What function is white oval conduit supposed to provide ?

[bernardgreen]

Chase out the last few inches of the slot for the conduit a little deeper.

Then the end of the oval conduit can go easily through the hole in the box and the curve in the conduit is still gentle enough to not prevent cable being replaced if needed.

 

[sparkwright]

Which just about confirms what I have been saying.
The obvious function of using conduit (to allow future cable replacement) is something you pay lip service to. If you are only "fairly likely" to be able to replace a cable, then that's a fair admission that it's not guaranteed. If you look at the photo I posted last, and imagine how little of the green overlaps the red if the box is sunk just a few mm deeper, and it's not hard to imagine that there'll be ****-all area left - is that what you mean by "line up reasonably well" ? And of course, since you'll have (in many cases) the ends of the cable plastered in (depending how hard the plasterer pressed) ...

So like I say, it seems that consensus is that it's quite possible (and not hard in general) to guarantee no problems (by getting the conduit actually into the box), but that's not common practice.

The main function of the oval conduit is still to protect it from damage whilst the plastering is taking place. I would say most pros use it (or capping), and a new house without it would look pretty rough to me without it (with the possible exception if the wall is to be dot and dabbed). There is no requirement to use it though. The replacement of cables is just a bonus, so no real effort in the installation of this is usually made. In many cases it would still be a job to do if joists or lowered ceilings etc prevent access.

To install a system that's conduit and rewirable you need a complete round conduit system wired in singles. This is not as common in flats etc now, for cheapness, lowered plasterboard ceilings, and that it was noticed that by the time a re-wire was due different demands needed to be met - eg more sockets, different heights and positions etc.

 

[holmslaw]

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[sparkwright]

To install a system that's conduit and rewirable you need a complete round conduit system wired in singles.

No you don't, every house I have ever wired can be completely rewired without any damage to plastered walls, because I've properly installed oval conduit.

I agree, but I should have mentioned a full round conduit system in singles could be rewired without pulling up floors and going in the loft.

If you want to rewire (t+e of course) oval conduit drops, you often need two conduits, mainly for sockets, particularly if long drops. I imagine this is part of what you mean.

 

[holmslaw]

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[sparkwright]

Who's necessarily talking about standard houses? I'm primarily talking about concrete blocks of flats, and jobs where round conduit is specified, like police stations, fire stations (I choose these as these are recent examples where I have installed much round conduit flushed in).

Houses are rarely (if ever) wired in round conduit, though council houses of around the 50s spring rapidly to mind.

The point I am trying to make is that if you want a system that can be fully rewired easily, without disruption, then round conduit in singles can be used.

I'm not larfing.

 

[SimonH2]

The replacement of cables is just a bonus, so no real effort in the installation of this is usually made.

I was coming to that conclusion.

In many cases it would still be a job to do if joists or lowered ceilings etc prevent access.

Agreed. I guess I've been spoiled growing up in a "real" house - with an attic for access to the upstairs lighting, and proper "floorboard" floors where you can fairly easily lift up a board or two for access underneath.

Until this house I've not had the problem of **** builders putting the end joist right against the wall. Just leaving an inch or so gap would have made so much difference with no effect on strength or rigidity. And of course in the flat there's a concrete floor so everything has to go through the ceiling with no access from above - now that is going to be a job and a half when it comes to sorting stuff out (it's still more or less as built).

I've been confused about the perceived problems raised in this topic with installing oval conduit. But its dawned on me that these problems are caused by not cutting deep enough chases, is that laziness or incompetance?

Normally the wall isn't chased at all. Once the bricks or blocks are up, the leccky will put the boxes where needed (they'll need sinking in, unless they use very shallow boxes for the light switches), run the cables and nail the conduit to the bare wall. The plasterer will then bury the conduit when the room is plastered in one go. Because the boxes are sunk, and the conduit isn't, the conduit isn't in line with the hole in the boxes, and the quickest and easiest way to deal with this is just dogleg the cables between conduit and box. I have seen cases where there is no overlap at all between the conduit and any hole in the box.

I think the answer to my original query is that it's just to hold the cable in place and stop the plasterer getting at it with his float. Future maintainability isn't really a consideration in a domestic setting - I'd guess because most is built down to a price rather than up to a spec.
And of course, the majority of house purchasers would never think to even ask about it.

