TYPE C RCBO Fails to trip on 1 Times RCD Test

[DomB78]

Hi

Can anyone help ?

Recently fitted 2 separate Eaton 32a Type C RCBO, on the RCD test it fails to trip on the 1 times test and gives result as >400ms. It trips fine on 5 times test in 7.1ms. Using Megger 1552. They are fitted on 2 new 6m2 radial circuits with Blue commando sockets. IR results where fine.

They were bought from 2 different suppliers on 2 different days cannot believe they are both faulty


Any ideas ?

Thanks

Dom

 

[Wilko]

Hi Dom, it's a long shot but these may be type A and perhaps confirm tester is set to that option.

 

[Octopus]

Do these need to be tested on the end of a short cable ?

Are the loads connected?

 

[buzzlightyear]

op what job are you doing ?

 

[buzzlightyear]

to trip on the 1 times test and gives result as >400ms. It trips fine on 5 times test in 7.1ms.

is not 40ms

 

[DomB78]

Thanks for the replies

Yes. Had to make a short lead to test at commando skt. No loads connected.

Job is new supply for oven.

It is definitely >400ms and no trip.

 

[DomB78]

Hi Dom, it's a long shot but these may be type A and perhaps confirm tester is set to that option.
View attachment 39438

Wilko. Sorry Not sure what you mean. Type A ??

 

[Ian1981]

Test at the rcbo not the socket ,set meter to auto rcd test and make sure test leads are making good contact between line and earth

 

[DomB78]

Ok, I will do. I'll let you know.

 

[DomB78]

Sorry thinking about that. Just checking there is no earth connection on these RCBOs ??

 

[DomB78]

Test at the rcbo not the socket ,set meter to auto rcd test and make sure test leads are making good contact between line and earth

Sorry Ian. thinking about that. Just checking there is no earth connection on these RCBOs ??

 

[westward10]

Sorry Ian. thinking about that. Just checking there is no earth connection on these RCBOs ??

Ian means good connection to earth with the meter leads. Assuming they are Memshield 3 they do not have earth fly leads. These mfts are a pain you need an old standalone rcd tester it will trip straight away.

 

[DomB78]

Ian means good connection to earth with the meter leads. Assuming they are Memshield 3 they do not have earth fly leads. These mfts are a pain you need an old standalone rcd tester it will trip straight away.

Hi Westward

I see, I will check the earth connection is good. Thanks

 

[ChipFanDave]

I had a very similar problem, turned out the MFT was knackered ! Fault on the board that proved to more expensive to get fixed and calibrated than buying a new one. May be worth getting it tested or at least trying it on a RCD you have tested recently and now it working.

 

[Wilko]

Wilko. Sorry Not sure what you mean. Type A ??

Most common RCDs are AC and have the squiggle sinewave symbol. Type A, which I think is what you're testing are sensitive to AC and pulsating DC and so have squiggle sinewave and lumpy half wave symbols you see in the pic. My MFT has a test option to specify which of these types you are testing. I haven't tracked down how the MFT may perform the tests any differently, but I'd just check its set to the right type of RCD.

 

[DomB78]

I had a very similar problem, turned out the MFT was knackered ! Fault on the board that proved to more expensive to get fixed and calibrated than buying a new one. May be worth getting it tested or at least trying it on a RCD you have tested recently and now it working.

Hi David

Was worried about this possibility.

Thankfully all sorted now.

 

[DomB78]

Thanks for all of the advice everyone, I have sorted it out now and tested all ok.