I am about to undertake my first house re-wire project but am undecided on what consumer unit to use. I could either use a split board consumer unit with both sides rcd controlled, or use a split board with one side rcd controlled and the other side rcbo controlled on individual circuits. What are the advantages and disadvantages of both? And if going for the rcbo option which individual circuits would best be protected by the rcbo's?.
I'm a massive fan of all-RCBO consumer units: more wiring room in the box, more flexibility on circuit planning and more convenience for the customer. All this for a slight increase in parts makes it a no-brainer for me as it's a fraction of the cost of a rewire. On board swap only it can be different.
I use boards from Denmans or Wilts that are a bargain and as good as any other make in quality. They do ready loaded boxes or individual. For pricing it up RCBOs are a tenner this way, breakers a quid or two, the empty box 20-30 quid. One example is an 14way board with 8 rcbos for a ton!
Some factors to consider are:
Amount of space to mount the consumer unit. RCBO boxes are taller, but may take up less width than an equivalent split load one.
Number of circuits - the number of RCDs increases the cost.
Type of circuits. If you've lots of chunky cables you need more space to work with
It's common with a split-load to have two main RCCBs doing nearly half the circuits each, then some spare ways for non RCD protected or RCBO circuits. This is sometimes called high-integrity but IMHO and RCBO only board is the only way to achieve that.
I`ve never got my head around this one. Why would anyone EVER want to put in a separate circuit for a damn fridge?
Why stop there? Every appliance that you intend to have plugged in all the time could have its very own radial. Tv, skybox, DVD, `phone, kettle, toaster, fridge, freezer, hairdryer etc.
WHY!!!????
I think it's a convenience and cost issue rather than an electrical safety one to have a separate circuit. There is often hundreds of pounds worth of food in a freezer which is costly and a pain to replace if the power is off for more than 24hours. Better to have the freezer separate from other circuits so if the others trip while the installation is unattended then no food is ruined. If most other devices (apart from life-critical ones) lose power while the house is unattended than maybe the worst that'll happen is the sky+ won't record...
One advantage of radials in general is that if the circuit has failed, the appliance won't work. Quite a lot of kitchens are wired with individual radials from a big gridswitch arrangement.
I totally like friges and freezers on their own circuit without RCD protection. I've had so many call outs over the years to check out RCDs /
circuits that have tripped whilst the customer was on holiday and lost the contents of said appliances. It isn't always feasible to do this,
but IMHO worth doing if you can. As for smoke alarms as someone mentioned earlier, I do not like putting these on their own circuit as a
faulty lighting circuit gets noticed far sooner albeit most smokes (but not all) beep annoyingly these days if leccy is off.
Agree with the freezer, but the smokes issue I don't. Lighting circuits regularly trip and power outages to alarms should be minimised. BS5839 and Building Reg part B also recommend a standalone circuit. It's mandatory if the alarms have no battery back up. I appreciate in a retro fit situation it's easier to grab the nearest lighting point for power, but in a re-wire there's no excuse. I found some summary helpful info
http://www.safelincs.co.uk/pages/bs5839-6.html
Also, the 'beep' is designed to be annoying! Smoke/Heat/CO detectors are life-saving devices and should be welcomed not endured. I got criticised on a recent install as they didn't match the decor. When I pointed out there would be no decor/walls in the event of a fire maybe the little white box was worth the visual addition. Also, they didn't need to look up, and that some of us find alarms pleasant to look at!
Without yet finalising plans I think there will probably be ten circuits, three ring (upstairs, downstairs and kitchen), three lighting (upstairs, downstairs and bathroom), shower, cooker, boiler and possibly one for garage supply. Ideally using rcbo's on all circuits would be the right option but due to the higher costs of these it may not be practical.
I am a maintenance electrician in a manufacturing plant and am not up to date with the seventeenth edition wiring regs so will have to brush up on these before I start the re-wire which I am doing for a mate of mine.
I often split my lighting into 3 circuits as well but into 1,Upstairs rooms (incl Bathrooms), 2,Downstairs rooms, 3,Access areas - porch, hall, landing, loft etc. The theory being every adjacent area has lighting on a different circuit.
BTW If you go split-load then you need to put lighting and power from the same area on different RCDs so that a lamp can be on when a lighting circuit trips.
You might find radial power circuits will do for upstairs and locations with lowish current draw and save cable.
I'd consider separate circuits for Kitchen, Laundry, Garage, Shed/outside, Upstairs power, Downstairs power, Boiler, Immersion, Shower, Cooker, Hob, Alarms, Freezer, Lighting x 3. This is why some spare space in the board is handy, you never know what they'll want to add!
Cheers guys, will check out your recommendations. As for smoke alarms that will be something else to look into before finalising the plans.
I appreciate your reply's
As I've said above, smoke alarms are a must on a rewire. Check
http://www.aico.co.uk/electrical-contractor.html for loads more info on it.
Depending on customer and house size/layout I normally put at least 5 in - Heat Alarm in Kitchen, Multisensor or Optical Smoke(s) in Hall and on landing, Heat in Garage, CO in any room with a gas fire or hob or boiler. Ionisation Smoke alarms I have put in all bedrooms too, but that was a big extra. The Aico or Kidde ones I've used are flippin loud on the landing as it is!
Oh and a remote switch to do Hush/Test & Locate is a really nice easy addition put somewhere handy
Enjoy your wiring fun!
