18th Edition Compliant Consumer Unit

[RutlandFox]

Hello all.

Quick question: Are 17th reg 3rd amendment metal consumer units compliant with 18th edition regs?

eg Hager VML716RKO

Many thanks (Newbie)

 

[spark 68]

Oh I don't disagree, a full RCBO board is always nice to have if the customer will go for it, however they should always have been DP, or at least SPSN from the get go for obvious reasons.

 

[Toneyz]

I understand that Hager is going to install 100A as standard in the split boards you watch the assessors pulling us up on it.

 

[Ian1981]

Historically we have used diversity of the final circuits to ensure that the rccb is not overloaded.
Now it seems we can not rely solely upon diversity of the final circuits downstream of the rccb and overload protection must be ensured by other means like having the upfront ocpd rated lower or equal to the rccb and main switch or ensure that the final circuits added are not greater than the rccb and ensuing manufacturers instructions are complied with.
I know with Hager they have taken the approach of fitting 2x 100amp rccb’s (Also now type A) in their dual rcd consumer units so obviously they intend to ensure that their rccb’s are not overloaded and have defaulted to use 100amp devices.
This is certainly the guidance also given by my companies scheme provider.

 

[spark 68]

Which reg states that though Ian ? 536.4.202 doesn't as far as I read it, Hagar is only one manufacturer out of many.
I normally take what you have to say seriously as you are one of the few that happens to know what you are talking about.

I had a look at the corrigendum for the 18th (yes mistakes again!) and nothing was mentioned wrt to this.

 

[Wilko]

I think it's the last para of that reg that's the killer, where they state " OCPD rating shall be selected in accord with manufacturer's instructions" . Rightly or wrongly, Hager has jumped in with both feet.

 

[spark 68]

Yes I know, however the same regs also state manufacturers instructions shall only be taken account of they cannot have it both ways. don't you just love the IET

 

[Toneyz]

Manufacturers should have nothing to do with the writing of the regs.

 

[spark 68]

And another thing the RCD is not a OCPD so as long as you stick below its design current Ina things should be fine, and no you cannot just add the breakers up as that would have a massive knock on effect wrt to diversity, The effing IET don't there ar*e from their elbow.
CIBSE should take over at least they seem to know what they are doing.

 

[Ian1981]

536.4.202 states that overload protection shall not be solely based on the use of diversity factors of the downstream circuits.

536.4.3.2 states that rccb’s and switches to BSEN 60947-3 do not provide protection against overload therefore they shall be protected by an over current protective device

 

[spark 68]

Which is done by the downstream MCBs, your design current is what counts

 

[Ian1981]

The key sentence is that we can’t rely solely upon diversity of the final circuits and that manufacturers instructions are followed.
Given that Hager have jumped in and defaulted to using 100amp devices , my interpretation is that we must ensure the rccb is protected by not relying on the diversity factor

 

[Ian1981]

Sorry the pictures aren’t in order

 

[spark 68]

Are you telling me that say 3X 32A breakers plus a few 6A for ligting are going to exceed the 100A mains switch not to mention the absolute max of a 100A BS1361 type 2 incoming fuse ?

 

[Ian1981]

Are you telling me that say 3X 32A breakers plus a few 6A for ligting are going to exceed the 100A mains switch not to mention the absolute max of a 100A BS1361 type 2 incoming fuse ?

No however Jpel/64 or Beama who are on the panels aren’t they are tell us yes?
As if a domestic installation will ever exceed say 80 amps or even 63 amps depending on size and the likes of heavy loads like showers.
I think the fact the potential could be there to cause overload is the driving factor to the regulation(s)

 

[spark 68]

As I said, we always had to design around a split load board, ie. we divided the circuits up and tried to load split anyway, just the regs never explicitly said we should, although this was common? sense to anyone sparking professionally.