Possible electrical problem - loose connection arcing?

[Cigaro]

Hi,

I think I may have an electrical problem. The other day we heard a snap/crack sound a couple of times. We put it down to a failing CRT monitor which we had in the study, which we replaced (I am a computer engineer and have seen them make that noise sometimes when the HT circuitry is failing).

However, tonight I heard it again a couple of times a few minutes apart. My spidey senses are tingling now, as I'm familiar with all the odd little noises this house makes and I've never heard this one before. The noise actually seemed to be coming from somewhere downstairs, possibly in the kitchen, but I'm not sure where.

At the time we had an electric heater plugged in (note - this was not plugged in the first time we noticed it, nor were any other high-load electrical devices, though a 2kw fan heater had been on a few minutes beforehand). I decided to unplug it and didn't hear anything for about half an hour. Switched it back on and started hearing the same noise after about 15 minutes. It's like a click/snap sound, sort of like someone clicking their fingers but louder.

The noise is definitely not coming from the heater itself, seems like somewhere else in the house though we're not quite sure where.

Now perhaps I'm jumping to conclusions, but one possibility I thought is that I have a loose connection somewhere that is arcing when a high current device is connected to the circuit. Could I be a million miles off with this thought?

I know this may sound silly, and I think I'm a little overcautious when it comes to electrical safety, but I want to find out what's causing this noise - even small things out of the ordinary usually point to something amiss, don't they?

As an aside, we've not noticed any flickering table lamps or anything like that, but as the circuit is wired as a ring I'm not sure if a fault of this sort would cause any noticable effects on the connected appliances. MCBs haven't tripped either, but again a loose connection wouldn't make an MCB trip!

I'm going to turn the sockets off tonight - I know it may be nothing but I don't want a fire on my hands (who does?) Can a loose connection arcing over intermittently cause a noise of this sort?

 

[1john]

start by checking the terminals of the socket with the heater plugged in, check they are nice and tight, also other sockets on that circuit. Make sure you have the power isolated first!

 

[Taylortwocities]

Electrical socket circuits often have several sockets from one connection at the fuseboard. The sockets can be arranged as a ring or radial.

The sockets are in parallel and this means that if you put a high load on a circuit, the high load will go through all of the connections on the circuit. If there is a bad connection at any of the sockets (or at a 'hidden' junction box) then this may break down when you draw the high current.

You'll need to put on your fan heater and crawl around to locate where the noise is coming from. Start at the fuseboard and work from there.

 

[ericmark]

Noises can be very worrying when you can't work out what or why they are made. Our fridge / freezer as with many today has what it calls frost free. Really an auto-defrost. And when it operates it produces some odd cracking sounds which in dead of night can sound like electric sparks.

I have found that arching produces spikes on the circuit which in turn tends to trip my RCD. So with a modern house unlikely you would have a fault with lose wires without it causing some device to trip.

Also if no current then also no arcing so more likely to hear when high load then with light load.

You can of course test sockets and if you have tested and kept a record of readings then re-testing same socket and comparing will quickly highlight any bad connections when the two earth / line loop reading or line / neutral loop readings are compared.

Even if the records have not been kept one can normally work out the natural route cables would likely follow and again using an earth loop impedance meter quickly see the expected pattern where the ohms increase as one approaches the centre of the ring and then drops again as one returns towards the consumer unit. As electricians using the test equipment every day we get use to what readings to expect in each size of house and how much below the 1.44 ohms we would expect to see.

The correct tests are long winded and require one to switch off mains and remove wires in the consumer unit and temporary reconnect then measure the resistance at each socket with a special low ohm meter that uses at least 200ma for test and then reconnect. I would not consider this to be a DIY job.

One can also hire or buy meters able to measure temperature to find bad connections.

But bitter experience has shown the testing involving disconnecting and reconnecting can introduce as many faults as it finds. So where I worked we would keep careful records of results using a earth loop impedance tester and just compare new with old results which normally highlighted any faults without introducing new.

You can of course get all these tests done. However I think most likely the noises are not an indication of any faults and likely nothing will be found.

 

[wooffy]

Have you got a dishwasher? Mine had a small leak which now and again would make a pop or crack type of noise. (I didn't know it was the dishwasher at the time) Then it finally went and popped the breaker. I could smell a very faint burnt smell so switched off all the power and found it was the dishwasher. Pulled the back off it and the capacitor had blown open probably due to the leak.