RCD discrimination to a RCO board

[the pict]

I am doing a couple of board changes some re-wire, and replacing some VIR,However the PIR was not done by me, so I am more or less doing a new PIR and the remedial work as I proceed, I am using the original PIR as a guide also which, although done by a national company is pretty poor in some aspects, one comment I cant quite understand is: on a sub board there is no dicrimination between RCD 1 which supplys/isolates this board and the RCBO,s controlling the circuits contained within this board, the RCD is an 80A and no RCBO is greater than 32A, How would you interperate this, I do not have the folder with me to quote directly, can it be that the 80A RCD is suppling a 100A mainswitch in the sub, cant see it my self, it is not bothering me at all but I just wonder maybe I am missing something obscure.

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[malcolmsanford]

The 80 amp and 32amp is just the rating of the RCD, same as a 100amp double pole switch is the rating on a main switch. It just means that the appliance is rated at a certain limit.

The discrimination you are referring to is the mA rating, I assume both this 80amp RCD and the RCBOs are both 30mA, and so you have no discrimination on fault protection.

 

[telectrix]

what is the discrimination you mean? is it the Amp rating or the mA rating of the RCDs/RCBOs? don't forget that the 80A rating of the RCD is it's rated operating current, not a trip threshold.

 

[telectrix]

malcolm are we telepathic or something?

 

[the pict]

Cheers I am back at it today although I am sure that you may well be right as I was concentrating on a differant board yesterday, the board in question is todays target,
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[telectrix]

if both the RCD and RCBOs are both 30mA, then you have no discrimination. if they are in the same location, however, that is not a major problem.

 

[the pict]

Just a thought, as far as I remember which discrimination was not mentioned just the lack of it, so I really dont know, maybe he classed it as an outbuilding ( beer celler out back) and was looking for a 100mA rcd suppyling it as in the 16th ?? solution suggestions
anyone
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[telectrix]

without knowing exactly what you've got there, it's hsrd to comment further.

 

[Deleted member 26818]

When RCDs are in series, unless one is time delayed (S type), it's anyones guess as to which will trip first in the event of an earth fault.
The earth fault current will generally be much higher than the trip ratings of the RCDs.

 

[the pict]

Still no wiser, both RCD's have absolutly no writing left on them I can just about make out 30mA on one, here's another one not mentioned on the PIR, a 19A fryer fed from a service fuse used in the same way we would use a henly as connection point through a remote RCD 80A 30mA in 15 metres of 16mmT&E ran outside round the building in through the gable end and into a switch disconnector any way made me smile, and wonder where my 20mm masonary drill is, as I will have to go through a couple of walls on this one
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[paturback]

Any chance of a pic pict?

 

[the pict]

I have resolved some of the issues, however I will take a few pics tomorrow of some of the stuff still erected
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