Schneider RCBO's

steviez · 3 Aug 2011

Hi,

Im trying to source some Schneider RCBO's (type B) to fit their Merlin Gerin 3 Phase boards at the best price I can as my local wholesalers have quoted £70 + each. Is there any reason that the only ones I can ever find online seem to be type C?

Anyone know a good place to buy them from?

Thanks

ricicle · 3 Aug 2011

As far as I know only type C's are available. £70 is about right I'm afraid.

steviez · 3 Aug 2011

ricicle said:
As far as I know only type C's are available. £70 is about right I'm afraid.

Oh.... They are needed to protect socket outlets in a cooking area and others too. Type C would not be any good?

ricicle · 3 Aug 2011

Type C will be fine as long as the Zs and short circuit protection is within limits. (An RCD is not a plaster for a poorly designed circuit with high Zs)

steviez · 3 Aug 2011

ricicle said:
Type C will be fine as long as the Zs and short circuit protection is within limits. (An RCD is not a plaster for a poorly designed circuit with high Zs)

Is there any reason why they only come in type C? you can get type B in all other makes.

333rocky333 · 3 Aug 2011

Merlin gerin tend to cater more for commercial use.

Circuits designed to take "C" rated tend to be more common in commercial installs, same with Mcb's, I assume because nuisance tripping can cause more inconvenience, etc and
"B type tends to be more common in domestic.

steviez · 3 Aug 2011

333rocky333 said:
Merlin gerin tend to cater more for commercial use.

Circuits designed to take "C" rated tend to be more common in commercial installs, same with Mcb's, I assume because nuisance tripping can cause more inconvenience, etc and
"B type tends to be more common in domestic.

Whats the alternative to this then? The board is a 24 way 3 phase with no RCD protection. There are 4 socket circuits for use with microwaves, kettles, toasters etc.

ricicle · 3 Aug 2011

ricicle said:
Type C will be fine as long as the Zs and short circuit protection is within limits.

333rocky333 · 3 Aug 2011

steviez said:
Type C would not be any good?

Why is that.

You could use another make RCD's and mount them in an enclosure external to the board, fed from Mcb's within the merlin gerin board

mfarrow · 4 Aug 2011

ricicle said:
(An RCD is not a plaster for a poorly designed circuit with high Zs)

Can you point me towards the regulation for that please?

ricicle · 4 Aug 2011

mfarrow said:
ricicle said:

(An RCD is not a plaster for a poorly designed circuit with high Zs)

Click to expand...

Can you point me towards the regulation for that please?

More poor practice, in my opinion and many others, to stick an RCD in purely to overcome high Zs due to poor circuit design. In some cases it is unavoidable (TT systems)

EFLImpudence · 4 Aug 2011

415.1.2

JohnW2 · 4 Aug 2011

EFLImpudence said:
415.1.2

When 415.1.2 says "The use of an RCD is not recognised as a sole means of protection...", I presume it means that literally, in which case it is obviously true/sensible - an RCD obviously provides no protection against overload or L-N faults. However, as ricicle has just said, when it comes to TT systems, one usually has no option but to rely on an RCD as the 'sole means of protection' in the presence of L-E faults - since most TT electrodes would not result in enough L-E fault current to operate even a 6A MCB, let alone one of higher rating.

Kind Regards, John.

EFLImpudence · 4 Aug 2011

JohnW2 said:
When 415.1.2 says "The use of an RCD is not recognised as a sole means of protection...", I presume it means that literally, in which case it is obviously true/sensible

As 415 has the heading of ADDITIONAL PROTECTION I read it as meaning, as it indeed states, that 411 to 414 must still be complied with.

an RCD obviously provides no protection against overload or L-N faults. However, as ricicle has just said, when it comes to TT systems, one usually has no option but to rely on an RCD as the 'sole means of protection' in the presence of L-E faults - since most TT electrodes would not result in enough L-E fault current to operate even a 6A MCB, let alone one of higher rating.

This is a 'no other option' proviso if usual methods CANNOT be met - unavoidable as ricicle says.

In a 'normal' dwelling, mansions apart, it would be very poor practice to apply an RCD because the installation was faulty and did not meet the normal disconnection criteria.

JohnW2 · 4 Aug 2011

EFLImpudence said:
As 415 has the heading of ADDITIONAL PROTECTION I read it as meaning, as it indeed states, that 411 to 414 must still be complied with.

Yes, but as we've discussed before, 411 actually appears to allow that 'primary' automatic disconnection of L-E faults can be provided by an RCD (the footnote to Table 41.1 says "Where compliance with this regulation is provided by an RCD ...."). Hence, it would appear that an RCD can provide both 'primary' and 'additional' fault protection - or am I misinterpreting?

EFLImpudence said:
This is a 'no other option' proviso if usual methods CANNOT be met - unavoidable as ricicle says.

As above, the regs seem to imply (actually, say) that an RCD can be used as a 'usual method' of satisfying 411.3.2.2 for primary L-E fault protection.

EFLImpudence said:
In a 'normal' dwelling, mansions apart, it would be very poor practice to apply an RCD because the installation was faulty and did not meet the normal disconnection criteria.

No argument there. I would personally actually say that that it was always bad practice to use an RCD 'because the installation was faulty', even if were a mansion!

Kind Regards, John.

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Schneider RCBO's

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