Shower Installation 8kw to 8.5kw

Mikedry · May 24, 2018

Hi

I have an 8.5kw shower which I wish to replace an 8kw shower with.
I'm not sure which thickness cable I already have but I think its 6mm. Will this be ok for the 8.5kw shower? I attach a pic of the current 8kw shower with cables

Baker1988 · May 24, 2018

Whats the installation method? Is it in insulation or any thing like that? What size mcb/rcbo is it on in your consumer unit?

Gavin John Hyde · May 24, 2018

couple of points...
How is the cable installed... surrounded by insulation etc...
How long is the cable run?
Does the circuit have rcd protection back at the board?

Also im not fully 100% on the rules in scotland... but does the part p special locations apply up in scotland? if so you might need to get a suitable electrician in to do the actual connections and test it.

Mikedry · May 24, 2018

Cable goes into roof so could be under insulation. Will have to check tomorrow. Not sure how to tell the size of the MCB? Sorry a bit of an amateur!

Mikedry · May 24, 2018

Run is about 8 metres

Octopus · May 24, 2018

Most shower installation instructions ask for rcd protection on the circuit. Does your fuse board have rcds ?

Mikedry · May 24, 2018

Yes it does. Just not sure what the rating of the shower one is. A new board was put in about 5 years ago and I'm assuming all was ok for the 8kw shower we already have.

Baker1988 · May 24, 2018

It will more than likely be a 32A mcb but im not sure is there not any markings or labels on your consumer unit saying shower as the ine above it will say the size on it, and if the cable is covered by insulation then i would say it is defiantly not sutable for a bigger size shower, i wouldnt even put the shower you have on a 6mm cable that is covered in insulation.

Wilko · May 24, 2018

Hi - just a friendly reminder that those cables may be live and be a hazard to you. Even if you have turned off the circuit breaker it may not be wired right and so still be live. I always recheck with an approved 2 pole voltage tester to ensure its dead and not me

. The cable should have its size written on it, as anything else is a guess from a pic.

Mikedry · May 24, 2018

Pic attached of board. Blue RCD says 63amp on it but nothing on the actual shower switch to give an indication of rating

Baker1988 · May 24, 2018

It says on the mcb B40 so it is a 40A mcb and if it is actually 6mm and not 10mm then i hope it is not in insulation and is actually in free air or clipped direct as its called as any method other than clipped direct the current carrying capacity is to low for the MCB and too high for a 8.5kw shower, does it say on the cable the actual size, but please be carefull and dont poke around to much as it may give you a shock turn it off at the isolator first if you have not already

Wilko · May 24, 2018

If you make this change, how do you plan to test it?

Mikedry · May 24, 2018

Think I'll have to get someone in as I'm a bit lost with all this. It doesn't say a cable size on it. I had hoped it may be an easy swap but I better get it checked and tested properly

Gavin John Hyde · May 24, 2018

To be fair to the op he sounds quite reasonable and took time to reply and listen. And hopefully a local spark will help him out.
Hence the replies were good. If all the people coming on asking for advice were like him life on here would be dandy... sadly we get too many diyers wanting to save a few quid getting funny when told something they dont like.

MDJ · May 25, 2018

Personally from the info supplied I think it will be fine, 8 mtrs of cable and it is 6mm2, can't see a problem with it handling 8.5 KW, now the 40 amp MCB? well it is there to protect the cable, can the 6mm2 cable cope with 40 amps? something for you new sparks to work out, we cannot tell you everything

Risteard · May 25, 2018

MDJ said:
can the 6mm2 cable cope with 40 amps?

It doesn't need to. It only needs to cope with the load. The 40A circuit breaker only needs to provide adequate fault protection.

telectrix · May 25, 2018

for 8.5kW, Ib= 36A, so unless the cable is covered in insulation, 6.0mm will be fine.

MDJ · May 25, 2018

Risteard said:
It doesn't need to. It only needs to cope with the load. The 40A circuit breaker only needs to provide adequate fault protection.

I know, but you were not supposed to say that, hence my post to the young sparks, now where is the "I'm angry an experienced spark has trashed my post emoji?"

MDJ · May 25, 2018

telectrix said:
for 8.5kW, Ib= 36A, so unless the cable is covered in insulation, 6.0mm will be fine.

Agreed, no problem at all, the only question now to the OP is "why isn't it already up on the wall?"

telectrix · May 25, 2018

Who mentioned The Wall?

Deleted account · May 28, 2018

Mikedry said:
Yes it does. Just not sure what the rating of the shower one is. A new board was put in about 5 years ago and I'm assuming all was ok for the 8kw shower we already have.

Assume! Not a good idea.

Did you get certification and building control notification when it was fitted?

If you did then I possibly would lean towards assumption everything is ok, but if it didn't I wouldn't.

Also it's had 5 years of deterioration.