My Mains fusebox keeps tripping at between 3am and 6am every

[joe-90]

Joe

It is perfectly possible to have intermittent faults on hard wiring and appliances that cause intermittent tripping.

I never said it wasn't. I said it had no permanant short.

Another thing I've heard of (but not sure it is true) is that if you have a sensitive RCD and next-door have an old fuse wire box, that it is possible for their washer to introduce voltage spikes into the supply that trip the RCD of the house next door. Is this possible? Anyone know?

 

[securespark]

You said it was a transient fault, not a hard-wired fault. I'm saying it could be both.

 

[Softus]

Joe

It is perfectly possible to have intermittent faults on hard wiring and appliances that cause intermittent tripping.

I never said it wasn't. I said it had no permanant short.

The fact that you can switch the thing back on again indicates that it is a transient fault rather than a hard wire fault.

This implies that you think transient faults and hard wire faults are mutually exclusive, whereas they aren't.

Edit: just noticed that securespark already had this point covered.

 

[joe-90]

Transient means 'enduring for a very short time'. A fault in 'passing' rather than,say, two wires touching each other.

 

[Softus]

You're missing the point - there are all kinds of transient faults.

For example, worn or damaged insulation can result in bare conductors making intermittent contact with each other or with an appliance casing.

Another example - heat damaged insulation can break down and lose its ability to insulate effectively.

Another one - a CPC without any sleeving touching a live terminal in a light unit operated by a pull cord, where each pull of the cord made or broke the wire contact, and apparently randomly.

I've seen all of these, and more; all were intermittent, and all were hard wire faults. It's misleading to say or imply anything different.

 

[Adam_151]

Another thing I've heard of (but not sure it is true) is that if you have a sensitive RCD and next-door have an old fuse wire box, that it is possible for their washer to introduce voltage spikes into the supply that trip the RCD of the house next door. Is this possible? Anyone know?

There are situations that can cause things like that to happen, there is no reason why it would have to be a washer though, and having old hot wire fuses isn't neccessaaly a requirement either.

Quick one off the top of my head... TT system in a village, house one has an appliance with phase/cpc intermittant fault, house two has a cpc-> neutral short, but the resistance of the fault combined with the Zs conspires to keep the current down and the RCD doesn't trip. The fault occurs in house one, and quickly takes out the the RCD in that house, but before it trips, the current drives the voltage up across the neutral-> physical earth bond at the local tx, and a greater voltage between neutral and earth, means a greater curent flows through your neutral/earth fault and the RCD in house two can be made to trip from an event occuring in house one! (or cours if they fixed their neutral/earth fault it wouldn't happen!)

 

[diablo1952]

Joe

It is perfectly possible to have intermittent faults on hard wiring and appliances that cause intermittent tripping.

Well we turned everything off and the RCD did not trip
so we are now isolating parts of the house and trying to see if this is the problem. I will inform you all of the result when I find it.
I must say you are a superb bunch of guys and we thank you for your guidence,patience and support.
What a brilliant forum
Paul & Jan + Tribe

 

[JohnD]

We'd still like to see a photo of your CU. The way it's set up isn't ideal (as you have observed).

 

[joe-90]

You're missing the point - there are all kinds of transient faults.

For example, worn or damaged insulation can result in bare conductors making intermittent contact with each other or with an appliance casing.

Another example - heat damaged insulation can break down and lose its ability to insulate effectively.

Another one - a CPC without any sleeving touching a live terminal in a light unit operated by a pull cord, where each pull of the cord made or broke the wire contact, and apparently randomly.

I've seen all of these, and more; all were intermittent, and all were hard wire faults. It's misleading to say or imply anything different.

But why between one and three in the morning? When the house is busy there is no problem. When the house is quiet then there is.

 

[Softus]

But why between one and three in the morning?

How should I know? When the fault is tracked down then I'm hope the OP will tell what he found.

You could open a book and give odds on the fault being each one of the many possible; however I, for one, don't gamble.

In the meantime, he's been given the knowledge he needed to perform the fault-finding, and I expect he's applying that knowledge.

 

[Pensdown]

But why between one and three in the morning? When the house is busy there is no problem. When the house is quiet then there is.

The time the fault occurs may be relevant, it may not. Without test equipment the only way to find the fault is to methodically narrow it down.

The OP has unplugged all appliances and isolated the out buildings but the fault is still there.

However, with everything off the RCD doesn't trip so the fault is somewhere within the property and it's not a N-E fault. Because it's a 100mA RCD either the RCD is faulty (easy to diagnose with the right test equipment but not via a forum) or the fault is quite serious (100-300mA RCD's protect against fire not electrocution).

It's very hard to fault find using a forum instead of a tester so sometimes it better to keep quite and let just a few work though the options.

Once all of the normal reasons for tripping have been eliminated we can start to look outside of the house for transient faults but before then it might confuse/scare the OP.

 

[diablo1952]

But why between one and three in the morning? When the house is busy there is no problem. When the house is quiet then there is.

The time the fault occurs may be relevant, it may not. Without test equipment the only way to find the fault is to methodically narrow it down.

The OP has unplugged all appliances and isolated the out buildings but the fault is still there.

However, with everything off the RCD doesn't trip so the fault is somewhere within the property and it's not a N-E fault. Because it's a 100mA RCD either the RCD is faulty (easy to diagnose with the right test equipment but not via a forum) or the fault is quite serious (100-300mA

RCD's protect against fire not electrocution).

It's very hard to fault find using a forum instead of a tester so sometimes it better to keep quite and let just a few work though the options.

Once all of the normal reasons for tripping have been eliminated we can start to look outside of the house for transient faults but before then it might confuse/scare the OP.

Just to let you know what I have found

1. With everything switched off the RCD does not trip
2. With the outbuildings isolated the RCD still tripped
3. With only the two freezers and the fridge on RCD does not trip
4. With upsatirs and downstairs lights + standby tv/dvd/video/sky but no upstairs mains plugs the RCD does not trip
5. With 4 + all upstairs ring mains RCD does not trip
6 With 5 + MOD server + 3 computers RCD does not trip
7 With everything on ( did not trip for 2 days ) then @9.15am this morning it tripped the RCD. Tried to reset it to no avail then 60secs after I could reset the RCD and it seems okay.

We have now isolated everything, this only happens when everything is switched on. I have beed using a 30ma isolator and plugging in all the appl;iances to this ,but it has never tripped.

I assume by doing this the 30ma isolator will trip before the 100ma RCD !!!

Best regards
Paul ( Still confused as to the problem )

 

[RF Lighting]

Do i take it you have quite a bit of electronic / IT equipment then?

Do you leave your computers switched on through the night?

 

[plugwash]

i'm guessing this is a cumulative affect possiblly in combination with an outside event that causes it to trigger at a particular time (e.g. if the voltage surges then ALL currents will increase including earth leakages)

if i were you i'd get all your appliances pat tested and make sure the person doing the testing does a run test with leakage measurement. if they add up to more than about a quater of the rcds rating you are probably getting dangerously close to a potential trip under a surge or similar.

 

[JohnD]

Are we going to see a picture?










RCBOs are the answer