RCD doesnt trip on test.

[Templer]

Hi I have a 6 way split load board located in the shed and served by 10mm SWA. Anything on the unprotected side of the board tests and works fine. However this is not the same for the protected side. I can plug a radio in and the circuit does not trip, but if I use the lawn mower or a drill the RCD trips immediately. In addition, the RCD does not trip when the test button is pushed. I have swapped out the RCD too. Nothing trips on the house board when the RCD in shed trips. All connections are secure in CU. Any ideas where to go next?

 

[Octopus]

Hi Murdoch, looking at it, the swa comes from a protected circuit on the main house cu. This runs 150' to the end of the garden into the 6 way. SWA is earthed at house CU.

So you do have 2 RCD's in series then.

Time to get my coat

 

[Templer]

So you do have 2 RCD's in series then.

Time to get my coat

So is that the problem?

 

[telectrix]

that's not the problem, but it's bad design as a fault on the sub-main circuits can cause the house RCD to trip, thus losing part of the house installation. i have had a similar fault caused by a N-E reversal in back of a socket outlet.

 

[Templer]

that's not the problem, but it's bad design as a fault on the sub-main circuits can cause the house RCD to trip, thus losing part of the house installation. i have had a similar fault caused by a N-E reversal in back of a socket outlet.

I can move the load to an unprotected side of the board.

 

[telectrix]

that would eliminate the series RCDs. i think you need to look more closely at the garage installation for a fault once you have determined that you have a good RCD.

 

[Templer]

that would eliminate the series RCDs. i think you need to look more closely at the garage installation for a fault once you have determined that you have a good RCD.

Tomorrow I will power up the garage CU from an extension and see if this removes the fault.

 

[somersetsparks]

Tomorrow I will power up the garage CU from an extension and see if this removes the fault.

I think you would be wasting your time doing that, as the garage rcd can't 'look back up the supply cable' for a fault.

 

[somersetsparks]

Right I'm gonna suggest something that I may get screamed at for by some on here, I don't recommend doing it but as you have no test equip. It may be the only way to test (ish) an RCD. I would remove rcd from board, connect a flex with plug top on one end into the top L and N terminals and plug into working socket outlet in your house, then push test button, if it trips the rcd then you at least know it fuctions and its your wiring at fault.

 

[Templer]

I think you would be wasting your time doing that, as the garage rcd can't 'look back up the supply cable' for a fault.

I can run a temporary from the CU to the garage, that should work?

 

[somersetsparks]

I can run a temporary from the CU to the garage, that should work?

Would be a waste of time though mate as if there was a fault it would be after the RCD in question not on supply cable to garage

 

[Octopus]

Or get a sparky with a MFT to come and ramp test your RCD?

 

[Templer]

Or get a sparky with a MFT to come and ramp test your RCD?

Do you ever get out this way?

 

[Octopus]

Do you ever get out this way?

Rarely travel more than 10 miles from my front door!

 

[guest119]

Rarely travel more than 10 miles from my front door!

Have you got one of them electronic tags on yer ankle M?

 

[somersetsparks]

Have you got one of them electronic tags on yer ankle M?

Ahh it all makes sense now, that's how comes hes on here not at the pub! 7pm curfew!