Shower Cable

[DuaneMHunt1976]

With shower say 10mm is dam hard to move, would 2x6mm or 6mm+2x2.5mm as being more manageable
Still the same cross sectional area

 

[gnselectricals]

Obviously depends on cable calcs, length of run, design current, presence of insulation and other de rating factors. 10mm is pretty easy as long as you dress it in tidy. Could do 2 6mm in parallel as long as they are run the same route same length but I wouldn't bother
Can't do 6mm and 2x 2.5 at all though.

 

[Andy78]

2 x 6mm in parallel easier to connect than 1 x 10mm ? A parallel supply for a final circuit ? The mind boggles.

As gns says, 10mm is not that hard to manage, and if that's what the calcs say, that's the cable you use.

 

[Flanders]

Like to see you get the four 6mm cables in the pull cord cheaper and easyer to use 10mm

 

[DuaneMHunt1976]

Its not about Cable Calcs.. im more talking about CROSS SECTION AREA

it DOSE say 10mm CSA .. what 2x6mm would be 12mm CSA ..

Thats a Darft Comment Flanders...
as for the 4x6mm to replace a 10mm .. i think you might of read things wrong there

 

[Leesparkykent]

it DOSE say 10mm CSA .. what 2x6mm would be 12mm CSA ..

Thats a Darft Comment Flanders...
as for the 4x6mm to replace a 10mm .. i think you might of read things wrong there

It's not the daft really though is it? If you had two cables in parallel that would make 2 cables on the supply side of the switch/pull cord and two cables on the load side of the switch/pull cord making 4 cables.

 

[DuaneMHunt1976]

But the comment Flanders made suggest putting 4x6mm Cables in one HOLE..

But at least the CSA would be ok.. im just shocked that some people dont see that 2x6mm CSA is 12mm CSA and would be, but BIGGER than a 10mm CSA.. I know i come from a Electronics buts basic.

 

[7029 dave]

Doubling up to make the csa of an cable Is not an option for me.

 

[Selfmade]

I think I've said this before, but using 47mm deep backboxes helps, as does using a 2 gang (tall) switch if possible. As said, dress the cables well and arrange them carefully so there is room for them as you offer the switch to the box.

 

[hasel5]

Id rather pull in and terminate one 10 mm2 than 2 6mm2 cables any day.

What is the point double the work all for not dressing right ?

 

[DuaneMHunt1976]

Point was that some guy on another forum had 6mm cable put in with 40A MCB that went in to the loft ..
Now with cable calcs that can drop to about 37A also the shower I think was 10K

He had a few electricians, in about it some say 6 and some say 10mm
As the 6mm was it might of been cheaper to put in a 4mm to make it up to 10mm CSA


The other thing was that lot of people didn't seem to understand that a 10mm CSA cable would be that same as 4x2.5mm CSA
What shocked me as I did think that kind of Maths was basic

 

[hasel5]

Sorry very confused on this and will leave to you but think you need to get in the real world.

 

[Andy78]

Plus ten points for thinking outside the box. Minus thirty points for lack of understanding of the regulations and practicalities of installation.

 

[davesparks]

Point was that some guy on another forum had 6mm cable put in with 40A MCB that went in to the loft ..
Now with cable calcs that can drop to about 37A also the shower I think was 10K

He had a few electricians, in about it some say 6 and some say 10mm
As the 6mm was it might of been cheaper to put in a 4mm to make it up to 10mm CSA


The other thing was that lot of people didn't seem to understand that a 10mm CSA cable would be that same as 4x2.5mm CSA
What shocked me as I did think that kind of Maths was basic

The reason that paralell cables are commonly used in larger circuits is that the sum of the parts is greater than the whole. If you look at the current carrying capacity of cables you will see that when the csa doubles the ccc only increases by about half. This leads to a situation where, say, 1x 70mm 4core can be replaced by 2x 25mm 4core and still have the same ccc.
However there are special requirements for parallel cables in he regulations and you need to carefully consider the protection arrangements and ensuring correct current sharing between the cables.
It is forbidden to install different size cables in parallel or for the cables to be different lengths or follow different routes.

As for the 10KW shower on a 40A mcb, it should have a running current of 42A so should be on a 45A supply to start with, however as it is a fixed load you would calculate cable size based on 42A not the rating of the OCPD as overload protection is not required.

 

[DuaneMHunt1976]

Omg so this guy who has a shower installed by and electrician with 6mm cable 40A MCB going via loft.. Is OK with you guys
Sorry I must be in the wrong forum my error minus another 60


Forums ain't for me, I can't read them and tones just don't work for me...

