9.5 kw shower on 6mm ?

[Top Cat]

I'm just wondering how many of these manufactures stated KW ratings are actually achieved in the real world??

I posted a thread about a month ago where i accidentally put a temporary socket on a 6Amp RCBO. A 3Kw kettle was used all day long and it didn't trip. Someone said to put an Amp meter on it, i did and got 9.5 Amps so just shows that elements are not always what they apear to be!

 

[steveberry11]

What an insult to good electricians. A proper electrician will always follow the green book. Why have regs if you second guess them they are there for a reason. To protect you and the customer. In law your only defence is that you carried out your work to the current regulations at the time of installation. As the electricity at work regs state. This will form part of your EIC. I have not yet seen a EIC with a tick box with the wording how were cables sizes worked out GUESSED or CALCULATED perhaps they should it is not only about saving the customer money. Is it not our duty to ourselves and our customers to give them the best job possible and to the current regulations. If we do not do this are we no better than DIYers Perhaps it is a judgment call if you can't calculate cable sizes.

 

[telectrix]

all very well there. perhaps then the manufacturers of showers could then be made to calculate the KW ratings instead of guessing them, as i've yet to see 1 that draws the stated wattage.

 

[sedgy34]

A lot of shower manufacturers state a minimum cable and MCB size. All this has been said so many times before, yet still people are arguing about whether to work from "experience" or adhere to the regs! We know that everything has a safety margin built-in, but that's exactly what it's for, safety.
I think that the phrase "well, the last house didn't burn down", is not going to be much use if it all goes belly-up.

the scams would love this thread saying yep thats why we are here boys

 

[Guitarist]

And here we have the difference between a proper sparky and a regs jockey.

I think you have to be a bit careful with comments like that Dave. There are many times on here when sparkys who know the regs inside-out help the ones who claim to be "experienced".

 

[randym68]

also lets all remember we all use a nominal 230V to calculate Ampere, in reality most supplies are 240-249 V , which is 39.5A to 38.5 A, as Richard Burns says clamp it on start up when amps is highest, i have had 20 meters 2.5mm at 27A and no change in temperature, so 6mm will take at least 60A, make sure if cable goes in loft no insulation can be put over cable, and put a note in the consumer unit that must remain 40A cover your self. also do a Zs at the shower itself , i have had exactly same thing on a 5m run, so in theory passes but the Zs failed, so that means it had to be upgraded to 10mm.

does anyone else wonder why they don't do 8mm , seems most would find it useful in domestic. especially showers and ovens/hobs.

 

[Silly Sausage]

does anyone else wonder why they don't do 8mm , seems most would find it useful in domestic. especially showers and ovens/hobs.

A pair of 4 mils in parallel

 

[telectrix]

we used to have the very thing 7/044 , till the foreign metric rubbish took over. 50A and still not warm.

 

[randym68]

oh archy nice thought but i have replaced many a 2x 4mm in parrallel, (and due to poor fitting really) load transfered over to one cable and melt down..... really don't like using paralleled , which i know is really a ring with one point....just seen too many issues, of one cable damaged or not good connection and transfer/share load over.

 

[trev]

He wasn't serious Randy

 

[randym68]

lol i know trev but from what ive seen some electrician have been serious and you know some read this and are not as experienced/DIYers on here may miss read that lol... but i have looked and I've never found anything yet saying in regs that you cant do it...i just know its bad practice....anyone knows the actual regulation love to have it...just to tell this electrician i know he's wrong lol

 

[telectrix]

well getting 4 4mm cables into pull switch might cause a bit of swearing

 

[trev]

Just give em a haircut Tel
The sad thing is I've seen it done

 

[Engineer54]

randym68.... does anyone else wonder why they don't do 8mm , seems most would find it useful in domestic. especially showers and ovens/hobs.

8mm cables and wires are freely available all over South East Asia, this probably has more to do with European standard cable/wiring sizes than anything else!!

Absolutely nothing wrong with single point parallel wiring either. So long as the parallel wiring rules are adhered too, along with the connections at both ends being correctly made, i can't see what possible exception you can have with such an arrangement!!

If you opt for 2 X 4mm, (let's say clipped direct) that would give you a CCC of 72A!! lol!! 2 X 2.5mm would give you 54A!! Perhaps now you can start to see the advantages of parallel supplies and feeders. And that's before you start looking at VD and Zs value improvements....

 

[telectrix]

interesting point. 2 x 2.5mm has a greater csa than a single 6mm by 10A. i can only surmise that this is because the 2.5mm can dissipate heat more efficiently. therefore, for most showers, it would be feasible to use a 2.5mm parallel arrangement, rather than going up to 10mm ( ccc 64A ).

 

[Guitarist]

interesting point. 2 x 2.5mm has a greater csa than a single 6mm by 10A. i can only surmise that this is because the 2.5mm can dissipate heat more efficiently. therefore, for most showers, it would be feasible to use a 2.5mm parallel arrangement, rather than going up to 10mm ( ccc 64A ).

As Eng pointed out...

So long as the parallel wiring rules are adhered too, along with the connections at both ends being correctly made....
​

A fair few "electricians" have a job terminating one cable correctly, let alone two in parallel....

 

[somersetsparks]

I like the good engineers point, Its something we use regularily on the industrial side (may have something to do with the fact that 2 x175mm 4 cores are a bit easier to manoevre then a b*stard 400!)
On a side note many 6mm T+E shower installations on a 32A MCB or 30A fuse now do not comply as method 101 only rates the cable at 27A (over 4" of insulation in loft).

 

[nickblake]

cant belive there is 216 replies on this thread opps its now 217

 

[steveberry11]

also lets all remember we all use a nominal 230V to calculate Ampere, in reality most supplies are 240-249 V , which is 39.5A to 38.5 A, as Richard Burns says clamp it on start up when amps is highest, i have had 20 meters 2.5mm at 27A and no change in temperature, so 6mm will take at least 60A, make sure if cable goes in loft no insulation can be put over cable, and put a note in the consumer unit that must remain 40A cover your self. also do a Zs at the shower itself , i have had exactly same thing on a 5m run, so in theory passes but the Zs failed, so that means it had to be upgraded to 10mm.

does anyone else wonder why they don't do 8mm , seems most would find it useful in domestic. especially showers and ovens/hobs.

Is this for real

very worrying

 

[Guitarist]

Is this for real

very worrying

Are you saying that it's a bad idea to suggest to DIY'ers that "6mm will take at least 60A"?