Determining the size of already installed cable

[Ihavenojob]

My son has just got his first flat and already has issues with a shower. Existing is 8.5kw and I'm wondering if the cable already there would be big enough for 9.5kw, cable is approximately 25mm across, and also, would the installed RCD (B50) be ok, or would an MCB be better? Can you mix and match RCD's and MCB's?

 

[terryplumb]

Is the existing shower circuit protected by the 50 amp MCB in your pic ? If so ,a 9.5kw shower can be connected. The circuit should also be protected by an RCD ,but there isn't one in your pic. Show full pic of consumer unit and any other electrical installations around / near it.

 

[davelx]

The circuit should also be protected by an RCD ,but there isn't one in your pic. Show full pic of consumer unit and any other electrical installations around / near it.

What's that on the far right, with a trip rating of 0.03A?
Please can we have an in focus photo showing the whole of the CU so that all devices are fully visible?

 

[oldbutnotdead]

The performance difference between 8.5kw and 9.5kw isn't really enough to justify replacement. Either will deliver a deeply average shower experience in winter (though if cold water supply is tanked either will be ok. Not good but ok).

 

[ericmark]

I use a yellow crimp, if it's a tight fit 6 mm, loose 4 mm, and will not go on 10 mm.

The overload should be matched to cable, so with a 50 amp should be 10 mm. But one can't trust those before followed the rules.

Shower with correct head is fine, but if wrong shower head it can be very weak.

 

[Ihavenojob]

I'll try and get a better picture

The performance difference between 8.5kw and 9.5kw isn't really enough to justify replacement. Either will deliver a deeply average shower experience in winter (though if cold water supply is tanked either will be ok. Not good but ok).

The reason for upgrade is a) his existing is faulty, and b) the one he likes is cheaper in 9.5kw than 8.5

 

[Ihavenojob]

Is the existing shower circuit protected by the 50 amp MCB in your pic ? If so ,a 9.5kw shower can be connected. The circuit should also be protected by an RCD ,but there isn't one in your pic. Show full pic of consumer unit and any other electrical installations around / near it.

The shower is on the 50 amp mcb, can I just replace it with the correct size rcd? also, any idea of the cable size, 6mm or 10mm?

 

[EFLImpudence]

cable is approximately 25mm across,

That's huge. Are you sure?

 

[oldbutnotdead]

I'll try and get a better picture

The reason for upgrade is a) his existing is faulty, and b) the one he likes is cheaper in 9.5kw than 8.5

Both fair enough reasons to go for the 9.5 then. I was assuming existing worked...

 

[Ihavenojob]

That's huge. Are you sure?

It is big, maybe not 25 (didn't measure it) but I would say 15mm+

 

[EFLImpudence]

It is big, maybe not 25 (didn't measure it) but I would say 15mm+

You said 25mm. Probably best if you do measure it. HTF will you know otherwise?

Electrics:flatpvccables

www.diynot.com

 

[davelx]

The shower is on the 50 amp mcb, can I just replace it with the correct size rcd? also, any idea of the cable size, 6mm or 10mm

There appears to already be an RCD in your CU - the module on the far right of the photo. Iooks to me as if it has an IΔn value of 0.03a marked on it - that makes it a 30mA RCD.
That's why we need a better photo - we need to be sure what is in the CU, and if that module is an RCD, to help you confirm whether it protects the shower circuit (very likely)
If that is the case then you just need an MCB appropriately rated for the cable size and cable installation method.. If not, then it's not an RCD you need for the shower, it's an RCBO (combined MCB and RCD)

 

[RandomGrinch]

Contactum B8003/2 RCD...

 

[Ihavenojob]

My son just sent me some pictures of the consumer unit, and the cable looks to be about 19mm. Sorry if they aren't that clear, dark cupboard.

 

[conny]

Is there a cable size on that clip?
Some do have them, but others don't. If it is on there, and the cable fits very snugly without being squashed, then it's probably that size.