Any seen a RCBO like this before?

[Raptor0014]

Whilst looking for something else I noticed this on CEF and wondered if they had marketed it wrong and it was infact a RCCB and not a RCBO.

63A Double Pole 2 Module B Curve 10kA 30mA Type A Mini RCBO

Compact modular design

www.cef.co.uk

But looking at the data sheet it appears it is indeed a RCBO. Just curious as it doesn’t appear to have a neutral fly lead. So can only assume it is meant for the incoming supply rather than an individual circuit.

Has anyone used one before?

 

[pc1966]

I posted a thread here locally 2 days ago asking Irish sparks how they felt about the new single module rcbo,s that don t break the neutral. The response is disbelief.It would appear the both regulators and rcbo manufacturers have decided to not publicise this developement.Lets see how things develope

I would have to check, but I think the UK regs for TT require DP switching.

Now if you have a 100mA DP RCCB as incomer then some 30mA RCBO for shock protection you get most of that, but personally I feel it should be DP anyway, not just for the risk of a high-N voltage under fault conditions, but also so you get the desired selectivity between RCBO and any up-front RCCB.

 

[westward10]

For ADS on a TT system there is no requirement to switch the neutral, for isolation however all live conductors must be switched.

 

[pc1966]

For ADS on a TT system there is no requirement to switch the neutral, for isolation however all live conductors must be switched.

Thanks for that!

I might have been thinking of the caravan case which (again from flaky memory) have to be DP.

 

[nicebutdim]

I posted a thread here locally 2 days ago asking Irish sparks how they felt about the new single module rcbo,s that don t break the neutral. The response is disbelief.It would appear the both regulators and rcbo manufacturers have decided to not publicise this developement.Lets see how things develope

I hope you highlighted to them the manufacturers who provide single module options for isolating both conductors. Hagar seem to be a very popular brand, both in the UK and IE, but more than once I've found myself looking at their products and asking how this came to be the case.

I note that SBS have since been mentioned in this thread. They're another brand offering 1P+N RCBOs and their dual busbar means no neutral flylead.

 

[Peter - Retired Engineer]

One issue is the lack of discrimination between this upfront RCBO and downstream RCBOs in the new board. Is there a reason why a switchfuse wouldn't provide sufficient protection for the armoured cable?

Will the workshop have its own DB or is everything running directly off that one circuit? If it does have its own DB, can you tell more about it?

Hi, A bit of a delay in replying: Our electric 1/2 AGA 60, arrived a day early!
I agree with you that I'm not sure how any discrimination between the inline RCBO's will work. The one I have fitted today (As in the original post) is a 'C' curve, so hopefully will not cause any nuisance trips and the electric gates and workshop 'B' curve RCBO's will work on their own... I have just connected the EV up to the Zappi (protected just by a 32A MCB) - that's working fine.
As to a 'switchfuse', that would have been the simplest idea and bad planning on my part. I had fitted a 65A Isolation external switch, (just outside of the meter cabinet), but forgot about any overload protection. So I'm hoping everything is covered now.
My workshop when built (Builders did not turn up today), I will add another consumer unit inside with AFDD (18th Amendment 2 - wood construction), a lighting circuit and 2 radial circuits for the sockets.
Thanks for your professional comments.

 

[nicebutdim]

The issue of discrimination will not be affected by the different trip curves, as they relate to overload protection, and it will be pot luck as to which trips in the even of any fault involving imbalance between line and neutral. As the garage board is also to be populated with RCBOs, this would add a third possibility in the event of such a trip - not an ideal situation from the perspective of design or practicality.

 

[Peter - Retired Engineer]

The issue of discrimination will not be affected by the different trip curves, as they relate to overload protection, and it will be pot luck as to which trips in the even of any fault involving imbalance between line and neutral. As the garage board is also to be populated with RCBOs, this would add a third possibility in the event of such a trip - not an ideal situation from the perspective of design or practicality.

Thanks, I'll have to think about it before progressing any further. Will probably be a month before the workshop is built and ready for electrics... It might be easier to swap the first RCBO for a switchfuse...

 

[DPG]

Thanks, I'll have to think about it before progressing any further. Will probably be a month before the workshop is built and ready for electrics... It might be easier to swap the first RCBO for a switchfuse...

That sounds like a better idea to me.

Out of interest, what make of AFDD are you going for, and how much are they each?

 

[Raptor0014]

That sounds like a better idea to me.

Out of interest, what make of AFDD are you going for, and how much are they each?

Cheapest ones I’ve found I can get so far are Fusebox at £106.92 inc VAT

Had a customer last week asking for a quote for a full AFDD board which had 15 circuits.

Soon changed his mind when I said that’s £1600 in circuit protection before we even start with the rest of the materials, labour, testing, certification etc.

 

[pc1966]

Thanks, I'll have to think about it before progressing any further. Will probably be a month before the workshop is built and ready for electrics... It might be easier to swap the first RCBO for a switchfuse...

If you want reasonable selectivity that is the way to go, at least where the sub-main is in SWA so has no need for "30mA additional protection" itself.

Generally I would push the sub-main's supply fuse as high as the sub-main end of cable Zs will allow, but ideally still two steps down from the DNO fuse so it has selectivity with that. (e.g. DNO = 100A then 63A, or DNO = 80A then 50A should have total selectivity with it).

Your high-current selectivity between fuse and RCBO will depend on type and make, etc. For Hager their commercial distribution catalogue has handy tables of selectivity between BS88 fuse & MCB, MCB & MCB, etc. As an exercise, for 50A fuse and Hager 32A B-curve RCBO the selectivity limit is 1.1kA, so faults in the garage below that current ought only to trip the RCBO.

