Yeah, I was going to ask that, too :-)
Old fridge and worn compressor mounts might produce a thump and flickering lights when the compressor starts. Our old one certainly did the flickering lights thing - sadly it kicked the bucket last week, but
35 years wasn't bad...cheers
Jules
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Words a commodity. Whatever next.
Without hearing it, I am not sure I have one to be honest...
A motor kicking in would be one option. Slightly percussive ignition of a boiler could also cause a thud (although that would not typically be associated with any electrical drop out).
Big transformers at switch on can have similar effects.
Automated systems like heating and cooling devices would obviously be prime candidates.
I've pretty much convinced myself it's something electrical blowing itself apart in a self resettable way. Maybe water gets into a joint and is instantly and explosively superheated, Do you think that could happen on a circuit protected by a 30 amp fuse, again and again without it blowing? I think the answer is yes if the loop impendence is high and the events are of short enough duration.
I'm just afraid that it might be a cable protected by a fuse 10 times that value in a substation!
Can't you sleep?
Well does it affect other properties or not? If not then as it could be pre meter, I'd suggest a call to the supplier who may be able to test for problems where you cannot.
Brian
Isolate the circuit to the conservatory for some hours to see if it stops, but from the description, I have a nasty feeling its before the fuse boxes. Near here some houses reported similar issues some time back, then one day a cable blew a hole six feet wide in the pavement outside. It was due to a leaking sewer near a cable in the street and the sound of the minor problems was conducted by the cable to nearby properties, one must assume that eventually the partial short became a major one. Luckily nobody wa hurt but the power was off for several houses for a day or so while they fixed it.
Brian
Probably the design of the incoming cable makes bypassing the meter easier.
Brian
Personally I would isolate *every* non used appliance for a few hours, fridge, freezer, any heating etc and then reduce the fuse capacity to 15a and switch a circuit on one by one individually to see if it's house side of the CU.
If the incoming main is damaged there is an immediate need to get the board in to investigate as shared runs for water, leccy and gas often result it a far larger problem when any two coincide during a failure :-(
A scan with a CAT device might be used to determine where any incoming supply issues might be.
A local "engineer" for the high power supply bods round here who is one of my customers used to check for blown cables underground at streetlamp circuit problems by shoving a 6" nail in the last known live feed at a pole and watching where the ground erupted nearby so he knew where to dig and repair .... dodgy but it worked. Can't imagine where he got the nickname dodgy digger from......
No such word.
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The water in the cable theory was my first thought too. But can't the OP just turn the whole house off at the CU for an hour or so to determine whether the thump still occurs (or doesn't) even when the house is isolated. That would narrow the fault down a bit.
That's typical for LA housing long before the Right To Buy legislation. Ofc, it causes all sorts of issues now, but at the time it seemed perfectly reasonable and economical.
It happens that Graham. formulated :
Why not start by logging the events?
My guess would be your mains supply cable, underground. Typically the duration of the event and its timing will vary depending upon the surrounding moisture in the ground.
We had a similar problem between us and the sub-station. The brown out would last anywhere between a fraction of a second and several seconds and took months before it became a real issue. Eventually it blasted a large hole in the pavement.
You should JFGI
A dull thud can be water hammer from a neighbour?
However that does not usually make the lights dim... if it IS the supply ca= ble then the eventual bag can be quite destructive. It comes down to how fa= st a fault disconnects and how much moisture there is around - moisture fla= shes to steam and this can be particularly brutal under a concrete floor.
400A upstream fuse may need >4500A to blow
Is this one of those cases where the Board* will shove a monitor on the line?
*or whichever bunch of charlatans does the same function these days
My bench saw does, 1.2kW induction motor IIRC. No soft start either so it makes quite a bang in itself as well as dipping the lights.
Our "800W" microwave and the Dyson vac does that as well not as much as the bench saw though, though the Dyson is close.
The pole transformer is quite small probably only rated at 100A. We do have some E7 heating but I suspect that when that was put in by one of the previous owners they didn't bother telling the REC...
There are online and offline monitors, they can "spike" the line to force a soft fault to become a hard fault. It is a yellow pelicase box, indeed there are a few re fault tracing on LV.
The OP should report it at least rather than wait.
100A? when I were a lad.....I don't think it looked like it would do 3KVA frankly...
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I had exactly this problem 20 years ago soon after I moved in to a house I had just bought. The bangs seemed to be days/weeks apart, though
Eventually diagnosed to a blocked underground watercourse running through the front garden, water coming in under the floorboards, and some plonker having left a dangling unterminated live mains cable lying on the rubble under the floor. The end of the cable was clearly split and blown apart. I still haven't worked out the exact mechanism: mains is A/C so electrolysis producing hydrogen shouldn't be the answer.
whats AC got to do with it?
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