Cable routing, pipes and beams

[clydekeegan]

Hopefully one of you bright sparks out there can help me.

Firstly, a little about myself. I do have some electrical experience, though nothing recent and I did pass my 16th edition about 3 years ago in preparation of a career change that never happened. So I think I understand some of the theory but lack a bit in the practical.

Recently I have moved into a Victorian house with no central heating and wiring dating back to the 60s. So I have decided to put my 16th edition to use and rewire my house, my local building control office have been informed.

Question 1: I have created a riser in my house to run cables between floors (from basement to loft). The cables are being run in trunking (Method 3 with grouping factors taken into account) and then boxed in. I have plumbers coming around shortly to install a boiler and central heating. I intended to have the water and central heating pipes in the same riser. Are there any stipulated rules about the distance between cables and hot water pipes? If pipes are not touching but in the same riser or boxed in together will I have to take into account the temperature factor on the current carrying capacity of the cables? I'm sure cables and pipes must often be boxed in together or is that old practise.


Question 2
I thought I knew the rules for drilling holes in joists (5 cm down, no bigger than 25% of depth, 3 diameters apart, etc) but I have just noticed the following on this web site 'and the holes must only be drilled in a zone which extends 25% to 40% of the beam length from both ends.' So does this mean all holes have to be at least a quarter of the beam length away from either wall? It was my intention to run cables close to walls especially in the basement ceiling/ ground floor to allow for plaster board to be inserted between beams in most of the room to maximise ceiling height. So is this a regulation that the inspector will pick me up on?

Thanks

 

[Adam_151]

1) The phrase of the the day is 'mutual deterimental influence' this is something that you should take care to avoid (although don't expect the plumber to care very much...in the same way that rock beats scissors, pipe beats cable ), you'll also have to correct for Ca, yes


2) Cant remember off hand, have you got the 'electricians guide to the building regulations' about the same price and size as the OSG and explains everything you need to know about this type of thing

 

[bernardgreen]

Holes in joists should be as close to the centre line ( between top and bottom ) as possible as this is the area of timber under least stress. A joist under load and bending down has the top under compression and the bottom under tension.

The advice we had when we built was to try and not put holes closer than 2X from points of support where X is the top to bottom dimension of the joist.

 

[kevnurse]

Is there any way that you could partition the riser? Or, maybe, route the cables through a poly pipe (plumbers merchants) fixed a few inches away from the water pipes in the riser.

 

[TicklyT]

Here's some notes on notching & drilling joists.....
http://www.selby.gov.uk/upload/timber_joists_guidance.pdf

 

[clydekeegan]

Thanks for your help.

I have also made my own further enquiries. Basically both my queries are issues.
It will be safer to ask the plumber to bring the pipes up on the other side of the wall i.e. a seperate riser.

The holes in joists are suppossed to be in a zone between 0.25 to 0.4 of the joist span as in link above and other Building Control info. So I will have to re-think my cable routes and lift up even more floor boards.