Conduits in insulated walls

[RF Lighting]

A straight drop of 25mm probably would be ok, but to cover all bases I'd be installing 2no. 25mm steel conduit drops to each 35mm box. You'll also need to use box extenders to allow the plasterboard to fit.

Was my answer no good for you?

 

[SimonH2]

This is a complete waste of time and energy – most of which is way off the OP

I am done with this thread.

Well done BAS - you've done it YET AGAIN. It's not about standards, morality, etc, it's about knowing how to shut up when your contributions are past their sell by date and all you are doing is detracting from the message you've now failed to get across, YET AGAIN, by your OTT and abrasive attitude to others.

For as for the OP, another thought comes to mind ...
How are the boxes fixed in this "lego" system ? Long screws through to the concrete fill - bridging the insulation ? Sat behind the plasterboard, clamped by the accessory screws ? Something else ?

 

[DaveHerns]

I got bored with BAS's comments so I hit the "ignore" button. He can prattle away to his heart's content and I don't have to see it. Joy.....

 

[ban-all-sheds]

Well done BAS - you've done it YET AGAIN. It's not about standards, morality, etc,

It absolutely is when you try to tell me that I don't have a duty of care just because the law does not force me to have one.

 

[SimonH2]

And there you go yet again BAS - you have completely failed to comprehend what's being told to you, decided what you are being told according to what you want to criticise, and then blast away. Go read the post again, and don't blame others for your comprehension skills and your complete lack of ability to act in a civilised manner on forums - even when people have told you time and time again that you are being a complete dick about it and through your failure to understand this, failing in what you claim to be trying to do.

And no, you do NOT have a duty of care in this - those words have a specific meaning. Your own personal moral standards may mean that you feel you have an obligation to others (and I do not disagree with that) - but that is not a "Duty of Care".
But as I and others have pointed out before - it is the WAY you do it that makes your efforts self-defeating. Have you never heard the expression that "You catch more flies with honey than you do with vinegar" ? If you moderate your attitude a bit, then you'll find that you'll actually get the message across - rather than getting it ignored.

 

[ban-all-sheds]

And there you go yet again BAS - you have completely failed to comprehend what's being told to you, decided what you are being told according to what you want to criticise, and then blast away.

I have not failed to comprehend what you said.

You said I do not have a duty of care, and your justification was that the law does not impose one on me.

And no, you do NOT have a duty of care in this

Yes I do.

those words have a specific meaning.

Your own personal moral standards may mean that you feel you have an obligation to others (and I do not disagree with that) - but that is not a "Duty of Care".

Duty of care, obligation of care, responsibility of care....

But my obligation of care to you means that I have to make sure I do what I can to alert you to the problem that somebody is going to have to sign certificates, and that you can't.

would you all be telling me that I don't have such an obligation?

But as I and others have pointed out before - it is the WAY you do it that makes your efforts self-defeating. Have you never heard the expression that "You catch more flies with honey than you do with vinegar" ? If you moderate your attitude a bit, then you'll find that you'll actually get the message across - rather than getting it ignored.

The only "immoderate attitude" I have displayed here has been towards the useless project manager.

 

[SimonH2]

As my teachers used to say, QED. BAS, you really just don't get it.

 

[sparkwright]

Ban has got a point though. No electrician appointed, that's weeks away, then he wants to install conduits without knowing how many, what size, and what size cables to go in them.

This is for the electrician to decide.

 

[SimonH2]

Yes I agree, and have stated so earlier. But once again his "abrupt" approach has alienated the OP - so positive message lost because he just can't won't listen to anything that doesn't suit his prejudices.

 

[skenk]

....Cables don't have to be installed in safe zones where other protection such as an RCD exists...

I don't do my 3rd amendment update course until next month, but that's a new one on me.... mechanically protected, or earth shielded cable, or earthed conduit yes, but install normal cables anywhere just because they're on an RCD? No.

 

[EFLImpudence]

A bit like "cables less than 50mm. deep must be protected by an RCD" doesn't mean go deeper.

 

[jamesph]

Hello – it’s me again. Just popped back to see what happened after I left. And as I am now ignoring Bas I will respond to some of the questions raised or inferred.

RF Lighting: Thanks for your post – it was helpful but I thought a bit overkill – see later.

SimonH2: I did feel a bit guilty about leaving without thanking you as you have been most supportive. You did early on try to get me to ignore Bas but he just would me up – jumping to conclusions and getting his inferences all wrong.

Part of the problem (as you pointed out in post eight is that I am the “useless incompetent t**t”. I have designed and built this house so far almost entirely on my own with just the help of a labourer and a few additional hands when concreting the walls. Consequently it’s my baby. I am proud of it and I will be living in it for the rest of my life.

