Burning cable, what should i do??

[theshogun]

And as for you pointing out that 6mm can be used to supply more power if it is ventilated is about as much use as farting in a lift. Have you EVER seen perforated tray in a well ventilated area in a DOMESTIC premises..Nope, thought not, so there is no point mentioning it.

See reference method 1 clipped direct 6.0mm=47amps.

OBTW..6mm T&E does not have a 2.5mm Earth core, it is and always as been 4.0mm. The designation on the cable mentions above is 6 stranded 2.5mm, which is OLD 2.5mm at that as all 2.5 mm is solid cored these days, and has been for over a decade.

Old (2.5mm) is 7strands referred to as 7029.
6.0mm has 2.5mm earth core
Dam, we have already establish that the cable is 2.5mm NOT 6mm. [/quote]
No you assumed.
He has already stated that he used cooker sized cable in his replacement.
This i would have advised uprating to 10.mm incase he upgrades the shower as has already been suggested.
As mentioned earlier the problem is most likely due to loose connections in the switch more than the cable .

 

[Big_Spark]

Shogun, 6.0mm has a 4.0mm Earth core OK..it has done for the last 22 years that I have been in the industry.

The cable is UNDER RATED..

Will you stop talking absolute shiite about 47A for 6mm...THIS IS FOR INSTALLATION ON PERFORATED TRAY NOT INSTALLATION IN WALLS AND ACROSS CIELINGS WHERE THE CURRENT CARRYING CAPACITY IS SEVERALLY RESTRICTED AND REDUCED TO 32A.

If you Guys are going to quote from the Regs book, please learn to understand it and don't just take the biggest current rating as the one to go by.

Lets assume for the moment that this cable is 6mm that he has..IT IS STILL UNDER_RATED FOR A 9.5kW SHOWER and should be changed.

 

[big-all]

i am no electrician

but £3 or 4 for larger cable or house burnt to the ground mmmmmm let me think
i am not trying to freighten any body but----------

 

[ban-all-sheds]

See reference method 1 clipped direct 6.0mm=47amps.

Will you stop talking absolute s**** about 47A for 6mm...THIS IS FOR INSTALLATION ON PERFORATED TRAY NOT INSTALLATION IN WALLS AND ACROSS CIELINGS WHERE THE CURRENT CARRYING CAPACITY IS SEVERALLY RESTRICTED AND REDUCED TO 32A.

If you Guys are going to quote from the Regs book, please learn to understand it and don't just take the biggest current rating as the one to go by.

4A1: Method 1 is clipped direct to or lying on a non-metallic surface, or embedded directly in non-thermally insulating brick, concrete, plaster etc. Perforated trays are Method 11.

4D5A: The rating for 6mm² Twin & Earth, Reference Method 1 (clipped direct) is 47A. The circumstances in which the rating becomes 32A is Installation Method 6 - in conduit in a thermally insulating wall or above a thermally insulating ceiling.

To be fair, 4D5A does say that Method 6, and Method 15 (cable directly installed in or above an insulating wall or ceiling, 35A) are the Reference Methods for T/E in that table. And would I advocate the use of 6mm² cable for a shower circuit? Probably not.

But please don't shout abuse at someone for posting the facts about cable ratings, and the correct values that are in the tables, and accuse them of not understanding the tables when it appears that it isn't them that's not reading them properly.....

 

[ban-all-sheds]

Also worried about your 40A fuse ( In ) when your Ib figure is 41.5A

It's probably not. I've not gone seeking the small print for the T80, but generally speaking shower manufacturers' headline power ratings are at 240V, so a 9.5kW shower would be 39.6A. Or about 38A at 230V.

 

[liveandlearn]

Umm I am getting a little curious and concerned about this topic.

Reason being, mother in law has had a shower fitted by the local council Triton T80si dont know what the cable is but i did notice one day when looking at her consumer unit was that it was rated at 32 amp on the shower circuit. I have never given it a second thought just assumed it was a low powered shower but if it is a 9.5 KW unit then where does leave things?

