Earth Leakage?

[flukeyspark]

Hi all,

Hope you can help..? Here goes... I split a kitchen/garage ring final and added 2 sockets, all end to end tests are fine, IR test >299 on megger so thats fine..The board is an old MK Sentry with 80A 30mA RCD as main switch. The circuit is fine until the washer is pulled in, then it trips, I've tried the washer on another circuit and again it trips...So im thinking its the washer? The customer says the washer never tripped the RCD before? I've tried to test the RCD but as soon as I plug my meter in it trips, same when trying to get a Zs reading. I've taken the kitchen/garage circuit off the board completely and still can not get a RCD or Zs reading due to tripping..So now im thinking its a dodgy RCD?
The customer has today called me to say a washing machine engineer has been out to look at the washer and told him its not either the washer or the RCD! He has told the customer he thinks its a problem with the circuit? As i said earlier all test for the circuit were fine... Anyone out there got any ideas? I've spoken to the NICEIC and they think is due to combined earth leakage and advised to put a meter on and test but doesn't a ramp test do the same thing?
Any help on this would be really appreciated

Thanks in advance

 

[rytech]

Sounds like a neutral to earth fault to me but this would be picked up by an insulation resistance test which you say has been done with good readings. Have you unplugged switched off everything on that RCD and tried an RCD test again?

 

[richy3333]

Clamping with an earth leakage tester will give you an indication of what leakage there is. A Ramp test will tell you at what level of mA the RCD trips at, so they are different beasts

 

[flukeyspark]

Sounds like a neutral to earth fault to me but this would be picked up by an insulation resistance test which you say has been done with good readings. Have you unplugged switched off everything on that RCD and tried an RCD test again?

Yeah insulation test at first found a fault on a garden pond pump, so took that off and then was spot on.. I can try to unplug everything but that may be difficult as the RCD is a main switch for the whole board/house. NIC said that maybe the IR test has mashed the RCD and is now tripping too soon? The RCD is an old MK one which they dont make anymore and the new ones wont fit the board..

 

[flukeyspark]

Clamping with an earth leakage tester will give you an indication of what leakage there is. A Ramp test will tell you at what level of mA the RCD trips at, so they are different beasts

Im going back armed with a earth leakage meter...Never used one before..Do I test each appliance or the CPC at the board?

 

[MDJ]

But did you carry out all dead tests?

 

[TaffyDuck]

Best way is to put the EL meter over the main earth, Turn off all other circuits and see what the offending circuit is leaking to earth with each appliance turned on in sequence. You can only put one on a earth, it wont measure a peice of flex with a LNE in it. A ramp test will only tell you how much fault the MFT has to introduce to trip the RCD, if there is already a fault present that will effect the reading

 

[flukeyspark]

But did you carry out all dead tests?

All continuty tests, end to end, r1+r2, IR test.. yeah

 

[flukeyspark]

Best way is to put the EL meter over the main earth, Turn off all other circuits and see what the offending circuit is leaking to earth with each appliance turned on in sequence. You can only put one on a earth, it wont measure a peice of flex with a LNE in it. A ramp test will only tell you how much fault the MFT has to introduce to trip the RCD, if there is already a fault present that will effect the reading

Sorry i didn't explain properly, I have a small extension with the cpc cut out of the flex. So I plug my extension in the mains, the appliance in the extension and clamp the cpc in the extension? The problem is i don't know which is the offending circuit because when i plugged the washer into the dining room circuit it tripped the rcd...

 

[TaffyDuck]

By pass the RCD, as long as you remove bypass before it is returned to service you have no worries. A link in 2.5mm between L in and L out plus N in N out and you then can test it all to your hearts content. Before that ramp test the RCD at the board with all circuits off, that will give you an accurate indication of the RCD trip amperage. Below 17/18 mA and it needs replacing. 23-25 is ideal

 

[flukeyspark]

By pass the RCD, as long as you remove bypass before it is returned to service you have no worries. A link in 2.5mm between L in and L out plus N in N out and you then can test it all to your hearts content. Before that ramp test the RCD at the board with all circuits off, that will give you an accurate indication of the RCD trip amperage. Below 17/18 mA and it needs replacing. 23-25 is ideal

May be solved..! I've just spoken to the washing machine guy, who incidently told the client that it was the circuit at fault, and I asked him what result he got when ramp testing the rcd...He said he got a reading of 19mA in the hall and 9mA in the kitchen. Faulty RCD? Only thing is why 2 different readings?

