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https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl DIY Forum >> Electrical Questions >> Trunking https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl?num=1099181794 Message started by John Davies on Oct 31^st, 2004, 1:16am

Title: Trunking
Post by John Davies on Oct 31^st, 2004, 1:16am

I am finally about ready to start my rewire, but have hit a snag at the planning stage.

The current consumer unit is under the stairs, which curve round 90 degrees. The existing cable runs to the upstairs go under the flooring of the understairs area, under the hall floor, and then up the other side of the hall wall, running between the living room and dining room doors in deep PVC trunking.

This is the only really sensible route - there is about 6 " (i.e., the width of a block wall) between the two doorways.) However, to have the conduit sticking out into the hall at this point as at present is a pain, and I am wondering about following the same route with the new cables but either rebating them into the wall and protecting them with standard metal protectors or doing a little better and using metal conduit. I could then plaster up and have a neat and tidy job. I am however concerned about anyone trying to, say, put up a picture in the dim and distant future and finding my main cooker feed, so want to protect the cables as much as possible........

So:-

1. How many cables can I run in one conduit? I am reckoning on running nine or ten cables in all, 2 off 1.5 and 7/8 off 2.5mm, plus cooker feed.
2. Do ordinary metal protectors now have to be earthed? I know conduit has to be. If so, is it sufficient to just screw a terminal to the metal, or do I need a special fixing?
3. Am I best off using standard, round 25mm conduits or is there a conduit on the market which is rectangular in cross section which would suit me better. In any case anything I use would have to be plastered over.

Thanks

John Davies

Title: Re: Trunking
Post by L.Spark on Oct 31^st, 2004, 1:31am

Heya John

A few points as im falling asleep ;D

Idea type of conduit for your sockets is oval conduit in 20mm, this is almost rectangular, but its well oval �:)

You would be looking at getting 2x 2.5mm cables in this most, for your rings etc.

Small metal protectors e.g. plates for protecting cables in notches don't need to be earthed.

I wouldn�t suggest using steel conduit unless you can thread it properly with appropriate equipment, Price of this would also set you back a fair bit.

Steel capping/channel is fairly cheap, and fairly nasty too, however this would do the job and give you the protection you require, obviously is not as good as a deeper chase and using round or oval PVC conduit in permitted zones

Otherwise PVC conduit and cables must be run in permitted zones which is vertically below and above sockets, and directly horizontally to accessories etc

Title: Re: Trunking
Post by tellondon on Oct 31^st, 2004, 2:41pm

Was you drunk last night LS or just very tired?
Half of that advice you gave is wrong
You cant run diagonally even if you place metal capping over cable
You cant use oval plastic conduit if the cable run isnt in a designated area

Title: Re: Trunking
Post by sparkyjonny on Oct 31^st, 2004, 3:39pm

You can use metal capping on a diagonal run - its earthed mechanical protection.
You may not need to thread steel conduit if you are only using straight runs (its in around 12' lengths)

Title: Re: Trunking
Post by L.Spark on Oct 31^st, 2004, 4:23pm

wrote on Oct 31^st, 2004, 2:41pm:

lol yes tired not drunk, anyway I don't have time to check the posts and check what I said so if it's wrong you advise him ::)

thx LS

Title: Re: Trunking
Post by dingbat on Oct 31^st, 2004, 5:10pm

wrote on Oct 31^st, 2004, 3:39pm:

You can use metal capping on a diagonal run - its earthed mechanical protection.

It's neither earthed, nor is it suitable mechanical protection.

Title: Re: Trunking
Post by JerryD on Oct 31^st, 2004, 5:38pm

Metal capping is not acceptable on diagonal runs. It must be metal conduit, metal trunking or metal ducting, in other words "fully enclosing" the cables. It must also be earthed if diagonal (and less than 50mm from the wall surface).

If it's in one of the zones (vert/horiz/150 from corner or ceiling) then no protection is required.

