chasing cables

[samohtom]

Hi. I have an earth cable that I've made a vertical chase for in my kitchen (to earth the sink). Does this need to be run in some kind of conduit according to regs? It's not in a safe zone (above a socket or outlet) because it's just an earth cable. Also what is the normal method or covering the chase (presumably just plaster over it...any particular type of plaster?).

Also I have a lighting cable to chase in that is in the safe zone (vertical above the light switch). Is it ok to just plaster over this rather than run in conduit, as you shouldn't drill into safe zones anyway?

Thanks

Tom

 

[tonyelectric]

You should either run the cables in oval PVC tube or cover them with PVC or galvanised steel capping, the idea is to stop the plaster, which is highly alkaline coming into contact with the cable sheath as this can be damaged by the alkali, also if you ever need to replace a cable you can draw it through the tube capping so as not to rip up the wall again.

Also an earth is a vital part of the wiring, very important, it's not just an earth, it's there for safety and should be treated as any other cable.

 

[crystal ball]

Two questions

Why are you "earthing" the sink

When did PVC start becoming damaged by plaster

 

[tonyelectric]

Ah my past in injection moulding and extruding comes back to haunt!, there a two types of PVC in common usage in electrics uPVC for conduits etc and PVC for cable sheaths, uPVC is basically PVC with the plasticising agent largely removed and stabilised so is far more resistant to chemical and UV action. PVC still has a plasticiser like an oil in it, exposure to certain chemicals like lime can dry this out and cause premature aging just as UV can - cable makers would recommend against exposure to such chemicals.

 

[ban-all-sheds]

Can you find any official manufacturer or BASEC etc advice about that?

I didn't think that plaster, even lime plaster, would damage PVC. What sort of containers does premixed plaster come in?

 

[crystal ball]

Thats a new one on me, I have been sparking for 35 years and never come across pvc cable degraded by plaster

 

[Monkeh]

I didn't think that plaster, even lime plaster, would damage PVC.

The plonker holding the oversized cake knife, on the other hand..

 

[tonyelectric]

Probably something somewhere, i'm just recounting what I picked up working for a cable maker as a yongster. Not sure what those tubs are made of, you'd have to check the moulding marks on the bottom, many many plastics and variants of recipes for them, the PVC on T&E is very soft and prone to UV damage whereas the PVC used on SWA is stabilised and the PVC used on Pyro is stabilised but not colorfast so it fades but does not crumble as much as say the stuff they make RS screw terminals from for example.

Too much plastics for me, I thought i'd left it all behind - I still say cap the cables, if for nothing else to make future replacement easier.

 

[crystal ball]

So is that a retraction of the plaster damges cable statement.

Just got to find out why the OP is earthing a sink now

 

[Taylortwocities]

Two questions

Why are you "earthing" the sink

When did PVC start becoming damaged by plaster

Yes WHY are you earthing the sink??????

 

[tonyelectric]

Just found this, admittedly from a source dated 2007

GN1 4.7 page 76 materials likely to cause such attack include:

plaster coats containing corrosive salts

lime, cement and plaster

a few examples of this are:

plasticicers migrate to polystyrene from thermoplastic and also some types of plaster (see7.5 also)

Theres a thread on IET forum related to the whole plaster/cable dynamic


[/i]

 

[samohtom]

Hi. I thought you are supposed to earth kitchen sinks for safety (and possibly to meet building regs?). My electrician who came and removed some old storage heater wiring for me said I should leave the kitchen sink earthed (I was about to rip out the wiring). The sink is earthed all the way back to the incoming supply at the front of the house (there's a meter box on the wall outside).

Tom

 

[Taylortwocities]

Hi. I thought you are supposed to earth kitchen sinks for safety (and possibly to meet building regs?). My electrician who came and removed some old storage heater wiring for me said I should leave the kitchen sink earthed (I was about to rip out the wiring). The sink is earthed all the way back to the incoming supply at the front of the house (there's a meter box on the wall outside).

Tom

No you do not.

There must be an earth connection from the consumer unit's earth to the incoming mains water pipe (Main eqipotential bonding conductor). This should be 10mm². It should already be in place. Maybe that was what he was talking about??
If you have run a 10mm² conductor then you should connect it (using a BS951 earthing clamp) on the house side of the stop cock. The other end should connect to the main wearthing terminal (near, or inside the consumer unit).

Deatils here //www.diynot.com/wiki/electrics:main_equipotential_bonding

You do not need (and have never needed) to run an earth cable to the kitchen sink to meet any regs. A long time ago it was necessary to connect the hot & cold pipes together and also connect these to the sink if it were metal. Even then, you did not need a separate earth cable back to the fuseboard - if you did that it could make things more dangerous than more safe...

 

[samohtom]

There must be an earth connection from the consumer unit's earth to the incoming mains water pipe (Main eqipotential bonding conductor). This should be 10mm². It should already be in place. Maybe that was what he was talking about??
If you have run a 10mm² conductor then you should connect it (using a BS951 earthing clamp) on the house side of the stop cock. The other end should connect to the main wearthing terminal (near, or inside the consumer unit).

Deatils here //www.diynot.com/wiki/electrics:main_equipotential_bonding

You do not need (and have never needed) to run an earth cable to the kitchen sink to meet any regs. A long time ago it was necessary to connect the hot & cold pipes together and also connect these to the sink if it were metal. Even then, you did not need a separate earth cable back to the fuseboard - if you did that it could make things more dangerous than more safe...

Hi...I haven't run the cable, it was already there. I'm just redoing my ceilings (asbestos - had to have it ripped out and have started putting up new plasterboard) so have clipped it in place. I don't understand the 10mm2 term (cross sectional area?)...the cable is green/yellow and looks to me to be about 7 or 8mm diameter. When I said I earthed the sink, that's possibly not quite what i meant - it's connected at the sink end to the house end of the stopcock (just the other side of the water meter). My hot and cold water pipes are also bonded together under the sink and in the bathroom. Anyway, the other end of this cable is connected to a visible earthing terminal in my meter box outside, where the consumer supply comes in. Looking in the mter box, my supply from the grid comes in, goes through the meter and to another box (which says protective multiple earthed installation on it) and from there I assume it must go to my consumer unit - I can't check without interfering with the box I'm not supposed to interfere with. My consumer unit itself is a modern one with switches and a test button etc. The old one must have been replaced at some point as the property was built in 1973.

 

[ban-all-sheds]

There must be an earth connection from the consumer unit's earth to the incoming mains water pipe (Main eqipotential bonding conductor). This should be 10mm². It should already be in place. Maybe that was what he was talking about??
If you have run a 10mm² conductor then you should connect it (using a BS951 earthing clamp) on the house side of the stop cock. The other end should connect to the main wearthing terminal (near, or inside the consumer unit).

Deatils here //www.diynot.com/wiki/electrics:main_equipotential_bonding

You do not need (and have never needed) to run an earth cable to the kitchen sink to meet any regs. A long time ago it was necessary to connect the hot & cold pipes together and also connect these to the sink if it were metal. Even then, you did not need a separate earth cable back to the fuseboard - if you did that it could make things more dangerous than more safe...

But you didn't write that, did you...

You need to use the

button

I don't understand the 10mm2 term (cross sectional area?)

Yup - the csa of the conductor.

...the cable is green/yellow and looks to me to be about 7 or 8mm diameter.

Sounds like 16mm².

When I said I earthed the sink, that's possibly not quite what i meant - it's connected at the sink end to the house end of the stopcock (just the other side of the water meter).

Yup - that's your main bonding cable.

Don't remove it.