Heating and elelctric down same channelling?

[Robert Irwin]

Plumber did some channelling about 7 cm wide to put 10mm rad pipes down wall, around which he has put some kind of PVC sheath. I had asked him to leave enough space to run electric cable in there too, but its looking a bit tight. I can either just put the cable in up against the edge unprotected, but at least that should give a good cm of plaster between gas pipe and cable. Or I can put in thin pvc T&E shielding, but that eats into space and butts right up against pipes in places. It standard grey T&E 2.5mm cable.

Any advice? Do I just abort it and cut yet more channels (very much NOT keen on doing this)

TIA

Robert

[Harry Bloomfield]

On 06/01/2004 Robert Irwin opined:-

The regulations require them to be in a completely separate channel or duct.

[stefek.zaba]

I'm afraid this seems like the Only Right Answer from what you've written. Running mains cable right next to CH pipes is a poor idea: the CH pipe surface temp will for a conventional boiler be around 70 to 75 degrees C: that's close to the point at which the PVC insulation on the mains cables gets too soft to work - any bending in the cable can make the conductors squeeze together. The 1cm separation you mention is much too small to escape the heating effect.

Or, if you prefer written regulations rather than reasoning from principles, the IEE On-Site Guide speaks thus at 7.3.4, based on Regulation 528-02 and

528-02-02 specifically: "Electrical and all other services must be protected from any harmful mutial effects foreseen as likely under conditions of normal service. For example, cables should not be in contact with or run alongside hot pipes." Seems pretty explicit to me...

Sorry to bring unwanted news... Maybe you can find another route which won't need chanelling? (The spirit world is always prone to sudden bouts of non-cooperation ;-)

Stefek

[Robert Irwin]

Thanks for info even if its bad news. I'm a bit annoyed at plumber as he agreed to make them wide enough. Looks like I'll just have to hack up yet more wall and rehire angle grinder for dust-piling session. Had just hoped someone would've come up with some kind of heat-protective coating but wasn't convinced.

.Robert

[stefek.zaba]

Well, he's got the Nuremberg defence: he was only following [your] orders! And I'm sure he's seen leccy cables running through the same routes as hot pipes before now - it's a common enough oopsie, and not immediately dangerous without some mechanical strain on the cables and/or trying to pass sthg like their full design current through them.

Semi-seriously, you might find it a good release for your off-pissedness to make the channels by hand with bolster and chisel: it'd certainly make less dust than the grinder! I s'pose in a theoretical sense you might think idly about using MICC cable (mineral-fill insulation separating the live (phase+neutral) conductors inside a copper outer acting as the earth) which works fine at up to 150C or so; but in practice it's not easy to buy, and needs careful making-off at the ends so that moisture doesn't wick its way up the insulation. Few sparks get trained in installing it these days; you sometimes see it in places where something just has to be surface-run but look decent, like inside walls of cathedrals and other historic properties (such as Dave Plowman's conservatory ;-) or where extened fire-resistance is needed (hence its other trade-name, "pyro").

Cheers, Stefek

[Peter Taylor]

[e-mail] wrote

Isn't it also carved in stone somewhere that thou shalt not bury water pipework in walls?

[The Natural Philosopher]

Only if not in direct contact with e.g concrete/plaster.

>

[IMM]

Plastic can be buried directly.

[Robert Irwin]

Its metal pipe inside some sort of loose plastic coating - I assume thats okay / made specifically for this job? My basic grasp of physics tells me it leaves enough room for expansion / contracting / getting squished, but on the other hand I don't know jack about building...

Robert

[The Natural Philosopher]

Sounds like you know more than the avearge plumber. Or indeed that Tory-in-waiting, IMM.

Differential expansion and physical corrosion are teh two mechanisms that allegedly cause troubles.

Plastic coating solves both.

[Peter Taylor]

TNP replied:

IMM replied:

I never heard of this before. What Regulations are you quoting from? All I can find is this, from the Guidance Document to The Water Supply (Water Fittings) Regulations 1999

Peter

[IMM]

I have seen much of it buried in plaster, well under the plaster boards of dot and dab really, so no plaster is touching it. You can buy plastic pipe with a ready made sleeve, which means you can feed in a new pipe.