I can't help thinking the use of 8x2 sheet for the floor is the same. This house is the first where I've had to tackle this, and also the first where the walls (stud) were put on top of the floor rather than the floor laid between the walls. Educational is one word I could use.

 

[JohnW2]

... its dawned on me that these problems are caused by not cutting deep enough chases, is that laziness or incompetance?

Exactly the same thing dawned on me. It could be for one of the reasons you mention, probably usually called 'economy' or 'expediency'. However, I think one of the main problems is that it's often the case that "they don't make plaster as thick as wot they used to", coupled with a desire (presumably for one of the reasons above) to restrict the chase to plaster depth, so as not to have to cut brick/block/whatever. In my (old) house, most of the plaster is at least 20mm thick - so I usually can get oval conduit to a sensible depth by only cutting plaster,although I've sometimes had to go a bit deeper in the vicinity of boxes, for the reasons being discussed.

What does surprise me a bit is that if conduit were installed as shallow as the OP seems to be talking about (per his photo), I would have expected the plaster to crack over it pretty quickly - and even that is asuming that one managed to cover it with plaster satisfactority in the first place.

Kind Regards, John.

 

[holmslaw]

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[SimonH2]

Normally the wall isn't chased at all. Once the bricks or blocks are up, the leccky will put the boxes where needed (they'll need sinking in, unless they use very shallow boxes for the light switches), run the cables and nail the conduit to the bare wall. The plasterer will then bury the conduit when the room is plastered in one go. Because the boxes are sunk, and the conduit isn't, the conduit isn't in line with the hole in the boxes, and the quickest and easiest way to deal with this is just dogleg the cables between conduit and box. I have seen cases where there is no overlap at all between the conduit and any hole in the box.

As someone that did a proper apprenticeship with structured practical and technical training, got meaningful qualifications, and have installed miles of conduit in all types of buildings.

I can honestly say I have rarely read such nonsense, but you have described exactly why you have problems carrying out a flush installation, you haven't got a clue.

Please go and re-read the thread, then come back and apologise when you realise just what an insult that is to me.

Because then you'll realise that what I describe above is what I observe as being standard practice and NOT what I prefer or do myself. You'll also see that I'm somewhat critical of it as a practice.

Of course, there's a big difference in the work involved in just nailing the conduit to the bare brick/block and chasing it all in to sink it. Since most work is (as I've mentioned earlier) done down to a price rather than up to a spec, I have to admit that it's hard to criticise someone for trying to get a job done in few enough man hours to make a profit.

 

[slaterlp]

Your original question was about what use is oval plastic conduit.

NONE, apart from possibly protecting from the mechnacial damage inflicted, prior to and during palstering.

Apart from that Its useless. Capping is just as bad, and the metal capping better at protection, only just.

I too have served an apprenticeship. Work course A and B , and registered as an approved Sparks 40 years ago.

Back then even for flat t and e, we used round steel conduit for the drops down the wall.

Grommet on the top, and bushed into the box. Easy to rewire and FAR better protected. It used to be insisted on by the councils. Labourers did the chasing, or we did it ourselves. I destroyed many a breeze/thermalite wall as an apprentice, by chasing too deep. LOL.

Anyway, I lament the drop in standards that see so called professional electricians claim, or even think that plastic oval is sufficient.

Yup its cheaper, and perhaps today, steel round is cost prohibitive to install.

BUT, I think that its mostly laziness for speed, combined with a much reduced thickness of plaster. AND I have worked with sparks who dont see any reason to even try and chase it in. Just bang in nails, bang 'em round the oval, and leave it to the plaster to really hold it all in place.

What's wrong with using a chaising machine, (with dust extraction) to sink steel round then? Or even the oval if you must use it.

OR chase and use plastic ROUND. Fill the chase with mortar. No? No I suppose not. Not today.

As for the plastic offering protection from the plasters trowl, well that's the least of the worries. Most good plasters are pretty good at being careful from my experience.

AFTER the job is done, and the house is lived in by mr/ms/mrs jones, it comes round to christmas.

They want to put up a decoration or several. So they put a nail in the wall, to below plaster depth and go straight through the plastic oval and into the cable.

Of course it was stupid to do that, and anyway didn't they know that there was a cable there? It was obvious as cables run vertical to the box and so they should have known. Well you and me would know, but its my observation that most people dont know. Why would they?

