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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).

I'd be using 2 X 150mm cables in place of a single 400mm cable!! The easier install is just another benefit of using a parallel supply. As a cables CSA get's bigger, it is able to carry less current mm for mm in real terms. A parallel supply is not limited to just two cables either, ...you would probably have a pink fit and die in it if i tell you how many single core parallel i've used in main distribution supply runs!! lol!!

I'm sure you meant to say 185mm rather than the stated 175mm above?? lol!!
 
guitarist your right that wasn't my intention to suggest you should wire a 60A load through 6mm, i was trying to say and badly obviously, the safety factors mean 60A would be carried by 6mm and not over heat (depending on installation), however the REgs and engineer sense mean you should stick to 40A ish depending on installation method etc etc etc. as long as the MCB is 40A then should be fine, in the example at beguining, unless you get nuisance tripping.

as we electricians who have qualified in 2391 2382 know you have to calculate it out, and my Metrel meter is very kind and tells me if Zs complies with MCB rating, and I find in periodics ( now DEICR) its the Zs that fails more than current carrying capacity. especially if the Ze is up at .21-.30 ohms...

intresting point just to go of subject (i can here the groans) Connect engineer (dno = YEDL) says they disconnect at .31 ohms Ze, irrespective (i did mention TT but thats what he was told) !!!
 
Ib = 41.3 A then In 45A so use a B45 mcb then It from Table 4D5 6mm Ref C = 47A So

Regs state Ib less than or = to In and In less than or = to It

Conclusion 6mm Ref C = 47A use a B45 Breaker and 9.5Kw shower at nominal current 41.3A everything OK
 
that's fine, platty, until the insulation muppets arrive and reduce your ccc to 27A.
 
I'd be using 2 X 150mm cables in place of a single 400mm cable!! The easier install is just another benefit of using a parallel supply. As a cables CSA get's bigger, it is able to carry less current mm for mm in real terms. A parallel supply is not limited to just two cables either, ...you would probably have a pink fit and die in it if i tell you how many single core parallel i've used in main distribution supply runs!! lol!!

I'm sure you meant to say 185mm rather than the stated 175mm above?? lol!!

The most I seen engineer is a meagre 3 630awa's per phase, and I thought that was a lot lol!
 
wow!! whos gonna last longer this thread or our forum dinosaurs? lol no insults intended the love on here is awesome
 
Ib = 41.3 A then In 45A so use a B45 mcb then It from Table 4D5 6mm Ref C = 47A So

Regs state Ib less than or = to In and In less than or = to It

Conclusion 6mm Ref C = 47A use a B45 Breaker and 9.5Kw shower at nominal current 41.3A everything OK


Don't forget all those correction factors that need to de applied to the tables you have refured to.
 
The most I seen engineer is a meagre 3 630awa's per phase, and I thought that was a lot lol!

Try 19 X 95mm per phase+N run Trefoil + N on tray for around 150m and more from TX to Main Switchboard, via Stand-by Genny changeover switchboard... There were 6 TX's supplying that building, all with similar numbers of supply parallel feeders...

TX's were mainly 127/220V, (Malcolm will recognise that voltage band instantly!! lol!!) with a couple of 220/380 TX's supplying the bigger equipment...
 
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that's fine, platty, until the insulation muppets arrive and reduce your ccc to 27A.

First post says NO INSULATION so i was just answering the original question and stated that 6mm is ok for REf C

If REF method 101 then 16mm cable is just big enough but i would not like to wrestle it into a pull switch !!
 
i totally agree with you. we design a circuit to comply under existing conditions. if these itchysnot installers don't know any better than to smother cables, then they should get fresh employment selling the big issue.
 
i totally agree with you. we design a circuit to comply under existing conditions. if these itchysnot installers don't know any better than to smother cables, then they should get fresh employment selling the big issue.

Tel, the insulation installers is monkey see monkey do they don't know about all the Calcs to do with cables etc they just fill the area with the stuff off the van and move on to the next job.
its us poor guys who have to think of all that derating factors etc
 
Just or all the posts about insulation (itchy Snot, I think some of you call them). You can't future proof for every eventuallity. If you did, then you may as well put cabling in from the roof just in case customer wants PV later on.
 
Just or all the posts about insulation (itchy Snot, I think some of you call them). You can't future proof for every eventuallity. If you did, then you may as well put cabling in from the roof just in case customer wants PV later on.

Totally agree mate. If the loft has only 4" of insulation tho, it is very likely that at some point in the foreseeable future there will be some addition. I always take my oval conduit 6 inches above existing insulation for just such an eventuality :)
 
Totally agree mate. If the loft has only 4" of insulation tho, it is very likely that at some point in the foreseeable future there will be some addition. I always take my oval conduit 6 inches above existing insulation for just such an eventuality :)

Good thinkin' bonny lad .. are ye a Geordie by any chance?? ....... If yer not, divven't worry ... aahl make ye an honourary one for noo.
 
Havnt bothered to read the other pages so this may have been said. 6mm will do for a while, id never put a 6mm cable in for anythin over 8.5kw shower, simply because ive been to far too many homes where a 9.5kw has been on an 6mm and the cable is burnt out/switch etc. Over a period of time, the 6mm will begin to melt, usually from the women who spend an eternity in the shower ! 10mm everytime for showers over 8.5kw every time.
 
Tel, the insulation installers is monkey see monkey do they don't know about all the Calcs to do with cables etc they just fill the area with the stuff off the van and move on to the next job.
its us poor guys who have to think of all that derating factors etc

I think that we must recommend that all new circuits installed in lofts that have no loft insulation, should be installed, at least 300mm above the plasterboard, on the loft wall or along appropriate battens installed for the purpose.

This would circumvent the "monkeys".
 

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