Power Cut at Socket

[BobbyTrigger]

Having some problems with the electrics in my house. I have 2 single sockets (either end of a wall) in a bedroom upstairs and they occasionally have a power cut. I know this because both of the alarm clocks reset. I’m not 100% sure if this is happening elsewhere upstairs, but I know it isn’t downstairs as clocks etc downstairs remain unaffected. I had a very quick look at the wiring inside the sockets and I found 3 sets of wires going into 1 singles socket (3 live, 3 neutral, 3 earth) and 2 sets going into the other socket so I’m guessing at some point over the years some sockets have been removed.

I don’t know if it’s in any way connected, but the main light in the dining room downstairs has never worked (don’t think there’s any power getting to the light fitting) and very strangely I’ve been through 3 power supplies for my pc in one year which makes me wonder is there something weird going on with the current?

Anyway, any ideas what could be:

1) Causing the sockets to briefly lose power
2) Is it possible that the current in the house could fluctuate and pop my power supply in my pc – or is it just weird that I’ve blown 3 supplies in one year?

Wishing I’d had an electrical survey done before I bought the house!

Thanks in advance,

Phil.

 

[Steve]

CURRENT, measured in amps is decided by how many appliances you are using. It cannot vary by itself.

VOLTAGE, measured in volts however CAN vary, and is something the suppliers can sort.

The two sockets in the bedroom sound like they are wired correctly. They are probably on a "ring main" (one is also supplying a spur). However, a ring main relys on a loop of cable starting and finishing in the fuse box / consumer unit. If the loop is broken, all the sockets will still work, but it is dangerous. I suspect here you have a loose connection somewhere, AND that your ring is incomplete. Do you have access to a multimeter and know how to do continuity tests? This would let us verify if the ring is complete.

Start a seperate topic for the light -we can probably sort this - its not likely to be related.

The PC's PSU - an odd one, but it could be linked to voltage fluctuations or over voltage. It wont be under voltage - nearly all PSUs nowadays can take any voltage from 100 to 250 volts, though powering them at 250 will certainly strain them. Again, do you have access to a MM and know how to test mains voltage AC?

 

[BobbyTrigger]

i can borrow a multimeter - have no idea about the tests though? i understand the concept though - i think

 

[aptsys]

What brand power supplies are you buying? There are a lot of crap ones out there which randomly stop working or blow up, so stick with the good ones like Antec, Corsair, Enermax, PCP&C, OCZ etc. and you shouldn't have a problem.

 

[Steve]

A simple test is voltage. WARNING: Only do this if you feel confident working near live wires.

Set the meter to volts AC ~ . If its not auto-ranging, set it to something between 300-1000 volts.

Now, turn off the power. Open up a socket. Once you have esteblished that the wires are secure in their terminals (with the terminals accessible), re-energise. Now, touch one probe to the live screw/terminal, keeping your hands away from live parts. Touch the other probe to neutral. It should read something between 215 and 250 volts. This is acceptable. If its outside this, you should contact your supplier and tell them your voltage is outside of tolerance.

_______________________________________________________

As for continuity, thats where you have to start removing wires. This test is carried out dead. So turn off the mains. At the socket in question (or any on the circuit really), remove the face, and disconnect the wires from it, and separate them out. You'll have one of each live, neutral and earth.

Set your multimeter to ohms (a greek omega sign), or if it has one, a continuity setting, it might have a musical note on it. Now, connect the probes in turn to both lives, both neutrals and both earths. Each pair should produce continuity, or a reading in the region of less than a couple of ohms. Anything more than that is a bad sign. You CAN try to remedy it if this happens though, by going round the whole circuit and tightening everything up, making sure everything's connected properly.

As I said though, its not a job if you're not confident with live wires being exposed.

 

[BobbyTrigger]

right, borrowed a multi meter today - will have a bash tonight. i'll check the voltage readings of the 2 offending sockets and also check the continuity.

 

[Space cat]

Intermittent faults like yours are an absolute pig to sort out. Testing for undervoltage and ring continuity is fine but you could spend days and find nothing.

Gather some extra evidence. Unplug one of those alarm clocks and use it to test all the other sockets upstairs. Does it reset in the same way? Now try the downstairs sockets.

PS: This is a long shot but I once found myself in a friend's house with some very unconventional wiring. Power for a socket upstairs came from a 13 amp PLUG wired with 2.5 sq mm flat twin and earth and plugged in downstairs! They wondered why stuff plugged in upstairs didn't always work.

 

[BobbyTrigger]

cheers - will do. i'll post again on monday after ive had some fun with this meter.

 

[ColJack]

how far from the substation do you live?
is there any industrial units or garages nearby?

the voltage is higer the closer you are to the substation ( 252V some places.. ), and heavy but intermittent current use ( such as welders or large machines ) can cause voltage fluctuations and harmonic spikes..

 

[DCC]

A simple test is voltage. WARNING: Only do this if you feel confident working near live wires.

Set the meter to volts AC ~ . If its not auto-ranging, set it to something between 300-1000 volts.

Now, turn off the power. Open up a socket. Once you have esteblished that the wires are secure in their terminals (with the terminals accessible), re-energise. Now, touch one probe to the live screw/terminal, keeping your hands away from live parts. Touch the other probe to neutral. It should read something between 215 and 250 volts. This is acceptable. If its outside this, you should contact your supplier and tell them your voltage is outside of tolerance.

_______________________________________________________

As for continuity, thats where you have to start removing wires. This test is carried out dead. So turn off the mains. At the socket in question (or any on the circuit really), remove the face, and disconnect the wires from it, and separate them out. You'll have one of each live, neutral and earth.

Set your multimeter to ohms (a greek omega sign), or if it has one, a continuity setting, it might have a musical note on it. Now, connect the probes in turn to both lives, both neutrals and both earths. Each pair should produce continuity, or a reading in the region of less than a couple of ohms. Anything more than that is a bad sign. You CAN try to remedy it if this happens though, by going round the whole circuit and tightening everything up, making sure everything's connected properly.

As I said though, its not a job if you're not confident with live wires being exposed.

Unless I'm being even more stupid than usual one of the sockets in question had a spur on it and once the conductors have been separated out there will be no continuity between the ring and the spur (thats in case the original poster gets confused).

 

[Space cat]

once the conductors have been separated out there will be no continuity between the ring and the spur

Quite right! BobbyTrigger, if you do the continuity tests at the socket with three wires in each terminal, you should get a low reading between only two each of the lives and neutrals. The third one should read high resistance to both of its mates. Let us know if it doesn't. The earth wires are less predictable but you should certainly have continuity between at least two of them.