RCD cutting without physically tripping. a

[Brian Mack]

Hi I’m new.
I have a flat in Madrid which was re-wired in 2011.
The fuse box has a single pole 25A breaker, plus a 2P 25a breaker. These feed an RCD known here as a “diferencial”. When I use the oven plus hob plus aircon the power goes off but none of the consumer unit switches physically trip out. I can restore power by re-making the 40A - 300ma rcd. None of the 25amp breakers throw. Test button works fine and I’ve even tried a new RCD.
Any ideas?

 

[Octopus]

Neutral/earth fault somewhere in the flat .............

 

[James]

Hi I’m new.
I have a flat in Madrid which was re-wired in 2011.
The fuse box has a single pole 25A breaker, plus a 2P 25a breaker. These feed an RCD known here as a “diferencial”. When I use the oven plus hob plus aircon the power goes off but none of the consumer unit switches physically trip out. I can restore power by re-making the 40A - 300ma rcd. None of the 25amp breakers throw. Test button works fine and I’ve even tried a new RCD.
Any ideas?

could be overloading the rcd (differential)
can you send a picture?
some rcd devices monitor only the difference between live and neutral currents, known in the uk as an rcd. this will not trip due to an overload, only a difference of current going out the live and returning to neutral.

some monitor the same but also the current being drawn. known here as an rcbo, this will trip if the current (load) is to high.
I suspect that you have the rcbo type of device.
working on some assumptions here is the maths.

oven 10 to 15A
hob 10 to 20A
A/c 10 to 20A
other loads 5 to 10A

giving a total load when all 3 of your main devices are on of between 35 and 65A
could be tripping an rcbo?

 

[Brian Mack]

Thanks Murdoch and James.
It isn’t an RCBO by the look of it. I understand that an earth leakage will trip it but it’s the fact that it never physically moves when the power cuts out that I don’t understand

. Have you ever heard of that before?
This first happened using the oven so I assumed there could be a leak in that circuit under a high load but I also managed to get the same condition by running everything else in the flat bar the oven.

 

[James]

I have known breakers of all sorts to fail in that way, i.e. go open circuit without moving physically.
I would suggest trying a replacement rcd. Get someone qualified and authorised to work in that location ideally.
This is probably not a diy job, unless you have an rcd tester to confirm all is working after changing it.

 

[Deleted member 26818]

It could be that you have high earth leakage and the oven has a fault which took the earth leakage over the top for the RCD.
The new RCD may have a lower earth leakage threshold and is tripping because the earth leakage is above that.

 

[Brian Mack]

Thanks James and Spinlondon.
Interesting to know that breakers can go open circuit without physical movement.
I’m afraid I have not yet found a professional out here in whom I have much confidence. I have changed the RCD but the results are similar. I do seem to be having to put larger loads on to re- create the condition so does it matter or is it important to find the underlying cause?

 

[James]

It would be useful if you could find out what current is drawing when you get the fault.
There is a device called a clamp meter, you just clip it round the live incoming tail and it will tell you what the current draw is on that cable.

 

[Wilko]

Hi - my experience is it’s best to find the route cause of a fault. Once it’s known, then one can make a judgement of the best way forward. Safety on the plus and a shopping list of negatives if it festers and gets worse over time.

 

[itech security systems]

Hi I’m new.
I have a flat in Madrid which was re-wired in 2011.
The fuse box has a single pole 25A breaker, plus a 2P 25a breaker. These feed an RCD known here as a “diferencial”. When I use the oven plus hob plus aircon the power goes off but none of the consumer unit switches physically trip out. I can restore power by re-making the 40A - 300ma rcd. None of the 25amp breakers throw. Test button works fine and I’ve even tried a new RCD.
Any ideas?

 

[itech security systems]

simple solution. I come across the same issues in these type of flats.
The air conditioning should not be wired up to any normal type B mcb or rcbo. When the heat pump kicks in ( which is a motor load under high load) at start up it will trip the type b rcbo. They normally require a type D seperately radially wired with the correct rcd protection. Try using the oven normally then turn on the air con withing 30 secs the heat pump will activate and trip the rcbo guaranteed. loud click and thump. Hope that helps.

