can two 6mm csa cables each with 30A mcb in joined at 50A dps to supply 9.5kW shower

[mikejd]

Hi I have two 6mm csa cables in the loft each going back to a separate 30A mcb in the CU. One is redundant, the other goes to a broken 8.5kW shower. I want to fit a new 9.5kW shower and would like to join both 6mm cables together at a 50A dpst shower switch, then run a short length of 10mm csa cable from the switch to the shower. Can anyone see a problem with doing this. Both 6mm cables are approx same length (12m), there is a RCD in the CU.
Thanks

 

[telectrix]

Re: can two 6mm csa cables each with 30A mcb in joined at 50A dps to supply 9.5kW sh

Just a thought -

9500 / 240 = 39.6A

perfectly OK till the insulation monkeys smother the cable.

 

[mikejd]

Re: can two 6mm csa cables each with 30A mcb in joined at 50A dps to supply 9.5kW sh

Thanks for the reply. Please help, I cant see the down side. Each of the two 6mm cables have individual 30A mcb's in the CU. The two 6mm cables fit easily into the 50A isolator switch. If somehow one cable became damaged in the future, then the current draw down the other cable would trip the other 30mcb.
What have I missed?

 

[sparks1234]

Re: can two 6mm csa cables each with 30A mcb in joined at 50A dps to supply 9.5kW sh

As Tele said, if it was a short run, no insulation you might get away with one cable on the limit but chuck some fluffy stuff on it and start the derating

 

[Alex Ramage]

Re: can two 6mm csa cables each with 30A mcb in joined at 50A dps to supply 9.5kW sh

:rolleyes4::rolleyes4:

Thanks for the reply. Please help, I cant see the down side. Each of the two 6mm cables have individual 30A mcb's in the CU. The two 6mm cables fit easily into the 50A isolator switch. If somehow one cable became damaged in the future, then the current draw down the other cable would trip the other 30mcb.
What have I missed?

Missed? Poor practice, non standard circuit/cable size, how to test it correctly not to mention the embarrassment of allowing any other electrical professional or inspection authority the satisfaction of outing your handy work. No argument you offer can excuse this as an electrical installation. Installation certificate would be interesting. Would you be so good as to forward us a copy?

 

[Silly Sausage]

Re: can two 6mm csa cables each with 30A mcb in joined at 50A dps to supply 9.5kW sh

Thanks for the reply. Please help, I cant see the down side. Each of the two 6mm cables have individual 30A mcb's in the CU. The two 6mm cables fit easily into the 50A isolator switch. If somehow one cable became damaged in the future, then the current draw down the other cable would trip the other 30mcb.
What have I missed?

Numerous regulations which you need to comply with.
They can easily be found in the latest edition of BS7671.

 

[Sintra]

Re: can two 6mm csa cables each with 30A mcb in joined at 50A dps to supply 9.5kW sh

Mate you can't put the cables on separate MCB's end off. You need to read the part in bs7671 regarding conductors in parallel.

 

[mikejd]

Re: can two 6mm csa cables each with 30A mcb in joined at 50A dps to supply 9.5kW sh

But the (40A) current is shared down two 6mm cables (approx 20A down each). And each 6mm cable has its own 30A mcb back in the CU. From the 50A isolator pull switch near shower, where they join, the single cable to the shower is then 10mm. I cant see any over loading / overheating at all. Am I still missing something here.

Except for failure to comply with regulations why would this not be safe?
Any advice really appreciated
Thanks

 

[gazj82]

Re: can two 6mm csa cables each with 30A mcb in joined at 50A dps to supply 9.5kW sh

perfectly OK till the insulation monkeys smother the cable.

I agree, but should we have to comply with every idiot that might come along and do something like this. The insulation monkeys should be educated, before stuffing the loft full of the stuff!

EDIT: Just read this again, I don't think you was implying we should

 

[jackhammerJIM]

Re: can two 6mm csa cables each with 30A mcb in joined at 50A dps to supply 9.5kW sh

2 separate supplies joined together .

your having a laugh mate .

DIY FORUM

 

[Sintra]

Re: can two 6mm csa cables each with 30A mcb in joined at 50A dps to supply 9.5kW sh

But the (40A) current is shared down two 6mm cables (approx 20A down each). And each 6mm cable has its own 30A mcb back in the CU. From the 50A isolator pull switch near shower, where they join, the single cable to the shower is then 10mm. I cant see any over loading / overheating at all. Am I still missing something here.

Except for failure to comply with regulations why would this not be safe?
Any advice really appreciated
Thanks

If you think a 30A mcb will trip out at 30A you are mistaken.

 

[Octopus]

Re: can two 6mm csa cables each with 30A mcb in joined at 50A dps to supply 9.5kW sh

But the (40A) current is shared down two 6mm cables (approx 20A down each). And each 6mm cable has its own 30A mcb back in the CU. From the 50A isolator pull switch near shower, where they join, the single cable to the shower is then 10mm. I cant see any over loading / overheating at all. Am I still missing something here.

Except for failure to comply with regulations why would this not be safe?
Any advice really appreciated
Thanks

What training/competence/test kit do you have?

 

[Sintra]

Re: can two 6mm csa cables each with 30A mcb in joined at 50A dps to supply 9.5kW sh

Op can I ask your qualifications please as this is basic stuff.

 

[Plonker 3]

Re: can two 6mm csa cables each with 30A mcb in joined at 50A dps to supply 9.5kW sh

I just think we need to leave this thread alone, no matter what we tell the OP it just seems to fall on deaf ears.

I want to know who is going to get here first Glenn or Biff.

 

[Octopus]

Re: can two 6mm csa cables each with 30A mcb in joined at 50A dps to supply 9.5kW sh

This thread is the classic example of how Dan needs to change the forum. If the OP is unwilling to attempt to answer some of the questions he should be put on a ban until he does.

 

[Specialist]

Re: can two 6mm csa cables each with 30A mcb in joined at 50A dps to supply 9.5kW sh

According to his profile he's a teacher, hope he knows a bloody sight more about that than he does about electrics .