Of course, faults off a 13A fused plug or FCU will be totally selective with any supply fuse of 32A or above.

If you plan this as a workshop then supply selectivity is a bit more of a concern as a fault taking out the lights as well is a real danger. You might also want to put in some emergency lighting just in case (even for mains supply failure) so you are not plunged in to darkness with tools still spinning, etc. You can buy baton-style LED strip lights with battery back-up built in, that is a simple options.

 

[pc1966]

Cheapest ones I’ve found I can get so far are Fusebox at £106.92 inc VAT

Had a customer last week asking for a quote for a full AFDD board which had 15 circuits.

Soon changed his mind when I said that’s £1600 in circuit protection before we even start with the rest of the materials, labour, testing, certification etc.

Yes, quite eye-watering for now!

If concerned, I would probably look at 32A AFDD just on a couple of RFC for the sockets, rather like amendment 2 suggests (I think, not got it yet!), rather than all circuits.

 

[Raptor0014]

Yes, quite eye-watering for now!

If concerned, I would probably look at 32A AFDD just on a couple of RFC for the sockets, rather like amendment 2 suggests (I think, not got it yet!), rather than all circuits.

That’s what I suggested. Stick to the sockets only and at a push the shower, cooker and planned EV charger as they’re quite high loads.

But they decided on just having an all up RCBO board given it saved them a good chunk of ££’s

 

[pc1966]

Generally I would push the sub-main's supply fuse as high as the sub-main end of cable Zs will allow, but ideally still two steps down from the DNO fuse so it has selectivity with that. (e.g. DNO = 100A then 63A, or DNO = 80A then 50A should have total selectivity with it).

Just to add that obviously the sub-main has to be overload protected as well.

If the supply fuse is too high for that (i.e. chosen for only fault protection and good selectivity) then you should make sure the sum of MCB/RCBO fed off the sub-main provides such an overall limit.

For a garage/workshop you might only be talking 6A circuit for lights (fixed load, probably 0.5A these LED days) and something like 20A-32A for socket outlets. So if the sub-main has a CCC of, say, 40A installed, then 2*20A radials or 32A RFC would not overload it, etc.

 

[Peter - Retired Engineer]

That sounds like a better idea to me.

Out of interest, what make of AFDD are you going for, and how much are they each?

Hi again,
I have been into CEF and they don't have a custom made consumer unit with an AFDD already 'plumbed' (sorry rude word!) in yet as they do for SPD - Just looked at the price for an AFDD - £130!!, never mind the CU! I can see why you asked now...

 

[nicebutdim]

It's likely that AFDD prices will start to reduce as more manufacturers introduce them to their ranges, but dramatic price reductions will likely only happen if they are mandated at some point in the future and production ramps up significantly.

 

[Mike Johnson]

The problem with dual module RCBO's is the size of UK boards, soon run out of room on a decent size domestic installation, but agree that going back to fly leads is a retrograde step, how about the white earth lead as well.

FYI In Europe the dual module RCD's and MCB's have the incoming across the top with off set terminals to allow horizontal bus bars, on the multi row boards there are vertical bus bars also available to power the RDC for each row, even for three phase.

Or if you want to use a non offset dual RCD/MCB combination there is this available: A9XPH224 | Schneider Electric Acti 9 2 Phase Busbar, 415V ac, 18mm Pitch | RS Components - https://uk.rs-online.com/web/p/busbars/7762724

 

[DPG]

Hi again,
I have been into CEF and they don't have a custom made consumer unit with an AFDD already 'plumbed' (sorry rude word!) in yet as they do for SPD - Just looked at the price for an AFDD - £130!!, never mind the CU! I can see why you asked now...

Indeed, and don't forget they are per circuit rather than one per consumer unit like SPDs.

 

[pc1966]

Indeed, and don't forget they are per circuit rather than one per consumer unit like SPDs.

Yes, I think we will start to see "one RFC for the house and one RFC for the kitchen" becoming the norm!

Unless the prices really do drop to RCBO like levels, which remains to be seen. Mind you, I have seem them come down from £120+VAT to £99+VAT so only a couple more years...

 

[Mike Johnson]

Indeed, and don't forget they are per circuit rather than one per consumer unit like SPDs.

And also don't forget they don't work?

 

[pc1966]

And also don't forget they don't work?

And (to my knowledge) not testable for the arc-part on any MFT.

 

[DPG]

And (to my knowledge) not testable for the arc-part on any MFT.

To be fair, neither are MCBs.

 

[pc1966]

To be fair, neither are MCBs.

True, but they are somewhat simpler and less likely to fail!

Also it is easier to test for a fault that would trip them using the IR part of the MFT's capabilities (and Zs for those faults leading to them not being able to trip).

 

[Raptor0014]

And (to my knowledge) not testable for the arc-part on any MFT.

I was told recently at an Expo that as part of the certification process for AFDD they have to self test and will indicate if it fails.

Dave Savery did manage to build his own test rig. But as it’s supposed to be a manufacturing process test then there’s no requirement, currently, to test them on installation. Other than to check the self test has performed and indicates all is ok.

 

[Mike Johnson]

So if they self test and indicate that all is OK should I sell my MFT? Will this be the demise of the EICR and the electrician?

 

[Raptor0014]

So if they self test and indicate that all is OK should I sell my MFT? Will this be the demise of the EICR and the electrician?

It’s only the AFDD part that’s the self test.

Still need to test the RCD function. But remember as per Amdt 2 it’s only the 1x test that is required now.