Really struggling to find cause of tripping

[ekmdgrf]

Can you think of anything else that might be running on a timer or is only switched on when you get up? Immersion heater? It could be cumulative tripping where several appliances leak a little bit and that adds up to the threshold for tripping the RCD. Heating elements are a prime suspect as the insulation breaks down over time.

One thing though: why when you have Central Heating, do you switch a load of fan heaters on?

 

[midas]

Can you think of anything else that might be running on a timer or is only switched on when you get up? Immersion heater? It could be cumulative tripping where several appliances leak a little bit and that adds up to the threshold for tripping the RCD. Heating elements are a prime suspect as the insulation breaks down over time.

One thing though: why when you have Central Heating, do you switch a load of fan heaters on?

I can't think of anything else on a timer.
The first thing to come on that uses electricity is normally the boiler but that didn't come on today until 6:30 so after the tripping happened.
My immersion is broken and is switched off anyway. My kitchen gets quite cold overnight because it's next to the conservatory so I normally have the fan heater come on with a timer during the colder months but it hasn't been on a timer since my problems started.

I can see why cumulative tripping might happen but why won't it do it during the day with all the same appliances running?

Thanks

 

[ekmdgrf]

I can see why cumulative tripping might happen but why won't it do it during the day with all the same appliances running?

It's a curious one. The most likely candidate is something that happens to be switched on in the morning but not during the day, that you've overlooked. Maybe could be the temperature, as you suggest. It makes it a slightly difficult problem to troubleshoot, as it's hard to reproduce the exact circumstances. Maybe you could have the heating on over night to keep the house warm and see if you get the same 6am effect?

 

[ericmark]

The problem is clearly a neutral earth rather than line earth fault this is hard to find. So options.

1) An electrician would PAT test all items looking for faulty ones but since there is such a variety of combinations causing the trip I personally do not think it is a plug in device causing the problem.
2) An electrician would use an insulation tester on the consumer unit but since does not happen in the day again he could likely not find it.

So if we for the moment assume it is not plugged in and only works at night then two items seem to be what we are looking for.
1) Timer you assure us nothing on timer is causing problem so next.
2) Photo cell.
3) Morning dew.

So looking at picture I see garage I wonder if you have an old outside light with photocell or some damp in garage which the morning dew point is allowing to cause a neutral earth fault?

The writing on the RCD is too small to read but one would expect a single RCD to be pre-2008 and be 100ma designed to protect with a TT supply. I have seen these swapped for 30ma but that is really too low for a whole house. I am out of the trade now and don't know that box but it looks tall enough to take RCBO's maybe some one can confirm if it will or not?

If it has a 100ma RCD fitted then fitting 30ma RCBO's will likely pin point the problem. However looked up your box The MEMSHIELD 2 MR30 30MA 10KA POD which turns the MCB's into RCBO's costs £99.99 each clearly it would be cheaper to renew whole consumer unit than to fit RCBO's in that one. Looked at Screwfix and RCBO's at £22 to give some idea of the problem with MEN prices.

Of course changing consumer unit you can have split system with two RCD's or combination of Main switch RCD and RCBO.

The Eaton Memshield3 Rcbo is cheaper at around £46 even they are expensive maybe some of the others on here recognise the board and can advise more.

 

[midas]

I can see why cumulative tripping might happen but why won't it do it during the day with all the same appliances running?

It's a curious one. The most likely candidate is something that happens to be switched on in the morning but not during the day, that you've overlooked. Maybe could be the temperature, as you suggest. It makes it a slightly difficult problem to troubleshoot, as it's hard to reproduce the exact circumstances. Maybe you could have the heating on over night to keep the house warm and see if you get the same 6am effect?

I really can't think of anything but will rack my brain. I'll try the heating overnight thing and I might disable all other circuits except one and try the kettle heater combo.

Thanks

 

[AndyPRK]

you could stop using the fan heater and see if the problem goes.

 

[mfarrow]

I would go around checking terminals as a first point, including those inside the CU, on both sides of the MCBs and RCD.

There are some perculiar occurences of loose terminals causing RCD tripping.

 

[midas]

you could stop using the fan heater and see if the problem goes.

I'm pretty sure I tried a kettle / cooker combo and it tripped but will double check.

Thanks

 

[midas]

The problem is clearly a neutral earth rather than line earth fault this is hard to find. So options.

1) An electrician would PAT test all items looking for faulty ones but since there is such a variety of combinations causing the trip I personally do not think it is a plug in device causing the problem.
2) An electrician would use an insulation tester on the consumer unit but since does not happen in the day again he could likely not find it.

So if we for the moment assume it is not plugged in and only works at night then two items seem to be what we are looking for.
1) Timer you assure us nothing on timer is causing problem so next.
2) Photo cell.
3) Morning dew.

So looking at picture I see garage I wonder if you have an old outside light with photocell or some damp in garage which the morning dew point is allowing to cause a neutral earth fault?

Very interesting...
A couple of months back I had a problem with a PIR sensor situated on my garage wall which kept tripping every time it would activate. Electrician said something about an earth fault. Can't remember exactly.
Given that I can't replicate it during the day, morning dew would make sense a lot of sense.

I assume if I switch off that circuit and run my usual tests that would pin point it as being the likely culprit?

Thanks

 

[EFLImpudence]

I assume if I switch off that circuit and run my usual tests that would pin point it as being the likely culprit?

Only if it is a double pole switch otherwise you will have to disconnect the Neutral.

 

[bernardgreen]

I assume if I switch off that circuit and run my usual tests that would pin point it as being the likely culprit?

As EFLImpudance mentioned you will need to isolate the neutral as well as the live because an earth to neutral fault on the PIR / lamp can result in an RCD tripping when there is a load on a different circuit.

When you have isolated both live and neutral to the PIR / lamp you need to measure the leakage impedance between neutral and earth as well as between live and earth.

One leakage path often overlooked is the path via a damp wall to ground. It is misleading to believe that a double insulated lamp which has no need for an earth wire cannot have any earth leakage.

 

[midas]

The problem is clearly a neutral earth rather than line earth fault this is hard to find. So options.


The writing on the RCD is too small to read but one would expect a single RCD to be pre-2008 and be 100ma designed to protect with a TT supply. I have seen these swapped for 30ma but that is really too low for a whole house. I am out of the trade now and don't know that box but it looks tall enough to take RCBO's maybe some one can confirm if it will or not?

It's 100ma

 

[midas]

Update
7:30 pm and electrics just started tripping
No obvious heavy duty appliances on this time.
Watching the main board the main switch was randomly buzzing but not always tripping.
I could stop the main switch buzzing by switching off one of the circuits didn't matter which one.
I've been running the house with only half the circuits on and it's held up for about 30 minutes.
Guess it's time to call an electrician but if anyone else wants to give my some more advice I'd appreciate it.

Thanks to all who have responded much appreciated.

 

[stillp]

the main switch was randomly buzzing

It needs replacing then.

 

[midas]

the main switch was randomly buzzing

It needs replacing then.

So could that be my problem then?