Team - I'm after some help on a fault find that I was at this week and to work out if there's something obvious that I've forgotten, overlooked. I've only been working as a spark for a couple of years, done my city & guilds 2365 - L2&3 and done my AM2, just wanting to finish my portfolio for my NVQ - (just ome back ground to get me out of the DIY forum).
Customer reports RCD trip on down stairs ring circuit, MK split load board, half RCD protected, and half isn't. After a lot of messing about working out what was and wasn't on the circuit, eventually removed all the loads (found a few hiding) and IR tests commence. RCD is a MK 80a - 3oma, fault appears to be intermittent but there is no issues when the down stairs ring is switched off - so I'm happy that is where the problem lies.
L-E 530 MΩ, N-E 383 MΩ, L-N >999 MΩ- I measured this at the board and at a socket on the down stairs ring.
There is a brake in the ring on the line conductor, which I think is a historic problem, contained within one of the spider web of junction boxes underneath floorboards upstairs, which are underneath a very expensive floor. I have explained the need to trace it. – however the customer has sold the house to a developer who is only a couple of months away from levelling the place.
RCD test - trips @ 1/2 rate when testing on that circuit. So I disconnected the down stair ring and ramp test it from upstairs - trips @ 19ma. I thought it was a bit sensitive, so swapped it out for a new one. Same story, however the RCD holds now and does so for some time. 4 days in one instance.
But when the loads start to be plugged back in – The only thing I had in was the fridge freezer and the TV (which is in three way adapter thing) virgin media box. I’ve checked the fridge freezer cpc with a clamp meter on an extension lead – no issues, trips whilst I’m there. I take the freezer out and fridge and trips 5 mins later. The only thing in is the tv / media thing. Checked that with a clamp meter and no issues. I’ve left the client after a good few hours and I started to struggle to see the wood for the trees by this point. So I told him to take that out and slowly put things back in at 30 minute intervals – thinking could it be an intermittent fault with an appliance like a compressor on a fridge that isn’t constantly running?
So my questions are this – why would the rcd trip at half trip current on that circuit only, with no loads, despite good IR tests - is it still likely to be fixed wiring?
Could the TV / media thing have a component that is intermittently working and faulty? – When I suggested the tv he did say his son had had the back off and fitted his own speakers to it……. (my ears did ----- up at that)
Testing with a new megger mft 1711 by the way.
Anything I’ve forgotten – if it’s obvious – please don’t shoot me, it’s been a long day!
Customer reports RCD trip on down stairs ring circuit, MK split load board, half RCD protected, and half isn't. After a lot of messing about working out what was and wasn't on the circuit, eventually removed all the loads (found a few hiding) and IR tests commence. RCD is a MK 80a - 3oma, fault appears to be intermittent but there is no issues when the down stairs ring is switched off - so I'm happy that is where the problem lies.
L-E 530 MΩ, N-E 383 MΩ, L-N >999 MΩ- I measured this at the board and at a socket on the down stairs ring.
There is a brake in the ring on the line conductor, which I think is a historic problem, contained within one of the spider web of junction boxes underneath floorboards upstairs, which are underneath a very expensive floor. I have explained the need to trace it. – however the customer has sold the house to a developer who is only a couple of months away from levelling the place.
RCD test - trips @ 1/2 rate when testing on that circuit. So I disconnected the down stair ring and ramp test it from upstairs - trips @ 19ma. I thought it was a bit sensitive, so swapped it out for a new one. Same story, however the RCD holds now and does so for some time. 4 days in one instance.
But when the loads start to be plugged back in – The only thing I had in was the fridge freezer and the TV (which is in three way adapter thing) virgin media box. I’ve checked the fridge freezer cpc with a clamp meter on an extension lead – no issues, trips whilst I’m there. I take the freezer out and fridge and trips 5 mins later. The only thing in is the tv / media thing. Checked that with a clamp meter and no issues. I’ve left the client after a good few hours and I started to struggle to see the wood for the trees by this point. So I told him to take that out and slowly put things back in at 30 minute intervals – thinking could it be an intermittent fault with an appliance like a compressor on a fridge that isn’t constantly running?
So my questions are this – why would the rcd trip at half trip current on that circuit only, with no loads, despite good IR tests - is it still likely to be fixed wiring?
Could the TV / media thing have a component that is intermittently working and faulty? – When I suggested the tv he did say his son had had the back off and fitted his own speakers to it……. (my ears did ----- up at that)
Testing with a new megger mft 1711 by the way.
Anything I’ve forgotten – if it’s obvious – please don’t shoot me, it’s been a long day!
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