 

[ban-all-sheds]

The T80SI comes in 7.5, 8.5, 9.5 & 10.5kW flavours....

 

[kavozzy]

Shogun, 6.0mm has a 4.0mm Earth core OK..it has done for the last 22 years that I have been in the industry.

That's really strange because my 50 metre roll of 6mm2 T&E cable has an earth continuity resistance of 0.37 ohms,
That makes the earth conductor 2.5mm2

 

[crystal ball]

Regarding the 6mm T&E debate, I stripped a piece today and compared the earth with 2.5mm, definitely the same size

 

[liveandlearn]

Thanks for that ban a sheds

 

[L.Spark]

FAO Jim Franklin

r.e. CPC sizes, 10mm T+E has a 4mm CPC, 6mm T+E has a 2.5mm CPC, perhaps they have changed it as I thought it was one size down too

 

[Big_Spark]

LS, I have been 2nd fixing some gear today (Nice bit of price work ) and I was curious about all this. The 10mm has a 6mm 7 stranded CPC, the 6mm has a 7 stranded 4.0mm CPC and the 4mm has a solid core 2.5mm cpc.

I asked the Guys in the office about this too, afterall they could have changed the cpc sizes without me knowing as I have been "off the tools" for over a year now, however they all said that to their knowledge the cpc's of T&E was still one size down.

The Site Engineer was curious (It's amazing how easy it is to start a conversation amongst sparks on site!!) so he phoned the IEE to ask the same question, they replied with EXACTLY the same information..cpc's in T&E are always one size down, they always have been and there are no plans to change this.

This got us intrigued as several here are certainly adamant about their responces and came the following conclusion..as the cpc is uninsulated, this could account for some thinking it to be small that it actually is, escpecially as most cable now has LSF Insulation which is thicker than standard PVC, and it does make the core look smaller in comparison.

Whether that explanation is partly accurate or not is a matter of conjecture, but the fact that any spark you speak to says the same, the IEE says the same....I feel confident we are correct.

 

[Big_Spark]

BAS..don't tell me what to post, you are trying to say I cannot read the effing tables when you concede above that the FIGURE (there is shouted..burn my britches!!) I quoted is the one that we are discussing here..so I did not misread it, the other posters did, as you have conceeded with your post(although not directly).

As usual your post is double meaning. I do not write the Regs, I simply follow them, and I know how to read the tables and interprete them to the real world environment we exist in. That is something amateurs will always lack the ability to do. We could sit and say "well in this situation ot that situation" until the cows the come home, but the simple fact is that we are dealing with a real situation and one that is important to be resolved for the original poster of the problem.

He has a shower with a serious issue, from the information he has posted the cable is under-rated. This could be the cause of the burning, or it could be a loose connection, more likely it is heat from the under-rated cable has caused a terminal to loosen exacebating an existing situation. The simple fact is he needed this problem resolved and a couple of people have told him what the right course of action is, but a handlful of wishy washers have come along going bla bla bla and diverting attention from what is a potentially dangerous situation.

Again this is the difference between rank amateurs and the professionals, we recognise a dangerous situation from little information, we do not need to prevaricate over it, then wonder why the house burnt down. (Ok a bit over simplified but I think you understand my point)

 

[theshogun]

Fwl i think it is you who should learn to use the regs book perforated cable tray is method11, method 1 as i said earlier is clipped direct.
regarding 6.0mm with 2.5 earth you say 4.0mm read your on sitre guide as well this referers to conventional circuits where they give phase as 6.0mm with a cpc of 2.5mm page 45.

 

[Big_Spark]

Fwl i think it is you who should learn to use the regs book perforated cable tray is method11,not method 1 as i said earlier is clipped direct.

I did not misread the Regs.. I misread the post I read it as 11 not 1..apologies for that.. (I'll get new glasses!!)