Consumer Unit... too many Amps

[flibberflops]

Hi,
I am having a new kitchen built and I assumed that I could just add an electric over + Induction hob without issue (it was previously Gas). However, as per the diagram below I have just realised that I am scuppered by a 32amp solar panel feed that is leaving me short on spare amps on the one RCCD side. I was intending to get a sparky in to just add the hob and oven wiring but i've just realised its probably going to be more involved than that. Can anyone recommend the easiest way to juggle what I have or tell me what is needed to do this properly? I haven't actually brought the hob/oven yet so I can tweak this if it makes things easier (but herindoors 100% wants to move away from gas)

 

[Robin0577]

Not a problem...

1. You can apply diversity. https://www.tlc-direct.co.uk/Book/6.2.3.htm

2, Your solar installation is an input, not a load. When generating at full capacity it might count as anything up to MINUS 32 amps in your calculations, depending on the external conditions. When it's dark outside, it will use a tiny amount of power to keep the electronics going but effectively counts as zero.

 

[ericmark]

My own 60 amp DNO fuse at 16 x RCBO's no problem. Where you may have a problem is the 80 amp RCD with 100 amp over load protection, we all know it will never reach 100 amp, and in real terms not a problem, but it depends on the electrician and how pedantic he is.

My induction cooker has a total load if all switched on and nothing cycling as up to heat of around 48 amp but it has never tripped the 32 amp supply.

 

[bernardgreen]

Also put one light circuit of each of the two RCCBs. Then if ( when ) an RCCD trips you will still have some lights in the house

 

[sparxxxx]

How do you know your main fuse is 100Amp? The 100Amp marking on the cut out just denotes cutout size. They are usually 60Amps, which is still more than adequate for your place

 

[flibberflops]

How do you know your main fuse is 100Amp? The 100Amp marking on the cut out just denotes cutout size. They are usually 60Amps, which is still more than adequate for your place

Someone has actually put a proper sticker on it saying so!

 

[sparxxxx]

Someone has actually put a proper sticker on it saying so!

Oh dear!!!!!

 

[ericmark]

Also put one light circuit of each of the two RCCBs. Then if ( when ) an RCCD trips you will still have some lights in the house

Yes looked at that with my consumer unit before changed, idea is if you do some thing to trip the RCD your not plunged into darkness as well, so for example down stairs sockets and up stairs lights together on one RCD and then upstairs sockets and down stairs lights on the other.

However splitting sockets side to side has many advantages to up/down, more even load, more even length, no need for emergency cables up/down stairs, so my house was split side to side for sockets, and up/down for lights, so it was simply not possible to arrange the circuits so tripping the socket RCD would not plunge one into darkness in all rooms.

The regulations say

314.1 Every installation shall be divided into circuits, as necessary, to:
(i) avoid hazards and minimize inconvenience in the event of a fault
(ii) facilitate safe inspection, testing and maintenance (see also Section 537)
(iii) take account of danger that may arise from the failure of a single circuit such as a lighting circuit
(iv) reduce the possibility of unwanted tripping of RCDs due to excessive protective conductor currents produced
by equipment in normal operation
(v) mitigate the effects of electromagnetic interferences (EMI)
(vi) prevent the indirect energizing of a circuit intended to be isolated.

It seems many do not consider the RCD as splitting the house into circuits, it is a grey area, with the old 100 mA type S RCD they did not tend to trip very often, so no one really worried, but with 30 mA RCD's they do seem to trip far more often for what is seems no good reason.

We are told the leakage in normal use for all circuits on a RCD should be no more that a 1/3 of it's rating, so 9 mA, but my clamp-on will only read down to 100 mA so I have no way to test, although the insulation test may show less than 1 mA, that is DC and we use AC, so we have inductive and capacitive linking which can mean quite a few mA is leaked.

So when I did this house I used all RCBO's so if even spread across circuits I could have 100 mA leaking without tripping the RCBO's but it cost more to install.

However if the RCD does not trip, then no problem, what I am not sure about with any item using a switched mode power supply is if there is a fault causing DC will we actually know? I consider with 14 RCBO's the risk they will be frozen by DC when required is low, so cancelled my order for type A, even with no RCD protection I would not say this house with a TN-C-S supply is potentially dangerous, to me the RCD is an extra protection, so not working is no real problem.

The point is not if perfect, but is it good enough, and I would not really be worried if my house was like yours unless if keeps tripping.

 

[Colin Brenton]

I think 'all RCBO' is preferable to 'dual RCD', I wonder if it might become required in the next edition of the regs??

Just a moot question, but presumably it's possible to mix type A and type AC RCBOs so each circuit has appropriate protection, without one type effecting the other?

 

[Astra99]

With both lighting circuits on the same RCD, I wonder if this is an older property, and the landing light is on the downstairs circuit's phase conductor with the neutral on the upstairs circuit! Very common setup in the days before RCDs.

 

[danechip]

Oh dear!!!!!

It also has the makers black sticker on the side too. Must be wrong

 

[sparxxxx]

It also has the makers black sticker on the side too. Must be wrong

The photo was posted after my comment

 

[flibberflops]

With both lighting circuits on the same RCD, I wonder if this is an older property, and the landing light is on the downstairs circuit's phase conductor with the neutral on the upstairs circuit! Very common setup in the days before RCDs.

Its a Dormer Bungalow, so there is only two lights upstairs. The downstairs circuits are split 50/50

 

[Lectrician]

The solar panels should not be sharing an RCD with other circuits.

 

[JohnD]

The solar panels should not be sharing an RCD with other circuits.

Perhaps so, but, Why?