RCBO's on a TT system.

[Bobster]

Shneider supply with their sp rcbos a warning label not to be used with TT or IT systems.

When they were first released the warning also warned for them not to be used with PME systems.

 

[SPARTYKUS]

Rob

isn't that for the one in 458 million chance that a house looses its Neutral, and also has a fault at the same time.....

 

[spark 68]

Here is a snippet taken from an online catalogue, it may also be buried somewhere on the Schneider site (which is a nightmare to find anything lol).

Schneider Electric A9D11820 iC60H 1 Module SP+N Type C RCBO 20A 10kA 30mA


The single-phase iC60H RCBO’s self-contained residual current device carries out complete protection of final circuits: protection against short-circuits and cable overloads, protection of persons against electric shock by direct contact (10, 30 mA sensitivities), protection of persons against electric shock by indirect contact (100 mA sensitivity), protection of equipment against fires set by leakage currents (100 mA sensitivity). The neutral is not interrupted when the device is tripped. Hence iC60H RCBO can be used on most circuits, except for the ones operating under TT or IT earthing systems.

I also think the same information was in MK literature.

I suppose an upfront TD 100mA RCD may make them suitable as far as the reg concerning disconnecting all Live conductors goes, as it would do with fuses in older boards, but then you have the problem that SP types don't disconnect the N-E fault which then trips the whole lot out as has already been said.


Edit: Rob beat me to it lol

 

[Des 56]

Thanks all,

I now feel more ill but at least I understand correctly the different types of RCBO available!

Still cant figure out if anyone has actually stated if an RCBO (solid neutral) meets the regs for a TT though!

I think, judging from everything I've read that it does. Better to use SPSN or DP but it does meet the regs.... I think!

ps.. I can almost hear you taking a big deep breath S68 and thinking, "ok, how can I write this any clearer?" :smile5:

In the link posted by Tony is a post by Malcolm,he gives an answer to your question

 

[mattg4321]

Dredging up an old thread here.

Shortly have a board change on a TT supply to do. Normally I'd fit 100ma S Type up front and then dual RCD as I don't really see a big benefit in solid neutral RCBO's when you have an upfront RCD.

On this particular job I have a couple of distribution circuits in the consumer unit that I want to achieve good discrimination on. I was thinking of fitting a high integrity (normally use Hager) CU and fitting 2x Hager ADA932U RCBO (1P+N) on what would normally be the 'unprotected ways'.

Hagers website states they can be used in Consumer units but I'm unsure how they fit, being double width. Is it a case of just cutting off the busbar prong where necessary? Seems a bit heath robinson.

Anyone have any better ideas?

 

[Midwest]

Just thinking this through, what are you putting in the rest of the CU, dual RCD & MCB's?

 

[Leesparkykent]

Dredging up an old thread here.

Shortly have a board change on a TT supply to do. Normally I'd fit 100ma S Type up front and then dual RCD as I don't really see a big benefit in solid neutral RCBO's when you have an upfront RCD.

On this particular job I have a couple of distribution circuits in the consumer unit that I want to achieve good discrimination on. I was thinking of fitting a high integrity (normally use Hager) CU and fitting 2x Hager ADA932U RCBO (1P+N) on what would normally be the 'unprotected ways'.

Hagers website states they can be used in Consumer units but I'm unsure how they fit, being double width. Is it a case of just cutting off the busbar prong where necessary? Seems a bit heath robinson.

Anyone have any better ideas?

I would contact SBS trade sales and tell Dave your requirements. He does a unit that uses two busbars (live and neutral) which the compact RCBOs attach to which are single pole switched neutral. In an ideal world though you don't really want to be supplying distribution circuits via an mcb/rcbo especially if you want to achieve discrimination which you have stated.

 

[Midwest]

Just thinking this through, what are you putting in the rest of the CU, dual RCD & MCB's?

I only ask cos wouldn't there be an S Type in there anyway, still pondering.

 

[mattg4321]

Thanks Lee, the problem I have is the 2 outbuildings supplied have consumer units fitted with a main switch and 3 or 4 MCB's. They are obsolete so not much chance of finding an RCD to swap the main switch with and leave the distribution protected by the 100ma S type and an MCB.

If a fault occurs in either of these 2 outbuildings then I don't want it affecting the main house. If it takes out the 3 or 4 circuits in the outbuilding it's no biggie. We all know in an ideal world you'd have the outbuildings on switchfuses or MCCB's but that's not really necessary here. I just want to try and separate a fault on these 2 circuits from the rest of the house really.

Out of interest what is your go to arrangement for TT supplies? Do you use RCBO's?

 

[Leesparkykent]

Thanks Lee, the problem I have is the 2 outbuildings supplied have consumer units fitted with a main switch and 3 or 4 MCB's. They are obsolete so not much chance of finding an RCD to swap the main switch with and leave the distribution protected by the 100ma S type and an MCB.

If a fault occurs in either of these 2 outbuildings then I don't want it affecting the main house. If it takes out the 3 or 4 circuits in the outbuilding it's no biggie. We all know in an ideal world you'd have the outbuildings on switchfuses or MCCB's but that's not really necessary here. I just want to try and separate a fault on these 2 circuits from the rest of the house really.

Out of interest what is your go to arrangement for TT supplies? Do you use RCBO's?

My go to arrangement would depend very much on the situation, customers budget, room to fit the board, how many and type of circuits etc. I'm not a fan of single pole solid neutral RCBO's tbh. As you are changing the board and if the customer has the budget for it I would still use what I've mentioned above. SBS compact spsn RCBO's for every circuit in a main switch amendment 3 board.

 

[Risteard]

Whilst Hager state that they are suitable for use in distribution boards they are probably referring to installations in other jurisdictions where the use of such devices is common. For example, 1.5 miles down the road from here there is a border, which if crossed you will never see single pole RCBOs used. The DBs used are very different to the ones you are used to seeing in domestic premises though.

Also, as stated, BS EN 60898/BS EN 61009 devices in series are not suitable if discrimination (Selectivity) is required. It won't be achieved under any fault.

 

[mattg4321]

I only ask cos wouldn't there be an S Type in there anyway, still pondering.

Not sure what you're getting at but I'll try! Yes there would be an s type rcd front end, but if you were to get a n-pe fault on either of the outbuildings it would trip the whole installation (including main house) if you used solid neutral rcbo's.

 

[mattg4321]

My go to arrangement would depend very much on the situation, customers budget, room to fit the board, how many and type of circuits etc. I'm not a fan of single pole solid neutral RCBO's tbh. As you are changing the board and if the customer has the budget for it I would still use what I've mentioned above. SBS compact spsn RCBO's for every circuit in a main switch amendment 3 board.

Thanks. Are sbs the only brand that do these does anyone know?

 

[Risteard]

Thanks. Are sbs the only brand that do these does anyone know?

No, there are other brands e.g. Garo.

 

[Leesparkykent]

No, there are other brands e.g. Garo.

I was just looking at meteor electrical at garo RCBO's. Do you know if they make an amendment 3 enclosure out of interest? If im correct I think they may come from Ireland? at http://www.meteorelectrical.com/dis...1/garo-16-amp-30ma-1-module-rcbo-type-b.html#