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- 4 May 2007
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Hi, just installed a new CU for someone. ELI, IR, ZS etc for every circuit are fine. They only have one ring for the whole house and I've protected this with a 30ma RCBO. The 2 lighting circuits and cooker circuit are also protected by RCBO's.
When I check the RCBO for the ring circuit it's slow to trip the first time; around 100ms for 1x and 35ms for 5 x. If I check it again immediately after it's fine (25ms and 8ms).
Leave it for an hour or so before testing again and it reverts back to slow tripping the first time and OK after that. I thought it was a dodgy RCBO but after swapping it I still got similar results. I've tested at the CU and at a socket with all the other circuits switched off. A ramp test show it trips at 25ma. I know the times are within limits but I'm just curious as to why this should happen Any ideas??
When I check the RCBO for the ring circuit it's slow to trip the first time; around 100ms for 1x and 35ms for 5 x. If I check it again immediately after it's fine (25ms and 8ms).
Leave it for an hour or so before testing again and it reverts back to slow tripping the first time and OK after that. I thought it was a dodgy RCBO but after swapping it I still got similar results. I've tested at the CU and at a socket with all the other circuits switched off. A ramp test show it trips at 25ma. I know the times are within limits but I'm just curious as to why this should happen Any ideas??