Best RCBO CU?

[pappasmurf]

hi all, have a similar problem..... would like to choose an RCBO consumer unit but am confused as to which brand to use even on here everyone seems to have their own preference as to which one is best!
project:- just bought a soon to be 8 bedroom house with one section of the house to be letted out. this letted out section of the house will consist of 1 bedroom, 1 living area, kitchen, and a shower/toilet. The shower will "not" be electric, and will be plumbed into the house plumbing.
The hobs will be gas, the ovens will be electric in both kitchens.
There will also be 2 immersion elements in the megaflow cylinder.
The property will also have an out-building (office) with an airconditioning unit.
Can someone tell me if i go down the route of using RCBO does that mean that it "replaces" the need for RCD's on the CU?
i was thinking of using 2 CU's one for my side of the house and the other for the flat to be letted out. Is this necessary or can i just get a say 20 way RCBO board for the whole lot?.... i know one of my neighbours with exactly the same lay-out had 2 CU's put in for this same purpose, and a seperate isolation unit also installed for their out-building.
i need to use the rolls royce of CU's so pls help, many thanks in advance

 

[ericmark]

Really no such unit each make has plus and minus with some RCD's with monitors built in and some auto resetting these can be linked to the MCB so they form a RCBO even the whole question of RCD or RCBO is not simple with the problem of a RCBO tripping without one realising.
It's all down to personal preference. Twin pole may be best but the CU size increases also tend to be more commercial in look.
With the problems with Part P and just not being worth doing DIY the best is to ask the electrician doing the job.

 

[PrenticeBoyofDerry]

pappasmurf,
There are a few things to consider with your intended installation of a single CU.
One is the metering, if you are to let a section of the property, how are going to determine to bill for your tenants electric usage.
The convenient practicality for tenant to be able to isolate/re-energise their power if needs be.
The maximum demand of the consumer unit.

There are number of different formats of consumer unit available.
The most common ones for domestic purposes will offer:
A single RCD protecting all circuits. (not really recommended)
Dual RCD protection protecting two banks of circuits.
Split protection where one bank of circuits are protected by RCD and a number of circuits can be protected by RCBOs.
or where all circuits are protected by RCBOs.
Prices will vary depending on which one you select.
In your instance you could be spending as little as £60 or over £800.
The make and model you select is personal choice as one man's robin reliant is another man's Lamborghini.
If you stick with the well known brands you want go far wrong, but each will come with it's own pro/cons.

 

[AndyPRK]

normally you would have a 2nd CU for the flat, and a seperate meter.

This small CU could be all RCBO.

But I wouldn't normally all RCBO a 20 way CU

 

[SimonH2]

Can someone tell me if i go down the route of using RCBO does that mean that it "replaces" the need for RCD's on the CU?

Yes it does - each RCBO has it's own RCD. It is generally a bad idea to have more than one RCD in the supply to any circuit since they will both normally trip* if there is an earth leakage fault.
As you've probably worked out, going all RCBO has the advantage that a single fault will normally only take out one circuit, which is far preferable to a fault taking out half the circuits in the house.

Using "budget" makes means the cost isn't too high, but then you do get budget quality. I've a couple of Pro-Elec boards sold by CPC with RCBOs at about £12 each - all I'll say on quality is that I have spares of each size and I've used one already (faulty from new). Electricians opinion was "about normal" for a budget plastic unit. Go with "quality" brands and the cost rockets somewhat - though not half as bad as it was only a few years ago.

As a landlord myself, I'd go with the other comments - you want the rented bit as separate as you can. Tenants can and will do things you "don't approve of", and I can't imagine having them knocking you up at 3am on Christmas day to reset the breaker will go down too well in the Smurf household. If something trips, they will knock you up no matter what the time as it will be your problem and they will expect an instant fix - I've had a tenant demand that I fix the boiler there and then, it was not acceptable 9to them) to wait for a qualified person to come like they'd have to do if it was their own boiler. You absolutely do not want a situation where a fault in their side will take out any of your circuits.

* There are exceptions where one of them is time delayed, but that's not common for a domestic CU.

EDIT: Also, if they are not metered for their lecky/gas/heat/whatever then they have no incentive to minimise their usage.

 

[pappasmurf]

SimonH2.... so which RCBO CU would you recommend?.... there are loads!.... wylex,MK etc.... it seems as though every electrician i speak to has their favourite pls advise.

 

[EFLImpudence]

it seems as though every electrician i speak to has their favourite

They have.

pls advise.

We can't - you may not like it.

hager

 

[JohnD]

MEM

 

[SimonH2]

so which RCBO CU would you recommend?.... there are loads!

EFLImpudence has summed it up quite well - every electrician has their favourite.

Obviously cost is a factor. Most users don't really understand why some kit costs more than others, hence if you are quoting for a job then cost is a big factor.
Reliability then comes into it. If you put in unreliable kit then it costs to go out and fix it - but then some of the "premium" brands haven't been immune to the cost cutting and reduction in quality that goes with it.

Before I leave costs, it's not uncommon for manufacturers or wholesalers to have promotions. Now, the chance for <some freebie> if you buy enough of <something> may well influence choice of what to recommend.

Then you have intangibles. How "nice" is it to work with for example, and what range of enclosure styles is there.
A large box makes wiring easier - particularly important when using RCBOs which are physically larger than MCBs. Metal cases (or at least internal trays) can make the whole thing more rigid which helps with getting everything to stay put - while some cheap units have incredibly floppy plastic enclosures that can be fiddly to get the lid on properly. If the customer wants a recessed CU, then a range without any recessed options isn't any good.
And so it goes on.

From the professional electrician's POV, there's also the issue of having to support what he's put in. If he installs what's available off the shelf at the local wholesaler then he knows he'll be able to get spares easily and quickly (most of the time). If it's something he's installed a few of, then he can afford to carry a few key spares (eg a spare breaker in the common sizes). If he fits some odd-ball that needs to be ordered in, then any spares will also need to be ordered in which may delay repairs.

As I mentioned, I've used several Pro-Elec CUs (such as this one) - mostly because of price. The cost is low enough to make a fully RCBO board competitive with a dual RCD board from many other manufacturers. But, the case is flimsy, there's not too much room inside (but enough if you are tidy), and I've had one RCBO that's been DOA. Most definitely from the "pile em high and sell em cheap" end of the market. But, I'm in a position where I can change a breaker if one fails in service - and I've got spares for each size I've used (that should tell you something about my expectations of quality). They have passed installation tests *.

Would I recommend them ? Well that depends. They appear to work, they aren't that nice, and the range of enclosures is very limited - but they are cheap. Take your pick !

* There are stories of cheap MCBs making it here from the far east that don't actually have any gubbins inside them, and hence wouldn't trip if there was a fault

 

[RF Lighting]