Title: Re: Trunking
Post by HandyMac on Oct 31^st, 2004, 6:21pm

Must admit, 50mm doesn't sound very deep to me! If I'm drilling holes in masonry it's not unusual for me to go deep to make sure the rawlplugs are biting on real brick and not some fancy plasterwork.....

Andrew

Title: Re: Trunking
Post by plugwash on Oct 31^st, 2004, 6:32pm

wrote on Oct 31^st, 2004, 6:21pm:

a hole is a very different thing from a channel

you can make a hole right through the wall to put a gas meter box in and the wall should be fine

but if you cut the wall in half from top to bottom i suspect you would have problems

Title: Re: Trunking
Post by JerryD on Oct 31^st, 2004, 7:35pm

wrote on Oct 31^st, 2004, 6:21pm:

I quite agree, I always drill about 60mm or more, in which case I could easily hit an unprotected and hidden diagonal cable :-[

Another of those silly rules from BS 7671 >:(

Title: Re: Trunking
Post by L.Spark on Oct 31^st, 2004, 9:07pm

My mistake, I gues capping really is of no use then :)

Title: Re: Trunking
Post by John Davies on Oct 31^st, 2004, 11:16pm

I am actually going straight up - from floor to ceiling - not diagonal.

From what you say, capping would therefore be ok, but earthed metal trunking or earthed round metal conduit would be best if I can make enough room for it.

Thanks

John D

Title: Re: Trunking
Post by L.Spark on Nov 1^st, 2004, 12:38am

Hey John

Trunking is only ideal if its surface, if you are running cables in the walls and want to use steel conduit that�s ok.

Title: Re: Trunking
Post by sparkyjonny on Nov 1^st, 2004, 10:58pm

wrote on Oct 31^st, 2004, 5:10pm:

It's neither earthed, nor is it suitable mechanical protection.

I didn't say the capping shouldn't be earthed - John already said he would earth it.
I know the regs mention mechanical protection, but little stands in the way of a masonry bit with hammer action and a determined driller! I'm pretty sure this could pass through SWA!

Title: Re: Trunking
Post by Beanzy on Nov 2^nd, 2004, 5:42am

But a masonry drill won't do diddly to metal conduit. You can tick away all day with your SDS on that and it'll just annoy you.

Back to J.D.s question. Can you not access between the floors from the under-stairs position?. If you're in luck and the joists run the correct direction you may be able to do away with much of the run and just go direct between the floors. May be worth a poke about. If not then, possibly go for singles in a conduit run, or two, right from the CU through the stairs/wall part of the run, and finish the conduit in a box once you're back in more normal territory. You can hire the benders for the conduit for about �7 to �10 +VAT per day. The conduit then could be channeled in the edge of the wall between the doors. Structurally there should be few consequences if this is just a block deviding wall. Just have a good look and maybe take some of the wall surface off to see how sound the core is first. once the conduit is cemented in place (not plastered, cement stronger between the doors) you'll probably be more solid than the original brick.

Title: Re: Trunking
Post by scotspark on Nov 5^th, 2004, 12:25am

bollox beanzy

i have seen on more than 1 occasion a sds masonry drill go straight into a steel conduit. you've got to be unlucky rnough to hit it straight on centre tho i reckon otherwise it'll probably bend past the side

Title: Re: Trunking
Post by Beanzy on Nov 5^th, 2004, 5:58am

Must have been a 'meaty' drill like one of the 4kg + ones. My Bosch GBH would never manage something like that, it'd 'bounce', but it's only 2.5kg. My other 240V drill may, but I only use that for chasing/chiselling so it's not really an issue as those bits wouldn't do in a conduit.

Do you use heavy drills for your normal stuff? I only ask as I've been thinking of getting a bigger 110v or battery drill, which would double up for the deeper chasing or 25mm bits, but thought they'd be a bit of a faff in terms of lugging to and fro and also using for longer fixes.

