Electrical Conundrum

[rossc]

I have no clue about electrickery and this problem is baffling my sparky as well, so any ideas from resident electricians gratefully received.

Basically we seem to go through periods of the main breaker on our fuse board tripping out for no reason. It can go months without anything then it happens a few times over a period of days/weeks. There seems to be no obvious reason why this happens although it does seem to happen more often in the early hours.

We were away for 2 weeks in August and it tripped out at least 6 times in that period. Only things left one were fridges, freezers, sky box etc. The reason we find out whilst away is the alarm monitoring company informing us there has been a power failure.

Since we have been back for over two weeks it has not happened once !

I had thought we were maybe getting power spikes causing the trip but the neighbours don't have any issues and our supplier has said nothing has been reported in the area so it is an issue for our electrician.

Any thoughts welcome !

[-Pete-]

This is not a professional opinion, but we used to have the same problem, our neighbours didn't. It turned out that we had an earth rod in the ground, but they had PME (protective multiple earthing). This is where your earth for the house is connected to the neutral wire in the meter box.

The problem with earth rods is that circuit breakers detect tiny currents flowing to earth. In the earth rod system, changes in the conductivity of the ground between your house and the substation can trip your circuit breaker, and so a change in weather conditions could, for example, cause your trip to go.

The elctricity company argued that it couldn't be the reason, but grudgingly switched us to PME, a 30 minute job. We've never had the problem since.

[hairyben]

-Pete- said:

This is not a professional opinion, but we used to have the same problem, our neighbours didn't. It turned out that we had an earth rod in the ground, but they had PME (protective multiple earthing). This is where your earth for the house is connected to the neutral wire in the meter box.

The problem with earth rods is that circuit breakers detect tiny currents flowing to earth. In the earth rod system, changes in the conductivity of the ground between your house and the substation can trip your circuit breaker, and so a change in weather conditions could, for example, cause your trip to go.

The elctricity company argued that it couldn't be the reason, but grudgingly switched us to PME, a 30 minute job. We've never had the problem since.

Sorry but that's horlicks, if anything a better earth connection will make an RCD more likely to trip as less resistance means more current will flow.

OP: I assume the spark has done the obvious ie test all the circuits on the RCD? Do funds allow for an RCBO consumer unit where all circuits have independent RCD protection? If not may be possible - depending on the unit you have- to install one or two RCBO breakers for important/suspect circuits

[rossc]

hairyben said:

OP: I assume the spark has done the obvious ie test all the circuits on the RCD? Do funds allow for an RCBO consumer unit where all circuits have independent RCD protection? If not may be possible - depending on the unit you have- to install one or two RCBO breakers for important/suspect circuits

Thanks for the replies.

We are about to go down the route of having the consumer unit changed to one with individual RCD protection (even though the current unit is only a few years old) as this will hopefully help isolate where the problem is coming from.

I guess if all the circuits trip at the same time after that its an external issue.

Any more thoughts, please let me know

Thanks

[cal72]

after reading your post it sounds like you either have a faulty trip switch or a bad earth to the property, the first thing I would do is replace the trip switch for a new one and see how that goes, I've had this type of problem before and when I have changed the trip switch the problem has gone away. If after you have changed the trip switch and it still keeps tripping I would check your earth coming in to the property and make sure it is at the desired rating for the type of system suppling the property ( TNS, TNCS or TT )if that fails then I guess it's back to the drawing board.
this was sent by my elecy mate pete.

[rossc]

cal72 said:

after reading your post it sounds like you either have a faulty trip switch or a bad earth to the property, the first thing I would do is replace the trip switch for a new one and see how that goes, I've had this type of problem before and when I have changed the trip switch the problem has gone away. If after you have changed the trip switch and it still keeps tripping I would check your earth coming in to the property and make sure it is at the desired rating for the type of system suppling the property ( TNS, TNCS or TT )if that fails then I guess it's back to the drawing board.
this was sent by my elecy mate pete.

Bit of a story but we can't change the trip switch as we cannot get the front access cover off due to boiler pipework being in the way (don't ask, but that's the way it is, f**k up i know...). Sooooo the consumer unit is being moved anyway along with the meter (which needs replacing anyway).

Therefore as we are getting the spark to move the consumer unit, it makes sense to replace it at the same time to one with individual trips...

[cal72]

Pete says it is possible that the heat from the pipes maybe the cause of the problem, but if you are moving it anyway it should be ok then.

[rossc]

cal72 said:

Pete says it is possible that the heat from the pipes maybe the cause of the problem, but if you are moving it anyway it should be ok then.

Surely if that were the case it would be happening more regularly ? But noted, thanks.