Neither is this house ordinary. It will be close to passive house standard with over 350mm insulation in the base raft, 214mm in the walls and 200mm in the roof – that’s not to mention triple glazing, airtight construction and appropriate levels of electrical generation on site. I’m not useless or incompetent – as for being a t**t others will have to judge.



I fully understand the need for competence and the involvement of a qualified person – but I don’t think I need one yet.

Part of the house consists of a wall of glass comprised of 8 glazed panels 1.5m wide x 4.6m high arranged as facets around a curve. 4 weeks ago just as I was about to place the order for this “curtain wall” the selected supplier (a Danish company) ceased trading. So far I have not been able to find another supplier at a similar price – actually the cost has doubled. Consequently I am now redesigning the curtain wall to reduce the cost of the glazing. This has also meant that part of the roof structure has also needed to be redesigned.

Consequently I have a delay of about 8 weeks to fill doing minor jobs that will not be spoiled because the build is still not watertight.

One of those jobs is installing conduit in the polystyrene walls. I will not be putting cable in at this time – just the conduit. I thought I had in my opening post indicated a number of options that would not phase (is that a pun) the electrician when he is appointed. And in any case plaster board will not be installed until after the electrician has finished first fix. So he will not be unable to see what has been done.

If my guess (educated guess – proposal based on research and knowledge?) of a 25mm conduit with two 4mm² T&E cables is wide of the mark them please tell me. It meets the fill requirements. You will note that I did not mention capacity. I know that the circuit will probably be de-rated so I am not attempting to specify the rating of the MCB – the electrician will decide on that.

I am only seeking some reassurance not a free design of an entire system.

Cost of cable: Yes 4mm² is more expensive than 2.5mm² but I only need half as much in a radial. The cable runs have been decided because of difficult geography and in most cases the return of a ring would be the same as the outgoing cable.

Simon also asked about fixing boxes. The walls consist of 57mm internal insulation, 147mm concrete core, 157mm external insulation and then brick slips or render. Cutting back the 57mm insulation to the concrete gives a clean surface to which a 48mm deep box can be fastened. So the box is only 9 mm below the surface. I suppose I will need box extenders when the plasterboard is screwed to the wall. The chase for the conduit will be less than 30mm deep, and the conduit will be held in place by dabs of expanding foam.

Simon you echoed my description of the walls as a Lego system which sort of indicates a Micky Mouse or Noddy construction method. It’s not. Take a look here…

https://www.google.co.uk/search?q=q...6xmuLMAhWhJMAKHU36BgIQsAQIQA&biw=1920&bih=983

http://quadlock.co.uk/

This will be 42nd post for what surely was a simple request clearly and (I think) intelligently presented. Whilst some of the discussion about the technical aspects has been interesting and no doubt informative much of the verbiage has done nothing to instruct. Please stick to the point. I have read a large number of threads on here and it is clear that often the discussion confuses OPs who do not have any real knowledge to start with. Yes, please warn of the dangers and the need for notification and certification, but please don’t further confuse the already confused.

And finally: Come on Bas, stop treating OPs like obliviots even if they are. (Obliviots: a new word for idiots who are oblivious to the fact that they are idiots.)

Kind regards to all.
Jim

 

[RF Lighting]

You could risk a single 25mm drop to each socket, but if for any reason this isn't enough then it's going to be a huge PITA to resolve at a later date, and in my opinion the time and cost of putting an extra drop of tube far outweighs the risk of a single drop being insufficient either during the initial installation, or as the installation evolves years down the line.

Also I would definitely use galvanised steel tube as it will never react to the polystyrene, it gives your electrician the option to omit RCD protection to wiring if he desires, it removes the risk of the wiring being damaged by nails or screws both during plasterboarding and day to day use of the property and it gives you a much better overall job.

Is it worth trying to save a few quid - which is nothing on the overall cost of the project at this stage, that could come back to bite you further down the line?

I saw the system you're using to build with on grand designs, and whilst I've never seen it in the flesh, it does look like a brilliant way of building, especially for sub terrainian walls.

 

[skenk]

if you've 8 weeks to get the conduit in, what's the delay in getting an electrician involved now? Even if they're just round to quote they will probably propose suitable/suggest preferred installation methods, which would likely save you money over forum-educated guesswork. As RF said one 25mm conduit per socket would be fine in the majority of cases but how is this conduit going to terminate into the box if the box is way back on the concrete 69mm from the wall surface? And won't that screw your insulation up?

plans, elevations, photos etc would be useful but it sound like you needs someone who knows what they're doing to design your installation

 

[SimonH2]

Part of the problem (as you pointed out in post eight is that I am the “useless incompetent t**t”. I have designed and built this house so far almost entirely on my own with just the help of a labourer and a few additional hands when concreting the walls. Consequently it’s my baby. I am proud of it and I will be living in it for the rest of my life.

