Intermitant tripping of RCD

[MalcyB]

Been to check out an RCD that seems to trip for no reason in a log cabin (someones home). Split load board. Circuits on RCD are: Kitchen skts, Bedroom skts, all other skts, Cooker, Boiler/alarm, Shaver skt.

TNCS.

Main incomer from meter goes to an isolating switch in a barn, from the switch it is split into two, one goes to a two way board with RCD main switch for this barn, the other goes to the log cabin. One of the ways in this barn board also feeds another barn.

The feed from the isolator to the log cabin looks to be 6mm SWA. Clipped along side of this is the a 10mm earth cable. Both these travel approx 50Mts to the log cabin.

All circuits in log cabin test ok for IR.

Because of the tripping happening at any time I wondered if there was a problem with water getting into any outside lights, but the lights are not on RCD.

What is puzzling, is some weeks ago a lamp blew in the barn, which tripped the RCD in the log cabin. How can this happen?

My heads hurting thinking about this.

Have I missed someting simple?

Anyone any ideas please?

Thanks

What has me puzzled is, some time ago

 

[monkey5]

how old is the installation? could be faulty cooker. also are any lights on same circuit as shaver point?

wayne

 

[MalcyB]

The instalation is about 4 years old.

I'm not sure about the cooker. It tripped three times in the space of about an hour at the weekend all they had on was the TV. He decided to get something done about it because he missed a lot of the Notts Forest match on the telly. :^O :^O

 

[septiclecky]

The instalation is about 4 years old.I'm not sure about the cooker. It tripped three times in the space of about an hour at the weekend all they had on was the TV. He decided to get something done about it because he missed a lot of the Notts Forest match on the telly. :^O :^O

Whilst they may have been watching the TV, there are still items still on unless they are physically switched off eg Cooker, boiler alarm etc.

ps Who is Notts Forest?

 

[Evans Electric]

Best to start with a 1/2 test on the RCD I think , get that ruled out first . Seem to be more of them failing these days, perhaps because there are more of them.

If the wiring tests are OK , its often a good idea to educate the customer into noting what was switched on when it tripped.

We beggered about for 1/2 a day with one that was tripping ,on a board change we had done . RCD tested OK (New C/tree Starbreaker) So we tested the Immersion htr, the cooker ,cold then hot, then for some reason we got sidetracked with the central heating for ages, then we opened up an outside light looking for water and we meggered the old dear's iron , got it hot and tried it , all seemed OK .

My mate had become obsessed with the C/H pump and was disconnecting it to test , I'm swearing quietly at the RCD , called it an illigitemate so-and-so and tapped it with a screwdriver, ..........it tripped out ....... reset it , tapped it .....tripped out again...... the little old lady appears and says.... "Thats what it does when the front door door slams" !!!

Moral of the story is always ask the customer what they were doing when these things happen.

---------- Post Auto-Merged at 20:07 ---------- Previous post was made at 20:05 ----------

Yes ..WHO IS Notts Forest ??

 

[sellers]

I stress to the customer to make a note of what time it tripped and what everyone in the house was doing at the time.

Give the rcd a ramp test to rule that out. Make sure you have operated switches when IR testing, get some of the appliances out of the cupboards and give them an IR test.

 

[steptoe]

Ive had one today,

turns out to be the sunbed after a while.!

 

[MalcyB]

Whilst they may have been watching the TV, there are still items still on unless they are physically switched off eg Cooker, boiler alarm etc.

Heating has been on and off when trips occured. Cooker is on but was not being used. I would have thought it would trip more regularly?

RCD results as follows x half delta300ms, x half delta300ms, x one delta n150ms, x one delta n35ms, x five delta n10ms, x five delta n19ms

Ramp test. 21ma, 70ms

I have asked them to keep note of all things they have on if it goes again.

Any ideas on why the lamp blowing in the barn would trip the cabin RCD?

 

[septiclecky]

Whilst they may have been watching the TV, there are still items still on unless they are physically switched off eg Cooker, boiler alarm etc.Heating has been on and off when trips occured. Cooker is on but was not being used. I would have thought it would trip more regularly?

RCD results as follows x half delta300ms, x half delta300ms, x one delta n150ms, x one delta n35ms, x five delta n10ms, x five delta n19ms

Ramp test. 21ma, 70ms

I have asked them to keep note of all things they have on if it goes again.

Any ideas on why the lamp blowing in the barn would trip the cabin RCD?

Are you saying the RCD trips @300mS? It should not be tripping at all on the x half test.

 

[MalcyB]

No it only trips on the 1x and 5x

 

[muffin]

think your missing the fact that a neutral earth fault is the main cause of an rcd tripping, and something plugged in but not turned on will still trip the circuit.

remove the main earth if its tncs and insulation test see if there are any low readings to n-e

if not then think along the lines of something that switchs on intermitently, central heating pump, water heater, outside pond pump, heater elements may be 100% clear when cold but as they heat up they short out.

ask them if its always tripping when they are home, and as someone else has said the owner usualy has the key to the answers.

the chance of it being a faulty rcd is rare, but if its easy to swap then try that for a bit.

sounds like you are near a farm due to all the barn referances, there maybe rodents eating cable.

hth

 

[MalcyB]

think your missing the fact that a neutral earth fault is the main cause of an rcd tripping, and something plugged in but not turned on will still trip the circuit.remove the main earth if its tncs and insulation test see if there are any low readings to n-e

if not then think along the lines of something that switchs on intermitently, central heating pump, water heater, outside pond pump, heater elements may be 100% clear when cold but as they heat up they short out.

ask them if its always tripping when they are home, and as someone else has said the owner usualy has the key to the answers.

the chance of it being a faulty rcd is rare, but if its easy to swap then try that for a bit.

sounds like you are near a farm due to all the barn referances, there maybe rodents eating cable.

hth

Insulation tests done on all circuits, all fine.

Heating was not on when it tripped off last time, so cannot be pump.

I've gone through everything that is in use in the cabin, the only things that would would have been in use when tripping occurs would be 2 fridges and a freezer. If it was one of those wouldn't it keep tripping out every time it kicked in?

There has been visable rodent damage to a lighting cable in the barn, it has nibbled away at the outer sheath but has not touched the insulation or gone through to bare wire.

 

[philbas]

It could trip any time two kicked in at the same time, just may tip the scales over the limit.