6kA (Not 10kA) RCBOs in commercial TP boards: Why not?

[Mark42]

I'm fitting two replacement sub-mains panels as part of a long-term upgrade from split-phase to three phase on a part-domestic part-commercial site (my own gaff). I'm using all RCBOs because I like them, but am less keen on the cost of the commercial variants ...
Fellow spark says one MUST use 10kA breakers in a TP board because it's commercial kit. I say rubbish, so long as 6kA-rated devices physically fit and the fly leads are long enough (Hager's are) and as the Potential Fault Currents are nowhere near 6kA anyway (at the end of long SWA runs), 6kA units are technically fine.
Am I missing anything?

 

[Deleted member 26818]

Do the boards comply with BS EN 61439-3?
Does the manufacturer list the 6kA devices as an option?

 

[Nigel]

It would depend on your measured Ka.

What is it?

 

[Deleted member 26818]

It would depend on your measured Ka.

What is it?

He says it’s less than 6kA.

 

[Baddegg]

CEF, MCG brand rcbos come in 10ka variant with long fly leads...cheap as chips as well

 

[ChrisElectrical88]

What was your PFC? Dobt forget to double your single phase value for a three phase installation if measured each phase to earth.

6kA will be fine if the manufacturer do that. Schneiders KQ boards for exanple also fit the SQ breakers in and allow it.

 

[Leesparkykent]

Hager 6Ka RCBO’s have a shorter neutral lead than their 10Ka variants. Depending on the size of the board the neutral tails will start to not to reach the further you get away from the neutral bar.

 

[Wilko]

Hi - I'm not aware of a restriction "must be 10kA for 3 phase switchgear", but there certainly are other factors to consider as have already been mentioned.

Interestingly, there is the 60947-2 standard where the rating is higher for pollution, voltage withstand etc. The 60947 devices are intended for industrial use, while 60898 /61009 are more suited to cleaner domestic / office situations. There are some devices where manufacturer has certified them to both standards, as mentioned in this article.
IEC 60898-1 AND IEC 60947-2: a tale of two standards - https://blog.schneider-electric.com/energy-regulations/2014/02/06/iec-60898-1-iec-60947-2-tale-two-standards/

 

[freddo]

For some brands the 6KA stuff wont fit the 3PH boards as the busbar terminal is too narrow for the busbar.

 

[Mark42]

Do the boards comply with BS EN 61439-3?

Yes, of course Hager Invicta 3
Technical Properties JK118BG - https://www.hager.co.uk/product-catalogue/energy-distribution/commercial-distribution/invicta-3-type-b-distribution-boards/125a-invicta-3-type-b-distribution-boards/jk118bg/67228.htm

Does the manufacturer list the 6kA devices as an option?

Good question. I just checked the spec sheet, and it appears not. They quote only the expensive 10kA variants. But this could be a 'so what?' situation.

 

[freddo]

IIRC Hager are ones that don't fit, the flyleads are too short as well. Their new compact RCBOs the flyleads are almost too short for the single phase boards...

 

[Mark42]

What was your PFC? ...

Less than 1.5kA phase to earth on the first run. Waiting for the second supply cable (25m of 5 core 16mm NYY) to be fitted on the second.
The whole lot is behind 3No. 100A cutouts anyway. It's effectively a domestic supply.

 

[Mark42]

IIRC Hager are ones that don't fit, the flyleads are too short as well. Their new compact RCBOs the flyleads are almost too short for the single phase boards...

I haven't tried the new compact RCBOs yet. They look useful in giving more space in a board full of the things. I may well go for these, but they are only available in 6kA I believe.
And I'd rather extend a few neutral leads than spend hundreds of pounds extra on unnecessary 10kA RCBOs. Unless there's an undiscovered technical reason why I must, which is why I'm consulting the Oracle here

 

[Mark42]

ps. I'm a great believer in 'commonality of parts' in designs. This is my own house: I want to carry on using Hager everywhere,
then it's easier to keep a few spares of everything.

 

[ChrisElectrical88]

I am sure you will be ok with the 6kA rated RCBOs. If they are suitable for the fault current then i personally see no issues.

Go in shops, hotels, schools and you will find tonnes of non 10kA MCBs in the three phase boards. I have seen lots of M3 breakers in three phase boards.