Title: Re: Trunking
Post by scotspark on Nov 5^th, 2004, 9:29pm

They were jus normal Makita drills, 110v about 2Kg not even sds.(I think) ::) it wasn't me I was jus left to sort it :'(

I have a 2.5Kg Bosch sds but would like to get a 4Kg+ one if I can get a job with enough chasing for me to justify another new toy ::) ::) I reckon it would be a bit ott for a couple of holes for red rawl plugs tho. been thinking about a batterry one but not sure if that would be any good for a lot of chasing or just drilling?????????????????

gotta stop before i talk myself into buying more stuff that i can't afford at the moment

Title: Re: Trunking
Post by tellondon on Nov 5^th, 2004, 10:53pm

I got myself the 4kg makita sds drill from screwfix for �280. its a different class, really powerfull, makes a 2kg hammer drill seem like a toffee hammer when your chasing, only slight drawback is is that it hasnt got reverse on it, then again its so powerfull drill bits dont usually get stuck

Title: Re: Trunking
Post by L.Spark on Nov 6^th, 2004, 1:36am

wrote on Nov 5^th, 2004, 9:29pm:

I have a 2.5Kg Bosch sds but would like to get a 4Kg+ one if I can get a job with enough chasing for me to justify another new toy ::) ::)

The bosch drills are quite good, I am really happy with my 2kg 110V, however I must get some SDS grease for it asap as its drying out ::)

A more robust battery drill would be a nice addition now, prehaps a keyless 24v bosch ;D

Title: Re: Trunking
Post by Beanzy on Nov 6^th, 2004, 2:05pm

The Bosch I have is battery and works fine, I even use it with meter long bits and it chuggs through the stone wall no prob. But for channelling I need something that can really stick the boot in I reckon.

Title: Re: Trunking
Post by scotspark on Nov 7^th, 2004, 11:49am

wot battery sds you got beanzy?

how much and what did you get with it?

if you don't mind me being nosey

I have used battery ones before with no problems drilling but didn't think they would be any good for chasing

Title: Re: Trunking
Post by Beanzy on Nov 7^th, 2004, 9:37pm

Bosch SDS 24VRE with a roto stop adaptor. It's good with a cranked channelling chisel or a flat chisel and copes ok with the Dash Chaser, but won't do the Box Sinker properly. I reckon next one will have to be bigger. The Bosch is great as a day to day drill. It came with 3 batteries and 6 bits for �290 two years ago, so they'd only come out then. Way cheaper now I believe.

Title: Re: Trunking
Post by scotspark on Nov 9^th, 2004, 11:17pm

is the one here like you have got? http://www.toolstation.com/search.html?searchstr=bosch+sds&Search=1

it's a bit more than you paid your price seemed pretty damn good

dash chaser??

Title: Re: Trunking
Post by The_Trician on Nov 10^th, 2004, 1:28am

If its anything like the 240v 4KG one which I have it'll be a belter - marvalous tool.

TT

Title: Re: Trunking
Post by Beanzy on Nov 11^th, 2004, 9:57pm

wrote on Nov 9^th, 2004, 11:17pm:

is the one here like you have got? http://www.toolstation.com/search.html?searchstr=bosch+sds&Search=1

it's a bit more than you paid your price seemed pretty damn good

dash chaser??

That's the boyo. Seems pricey there I got mine from www.sccdistribution.co.uk and they did the 3 batts 5 bits and the case etc .

TT it only comes in at about 2.5kg, so just lacks a wee bit for real 'head kicking' stuff.

Title: Re: Trunking
Post by scotspark on Nov 14^th, 2004, 7:01pm

tried to search there beanzy but it wont let me as i don't have an account

will do some looking about tho

Title: Re: Trunking
Post by Beanzy on Nov 15^th, 2004, 2:00am

Just had a check and they're only doing SDS bits at present. I think it depends on whether they buy in a bundle at a huge discount and kit out their installers then shift the remainder via the web site.

Will shout if I see any likely looking offers about.