Shower wiring

[bremen1874]

I need some rewiring in my kitchen. Due to my lack of success in finding an electrician willing to come and have a look I've had time on my hands and I've been looking for potential problems.

My shower is supplied via a small secondary CU next to the original CU. The secondary CU contains 63A/30mA RCD and what I assume is a 40A MCB (B40). There is then 10mm T&E to the shower via a DP switch outside the bathroom. I think the shower is 10.5KW.

The main breaker in the original CU has two pairs of cables connected to its ouput side. One pair feeds the original CU and the other pair feeds the secondary CU. The pair that feeds the secondary CU are 25mm and significantly larger than the pair that feed the original CU. It looks wrong to me, but is it a problem?

Thanks.

 

[jj4091]

It depends on the rating of the circuit breaker & the rest of the load on the consumer unit.It is unusual though.

 

[Adam_151]

Can we have a picture?

 

[bremen1874]

Having taken the CU covers off to take a picture I've realised that the tails supplying the shower CU are actually connected to the input side of the main switch along with the tails coming from the meter cupboard. The earth linking the CUs looks like 10mm.

Here are the pictures...

 

[Steve]

The old CU is due for replacement - its got a wooden back and those breakers are obselete. Nicely wired though (except the piggyback)

The small CU is wired in a questionnable way and has an exposed busbar when open. It is also a cheap and nasty brand, and the B40 is not enough for your shower. You need a B50. The spark who fitted it, i guess didn't want the hassle of installing henley blocks etc.

Replace the lot. The incoming tails are undersized.

 

[jj4091]

Not seen it done that way before, but I do not think it contravines any regs. as long as none of the strands of copper wire have been removed to allow entry into terminals. I would guess it has been like that for quite a time & would not be overly concerned about it. The meter tales do not meet current regs. but would have been ok when they were installed.

 

[bremen1874]

The wiring has been as it is for at least 5 years as it was there when I bought the house. The shower has always worked okay and neither the MCB or RCD have ever tripped. It appears to be 9.5KW rather than the 10.5KW I thought it was.

As far as I can tell all of the strands in both sets of tails are intact. They're a tight fit into the switch but look okay.

Replacing the CU isn't an option at the moment unless it's for safety reasons.

Is the current arrangement likely to cause me problems when I get an electrician in to look at my kitchen wiring?

How big should in the incoming tails be? The fuse in the meter cupboard is marked as 100A. Here's a picture...

 

[Steve]

The fuse CARRIER is marked at 100 amps. The fuse inside may not be, and should not be with 16mm tails. You ought to have 25mm tails, but getting the DNO to upgrade their tails to the meter can be more trouble than its worth.

 

[jj4091]

Is the current arrangement likely to cause me problems when I get an electrician in to look at my kitchen wiring?

It depends on what your requirements for the kitchen are, they will tell you when you ask for your estimates. You will probably have to have the main earth cable & bonding replaced as that does not look big enough either.

 

[bremen1874]

The kitchen wiring just involves moving a few things to fit the new layout and a couple of extra sockets.

The earth from the meter cupboard to the CU is 4mm, as are the earth cables that go from the CU to the bathroom and kitchen plumbing. How big do they need to be? Replacing the internal earth cables shouldn't be a problem, but the termination inside the meter cupboard is inside a box with lead seals.

Obviously all these questions will hopefully be answered when I do get an electrician in for a quote. Unfortunately I've so far I've failed to find an electrician willing to even come and have a look. I assume they're all busy on bigger more lucrative jobs.

 

[jj4091]

Keep trying. Good luck.