Neither is this house ordinary. It will be close to passive house standard with over 350mm insulation in the base raft, 214mm in the walls and 200mm in the roof – that’s not to mention triple glazing, airtight construction and appropriate levels of electrical generation on site.

I am seriously jealous, it's the sort of think I'd love to do - but short of hitting the Premium Bonds jackpot it's not going to happen

I fully understand the need for competence and the involvement of a qualified person – but I don’t think I need one yet.

I'd agree with the others, even if the electrical work is still some time off, I'd be looking to get a sparky on-board sooner rather than later. As others have said, he'll know what's available, what "fits", what the regs are, and is likely to have some ideas.
Also, getting one on-board now means that if you find you "don't get on"* after a couple of days, you still have time to find another one without affecting the project.

* It does happen

Cost of cable: Yes 4mm² is more expensive than 2.5mm² but I only need half as much in a radial. The cable runs have been decided because of difficult geography and in most cases the return of a ring would be the same as the outgoing cable.

You can, subject to the cable rating for the specific installation method use 2.5 cable for a radial on a 20A (or 25A if available) MCB. That still gives you the saving on cable length, but without the cost penalty of going up a size. And 2off 20A radials are theoretically a higher supply capacity than 1off 32A ring. I'm part way through "decorating" in our small house - I haven't decided completely, but I'm thinking of going for a couple of 20A radials and possibly a 32A ring for the kitchen.
For me, part of that is the flexibility a radial gives in terms of I can break the existing ring up without having to mess up the decoration in rooms I don't want to start yet to maintain a ring. Otherwise I can see that there will be times when I want to do something with the ring, but it's difficult because ideally I need to do several other things at the same time. As I'll be replacing teh CU after I've finished the room I'm currently working in, I'll have the opportunity to add circuits for negligible costs.

Simon also asked about fixing boxes. The walls consist of 57mm internal insulation, 147mm concrete core, 157mm external insulation and then brick slips or render. Cutting back the 57mm insulation to the concrete gives a clean surface to which a 48mm deep box can be fastened. So the box is only 9 mm below the surface. I suppose I will need box extenders when the plasterboard is screwed to the wall.

I think that will make your boxes a cold spot - quite badly. In theory your concrete core will be at roughly the median temp between inside and outside - so picking easy numbers, if it's 20˚ inside and zero ˚ outside, the concrete core will be at around 10˚. So you'll have a cold box that will draw condensation in from the room.
As an alternative, how about if you got a sheet of 40mm PUR foam (aka Kingspan etc) and use 25mm boxes. Cut a rectangle of the PUR, and use it as a spacer between the box and the concrete. By my reckoning, that'll put the face of the box about 5mm below the face of the plasterboard (assuming you use ½" board) while giving some insulation. It'll also put the conduit holes in the boxes in about the right place to be behind the plasterboard.
I'd suggest getting a selection of boxes and have a look at where the conduit holes are - this is especially important if you use steel conduit as you don't want to be making offset bends in every drop (which would make pulling cables a bit harder). Be aware that round conduit will need couplers and bushes which are a little larger than the conduit - possibly worth getting a couple from the wholesaler so you can see the sizes involved and have a bit of a "trial fit". You need a "female coupler" and "male bush", the bush goes from inside the box and screws into the coupler, and the coupler (when you install the system) threads onto the conduit. PVC conduit is similar except that the coupler has a plain end for unthreaded conduit - but PVC conduit will also be affected by the polystyrene.

Also, how is the plasterboard fixed ? If it's anything similar to dot-n-dab then there's an opportunity to use plenty of mix so that the conduits are definitely in thermal contact with the plasterboard rather than arbitrarily "in insulation" - which changes the installation method as I understand things (note the disclaimer in my sig).

Oh yes, and have you seen the Boxguards from Yoozybox ? Have little spikes to mark the back of the board so you can accurately cut the holes I've done (networking) jobs in the past where the holes have been cut so large that the sockets don't cover them.

Simon you echoed my description of the walls as a Lego system which sort of indicates a Micky Mouse or Noddy construction method. It’s not.

I've seen it before, though not in the flesh.

Yes, please warn of the dangers and the need for notification and certification, but please don’t further confuse the already confused.

And finally: Come on Bas, stop treating OPs like obliviots even if they are. (Obliviots: a new word for idiots who are oblivious to the fact that they are idiots.)

Unfortunately he's been oblivious to all the suggestions made to him that while his message is important, the way he delivers it is counterproductive. Some of us have ideas about why he's that way, but I won't go there.
"obliviots" ... I like that