 

[Brian Mack]

simple solution. I come across the same issues in these type of flats.
The air conditioning should not be wired up to any normal type B mcb or rcbo. When the heat pump kicks in ( which is a motor load under high load) at start up it will trip the type b rcbo. They normally require a type D seperately radially wired with the correct rcd protection. Try using the oven normally then turn on the air con withing 30 secs the heat pump will activate and trip the rcbo guaranteed. loud click and thump. Hope that helps.

Thanks but that doesn't seem to be the answer - I disconnected the aircon and I could still get the cut out. There are no RCBOs just an RCD. I have not been able to reproduce the open circuit condition without the oven/hob circuit but that could be because I don't have enough load.
I've also discovered that it is not just re-making the RCD which restores power - it also does so if I re-make the single pole main switch or the two pole main MCB. Just a reminder that none of the switches physically move.

 

[itech security systems]

Thanks but that doesn't seem to be the answer - I disconnected the aircon and I could still get the cut out. There are no RCBOs just an RCD. I have not been able to reproduce the open circuit condition without the oven/hob circuit but that could be because I don't have enough load.
I've also discovered that it is not just re-making the RCD which restores power - it also does so if I re-make the single pole main switch or the two pole main MCB. Just a reminder that none of the switches physically move.

ok. the rcd must be a relay trip requiring the loss of power from the mcb before it will allow current to flow again. i assumme there is a red flag that moves to indicate a trip ? you need to look up the model online and obtain reset procedure from manufacturer.
with regards to the trip that occurs i suggest using a clsmp on ma /A ammeter being placed at the consummer unit. first measure the leakage current under load of each appliance on singularly on there own and bote the ma reading (main bonding earth) there maybe enough leakage from more than one appliance to be greater than 300ma combined. if you dont find any excessive leakage start testing the fixed wiring without any appliances in the cct. look for N to E with very low meg ohm insulation readings below say 0.5 meg testing first at the
consumer unit. From experiences badly terminated dp cooker switches soxkets etc, then kitxhen units screwed through cabling next big issue. usually fixing base units where in close prox. to wiring conduits etc. Then in no joy movecto testing the individual appliances simulating load by turning on elements. the air con unit would need to be visually inspected including the outdoor unit which may have loose connections or water ingress. ok good luck. should the rcd not be greater than 30 ma on your systems or is it a 2 wire earth pole TT system supply.

 

[Brian Mack]

Thanks again for a thorough response.
There is no red flag or anything else to indicate a trip.
I tested earth to neutral and was getting mega ohms but did not have s clamp meter with me.
I’m back in the uk now so will have to put off further investigation until my next trip to Madrid.
I did get access to the supply for the block yesterday which is a recent upgrade. Apart from it looking like tns this end is definitely beyond my level of competence. Our flat was the only one with red lights on the meter (1000imp/krvh ?) I enclose pictures

 

[itech security systems]

Thanks again for a thorough response.
There is no red flag or anything else to indicate a trip.
I tested earth to neutral and was getting mega ohms but did not have s clamp meter with me.
I’m back in the uk now so will have to put off further investigation until my next trip to Madrid.
I did get access to the supply for the block yesterday which is a recent upgrade. Apart from it looking like tns this end is definitely beyond my level of competence. Our flat was the only one with red lights on the meter (1000imp/krvh ?) I enclose pictures

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ok. your meter show implusing red leds when loaded. others must be simoky under no load when your looked.
its not possible to tell you what supply system it is unless you see a clear label or a test certificate. Really you dont need to this at this point. you need a clamp meter to get anywhere along with a 500v1000v AC multimeter insulation tester. simple multimeters will not give you proper test results and lead you up the wrong pathway. The correct testing equipment simulates live use but at twice the voltages to give accurate test results.