Lightning (yes lightning not lighting) in the kitchen

[Rustic]

I've got a serious problem, potentially deadly, and I'm wondering where to start. Occasionally, say 8 times over the last year year, to no predicable pattern, my wall-mounted boiler sends what can best be described as a 240v lightning bolt (with a flash + a bang) down the wall to the floor. In my kitchen I have a Ferroli modena 102 combi boiler mounted high on the wall, with through-wall flue to the outside, and with visible wall-mounted copper feed and flow pipes to the floor. The boiler was new installed 6 years ago, to replace an older boiler, so much of the older wiring and pipe work was re-used because it was already in place. 99.9% of the time the boiler works great, controlled by the boiler mounted timer for central heating in mornings and evenings, to switch off at 23:00hrs. Now and again, randomly usually in the middle of the night when heating is timed off, there's is a visible arc of electricity from the boiler down the wall-mounted copper pipe, accompanied by a bang, and the fuse-box trips off. The boiler has it's own dedicated trip switch. I have been in the kitchen and seen this flash only twice, and it is very scary. But the incident has happened several times, as I hear the bang and find the fuse-box tripped more often. The boiler usually seems to be timed off when this happens, but maybe not always. After it happens, usually when I reset the trip, everything works perfectly again as if nothing has happened. There are no burn/scorch marks where the flash appears, and no smell of ozone or burning. Last time, when I resent the trip immediately after it happened, the trip fused/tripped again so the problem was still active. I waited a few minutes, and it reset no problem, and the boiler started up again as if nothing had happened. I've had two electricians (not boiler specialists) to look at it, and testing the house wiring and found nothing wrong. I've considered: condensation inside the boiler - but tonight it happened when 5C degrees outside, not so cold. Maybe it is mice eating the cables, but how come it resets ok back to normal - and why does it arc from the boiler down the water pipes? Maybe there is gas leakage and some spurious spark is igniting it, but no smell of gas, and that wouldn't trip the fuse. I need to fix this urgently. Can anyone suggest the problem, or how I can track what is happening by leaving voltage/current monitoring equipment or boiler diagnostic equipment connected to get data to work it out? Hopefully you experts will have experienced the same problem before? I hope so! Otherwise I'll have to rip out all the house wiring, and the plumbing, and the boiler, and replace all with new.

 

[gasbanni]

I'd get a electrician in first to check the house supply and make sure you have an earth, plenty of properties dont ! The boiler should be on its own fused switch unit 3 amp fuse.

It sounds as if you dont have an earth and its earthing down the (gas/water)
pipe (obviously shouldn't earth at all ) but without seeing it everythings a guess ! whether or not you have an earth can be determined in minutes !

 

[RigidRaider]

Describe the location of your house, nearby buildings, hills, chimneys, trees and power cables or sub-stations?

 

[Rustic]

gasbanni, OK there is no earth cable from my electricity meter to the outside supply. The supply company say they are not obliged to provide one, and as you say many others don't have one. Yes the pipes ere used as the earth. So I can pay to get earth cable to meter installed, and I will. That will be much safer. But will that will stop the problem of the boiler tripping the fuse box? If not, does it look like there is a fault in the boiler, an occasional shorting from live wire to the pipes, to no apparent pattern... is there anything in the boiler that can cause a build up of voltage/charge over time until it arc? The boiler sits happily for weeks, then in the middle of the night when all is quiet, bang! Then runs happily all next day!

RigidRaider, I'm in a stone built Scottish tenement block built 1884! wiring I guess is 15 years old, wrapped to today's standard. So the tenement is a street long block of stone built flats, 3 stories high, I am on 2nd floor, not not highest point which is 3rd floor then high chimneys and tv aerials. Many trees to the rear, same height as block of flats, not touching buildings. I considered lightning strikes, static, but the weather does not correlate to my personal firework show, and there is nothing protruding upwards from my flat to provide a route to earth for lightning.

Meantime I am trying to catch this flash on video.

 

[OwainDIYer]

RigidRaider, I'm in a stone built Scottish tenement block built 1884! wiring I guess is 15 years old, wrapped to today's standard.

But how old is the supply wiring outside the flat and is there any bonding to any common services?

Because you could have voltages floating all over the place ...

 

[expertgasman]

Rustic, you clearly have a problem, and you have been aware of it for about a year! For God's sake, man! Why pi55 about on a forum, where you won't even know whether the advice received is valid, and there will be no come back on the contributor. Engage a suitably qualified electrician, and make sure you get paperwork.

 

[5544]

I am a little worried about the reply from your electricity company. If your house has not got an earth then it is a death trap. earthing is the fundimental requiriement of any dwelling. Check with you electricity supplier what system they actually provide to the house (not who you pay the bills to but the people who sent it down the cable). it will be one of three systems. two of which, they must provide you with a safe earth, the other where the power supply called TT where you would have to provide an earthing rod at your house, and have electrical diversity in way of a 200ma RCD main switch then 30ma RCD at the breakers. Before you do anything else get this investigated and updated. Honestly it WILL Kill you if do you not.
As for the boiler it is very probably an earthing problem.

sorry to sound dramatic but earthing is tyour main form of protection on a domestic installation.

as a last thought is there evidece of your gas, water and heating being earthed?

 

[tryitandsee]

Meantime I am trying to catch this flash on video

Let your next of kin know you are catching it on the video, they could get the £250 from 'You've been framed', should just about pay for a large wooden box

 

[londonboy]

Your electricians are incompetant if they left you with no main earthing conductor.

Using a water pipe as a main earth electrode has been against regulations for years.

You need to have an earth rod/electrode installed, along with a 100ma RCD upfront and 30ma RCD's for other circuits.

The last time I saw this a heating engineer got a serious belt off a gas meter!

 

[chappers]

Also as this is a tenement so take it up with your freeholder there could be a potentialy deadly problem throughout the whole building

 

[Rustic]

Fixed thanks to guidance. Caused by two problems. The first, lack of proper earth, which I am getting fixed urgently by instructing the supply company to install an earth wire to the common stairway junction box.

I am told that because this is on the supply side of my meter, I must legally get supply company to install? At whatever ransom they feel like charging for 3 metres of earth cable. Your comments noted and I'll argue the case.

The second problem causing the sparks - a hungry rodent had knawed through the under-floor pvc-sheathed mains cable to the boiler, shorting positive or neutral to earth, and I suppose due to problem 1, it was earthing through the pipes. So mostly it happened at night. Cable replaced. Proper earth to be installed urgently; and rat poison.

 

[gasbanni]

Enough said ~ any decent sparks can fit you an earth not expensive either
problem now is your house might nead a rewire

 

[electronicsuk]

Enough said ~ any decent sparks can fit you an earth not expensive either
problem now is your house might nead a rewire

Not if there is no earth provided by the supplier. As already mentioned, you can go TT and have an earth electrode installed along with 30mA RCD protection for all circuits, but that is likely to be nearly as expensive as having the supplier provide a PME earth as it may well involve fitting a new consumer unit.

An electrician CANNOT provide a PME conversion. If there is no earth provided at the supply head then either you must TT, or enquire as to whether the supplier is able to provide an earth. In some cases out in the middle of nowhere and with an overhead supply, this may be a non-starter.