500v IR test shock?

[Bailey326]

when testing pipework to see if its extraneous using the 500v ir test is there a possibility of an electric shock if someone in the house happened to be touching the pipe at the same time of testing?

Yep, I'm prepared for some stick here so fire away ?

 

[James]

What is the theory behind testing insulation to see if it is extraneous?

 

[Lucien Nunes]

I think the point is measuring the resistance to earth of something suspected of being extraneous, using an insulation tester. Personally I think it is a daft idea for the reason the OP states, although it seems a lot of people do it.

 

[snowhead]

Is this a theoretical question or is it related to an actual claimed incident.?

 

[Bailey326]

Theoretical.

But would not want something like this to happen in future so thats the reason for asking.

 

[Ian1981]

Theoretical.

But would not want something like this to happen in future so thats the reason for asking.

You need to be touching both ends when doing an IR test at 500 v to feel it.

 

[davesparks]

Why are you testing at 500V for this?

I normally apply a continuity test first, if it is above the max reading of that tester then I'd switch to the IR range but at 50V or 100V
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What is the theory behind testing insulation to see if it is extraneous?

The continuity setting of most MFT's doesnt have the range required, so the IR setting is used because it has a much higher range.

 

[pc1966]

If it is extraneous (so well below 20k ohm or so) then you won't see anything like 500V during the test, as the IR testes can only deliver 1mA or so.

If isolated and someone touches it then yes, so you really should test at a low voltage if your MFT allows for it. A multimeter might work on ohms range and is safe, but they can be fooled by stray current voltage - basically if you see something strange (e.g. -ve R) or get different results on swapping + & - probes round, then you can't relay on the multimeter's value.

 

[Simon47]

You need to be touching both ends when doing an IR test at 500 v to feel it.

Yes, but from the PoV of an innocent bystander ...
Assuming the pipe is not earthed, it will take up 500V from the earth to which the other end of the IR tester is connected. So all that's needed is any path from the bystander to earth and you've got your circuit.

 

[static zap]

Could parallel it with 200k ,that will reduce test volts ,
a 20k result will now look like 18.8k ... yes that's theory too ...

 

[Bailey326]

Why are you testing at 500V for this?

I normally apply a continuity test first, if it is above the max reading of that tester then I'd switch to the IR range but at 50V or 100V
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The continuity setting of most MFT's doesnt have the range required, so the IR setting is used because it has a much higher range.

Yes my multimeter in continuity mode goes up to 19.99k and so then my next available option to get a higher range would be 250v.

Why do I see and read lots of people using it at 500v for this test?
I've never liked the idea of doing this.

 

[Simon47]

Probably because so many people have been taught "all IR tests at 500V" without teaching any of the thinking behind why you might use a different voltage in some situations. And because most of these situations are fairly modern, it's become on of those unwritten "laws" passed on from generation to generation of new leckys.

 

[Risteard]

You're supposed to warn anyone present before carrying out an insulation test to prevent them from receiving a shock.

 

[Ian1981]

You're supposed to warn anyone present before carrying out an insulation test to prevent them from receiving a shock.

Or if your at college, attach the leads to your mates ears

 

[Jim_e_Jib]

You're supposed to warn anyone present before carrying out an insulation test to prevent them from receiving a shock.

Unless it's the kitchen fitter who put a screw through your cable.

 

[Ian1981]

Unless it's the kitchen fitter who put a screw through your cable.

Then you attach the leads to his -------s