My Complete DIY Rewire

[JohnW2]

the "furthest point" of an RFC in a domestic house is most unlikely to be as "far" as on a radial that roams around the house.

I don't understand that statement. Having decided where one wants to place the sockets for a particular circuit, there is no reason why the distance to the farthest one need be any longer with radial wiring than ring wiring - don't forget that radials can, and do, 'branch'.

Kind Regards, John

 

[EFLImpudence]

Also (and in relation to a similar thread since started), if new or rewiring, two 32A 4mm² radials give double the available current with only 60% more copper.

(Please don't say you can't get three 4mm² conductors in a socket terminal.)

It's up to the designer to do whichever is thought more appropriate but it is difficult to think of a reason for a new ring.

 

[JohnW2]

Also (and in relation to a similar thread since started), if new or rewiring, two 32A 4mm² radials give double the available current with only 60% more copper.

Indeed.

It's up to the designer to do whichever is thought more appropriate but it is difficult to think of a reason for a new ring.

As I recently wrote, I agree - but I also suspect that, just like me, you probably continue to quite often install new ring finals, even though it is "hard to think of a reason" ... which all goes to show that human beings don't necessarily behave rationally!

Kind Regards, John

 

[EFLImpudence]

Mmm. Possibly for rewires - just replacing what is there to save having twice as many MCBs but not for new, e.g. new kitchen.

 

[JohnW2]

Mmm. Possibly for rewires - just replacing what is there to save having twice as many MCBs but not for new, e.g. new kitchen.

Fair enough. However, it sounds ('twice as many MCBs") as if you are talking about 20A radials, rather than 32A ones. As I've said, I'm not a particular fan of 20A sockets circuits in areas where there are quite likely to be large loads (e.g. a kitchen). In such an area, I'm not really all that comfortable with a circuit which has probably a dozen or more '13A outlets' that does not have enough capacity for even just two 13A loads (in fact, not even one 3kW load and one 2kW one).

Kind Regards, John

 

[EFLImpudence]

That's why I said replace what is already there rather than ...

I didn't write it very well, did I?
Of course, the same number of 4mm² radials would be possible.

 

[securespark]

You can get 3 x 4mm² into a terminal, but some sockets I have tried (just for fun) I can't get 2 x 6mm² into!

 

[PreferNotToDieOrBurn]

So guys I have a question with a photo.

Untitled

• PreferNotToDieOrBurn
• 19 Feb 2015
• 2

I've got a chase with 2 x 2.5mm cables, half way up the chase I've got a single back box for a light switch, and then two 1.5mm cables running vertical. So four wires in the chase in total.

I've run the 2 x 2.5mm cables behind the back box. Can anybody foresee any problems (safety/regs) with doing it this way? I'm not concerned about ease of replacing cables, if it comes to that then I've accepted it's a bit of a back to square one situation. I've checked and the back of the back box doesn't have any sharp edges so it's very unlikely to damage the cables itself.

Also note the grommet - see, PNTDOB does listen to advice. Speaking of which, I'll tell you what, Hot glue is absolutely fantastic for securing wires in chases.

 

[stillp]

Hot glue is absolutely fantastic for securing wires in chases.

I'm sure it is, if you use the correct grade of hot-melt.
It probably isn't, if you don't.

 

[bernardgreen]

Speaking of which, I'll tell you what, Hot glue is absolutely fantastic for securing wires in chases.

A: Cables need to be kept within an allowable range of temperature, otherwise the insulation or sheathing material may decay and crack, compromising safety. Each cable type is rated at a specific maximum conductor temperature, based on the materials used. Ordinary PVC and similar materials are usually rated at 70°C.

Conductor at 70°C would probably mean the PVC sheath is rated at 70 maybe 80°C before degredation of the sheath occurs. What temperature is the glue from the hot glue gun ? Did the use of the hot glue degrade the sheath enough to result in early failure of the cable ? Probably not.

But there must be a reason why electricians do not use it. Maybe it is the chemicals in the glue that do harm to the PVC , more than the heat from the glue.

 

[stillp]

That's what I was getting at Bernard. Some hot-melt adhesives can leach plasticisers out of some plastics, including PVC flex. IHNI if there are hot-melts that would damage T & E cable, but I suspect the OP doesn't know either.

I used to be a development engineer for a manufacturer of proximity switches. We used to have trouble in some applications with water ingress into the switches. I tried sealing some before assembly with hot-melt - reduced the water ingress, but the flex snapped if it was bent!

 

[EFLImpudence]

Untitled

• PreferNotToDieOrBurn
• 19 Feb 2015
• 2

That's actually not compliant as the 'safe zone' only applies to cables connected at the accessory position.

 

[flyingsparks]

Untitled

• PreferNotToDieOrBurn
• 19 Feb 2015
• 2

That's actually not compliant as the 'safe zone' only applies to cables connected at the accessory position.

But I expect the socket the two 2.5mm are going to is directly below the single box..

 

[JohnW2]

That's actually not compliant as the 'safe zone' only applies to cables connected at the accessory position.

I wonder if he is planning/hoping to get a back box screw between those two cables?!

Kind Regards, John

 

[333rocky333]

Looks like the box is glued in as well

Must say his chasings quite neat, would make a good electricians mate