 

[davesparks]

Omg so this guy who has a shower installed by and electrician with 6mm cable 40A MCB going via loft.. Is OK with you guys
Sorry I must be in the wrong forum my error minus another 60


Forums ain't for me, I can't read them and tones just don't work for me...

Is it definately a 10KW shower?

 

[DPG]

Point was that some guy on another forum had 6mm cable put in with 40A MCB that went in to the loft ..
Now with cable calcs that can drop to about 37A also the shower I think was 10K

He had a few electricians, in about it some say 6 and some say 10mm
As the 6mm was it might of been cheaper to put in a 4mm to make it up to 10mm CSA


The other thing was that lot of people didn't seem to understand that a 10mm CSA cable would be that same as 4x2.5mm CSA
What shocked me as I did think that kind of Maths was basic

No-one in this thread has misunderstood the maths of doubling cables up. People are disputing the advantages and practicalities of doing it in this particular case. And you should not use paralleled cables of differing csa's or type. Daz

 

[telectrix]

this makes me think i've gone all wrong with buying a toyota hiace van, when 2 astra vans in parallel would carry the same weight.

 

[Risteard]

A 10mm^2 conductor wouldn't need 2 * 6mm^2 in parallel for equivalent current-carrying capacity - probably more like 2 * 4mm^2.

Really parallel conductors are far more appropriate for a distribution circuit than for a final circuit, so I wouldn't be advising that approach at all.

As for other suggestions made, you cannot parallel two different cross-sectional areas of cable together as the current flow wouldn't distribute evenly.

 

[tigerpaul]

What about 10 x 1mm cables then? So that will be 20 in total? Using your simple infant school mathematics that would be fine.
Doesn't make it a good job though does it?

 

[codger]

Jaysus.....DuaneMHunt. Are you really a sparkie..??

 

[hasel5]

Jaysus.....DuaneMHunt. Are you really a sparkie..??

My thoughts as well.

 

[baldsparkies]

This is great !!
So now an existing 6mm supply cable needs up rating to 10mm to supply a shiny new 10kw shower.
Don't bother fitting a 10mm, just run another 6mm alongside and do it on the cheap.
Well carry on cus this is the kind of thing that sorts the electricians from the semi skilled bodge up merchants.
Do what any self respecting electrician would do and fit a 10mm, and if termination is a problem get an electrician to do the job for you.

 

[davesparks]

What about 10 x 1mm cables then? So that will be 20 in total? Using your simple infant school mathematics that would be fine.
Doesn't make it a good job though does it?

1mm has a ccc around 12/13A depending on conditions, let's say 10A for ease of maths.
So for a 40A supply you would only need 4off 1mm cables.

 

[baldsparkies]

1mm has a ccc around 12/13A depending on conditions, let's say 10A for ease of maths.
So for a 40A supply you would only need 4off 1mm cables.

OK how long you been in that pub Dave, I'm jealous. :wink_smile:

 

[hasel5]

1mm has a ccc around 12/13A depending on conditions, let's say 10A for ease of maths.
So for a 40A supply you would only need 4off 1mm cables.

This is the way forward

 

[baldsparkies]

This is the way forward

Use a 2.5mm and limit the running time of the shower to 2 minutes 12 seconds using a timer.
Set the timer to re energise after 10 minutes to allow for thermal effects.

Check the calcs yourself if you don't believe me:jester:

 

[hasel5]

Use a 2.5mm and limit the running time of the shower to 2 minutes 41 seconds using a timer.
Set the timer to re energise after 10 minutes to allow for thermal effects.
Check the calcs yourself if you dont believe me. :conehead:

I believe you but don't let everyone know lol.
I am retiring to the pub for the rest of the day.

to contemplate my future

 

[uksparks]

I have just read this and my thoughts are, why are people even talking of using more than one cable, just use the "correct" size and do it properly, anything other than that is just stupid IMO.

 

[hasel5]

See post 10

 

[Andy78]

I have just read this and my thoughts are, why are people even talking of using more than one cable, just use the "correct" size and do it properly, anything other than that is just stupid IMO.

I don't think anyone is being serious petal. Maybe the OP, but even then I think this thread was possibly a joke that didn't translate to the internet very well.

 

[baldsparkies]

I don't think anyone is being serious petal. Maybe the OP, but even then I think this thread was possibly a joke that didn't translate to the internet very well.

Well lets face it you either laugh or cry when reading the OP's comments.
Lets hope he IS joking, scary stuff.

 

[davesparks]

OK how long you been in that pub Dave, I'm jealous. :wink_smile:

I haven't got near the pub yet, but it's exactly the same maths that would give you four cables with a ccc of 100A to carry a 400A supply or of 1000A to carry a 4000A supply.