[dickymint]

Had similar 2 years ago. I suspected that on occasions we were getting a power spike. I set up my multi-meter to register and save the highest voltage chaage. Sure enough it recorded periods of about 280 Volts (from memory). Couple of days later during a storm I noticed my next door neighbours incoming supply was sparking at the porcelain insulator. Rang the Electric Board and they had a man out within an hour. He looked over my consumer unit and said he wanted to fit a bit of kit to monitor my incoming for a few days. Told him i've already checked that and showed him how - so he rang in to get a "crew" out straight away. Job sorted and no charge

[cal72]

rossc said:

Surely if that were the case it would be happening more regularly ? But noted, thanks.

In the main switch and mcb's is a bi metallic strip, when this heats up it moves apart and causes the contact to be broken, causing it to trip. This could of played a part in causing the main switch to fail as often as it has been, each time a main switch or mcb trips it becomes weaker, not dramatically but slightly, so if the heat from the pipes has been causing the bi metallic strip to trip this could of cause the premature failure of the main switch, if your changing the distribution board for a new one then the problem will stop. I'd recommend an MK distribution board, abit more expensive but well worth it, good piece of kit and very rarely any problems.

[-Pete-]

hairyben said:

-Pete- said:

(Just wrote what happened to me, and what I was told)

Sorry but that's horlicks, if anything a better earth connection will make an RCD more likely to trip as less resistance means more current will flow.

It's very likely you know more than me about this, but I and my neighbours had the main breaker tripping out around 5 times per year, and had an earth rod. A change to PME completely fixed the problem, with no other changes inside or outside. So even if I didn't catch the precise reason (something to do with changes in current flowing through the ground back to the substation) I still suggest that if the OP hasn't got PME, it might be a possible solution.

[dickymint]

-Pete- said:

hairyben said:

-Pete- said:

(Just wrote what happened to me, and what I was told)

Sorry but that's horlicks, if anything a better earth connection will make an RCD more likely to trip as less resistance means more current will flow.

It's very likely you know more than me about this, but I and my neighbours had the main breaker tripping out around 5 times per year, and had an earth rod. A change to PME completely fixed the problem, with no other changes inside or outside. So even if I didn't catch the precise reason (something to do with changes in current flowing through the ground back to the substation) I still suggest that if the OP hasn't got PME, it might be a possible solution.

Maybe Pete is right Hairy - Possibly tripping during wet weather?

[rossc]

dickymint said:

Maybe Pete is right Hairy - Possibly tripping during wet weather?

Hhmmmm....tripped twice yesterday, and its been damp the last few days. Coincidence ?

[hairyben]

rossc said:

dickymint said:

Maybe Pete is right Hairy - Possibly tripping during wet weather?

Hhmmmm....tripped twice yesterday, and its been damp the last few days. Coincidence ?

Dampness can affect RCD's in all sorts of ways

Given you can't get the cover off the con unit it's fairly pointless discussing it, personally I'm baffled that your "sparky" can be "baffled" at the fault when he hasn't actually tried looking for it because he can't...

[Brite spark]

rossc said:

dickymint said:

Maybe Pete is right Hairy - Possibly tripping during wet weather?

Hhmmmm....tripped twice yesterday, and its been damp the last few days. Coincidence ?

Possibly a coincidence, however could be damp getting in somewhere or a change in the resistance of the ground when wet

[Deva Link]

Brite spark said:

rossc said:

dickymint said:

Maybe Pete is right Hairy - Possibly tripping during wet weather?

Hhmmmm....tripped twice yesterday, and its been damp the last few days. Coincidence ?

Possibly a coincidence, however could be damp getting in somewhere or a change in the resistance of the ground when wet

Logically, it it tripped more in wet weather due to lowering the resistance of the earth, then it should trip all the time on a "better" earthing system.

Damp elsewhere in the wiring system (or one of the appliances attached to it) is a strong possibility though.

[-Pete-]

Perhaps http://en.wikipedia.org/wiki/Earth_leakage_circuit... - see Nuisance Trips.

Anyway, if the OP can confirm whether they have an earth rod (TT system) or PME (neutral connected to ground at the meter) it will decide whether this might / might not be a similar problem.

[sjj84]

Is the earth rod in a proper box sunken into the ground or is it sticking out? That's if you have an earth rod of course.

Edited by sjj84 on Friday 9th September 19:22

[rolando]

I had this a few years back. We had had a load of rewiring done and everything tested OK. Eventually found that it was the central heating pump on the way to meet its maker. It was only when the pump finally stopped running that it was found to be the problem.

[bullitinhead]

I cant see in it in previous post so I'll ask, Is it the rcd or mcb breakers or indiviual ones, that are tripping?


I'll add my own little story it may or may not be related.

We use to have a problem with our rcd tripping out on occasion, apeared to be random any time weeks would pass and no reset would occure, but as time went by there was a pattern emerging. I'll skip to the end as we did loads of testing and changed rcd's looked at earth cables etc..

turned out to be the boiler safety cut off, when the out flow condenced (in certain situations)it would drip back in to the boiler and puddle on top of the "firebox" which had a safety cut out on top, this shorted to earth with the water an caused the rcd to trip.

bullit