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Discuss shower cable in the Electrical Wiring, Theories and Regulations area at ElectriciansForums.net

B

beaver74

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9kw shower to run on a 6.0 swa clipped direct for 30m
but for 2 metres it goes through a boiler rm so what is the min amount you guys whould take including a temparature factor in calculation
although these results are addiquite i will be running 10.0mm but am i being over the top
any thoughts
 
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W

WarrenG

  • Thread Starter Thread Starter
  • #2
I think you would be wise to run a 10mm.

9000W / 230 = 39amps

Quick domestic cable circuit chart attached.
 
Last edited by a moderator:

ian.settle1

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Mentor
Arms
9kw shower to run on a 6.0 swa clipped direct for 30m
but for 2 metres it goes through a boiler rm so what is the min amount you guys whould take including a temparature factor in calculation
although these results are addiquite i will be running 10.0mm but am i being over the top
any thoughts

Volt drop should also be taken into consideration as well as the correction factor for going through the boiler room.

Not knowing ambient temp in boiler room for correction factor it could be that by time these factors are taken into consideration you could be looking at 16mm.
 
D

DanBrown

  • Thread Starter Thread Starter
  • #4
Bear with me for this one.. My calculations are working out to be 6mm cable. I have noticed that my cable size is considerably smaller than your 10mm and 16mm, but have you noticed that it is SWA? swa can take a lot more current that standard t+e. Anyway my calcs are;

Ib = 9000/230 = 39.1Amps
In = 40 Amp
So It = In / Ca-Cg - Cc - Ci
= 40 / 0.91 (In / Ca) (Ca - calculated at 40 degrees c)
= 44 Amps
4mm cable swa can actually take this current, but fails on volt drop (14.1v) max is 11.5v.
Next cable size is 6mm and can take 62 Amp with volt drop of (9.26v) and is below the max 11.5v.
If it were me i would be putting in 6mm.
Comments are welcome and hope i havent made a wrong judgment - still in training so be kind!!!

Hope this helps anyway!
 
M

maddfridge

  • Thread Starter Thread Starter
  • #5
Bear with me for this one.. My calculations are working out to be 6mm cable. I have noticed that my cable size is considerably smaller than your 10mm and 16mm, but have you noticed that it is SWA? swa can take a lot more current that standard t+e. Anyway my calcs are;

Ib = 9000/230 = 39.1Amps
In = 40 Amp
So It = In / Ca-Cg - Cc - Ci
= 40 / 0.91 (In / Ca) (Ca - calculated at 40 degrees c)
= 44 Amps
4mm cable swa can actually take this current, but fails on volt drop (14.1v) max is 11.5v.
Next cable size is 6mm and can take 62 Amp with volt drop of (9.26v) and is below the max 11.5v.
If it were me i would be putting in 6mm.
Comments are welcome and hope i havent made a wrong judgment - still in training so be kind!!!

Hope this helps anyway!

hi all

are you going to use a 90 degree thermosetting armour cable as bolier rooms can reach some pretty horendous temps in the summer

also in training for 2391-20

also what protective device is being used ?

cheers
 
B

beaver74

  • Thread Starter Thread Starter
  • #6
was not shore wether 70/90 deg swa but was really waiting to see if any one would bother making full allowance for just the 2m that cable will be subjected to any heat
 

andyb

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Arms
Esteemed
was not shore wether 70/90 deg swa but was really waiting to see if any one would bother making full allowance for just the 2m that cable will be subjected to any heat
I think Dan is right. He has allowed for thermosetting swa with an ambient temperature of 40 degrees.

There is only 2 metres going through the boiler room and with the shower pulling less than 40 amps in cable able to carry over 60 amps this should not be a problem.

It's intresting to note however that under the 16th edition with 4% volt drop, 10mm cable would have to be used. One of the very few instances of the 17th saving money. Dont forget that circuits in rooms with baths or showers will need RCD protection
 
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