 

[rytech]

I guess a faulty RCD could give two different mA trip values but did you not say you we're unable do test the RCD because it trips every time you plug in your tester? Try swapping the RCD but it still sounds as if there is a neutral to earth fault somewhere. Have you disconnected all neutrals from CU then re terminate one circuit at a time to see if this narrows the fault down. I had a very similar fault which gave the exact same symptoms and turned out to be a damaged cable neutral to earth.

 

[flukeyspark]

I guess a faulty RCD could give two different mA trip values but did you not say you we're unable do test the RCD because it trips every time you plug in your tester? Try swapping the RCD but it still sounds as if there is a neutral to earth fault somewhere. Have you disconnected all neutrals from CU then re terminate one circuit at a time to see if this narrows the fault down. I had a very similar fault which gave the exact same symptoms and turned out to be a damaged cable neutral to earth.

Yeah when i was there a couple of days ago I cannot get a result due to constant tripping and Im guessing the rcd had "warmed" up. The washing machine engineer is there today and he says he is now getting results...When you say a neutral to earth fault do you mean on the fix wiring to the property or on an appliance? How exactly do you mean disconnect all neutrals from the cu then re terminate? Sorry for being thick but fault finding isn't my forte..

 

[flukeyspark]

I guess a faulty RCD could give two different mA trip values but did you not say you we're unable do test the RCD because it trips every time you plug in your tester? Try swapping the RCD but it still sounds as if there is a neutral to earth fault somewhere. Have you disconnected all neutrals from CU then re terminate one circuit at a time to see if this narrows the fault down. I had a very similar fault which gave the exact same symptoms and turned out to be a damaged cable neutral to earth.

and surely a N to E fault would show up on the IR test?

 

[rytech]

It could be either fixed wiring or an appliance, I would start by switching off and unplugging everything from all circuits and see if the RCD holds then that will rule out any neutral to earth faults on any appliances/extractors/heaters/showers etc. if you are now getting ramp test readings it would be worth swapping the RCD, quick and simple to do and rules out the RCD being at fault. Hope you get it sorted soon

 

[rytech]

Yes it should have if its fixed wiring fault, if its a neutral to earth on an appliance it wouldn't have.

 

[telectrix]

think logical. assuming it was OK before you did your bit, then dis. the circuit yoiu have altered and then see if the fault has cleared. best way to use an earth leakage clamp meter is to clamp both L and E of the circuit together and the meter will then measure any difference. that will be the leakage.

 

[flukeyspark]

think logical. assuming it was OK before you did your bit, then dis. the circuit yoiu have altered and then see if the fault has cleared. best way to use an earth leakage clamp meter is to clamp both L and E of the circuit together and the meter will then measure any difference. that will be the leakage.

I disconnected my circuit totally from the board and tried to get rcd results and Zs results but the rcd was tripping straight away... I'm going back next week with an earth leakage meter and try again.. Thank you.

 

[monkeyelectric]

I disconnected my circuit totally from the board and tried to get rcd results and Zs results but the rcd was tripping straight away... I'm going back next week with an earth leakage meter and try again.. Thank you.

So you've left them with a tripping rcd and unable to wash their clothes till next week?

 

[flukeyspark]

So you've left them with a tripping rcd and unable to wash their clothes till next week?

No because they can have the washer working if the dishwasher isn't plugged in..but not at the same time... So everything on apart from washer, put washer in - trips. Everything on apart from dishwasher, plug dishwasher in and it trips.... This is why I'm think combined earth leakage is tripping faulty rcd? It's bizarre to be honest!