Different cable rating on circuit

[Dave Cabot]

Hi first post here, if during a rewire customer decides they want to keep existing 6mm cable from isolator point to shower so as not to rip up their bathroom wall (& of course keep same shower), but wants a new 10mm cable to isolator point for future use, is a fcu required between the different cables?

 

[almantle]

Just rate the MCB to the 6.0mm, note on test sheet

 

[Octopus]

There was a similar thread on here a couple of days ago and I seem to recall the news wasn't too good.

 

[Flanders]

Is this a home work question or are you doing the Job

 

[Guitarist]

To be fair, any electrician who decides to upgrade the MCB should be checking that the cable at the shower itself is the correct size anyway, and not just assuming that as a 10mm leaves the MCB, it's ok to pop a bigger MCB in. A 10mm from board to pull-cord may simply be there as it's required due to passing through insulation.
As already said, rate the MCB for the 6mm cable.

 

[micknew]

Hi first post here, if during a rewire customer decides they want to keep existing 6mm cable from isolator point to shower so as not to rip up their bathroom wall (& of course keep same shower), but wants a new 10mm cable to isolator point for future use, is a fcu required between the different cables?

It gets worse.

 

[micknew]

Why are posts like this receiving replies when the OP is obviously a DIYer?

 

[Darkwood]

Hi first post here, if during a rewire customer decides they want to keep existing 6mm cable from isolator point to shower so as not to rip up their bathroom wall (& of course keep same shower), but wants a new 10mm cable to isolator point for future use, is a fcu required between the different cables?

Why would you want to increase part of a circuit that won't gain any benefit as the last leg will denote the cable calculation and the shower isn't been upgraded ..... why spend money when its not needed?????

 

[Engineer54]

Why would you want to increase part of a circuit that won't gain any benefit as the last leg will denote the cable calculation and the shower isn't been upgraded ..... why spend money when its not needed?????

I think the customer is intending to install a larger shower in the near future, but not right now and doesn't want the mess and cost of making good a tiled wall.

I can't see a problem, if the OP is in the process of rewiring this house anyway. He can take the new uprated 10mm cable to the wall/ceiling isolator switch, which can be waiting for the the last leg of 10mm cable to the shower at a later date. So long as the OCPD is rated to protect the existing 6mm cable

To be totally honest, i haven't ever been able to see the point in having such large rated KW showers. I have a 4.2 KW shower over here and it's more than adequate in both winter (at around -1 c) and summer (up to 38 c)!! These silly 10 to 12 KW are just crazy money guzzling ratings, if you ask me!!

 

[Darkwood]

In that case it was just poorly explained by OP but yes agree if the OCPD is kept to the old set up then not an issue.... and up here in yorkshire we only heat the water to avoid it freezing other than that we do cold showers cos we aint soft southern nancies

 

[telectrix]

you have hot water???? soft yorkshire nancy! :21:

 

[Darkwood]

you have hot water???? soft yorkshire nancy! :21:

I wouldn't say Hot and even Warm is pushing it we just have anti-frost trace heating if i want a heated shower i go out in the rain in summer.....so just a seasonal option there! :sunny:
i find most ppl been so wrapped in cotton wool thas duno tha bin born yet!

 

[kingeri]

And what kind of FCU would he use on a shower circuit anyway?

 

[iamelectric]

i had the same problem 6mm for shower, was into a 40amp fuse , didnt want rewire , i put it in a 32amp rcbo and it has held so far , touch wood

 

[KINKY]

Why would you want to increase part of a circuit that won't gain any benefit as the last leg will denote the cable calculation and the shower isn't been upgraded ..... why spend money when its not needed?????

A possible answer could be the 6mm run from consumer unit to shower isolator is a long run and the VD has been exceeded.

 

[telectrix]

would need to be about 40m, assuming I=40A, before VD became excessive.

 

[Guitarist]

I came across a section, just a small section, of RFC a few months ago which was 4mm due to the cables passing through an insulated floor. Was amazed to find that somebody had actually thought about derating factors for once.