Shower pops MCB

[Loader]

Don't think just because the OP was a while ago, the information isn't still useful!
I have exactly the same problem, shower is ok on low, cuts out as soon as you turn it up. I have a 8.5kw shower and the push button fuse is 30amp. The slot it fits on the fusebox is marked as 30amps too, does this mean I can't put a bigger one in that slot?

 

[Chri5]

Like any electrical circuit a shower (which tends to have high load demands) requires a suitable fuse rating and a suitable cable size.

Cable size has to be designed against the shower kw, the length of cable run and the method of the run (open air- clipped, in trunking, buried in plaster- all change the characteristics of the cable).

So you have a 8.5 kw shower or 8500w divide that by 230v = 37 amps.

So your fuse even with some head room above its 30 amp rating ( + 10%) is doing it's job and tripping due to over load. Obviously with the shower set on lower temp the load isn't going to be 37 amps and hence why it's less likely to trip.

Rules on showers have changed and rcd protection is a 17th ed requirement.
I've not touched on the cable size since I have no knowledge of the method of cable installation, the length or the cable size. It's likely to be a 6mm sq cable.

Modern showers tend to have 9.5 - 10.5kw loads and it is usual to expect a 10mm sq cable to be used (although that could be under sized if the length is long, the cable is installed in insulated walls and over loft insulation).

In summary your problem won't go away and I'd suggest you consider a sparks quote for new cable and a rcd protected circuit.

 

[Steve]

cuts out

Define what you mean by "cuts out"

as soon as you turn it up.

Define what you mean by "turn it up". Which dial are you turning? I ask because electric showers generally run at full power regardless of the "temperature" setting. You may notice that the pressure changes as you alter the temperature setting - this is because you're altering the pressure, not the temperature. Its how electric showers work.

I have a 8.5kw shower and the push button fuse is 30amp. The slot it fits on the fusebox is marked as 30amps too, does this mean I can't put a bigger one in that slot?

If you have push button MCBs, these are quite old, and the fusebox is likely to be even older. MCBs are no safer than fuses. And you likely have no RCD protection. Consider getting an inspection report done and having the fusebox replaced. Its likely you will not get a fuse higher than 30A for that fusebox.

 

[Steve]

So your fuse even with some head room above its 30 amp rating ( + 10%) is doing it's job and tripping due to over load. Obviously with the shower set on lower temp the load isn't going to be 37 amps and hence why it's less likely to trip.

Again, it depends on what setting he's changing. Showers generally have two elements, switched by a "power" setting which has 3 options (most people use the highest one and leave it there). There is a seperate "temperature" knob for finer adjustments.

 

[Loader]

Cheers! its useful to have this stuff up, I won't be the last to have a crappy old electrical system!

 

[Chri5]

Cheers! its useful to have this stuff up, I won't be the last to have a crappy old electrical system!

No you won't be, but it does mean you now have knowledge of your system which means than any issues you have are in part your problem.

Like cars, like heating, decoration, electrics do require irregular upkeep.

There comes a point in time where cars go off for scrap since they become problematic- I'd suggest your wiring for the home and more so the shower circuit will require a budget in the near future.

From what you say about the description of the system- old wire fuse carriers replaced with push button mcb's then I'd hazard a guess that:-

40 years plus age
Incorrect earth bonding
No rcds or rcbo's
No earths to lighting circuits and metal lights in situ
Use of gang multi sockets to rooms with too few sockets
Older fittings, sockets and switches

If ever you sell, the property will be marked down by the cost of a rewire.

No problem if you intend to stay.

A half way house would be to have a inspection report (PIR) which will allow an indepth inspection of the system and includes recommendations regarding essential work and work that needs doing sometime.

 

[Loader]

You'd love this place - previous 'keen' diyer has had at the walls, doors, plumbing, and of course electrics. 3 fuse boxes, some with wire, some with buttons. Every day a new challenge. You think you've got it sussed, and then you realise the sad facts. Theres an outdoor security light I can't trace where it is wired to, but it doesn't work anyway. I'd feel safer in a tent...

 

[ban-all-sheds]

Did your solicitor ever ask him if he'd done any work which required Building Regulations approval?

 

[YorksSparks]

Did your solicitor ever ask him if he'd done any work which required Building Regulations approval?

Even if he did, he might a) have lied, b) been too stupid to know what is notifiable and/or c) did the work years ago anyway! I rectify loads of "DIY Dennis" jobs and very few are recent - it's wonder some have lasted as long as they have, but there you are.

 

[ban-all-sheds]

Indeed, but (a) and (b) might give Loader grounds for legal action.