clipped cable in chase

[ianphilip007]

hi guys

just wondering if anyone knows current best practice for running cables in plastered chases?

i have always clipped direct to wall and capped , but on reading some past posts many seem to use either 20mm conduit or oval tubing and class clipping to the wall as a DIY approach. i like the idea of using a conduit or tube (easier to install or remove cable) but surely it would change the ref method and derate the cable? or is this disregarded due to being a short run, that said a socket to a ceiling could be over 2m.

many thanks

 

[Electro-tech]

I would stick with capping method C, as you do have the choice of current carrying capacities may be higher,but not with method B.

 

[telectrix]

if using oval tube, i would not derate the cable. it's only like having capping under and over, but easier to replace cable if ever required.

 

[SPARTYKUS]

Clipping to wall is fine. I do this if dot and dabbed. Only cap if to be plastered onto as this is (99% of time) cappings use-to stop plasterers trowel damaging cable.

Oval tubing is a dream to find if rewiring and i should start doing it more often!

 

[ianphilip007]

i see your point telectrix, just when reading OSG caping/conduit enclosed in a wall would be ref meth b. which for 1.5mm lighting circuits would be fine, but for a ring main circuit 2.5mm would be right on the limit. so i guess its like you say it depends on which ref method you use .

 

[Electro-tech]

Maybe a oval tube but,could it be the same as a flattened conduit.Then would we go down the road of grouping factors or how much percentage of the enclosure should we take up ?

 

[ianphilip007]

i guess its like alot of things down to how you interpret the regs ???

 

[rocker]

Personally I always use oval, slide it on, put the bow toward the wall, clip in the top, clip in the bottom and ready for the spread. It's then easier to sort for me or the next guy when the builders or the customer puts a nail in it. And it looks a million times better (yea I know it's going to be covered over but come on, let's have a bit of pride in our work). I used to be an advocate of top hat, but as soon as I used oval I was hooked.

 

[Electricalserv]

Clipped direct is sound mate, whoever said its DIY approach needs to look at the regs. Aslong as your RCD protected capping is fine.

 

[pennywise]

20mm conduit for me and adaptors then no need for the grommets

 

[telectrix]

20mm conduit for me and adaptors then no need for the grommets

you must haqve strong arms to n chase deep enough for 20mm conduit in engineering brick.

 

[pennywise]

you must haqve strong arms to n chase deep enough for 20mm conduit in engineering brick.

Honestly I can do a chase just as quick for 20mm conduit as I can for capping, chasing machine plus SDS makes light work

 

[ianphilip007]

does anyone know how the regs class oval tube/conduit with regards to cables in chases.
as id like to use an oval tube but logic tells me that you would have to derate if you enclose in tube or conduit, is it classed as a protective measure like capping ??

 

[rocker]

20mm conduit for me and adaptors then no need for the grommets

But he does have a fetish, you know.

Doesn't get old.....

 

[rocker]

Derating? Come on, the only standard circuit that is realistically likely to be affected by the derating factor in oval is a shower circuit with a (240v) 9.5kW on 6 mil, and if that bothers you (it wouldn't bother me, it's in a wall not on a wall) then wire it in singles in conduit in or on a wall and there we are. If we are going to be worried about the derating factor of buried oval, we should be worried about top hat capping as well - the cable is not completely enclosed in plaster - there is a small void and one PVC surface, both of which will insulate and stop the dissipation of heat that you would get in purely buried plaster. It's all a load of tosh, and in real terms I doubt you would lose an eighth of an amp in top and maybe a quarter of an amp in oval buried in the wall, and on a shower, which is only going to be used at 10 minutes at a time and only at half-mast when it's hot outside, I don't think that amounts to a whole hill of beans.