Shower woes, including 6mm vs 10mm

[SteveDolphin]

Hello all,

I appreciate that this has been asked and covered a few times, and I think I've worked out an answer but I'd appreciate some additional feedback

First issue was that the shower cuts out after about ten minutes of running. Curious. The MCB in the consumer unit was warm, but I wasn't sure if this was an issue.

So I looked at working out what the MCB was rated at, and what the shower was etc, this lead me to also check the cables.

So the shower is 9.5kw, that's easy - it's written on it.

The MCB is labelled "type B, 5a M1, 14-45A m2" - internetting makes me believe this is a 5A MCB which confuses me, it looks just like the one for the lighting ring, but could it really be 45A?

I can't get to the cable that goes to the shower completely, but I can some of it, and so you can see in pictures that I've attached below that I can see the cores - they're about 5mm in diameter, from what I can see of the grey cable housing it looks to be larger than 10mm across which makes me assume it's not a 6mm2 cable, and probably a 10mm2 cable and therefore sufficient for the shower.

https://imgur.com/a/OrfEq

So, the questions are:
1) is that really 10mm2 cable?
2) does the MCB seem the right size?

I noted after taking off the neon isolator switch (I believe the previous occupants have re-routed the supply from the old immersion tank when they switched to a combi boiler) I also noticed that one of the black cables had basically fallen out, so I've re-terminated that now (could that have just been the problem all along?)

Thanks in advance,

 

[JohnW2]

The MCB is labelled "type B, 5a M1, 14-45A m2" - internetting makes me believe this is a 5A MCB which confuses me, it looks just like the one for the lighting ring, but could it really be 45A?

Could we have a photo?

Kind Regards, John

 

[SteveDolphin]

Of the MCB, sure - https://imgur.com/a/hfXGv

 

[EFLImpudence]

That just means that 5A ones are M1 (1000A) and 15 to 45A ones are M2 (2000A) breaking capacity.

Need a picture of the front - does it not clearly state its rating?

 

[DetlefSchmitz]

I believe the button colour tells you. I have a hunch that red was 30A, but don't have any evidence to hand...

 

[SteveDolphin]

There are no details on the front I'm afraid: https://imgur.com/a/yo6O3

 

[EFLImpudence]

The reset button has a coloured insert with the rating embossed.

That's just the switch-off button; they're all red.

 

[SteveDolphin]

Now I've posted that I can clearly see it says 30A on the front - d'oh!

Okay, so that's good - 30A - and the wires are 10mm? So why would it cut out?

 

[EFLImpudence]

30A is to low for the shower which is why it gets warm and has now become weak.

 

[SteveDolphin]

But based on the cables and the 9.5kW shower should I just get a larger MCB? Obviously I don't want the cables to melt and to start a house fire, but they seem huuge!

 

[EFLImpudence]

The cable is in no danger.

You may not be able to fit a 40A one to your fuse box.

Can we have a picture of the whole box?

 

[Simon35]

But based on the cables and the 9.5kW shower should I just get a larger MCB? Obviously I don't want the cables to melt and to start a house fire, but they seem huuge!

Have you confirmed for sure that it's 10mm cable? Is it bunched in with other cables? Clipped to a wall? In insulation?

 

[EFLImpudence]

Here are the sizes of cables.

http://www.diynot.com/wiki/Electrics:flatpvccables

 

[SteveDolphin]

Have you confirmed for sure that it's 10mm cable? Is it bunched in with other cables? Clipped to a wall? In insulation?

Well the pictures in the first post were there as more of a question to the experts here really - that's all I have to go on?

 

[SteveDolphin]

Here are the sizes of cables.

http://www.diynot.com/wiki/Electrics:flatpvccables

Yes, thank you, and that's why I *think* it's 10mm, because the bundle of live strands together appears to measure just under 5mm - but does anyone else think they could confirm or deny my guesses?