Think I'm losing my touch.

[SimpleSimon]

Customer today said to me can you come change my socket, it's melted because of a faulty old extension lead, she'd already thrown it away so couldnt inspect it but I'd thought I'd do a test to be safe on the circuit.
Ring continuity fine.
But when doing IR tests L-N coming as 0, short circuit. But as I'm inspecting the other sockets with appliances that run every day, fridge, washing machine all fine! At the board old rewireable fuses no RCD. Am I testing wrong? L-E fine and E-N fine. Am I right in saying a short would have taken the fuse or at least shown on another socket?

 

[Sparky Ninja]

Did you set up the circuit for IR tests? Can you assure all loads were removed?

 

[sjm]

IMO IR test giving 0 between L-N would mean a connected load. Hope you did the test at 230v first and haven't blown up some piece of sensitive equipment using 500v.

 

[SimpleSimon]

IMO IR test giving 0 between L-N would mean a connected load. Hope you did the test at 230v first and haven't blown up some piece of sensitive equipment using 500v.

Really? I thought 0 meant a short. This could be my problem. There must be an added soccer somewhere because me and the customer went through the whole kitchen disconnecting loads, and it weren't many.

 

[Sparky Ninja]

A reading of 0.00 Mega ohms on a tester will indicate a short or a connected load of very low impedance


Lets not forget that 0.01 Mega ohms is still 10,000 ohms

 

[tonys]

There must be an added soccer somewhere

New Technology or something?

Just trying out my signature

 

[SimpleSimon]

A reading of 0.00 Mega ohms on a tester will indicate a short or a connected load of very low impedance


Lets not forget that 0.01 Mega ohms is still 10,000 ohms

Right. That could explain it. Thanks Widdler. I disconnected everything what I thought was in sight but there must be something else connected.
I had a feeling I was doing something wrong because the customer said that the extension lead plug had melted, thinking it points to faulty appliance.

 

[Sparky Ninja]

One that often catches me out is the Immersion heater. A typical 3 kW household immersion will have a resistance of 17-20ohms, so on an IR test it will appear as a short.

 

[SimpleSimon]

One that often catches me out is the Immersion heater. A typical 3 kW household immersion will have a resistance of 17-20ohms, so on an IR test it will appear as a short.

Well if I had that I would have been stumped!!

 

[drywax]

Spent nearly 2 hours hours on one job trying to locate a similar fault only to find some bugger had plugged the fridge freezer back in

 

[rocker]

Neon!! Mate if you think about it almost anything that's plugged in is going to give you a reading of between 0 and a million ohms....... if you do a low ohm test you'll probably find it's very high (it may even read as 'open circuit' on a low ohm reading). There's always something you miss first time, a neon somewhere, or a phone charger tucked away in a corner. Boiler? Deep freeze in the shed? Could be anything, or indeed it could be a fault.

EDIT: Widdler put it better first time round.......

 

[rocker]

And for what it's worth I'd say from the look of your pic it was a definite external fault, but even if not it should be sorted when you replace the s/o.

 

[telectrix]

also, check the other side of kitchen walls. not unheard of to spur off kitchen ring through wall to add a socket in another room, save floors up and chasing.

 

[pushrod]

Widdler's point is very good remember that your IR tester will round down to zero MΩ any reading less than 5000Ω.

If you ever get a zero MΩ IR reading i would then do a continuity reading and you then get a much better idea of what is going on ie a neon, light or a true dead short. You probs had a high enough resistance to restrict the current to a value that is just not taking out the 3036 in the time that the appliance is on but still high enough to melt the socket.

 

[telectrix]

or it could be a b&q socket! 2 for £1 in the bargain bucket

 

[nickblake]

Just a point guys , its so difficult to locate every item plugged in especially on lighting circuits , there is always something plugged in some where you've not spotted , what i do is carry out the IR tests LN initially at 250 volts then if clear repeat the test at 500 volts doing this reduces the risk of equipment damage if there is some thing still plugged in

 

[rocker]

Just a point guys , its so difficult to locate every item plugged in especially on lighting circuits , there is always something plugged in some where you've not spotted , what i do is carry out the IR tests LN initially at 250 volts then if clear repeat the test at 500 volts doing this reduces the risk of equipment damage if there is some thing still plugged in

And that's exactly what I do as well. It's a top tip and it could save you the price of a widescreen.

 

[telectrix]

And that's exactly what I do as well. It's a top tip and it could save you the price of a widescreen.

but it wasn't a wide screen till i put 500volts up it

 

[whats an rb4]

tv booster in loft little buggars