Lurch you can fix mine now (that was easy). I have a TT system with an RCD MCB DB The intermittent tripping is a pain in the but. ive used insulation tester, issolated load the lot i recken som ferkin mouse is lickin the cable when im not there. Its been behavin itself for about a month and went again so shove it out with the RCD stuff the regs i want a constant supply.

Jef

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Is your property a thatched cottage or similar?

If not is your C/U a split load board, has the cooker panel got a skt outlet on it, have you got a garage or other similar outbuilding which is outside the equipotential zone of the home ie is it seperated from the house. The reason will become apparent and its not because i'm nosey. I recently got a call to a rural cottage and found the voltage trip inoperative and replaced it with a 30mA rcd and promptly tripped so put in 100mA one instead but to no avail and now am going down the route of putting individual RCBO'S on all circuits supply skt outlets and 1st floor lighting points (dont like lights on rcds) for obvious reasons because of thatch and fires. On a TT system your earthing comes from the rod what was your Earth Loop Impedance reading in an ideal world should be less than 200Ohms but with rcd you can get away with 1666Ohms. How old is the installation.

Is your property a thatched cottage or similar?

If not is your C/U a split load board, has the cooker panel got a skt outlet on it, have you got a garage or other similar outbuilding which is outside the equipotential zone of the home ie is it seperated from the house. The reason will become apparent and its not because i'm nosey. I recently got a call to a rural cottage and found the voltage trip inoperative and replaced it with a 30mA rcd and promptly tripped so put in 100mA one instead but to no avail and now am going down the route of putting individual RCBO'S on all circuits supply skt outlets and 1st floor lighting points (dont like lights on rcds) for obvious reasons because of thatch and fires. On a TT system your earthing comes from the rod what was your Earth Loop Impedance  reading in an ideal world should be less than 200Ohms but with rcd you can get away with 1666Ohms. How old is the installation.

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Looked at all of the above. I completely rewired the place two years ago. I have tested, tested, and tested again and cant find a fault. The problem with intermitent tripping is one trip about every 8 weeks. the problem is no one else is at the property when this happens. Ive tried issolating the usual suspects (both poles of each circuit a curcuit at a time) and still it goes. Its fixed now i just through th RCD away.

Jef

Looked at all of the above. I completely rewired the place two years ago. I have tested, tested, and tested again and cant find a fault. The problem with intermitent tripping is one trip about every 8 weeks. the problem is no one else is at the property when this happens. Ive tried issolating the usual suspects (both poles of each circuit a curcuit at a time) and still it goes. Its fixed now i just through th RCD away.

Jef

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Why have you thrown it away, could you not have linked it our with a rusty 4" nail just so you dont have a hole in the front of your DB ?

On a TT system your earthing comes from the rod what was your Earth Loop Impedance  reading in an ideal world should be less than 200Ohms but with rcd you can get away with 1666Ohms. How old is the installation.

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I know I'm diverting from the original subject, but is there a "standard" written down anywhere for ELI?

I ask because an appliance engineer said ours was too high and "probably" the cause of the fault he was fixing (no, I didn't believe him either). I think it was about 30 ohms via a rusty rod at the time. Anyway Southern Electric came and checked it, and as we're on overhead cables changed it around. They have earthing rods on every other pole apparently and linked it to those. It's now 0.15 ohm! Beat that!

30 ohms is low, 300 ohms is high. I've also seen much lower than 0.15 ohms.

Hmm try working at a power station if you want low readings........ 0.01/ 24kA+ meter doesn't go any lower/higher!

If you look in the consumer unit you'll see there are 2 neutral bars. You've connected the neutral of the alarm supply to the wrong bar.

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who says sparkys make the best alarm engineers...

re-appliance engineers,once had a fault with a new washer a relative bought kept tripping the rcd,called out (wont name names) blamed it on the spur supplying the washer,i was there when he turned up..' look he says the washer is live' with one lead on the live and the other the washer casing after much laughing and holding groin area to stop urine leaking,he promtly left in shame....last seen rocking back and forth in a chair mumbling the words gaz and B******d