I still use round steel for rewires if I can. But like most today am compelled to use oval or capping on new sites. But I make myself a real pain in the ass by insisting on deep chases filled with cement.

 

[DetlefSchmitz]

If you want to use conduit in general, then oval is often good for horizontal runs , where chasing is only permitted to 1/6 th of the wall thickness.

 

[SimonH2]

Your original question was about what use is oval plastic conduit.

NONE, apart from possibly protecting from the mechnacial damage inflicted, prior to and during palstering.

<rest of post snipped>
I think that's a pretty good assessment. I agree, it seems that in pretty well all trades (including mine - I'm in IT) standards have drppped and there doesn't seem to be any pride in being a tradesman any more. Occasionally I come across some old stuff and often it's a joy to behold with cables all neatly dressed and stacked, clips individually made to suit the size/shape of the cable stack, and so on (this is marine BTW). The back of a switchboard would be a work of art that should be on display. You don't see that workmanship now, it's still fairly neat, but cables just bundled and banded is the norm.
And don't get me started on the last bunch of cowboy electrician I had the misfortune to work with on a customer site. Apart from everything else, I just couldn't understand how any supposedly trained electricians could abuse cables like they did - especially in the sub-zero temperatures we were working in.

AFTER the job is done, and the house is lived in by mr/ms/mrs jones, it comes round to christmas.

They want to put up a decoration or several. So they put a nail in the wall, to below plaster depth and go straight through the plastic oval and into the cable.

Of course it was stupid to do that, and anyway didn't they know that there was a cable there? It was obvious as cables run vertical to the box and so they should have known. Well you and me would know, but its my observation that most people dont know. Why would they?

Cough, splutter. The guy that wired my house must have been on the bottle prior to first fit. I wasn't going to say anything, but since you bring it up ...

I've been putting in a larger conduit from the TV point in the lounge right the way up to the attic - it's either that or wait till the tenant gets Sky in and fix the mess their installer leaves. From the socket it slopes 4" to the left by the time it reaches the ceiling. Not too bad, seen a lot worse, and it's still in a "protected zone" as that takes it above the power point. I assume the power cables slope left as well.
Then I pick it up in the bedroom above (where there's no indication of anything being in the wall), and it slopes 8" to the right to end up 4" to the right of where it started. That's 1/2" to the foot in slope It must have looked a right cockeyed mess at first fix, especially with the vertical mortar joints accentuating the slope. And it's not as if there's anything (joists etc) to go round - straight up would have done.

Oh yes, and there are two gas pipes buried in the plaster in the living room wall. I found them when I had boards up upstairs to do the electrical jobs. One's the 22mm main from the meter (up into the ground floor ceiling, first floor floor, void), the other is a 10mm drop to the fireplace.

But that's digressing into a moan about lack of skill and pride. I could grump for England, that lot of "Grumpy Old Men" on telly were just a bunch of wuss's - call that being grumpy

Needless to say, before the first tenant moves in, I'll be doing some diagrams of places to avoid drilling or nailing. Actually I think I'll do photos and shade the danger areas in red

 

[slaterlp]

Yup I agree with all that.

I used to do a lot of industrial big stuff. dressed cables can look a work of art. Panel work is something to be proud of, or used to be.

But even the domestic customer consumer unit as it used to be called, was once a source of pride to the installing electrician. All the cables were brought into the box in a sequenced and designed way.

Now they are bunched in anyway they happen to present themselves, which is purely random as few bother to actually plan this in advance anymore.

I have to admit the new designs dont make it easy, often too little room. But still a better job could be made than many of the abortions I have seen.

I enjoy coming across old installations, pre war and older where the cables were sometimes run in wooden channel. EVEN INSIDE the channel the cables were neat and tidy. Even though they could not be seen.

Cablles used to be clipped as if they were surface and on display, even in lofts.

Today, most sparks just throw them across the roof space.

Again I have to be fair, loft insulation has made life a nightmare in roof spaces, but some effort can still be made.

Yup I'm a grumpy old man too it seems.

 

[ban-all-sheds]

most is built down to a price rather than up to a spec.

//www.diynot.com/forums/viewtopic.php?p=37825#37825

I can't help thinking the use of 8x2 sheet for the floor is the same. This house is the first where I've had to tackle this.