The only difference being that nobody in their right mind would use paralell cables to carry a 40A supply!

 

[GMES]

Totally agree with Dave on this one,when you are installing large supplies sometimes you have to install large cables in parallel because the cables can become unmanageable however the same does not apply when installing a shower cable.

 

[telectrix]

Totally agree with Dave on this one,when you are installing large supplies sometimes you have to install large cables in parallel because the cables can become unmanageable however the same does not apply when installing a shower cable.

agreed.most showers will run happily on a 2.5mm, strung over the bath and second duty as a knicker dryer.

 

[Dave OCD]

All joking aside though, I think anything over 9.5kW on an instantaneous electric shower is getting a bit ridiculous and unnecessary too.

 

[baldsparkies]

All joking aside though, I think anything over 9.5kW on an instantaneous electric shower is getting a bit ridiculous and unnecessary too.

That's the fun Christmas day, when Mums cooking the Turkey, Dads watching his 65" plasma with the electric log affect fire on full blast, and the teenage daughters washing her hair in the 10.5kw shower.
Poor old 60A cut out fuse says stuff this and pop !! Merry Christmas.

 

[Dave OCD]

Precisely.:tongue3:

 

[baldsparkies]

Totally agree with Dave on this one,when you are installing large supplies sometimes you have to install large cables in parallel because the cables can become unmanageable however the same does not apply when installing a shower cable.

Count me in.
Tri-rated is another that can make those awkward break your fingers and scuff yer knuckles moments an easier option.
Have needed to fit parallel sub main runs myself on heavy installs and that's perfectly logical.
But cabling a domestic shower this way is nonsense in the extreme.
I think common sense and good electrical practice are the words of the moment with this one.

 

[Marvo]

I'd be interested to know if there's actually a reg that forbids it in the UK, I know there isn't in our domestic regs. As said already, it's common practice with cables in larger distribution networks but the logistics of ensuring identical lengths, routes and connecting a parallel cabled domestic final circuit would make it a bad idea.

 

[uksparks]

I think id be more concerned about one of them being disconnected then overloading the remain one.

 

[Richard Burns]

I'd be interested to know if there's actually a reg that forbids it in the UK, I know there isn't in our domestic regs. As said already, it's common practice with cables in larger distribution networks but the logistics of ensuring identical lengths, routes and connecting a parallel cabled domestic final circuit would make it a bad idea.

BS7671 specifically permits paralleling cables, with certain provisos on cable route, type, etc. to ensure equal current sharing.
However I believe it is directed mainly toward the larger cable sizes in reality.

 

[davesparks]

I think id be more concerned about one of them being disconnected then overloading the remain one.

That's kind of why there is specific guidance on the design and protection of parallel feeds in bs7671

 

[vjsmarwick]

You will not need to worry in another few years because of the EU the power of vacuum cleaners are being restricted next they are going to restrict our power tools so soon your showers will be a maximum of 3KW and you will have a fine mist spray to that you reduce your need for so much water and then to round it off your bath towels will be the size of face cloths ! pmsl

 

[Leesparkykent]

You will not need to worry in another few years because of the EU the power of vacuum cleaners are being restricted next they are going to restrict our power tools so soon your showers will be a maximum of 3KW and you will have a fine mist spray to that you reduce your need for so much water and then to round it off your bath towels will be the size of face cloths ! pmsl

It's already in action. Companies are prohibited from manufacturing or importing any vacuums with motors above 1,600 watts and will have a further reduction in 2017 to 900 watts. What a joke lol.

 

[R G]

Cant see why the op doesn't go for 2 x 8Kw showers side by side with a 6mm T&E for each, LOL....

 

[baldsparkies]

And not 1 person as mentioned the common practice of connecting 2 x 2.5mm cables 2 a 32A breaker !!
Sound familiar !!! :icon12:

Yea but! no but! yea but!

 

[stevethesparks]

Cant see why the op doesn't go for 2 x 8Kw showers side by side with a 6mm T&E for each, LOL....

As long as the two pull cords are tied together to ensure isolation of both at the same time.

 

[Slowhand]

How would you test it? As a radial or a ring final circuit?
I'm not sure the resistances in parallel are such a good idea either.
Might be a good idea to check the fire insurance.

 

[Richard Burns]

A parallel circuit would be tested as a radial (possibly once for each cable), a circuit without identical conductors on the same route would be tested as a ring but must be constructed in accordance with the regulations with are fairly limiting on available design options and is generally not recommended except for the exception class of a ring final socket circuit.