Wiring regs re Spurs

[mikehardy]

Thanks guys for all the posts so far - can you tell me what SWA and FCU stands for (pic's please) as used in these posts. If this circuit is a fused spur inside a cavity Wall,l what load(s) can we safely use in addition to a 2kw heater.

Regards.

 

[malcolmsanford]

FCU or a Spur unit Fused Control Unit



SWA or Steel Wired Armour Cable

Even using a 13 amp spur to feed the sockets, the use of a 2kw heater will be fine as that is 8.6 amps, and even then the heater will switch on/off on the thermostat.

 

[Electro-tech]

Well done Nick, I only pointed out the insulation down the cavity as it is a famous dodge.
Not only rodent attack, but cables down the cavity was a usefull route to take at times,then along came chemical injection insulation and pvc cables up to 1970 subjected to, caused migration of the pvc, breaking down the insulation.Indicated by green gunge at light pendants and switches.Anyway Mike let us know how you get on.

 

[malcolmsanford]

Guidance from the Electricity Safety Council says "installing such cables in this way (external cavity walls) is generally an undesirable practice"

The reasons give are
1. Obstructions in a cavity wall, such create a risk of unseen damage during installation.
2. Long unsupported vertical drops may place undue strain on the conductors, leading to damage
3. Polystyrene used for insulation, if it come into contact with thermoplastic (pvc) cable sheathing, plasticiser can migrate from the thermoplastic to the polystyrene
4. Thermal insulation in the cavity may cause cable not to be able to carry the load current without overheating due to their current-carrying capacity being reduced
5. Presence of flora and fauna - unforeseen external influences

There is also a requirement in the Building Regulations 2000, Approved Document C, 2004 Edition, Section 5: Walls, paragraph 5.13 b
and NHBC Standards state that no cables other than electricity meter tails are to be located in the cavity of an external wall

And the following .............................

 

[mikehardy]

Just been in touch with Draka - Rob Kelsell thinks it could be counterfeit cable, sending samples today - should know on Monday - keep you all posted, and a big thanks for all your help.

Regards, Mike.

 

[mikehardy]

Is the use of 2.5 twin and earth banned for use in wall cavities? or is it a recommendation.

 

[SPARTYKUS]

Mike , a recommendation. Not banned but a bad practise. Should be chased into wall/ surface mounted.

Other point i thought of, are you positive its a ring being spurred from. If its already a radial then its fine , whats not fine is a 20 amp radial ciecuit on a 32amp circuit breaker. As has been suggested chat to the bloke doing the work first. Good luck.

ps - forgot to say Mike, if the socket has two wires in it (or three) it does not mean it is a ring. Also if it says "ring main" on the label under the circuit breaker, it still does not necessarily mean it is.

The only way to be sure would be to inspect and test it.

Also, you do not seem positive (100%) the cable is 2.5mm2. It may be 4mm2, which is fine as a radial on a 32Amp circuit breaker (most of the time....).

Can you get a bit you know for sure is 2.5 and use that to compare.

Cheers

 

[Electro-tech]

Basically as above,I think the answer would be is the sheathed cable,without mechanical protection,fit for purpose!

 

[Ponty Massive]

Seems like everyone is quick to point fingers at the electrician when none of us really know what has been done! Good old team spirt eh....

If your unsure, just speak to him and ask him to explain what he has done. As far as the 3-core and earth cable to the light fitting, my guess would be he's running a switched live and perimentant live to the fan so you can keep the fan running when you turn the light off!!

 

[Ponty Massive]

Should be chased into wall/ surface mounted.

He can't chase it as he's having exposed brick. The last thing I would want is trunking running around my new conservatory.

1. Obstructions in a cavity wall, such create a risk of unseen damage during installation.
.....in a 2 foot high way?

2. Long unsupported vertical drops may place undue strain on the conductors, leading to damage
.....again see above!!

3. Polystyrene used for insulation, if it come into contact with thermoplastic (pvc) cable sheathing, plasticiser can migrate from the thermoplastic to the polystyrene
......insulation in a 2 foot wall with 16 glass windows all around you?

4. Thermal insulation in the cavity may cause cable not to be able to carry the load current without overheating due to their current-carrying capacity being reduced
......with a 13a spur?

5. Presence of flora and fauna - unforeseen external influences
.......see answer 1.



PS, Malcolm this is not directed at you, just copied your list from the ESC.

 

[mickys86]

Seems like everyone is quick to point fingers at the electrician when none of us really know what has been done! Good old team spirt eh....

Yea we should all stick together but too many cowboys about to be able to put faith in everyone

Let's be honest. It doesn't sound good

 

[Guest123]

SWA or Steel Wired Armour Cable

Has to be the worst example of stripped SWA I've ever seen!!!

 

[SPARTYKUS]

Seems like everyone is quick to point fingers at the electrician when none of us really know what has been done! Good old team spirt eh....



If your unsure, just speak to him and ask him to explain what he has done. As far as the 3-core and earth cable to the light fitting, my guess would be he's running a switched live and perimentant live to the fan so you can keep the fan running when you turn the light off!!

** not everyone, some have noted it is best to speak to the chap. **

 

[SPARTYKUS]

He can't chase it as he's having exposed brick. The last thing I would want is trunking running around my new conservatory.

1. Obstructions in a cavity wall, such create a risk of unseen damage during installation.
.....in a 2 foot high way?

2. Long unsupported vertical drops may place undue strain on the conductors, leading to damage
.....again see above!!

3. Polystyrene used for insulation, if it come into contact with thermoplastic (pvc) cable sheathing, plasticiser can migrate from the thermoplastic to the polystyrene
......insulation in a 2 foot wall with 16 glass windows all around you?

4. Thermal insulation in the cavity may cause cable not to be able to carry the load current without overheating due to their current-carrying capacity being reduced
......with a 13a spur?

5. Presence of flora and fauna - unforeseen external influences
.......see answer 1.



PS, Malcolm this is not directed at you, just copied your list from the ESC.

Don't really get what you're trying to say here Ponty, you seem perturbed with my "chase / trunking" answer. These were just suggestions. I apologize if they have offended you in some way

Reading between the lines you appear to like the idea of ignoring the Statutory building regs quoted by someone else and all the guidelines. Good luck with that !

As for trunking around your conservatory, well maybe you haven't seen some of the trunking I have done

 

[Ponty Massive]

Reading between the lines you appear to like the idea of ignoring the Statutory building regs quoted by someone else and all the guidelines. Good luck with that !


Not at all, but I do like to incorporate my own common sense approach. I'm sure the undue strain on the conductors of the extremely heavy 2.5 T+E would manage to survive the un-supported vertical drop of the 2 foot cavity wall.



As for trunking around your conservatory, well maybe you haven't seen some of the trunking I have done

Correct, I haven't seen your trunking work; however I have seen mine, hense the reason I would stick it in the cavity

I have wired a conservatory in the past from a 13a spur and yes I have run the cable in the cavity. From memory I think I clipped the cable along the wall ties then came into the back of the sockets. Is this such a bad thing? Would this not be a better and safer option than chasing the wall all the way around the conservatory?

If the customer had an exposed brick front would you tell them the ONLY way you can have your sockets installed is by using trunking? Good luck with that!