'd be forgiven for thinking so...

522.6.7 Where Regulation 522.6.6 applies [ie IF CONCEALED AND <50mm COVER]... ....a cable installed in accordance with Regulation 522.6.6 (v) [ie A CABLE IN A 'SAFE ZONE'], and not complying with Regulation 522.6.6 (i), (ii), (iii) or (iv), [ie BUT STILL WITH NONE OF THE OTHER STUFF] shall be provided with additional [key word: ADDITIONAL] protection by means of an RCD having the characteristics specified in Regulation 415.1.1.



J

 

[ban-all-sheds]

(Are you a quick typer or do you have a digital copy...? Former would be very handy in the office...)

Neither - I just knew that the relevant regulations were included verbatim in this: http://www.theiet.org/publishing/wiring-regulations/mag/2008/27-cablesinwall.cfm?type=pdf

 

[JamesNorton01]

...thwarted...



J

 

[riveralt]

- not sure anything's been answered yet.

I agree you haven't answered any questions yet.

- engineer mate did v. rough and ready calc, no issues with supply/load, many ways more symptom of required and preferred isolation than total load:
4 storey lights and power on each, + kitchen and utility, light and power to front out side and rear, showers, cooker, hob, PV array, ventilation, immersion, alarm, towell rails + spares and interlinks between units
J

So how many Ring Final Circuits, Radial Final Circuits, shower(s) circuits, cooker circuits etc - what are the cable lengths, voltage drops, what is the total demand. More than 100Amps?
As I said earlier, methinks you are worrying too much about cable depths without actually understanding the capacity of your proposed installation.
Rough and ready is the last thing you want - a proper and considered maximum demand calculation is actually what you need now before determining your cable runs.
Once you have this then you can determine whether your installation can be met with single or three phase. 30 circuits including a couple of showers is going to cause you capacity problems.

 

[bernardgreen]

And in each of the paragraphs is a clause which gives permission to use an RCD to protect cables which are not installed in compliance with the other clauses in the paragraph.

No - there's no RCD get-out for 522.6.6

I was taking it for granted that cables would be only run in "safe" zones. It was the lack of depth / mechanical protection that was "excused" by the use of RCD protection for such cables

 

[JamesNorton01]

"I agree you haven't answered any questions yet."...

...now who's trolling...?

We are actually building two houses and the engineer is the owner builder of the other which has essentially the same demand pattern, in fact slightly lower.

The rough and ready look for me was derived from a more detailed consideration by him and his electrician. They are slightly further on in program and have a different wall / ceiling build up so less an issue for them.

As such we have no concerns about overal capacity. As I said its modest but tall house with lots of things that either have to be separate or are desirable to be so, hence the over large no. of fuseways required.

So back to the question that you haven't answered. As far as I can tell the proposal is compliant but you say "No", care to expand?

J