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?

 

[somersetsparks]

Ha s it ever worked or is it just something you have bodged in today?

 

[tony mc]

What tests on the protected side of the board have you done ?

 

[Marvo]

If the RCD is wired correctly plus there's power to it and it doesn't trip on the test button then replace it again, no if's or but's, it's faulty. The tripping under load could be a crossed/borrowed neutral or an insulation fault or it could also be a symptom of a faulty RCD.

Replace it then do global IR testing and recheck neutrals.

 

[somersetsparks]

Ha s it ever worked or is it just something you have bodged in today?

Sorry that sounded a bit mean, it sounds as if the neutrals are the wrong way around in the neutral bars.

 

[Templer]

Thanks for the reply (mean or not) . I didn't fit the board, we just moved in. The board looks like an off the shelf pre fitted one.

 

[Jabbajaws]

I have had this happen with the neutrals being crossed over to a different neutral bar. Id check that first and also treble check the wiring on all protected circuits but as Marvo says, if its wired correctly and the trip button doesnt activate then the RCD is faulty...

 

[Octopus]

Have you got 2 x fuseboards and 2 x RCD's in series?

 

[Templer]

Hi Jabbajaws. I have removed all circuits from the board and fitted a single socket and it still trips. I will check the neutrals. Would crossed neutrals cause the RCD not to trip on test?

 

[Templer]

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.

 

[somersetsparks]

Hi Jabbajaws. I have removed all circuits from the board and fitted a single socket and it still trips. I will check the neutrals. Would crossed neutrals cause the RCD not to trip on test?

One Neutral should come from the bottom of the Main switch into the first neutral bar, then from that neutral bar into the top of the RCD, then from the bottom of the RCD into the second neutral bar.

 

[Templer]

One Neutral should come from the bottom of the Main switch into the first neutral bar, then from that neutral bar into the top of the RCD, then from the bottom of the RCD into the second neutral bar.

All neutrals are where they should be.

 

[Octopus]

What test kit do you have?

 

[MDJ]

Faulty Rcd? or your on LSD? lol

 

[Templer]

Just a Martindale MM39. I can get a meg next week if needed.

 

[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!