Main RDS tripping with lightning
- Thread starter aytonboy
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Far left the RCD. Above the box of MCBs (previously push-in fuse wire containers) is an old front door bell transformer. Separate switch and two MCBs below covers separate garage and (now defunct) outside lighting. The board to which this is all attached is under a sink in the cloakroom. (Sink not leaking!) The board is on the inside of external cavity wall, near the external meter box of previous photos.
Far left the RCD. Above the box of MCBs (previously push-in fuse wire containers) is an old front door bell transformer. Separate switch and two MCBs below covers separate garage and (now defunct) outside lighting. The board to which this is all attached is under a sink in the cloakroom. (Sink not leaking!) The board is on the inside of external cavity wall, near the external meter box of previous photos.
As John said, I still can't see any green/yellow wires. Are there any, anywhere?
I have replaced several old sockets in the last weeks or so, certainly with earth connections of course. Do I need to take the front cover off the RCD to look for earth wire? Or perhaps loosen the indoors unit board to look at wires behind it. A bit worrying..... I'll go outside and examine the house external perimeter for a pin.
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A good start, but where's it connected in the house?
There should be a Main Earth Terminal (MET) somewhere near you consumer unit (the box of MCBs).
Particularly in installations of that vintage, it's not uncommon for the earth bar of the CU to be used as the MET, so there might well not be an 'external' MET to look at. I fear that this issue may have to be resolved by measurement.
Kind Regards, John
1. Having no real reason to assume the earth pin is not connected to the house system leaves me with the way ahead for my original problem of trip-outs. Perhaps I should go ahead with the fitting of an S type RCD of 300mA instead of the present 100mA unit and see if that helps?
2. Is there some way of testing the earth pin connection integrity with my simple multimeter or is something more sophisticated required.
2. Is there some way of testing the earth pin connection integrity with my simple multimeter or is something more sophisticated required.
You could, with a long lead on your multimeter, check for continuity between the earth rod and the earth conection to one of the sockets, but that won't tell you if the connection can carry enough current to trip the protective devices in the event of a fault, nor will it tell you if the earth rod is correctly installed.
That's before you start considering equipotential bonding...
Just fitting a less sensitive RCD will probably reduce the problem, but will also reduce the level of protection.
It might be worthwhile getting an electrician in to check the earthing and bonding.
That's before you start considering equipotential bonding...
Just fitting a less sensitive RCD will probably reduce the problem, but will also reduce the level of protection.
It might be worthwhile getting an electrician in to check the earthing and bonding.
When eric mentioned the 300mA RCD, he did not point out that whether or not that (rather than a 100mA one) would give an adequate degree of protection would depend upon the the 'earth fault loop impedance' provided by your TT electrode (assuming that it is connected). A measurement of that impedance (which you could not do) would therefore be necessary before one could contemplate such a change. I think it's probably fair to say that a good few TT installations are fairly marginal in this respect, which is probably why 100mA RCDs are, I believe, all-but-universally used to protect TT installations. You also would probably not be able to do the RCD change yourself, since it would involve getting your electricity supply temporarily 'switched off' (by getting supplier to remove their fuse).
With the aid of a long enough bit of wire, you'd be able to confirm that the earth rod was connected to your installations 'earthing' system, but you would not be able to undertake the measurement referred to above (to assess the adequacy of the earth rod,particularly for a 300mA RCD).
Kind Regards, John
Eh? Just use the ohms range on the multimeter.
Don't worry folks, I'm very grateful for your advice here, but I know replacing the RCD is too far outside my experience to attempt myself. I'm just trying to have a rough idea what is needed to be tested and done before getting an electrician in. (again)
Having found the TT pin I can confirm that it is connected. From a garage socket, via a 25m extension cable (socket turned off!) the circuit has a variable resistance of 0.5 to about 1.5 Ohm. (rather cheap multimeter I would admit.) Running a little A4 1.599V battery through this circuit produced exactly 1.599V.
The pin is embedded in well-rained-on Yorkshire soil so is probably much more effective than that of the Lunar Base. (have I missed something?)
I am reluctant to get an electrician in without some good ideas because we have already done this a couple of times to get where we are now. (i.e. couple of sockets replaced, then original RCD replaced and fuse wire outfit replaced with the MCBs) The farm next door and nearby houses also have the same set-up of overhead lines and their power stays on during the lightning.
Regarding equipotential bonding, I think I have seen earth wires to the water pipes in the attic but will have another look. No gas pipes to worry about and the only metal in the structure will be ties between brick and block courses. I will continue to replace old sockets, some of which were dodgy with loose connections and/or so much filth at the back that some current leakage looked likely. Doing this seems to have stopped all trip-outs that were occurring between the lightning episodes.
The last lightning tripout happened when we were away a week or so back and I had turned off all the MCB circuits except 3 covering circuits for boiler, freezer/fridge, two lights on timers and alarm in the hope this might prevent it.
Many thanks for your interest (if you still are!)
Having found the TT pin I can confirm that it is connected. From a garage socket, via a 25m extension cable (socket turned off!) the circuit has a variable resistance of 0.5 to about 1.5 Ohm. (rather cheap multimeter I would admit.) Running a little A4 1.599V battery through this circuit produced exactly 1.599V.
The pin is embedded in well-rained-on Yorkshire soil so is probably much more effective than that of the Lunar Base. (have I missed something?)
I am reluctant to get an electrician in without some good ideas because we have already done this a couple of times to get where we are now. (i.e. couple of sockets replaced, then original RCD replaced and fuse wire outfit replaced with the MCBs) The farm next door and nearby houses also have the same set-up of overhead lines and their power stays on during the lightning.
Regarding equipotential bonding, I think I have seen earth wires to the water pipes in the attic but will have another look. No gas pipes to worry about and the only metal in the structure will be ties between brick and block courses. I will continue to replace old sockets, some of which were dodgy with loose connections and/or so much filth at the back that some current leakage looked likely. Doing this seems to have stopped all trip-outs that were occurring between the lightning episodes.
The last lightning tripout happened when we were away a week or so back and I had turned off all the MCB circuits except 3 covering circuits for boiler, freezer/fridge, two lights on timers and alarm in the hope this might prevent it.
Many thanks for your interest (if you still are!)
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