If RCBO'S At £12 A Pop; And Reliable; Could Be Sourced

I wonder if these are any good, talking to someone in SF, about RCBO's on Monday, & he gave me this link, his brother in law had just bought a load of them.
Too cheap I say.

http://www.electricalcomponentsdire...-1E-1PB32-B-curve-32A-RCBO-30mA--4.html#SID=2

 

The problem is most RCBO's are single pole,yes you can get DP ones but they are not as common.

 

Why do you consider SP a problem then Phil?

 

There are some faults such as neutral earth faults where you can get circulating currents,particularly on tncs systems,plus you cannot use them on TT systems.Any fault should be cleared not just ones involving the phase conductor.

 

Wilts RCBO'S are that price and are good quality

Dual RCD Pffft!

 

For the majority of domestic installations RCBO's in single pole are very good.

I admit some installations do require a double pole and a far more expensive installation but the majority of installations in the UK are generally TNCS and a complete RCBO populated consumer unit either single or double pole is perfectly fine.

They trip just fine for residual faults, overload faults, short circuit faults appliance faults and so on which is what you want for a domestic property. They keep the property and life safe.
They are generally all rated at 6KA today as an industry standard and higher ratings are available if you have a higher energy circuit that requires it.

No one wants and exploding RCBO now do they...

In comparison, an 8 way fully populated RCBO board costs around £200 while a Split board cheap costs on average £100. I have seen some split loads cost around £180 so the extra cash for an RCBO unit really is not much.

Wylex do a fully populated 6 way for around £150 while a 8 way is around £190 so pricing is not that bad when purchased all together.

I am still scratching my head as to why ScrewFix or should we now call it ElectraFix has not stocked up on these RCBO populated consumer units yet.

City Electrical Factors have a consumer unit they have made for them specifically which has RCBO's the same size as an MCB and cost around £25+vat each i asked them to make up a fully populated board using them as a packaged price which looks to be around the £200 mark. That is a very neat Amend 3 mini RCBO unit with huge headroom for your wiring that gives you a true 10, 12 and 15 way board.

 

The question really is here:

Do dual RCD boards comply?

 

Of course they do if they're installed sensibly.

 

The regulation states - minimise. Is a dual RCD board 'minimising' disruption?

Definition of minimise is "Reduce something to the smallest possible amount"

Is an dual RCD board doing this?

 

As far as the IET is concerned yes they do if installed in the correct setting, depends how many circuits you have connected to each side.

I personally have never liked them as one fault can drop several circuits and create problems to connected equipment and home owners, after the first time i installed one i never bothered to continue installing them.
I since always use RCBO's, takes about 10 more minutes to test them though as you have RCBO's for all circuits. So sticking a plug into a socket circuit connected to a split load board to test the RCD is not possible.
You of course need attach via probes to RCD test each one individually which is not a problem if your tester accommodates for that.
The test sheet does get rather busy for an 8 way and above.

 

Upstairs lights, downstairs sockets on 1 rcd, and downstairs lights, upstairs sockets on the other one, doesn't always work that way of course but that's the general idea isn't it.

 

Well before we had dual rcd boards we had a single rcd, true the lights were not often on the rcd side but it still meant that all the sockets etc. went off together. No one made much of a fuss about that did they. And then of course there was the voelcb on TT systems, no one ever bothered too much about that either!

 

If backed up by a BS1361 type 2 fuse up to 100A and the consumer unit complies to BS 5486-13 and BS EN 60439-3. the maximum permitted PFC can be taken as 16KA

 

You can. There is still a double pole isolator with the main switch. Therefore the protective device does not need to break both poles (but is not suitable as an isolator in that case).

However if there is an upstream time-delayed (S-type RCD) then RCDs which do not break the neutral on a neutral/earth fault, i.e. single pole RCBOs, will leave the fault visible to the S-type RCCB and therefore risk operating it.

 

And BS EN 61439-3 in new money!

 

Indeed. A UK-only derogation in Annex ZA conditional rating (Annex ZB to BS EN 61439-3 I believe).

 

SP RCBO’s are not fit for purpose. The purpose of any protection device is to clear the fault not just some of it.

SP RCBO’s will not clear N→E faults, the one fault that has no over current protection.
BS7671 excludes them for TT supplies.
DP RCBO, SP+N RCBO or RCD will clear all faults.

Before you say N→E faults are nothing to worry about think about the consequences of upstream neutral faults and their effect on a local N→E fault. I’ve seen 40A+ on these faults.

Look at it as buying a new car on which half the brakes work. The manufacturer tells you the front brakes are too expensive so we didn’t bother.

 

I completely agree with much of what you say TonyS, however it isn't accurate to state that BS7671 precludes the use of single pole RCBOs in TT systems. As I mentioned above the means of isolation need not be the RCBO (or circuit breaker for that matter).

 

Not fit for purpose? You're talking rubbish! Mcb's don't break the neutral either, are they not "fit for purpose" either!