Consumer unit circuit ordering

[Jeff Phillips]

Can the panel cast their eye over the following circuit order for a 15- way high integrity split CU in a 3-storey house and make any suggestions for improvement?

100A MAIN SWITCH 6A 30mA RCBO Smoke Alarms <spare> 80A 30mA RCD covering: 32A Oven 32A Hob 32A Middle and Top Floor Sockets 6A Ground Floor Lighting <spare> <spare> 80A 30mA RCD covering: 32A Kitchen Sockets + Appliances 32A Downstairs Sockets 16A Immersion Heater 6A Middle Floor Lighting 6A Top Floor Lighting <spare> <spare>

[George Miles]

[ARW]

Any gotchas or is this a genuine question?

[spuorgelgoog]

I would always put them on a lights circuit, then you'll notice if that circuit trips fairly quickly (and get it fixed). Similarly for a freezer.

Will they not go on one circuit?

I put my lounge and main bedroom have ceiling and wall lights on different circuits/RCDs

Owain

[Jeff Phillips]

Apologies; genuine question! :-)

Doing a fair bit of DIY (including wiring) and have decided to replace the current whole-house RCD'd CU and so with everything out thought I'd ask for suggestions.

[Jeff Phillips]

Hmm... yes - that sounds a good idea. The smoke alarms have battery backup but of course that would only become apparent after some time, and the missing power LED would unlikely be noticed.

I did wonder that. There's a new kitchen going in with a new - as yet unspecified - electric oven and induction hob (to replace a gas hob). To maximise choice, both now and in the future, I was planning on running two circuits, but perhaps that's overkill?

[Jeff Phillips]

That makes sense, but then so does Owain's suggestion of having them tied in with a lighting circuit to make it obvious if they trip! I suppose there's no perfect way.

[Bob Eager]

I put them on a dedicated circuit, but also include a non-maintained emergency light halfway down the stairs (at eye level as you descend, on the edge of the landing floor if you see what I mean).

That will give some light to the stairs, and both floors, in case of a power failure, while also alerting you to a trip at other times.

[stephenten]

I actually put my intruder alarm, smoke detectors, carbon monoxide and cctv system all on a 6A rcbo.

All of the alarm keypads start beeping in the event of a power cut or if the rcbo trips so you get audible warning.

It also happens to be the case that one of the interlinked smoke alarms has an interface box which is then connected to a spare zone on the alarm panel.

Ditto for the carbon monoxide detectors which is on another zone.

So the main alarm panel goes off too if the smoke or CO detectors sound.

My cctv Recorder has a set of alarm interface terminals so if the recorder detects a fault such as loss of video or loss of hard disc drive, the keypads also pick it up as another additional zone.

I had to buy a UPS for the cctv and for the cable modem as neither has battery back up like the smokes or co or alarm system.

The alarm panel is also able to send me me text messages and the cctv system can send me emails.

It's all down to appropriate well thought out system design.

[John Rumm]

I would swap the middle and ground floor lighting, so you can't lose lighting on two adjacent floors from one RCD trip.

[stephenten]

P.s my consumer unit is an all rcbo design which means:

More room for more circuits as you can get 4rcbos in the same space as two RCDs

Improved circuit fault discrimination so you don't lose half the house circuits should a rcd trip.

I have also separated all outside stuff onto its own rcbo so nothing on the inside is affected should something go wrong outside. So I have a rcbo for outside lighting and another rcbo for outdoor sockets

The combi boiler is also on its own 6a rcbo so I minimise a chance of a burst pipe due to a trip caused by anything else connected to the same rcbo developing a fault condition.

Another point is that an rcd had a trip current of 30mA and with several downstream mcbs, they will all contribute that trip current via things such as switch mode PSUs. With a split load cu, nuisance trips are common.

I have 16 rcbos in my cu so each circuit has all of that 30mA trip current threshold each. Ever since I installed it, I have not had one single nuisance trip on any of my 16 circuits.

[Bill Wright]

Better with the freezers to have Brennan freezer alarms. Then you are notified immediately.

Bill

[stephenten]

P.s. the burst pipe I mentioned is for winter where I rely on the central heating with the thermostats set to frost protection or to ensure maximum availability of central heating and hot water.

[stephenten]

I found that the cost of 16 rcbos was not much more than the cost of two RCDs and 16 mcbs....

I have a 18 way consumer unit where 16 Rcbos would fit leaving me with two spare ways but 16 mcbs and 2 RCDs would not fit as that would require a 20 way cu.

[Jeff Phillips]

Thanks Bob, that sounds like a great idea. I see you can get recessed LED downlighter versions which should work well on our middle lighting for providing some illumination for both stairwells whilst not presenting any aesthetic issues.

Having only performed a cursory search for options it seems that they often only provide a 3hr illumination time. This would be fine for an alarm but perhaps not that useful for power failure notification. Perhaps I just need to do further searching?

[Jeff Phillips]

And I suppose would also cover other (non-power) faults too.

[ARW]

My suggestion is to put the kitchen sockets on their own RCBO and consider doubling up the smokes with a lighting circuit of your choice.

[Jeff Phillips]

Thanks Adam. Can you elaborate on the RCBO for the kitchen? Is it the likelihood of nuisance trips from likely leakage in that area?

[stephenten]

One thing I have heard is that an 32A rcbo is used for under counter appliances like washing machine, dishwasher, fridges and freezers. A 2nd rcbo is used for the wall sockets that are used for kettles, toasters, hand mixers etc.

The kitchen is easily the highest electrical load room in the whole house!

If you have a utility room, I would consider a separate rcbo for that room too.

[spuorgelgoog]

But *won't* give you emergency light if your ordinary light circuit fails but the dedicated circuit is still on.

It is a useful indicator though, and emergency lights are also good. On my list is one for the (internal) bathroom which is completely dark without power.

Owain