MCB size for reference method? & Mini Kitchen Consumer Unit

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First post after getting my first house.

So, I've traced the cables round and read up on the regs but I'm going round in circles with checking a few things. Do I need to get somebody in to put these things right before we start to decorate(over the next 5 years!)

I would pay for a proper inspection report, but funds are tight after piling everything into the purchase. First priorty is safety, second is not have to knock walls about in the future if a inspection report for selling(heaven forbid after the last move!) forced us to put defects right, e.g. the conduit in the walls.

I'd be grateful for any input you can give.

1) The ring circuits are in 2.5mm twin and earth with 32A RCBOs.

Is this normal for ring circuits fixed in conduit in plaster or do I need to get somebody to de-rate the RCBOs down(or worse, get the conduit removed), I've been trying to look the conduit issue up, but I'm getting confused by all the reference methods for fixing, not to mention grouping, which everyone seems to ignore anyway!

Here are the details;

  • cables are plastered into walls, often in plastic conduit(both oval and round),
  • None of the cable routes in walls or above ceilings are insulated,
  • The cables are grouped in a couple of plastic conduits(1 meter or so) fixed on the wall where they leave the consumer unit and also in one place where 2 of the circuits(plus a 2.5mm radial) run in an open channel on top of a steel beam.


2)The kitchen seems OK with a 2.5mm ring circuit to the above surface sockets, a 2.5mm radial for the fridge and freezer.
There is a 10mm supply to the oven. All seems good.

The unusual thing is the 10mm twin and earth supply to a small consumer unit fixed to the wall behind the lower cupboard.

The details are;
  • 10mm twin and earth in oval conduit in the wall, no thermal insulation anywhere.
  • fed from from a 40A mcb in the rcd side of the main split consumer unit.
  • there is no back on the cupboard so the mini CU is accessible
  • The 10mm cable has dp isolation and socket in the wall above the work surface before the mini consumer unit.

mini consumer unit has;
  • 2 x 20A mcbs for 2 single sockets for dishwasher and washing machine
  • 1 x 32A mcb for the hob outlet(isolator and socket)

Is this mini consumer unit normal practice nowadays and are the details safe and unlikely to give defect codes in a future inspection report?

Thanks!
 
1 is completely normal
2 was a waste of time and money for whoever installed it. The only defect was the person who decided it was necessary.
 
Thank you for your quick reply flameport! I'm very grateful!

Good to hear with regard to the conduit, being a bit of a geek, I'm probably over thinking and over reading it! It isn't easy to see what has been done practically in other friends houses with regard to conduit in the walls.

The installer of the mini CU in the kitchen may have been overthinking it also! I suppose the thinking was to relieve the kitchen ring(kettle, toaster, microwave, mixer, etc) of the load from the dishwasher and washing machine.
There may only have been one ring in the house in the past so the extra sockets for the under counter applicances were added to the 10mm before the kitchen ring was seperated out from the rest of the house?

I suppose it doesn't matter so long it is safe and will not give rise to defect codes that require redecorating when we eventually save enough pennies for an inspection.
 
So are you saying the feed to the consumer unit in the kitchen feeds a cooker control unit also?
 
Nope, the 10mm feeds the mini consumer unit, and the cooker(hob) control unit (and socket) is supplied from a 32A MCB in the mini consumer unit, alongside the two 20A MCBs for the 2 single sockets.
I guess this allows the hob to have its own mcb, as might be dictated by the appliance instructions.
The isolator(with socket) above switches off everything beneath the counter(dishwasher, washing machine and hob) as everything down there is connected to the mini consumer unit.

There is also a completely separate 10mm supply to the oven on the other side of the room.
.
 
Boolean said:
I guess this allows the hob to have its own mcb, as might be dictated by the appliance instructions.
Click to expand...

Appliance instructions don't dictate. They are guidance, so can be ignored if they are wrong, though I'm not suggesting they are in this case.
 
I agree that DIYers might not know but -

if a manufacturer 'dictates' that a hob must must have its own MCB, then it will be wrong.

(Especially difficult for cookers)
 
Also -

The manufacturer is much more likely to have stated that

"This appliance must be fitted by a qualified electrician", or words to that effect.
 
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