Stupid question about RCDs

[rocker]

If we have a double pole RCD which is, let's say 30mA 80A, will it trip in an overload situation above 80A in a similar manner to an 80A incomer? Or is it just 'rated' at 80A in the same way a switch may be rated at 6A or whatever?

I'm sure it's a dumb question that I should know the answer to nut I'm just trying to work out why RCBOs are RCBOs when RCDs have current ratings anyway......

 

[acat]

If its rated at 80A thats the maximum safe current it will handle before meltdown.


Chris

 

[james b]

Well isn't each rcd and mcb set at a setting above its stated amount like a 32A could hold 33A but for the regs sack they stat a set limit?

 

[ezzzekiel]

for a type b its 5xin for auto disconnection (which if you divided by voltage will give you zs without having to look in brb) and 1.45xin for overload.

 

[ringer]

If its rated at 80A thats the maximum safe current it will handle before meltdown.

So if (for what ever reason) more than 80A goes across the device will the meltdown leave the connection open or closed? I was about to ask 'are they designed to go open circuit under these conditions?' but then we're into RCBO territory. So presumably they may be either open or closed depending on the way the meltdown affected it. Would that be a fair assumption?

 

[Notsosmart]

It is likely to weld contacts shut; which is why mcb's or fuses are used in conjunction with rcd's.