Insulation Resistance - Low Reading on Ring

[deejay]

Newbie Testing Question:

I am getting a very low IR reading between L&N on a kitchen ring (0.01M). The ring was working fine with no tripping before testing. Can anyone shed any light on what may be causing this low reading? Thanks

 

[Baddegg]

Neon on fused spur somewhere......or something not isolated, cooker,hob,boiler....

 

[FatAlan]

USB socket?

 

[deejay]

USB Socket has already been disconnected (downstream).

There are several neon double pole switches for the appliances which I already turned off (not disconnected).

I've disconnected the sockets downstream of the neons and still getting the low reading.

 

[Baddegg]

USB Socket has already been disconnected (downstream).

There are several neon double pole switches for the appliances which I already turned off (not disconnected).

I've disconnected the sockets downstream of the neons and still getting the low reading.

Something somewhere in there mate.....welcome to the world of testing in domestics, good luck I’m sure you’ll find it and keep us posted ?

 

[7029 dave]

I would split the ring and test, then depending on your results drill down on one part/ test leg by leg.

 

[brianmoooore]

First thing I'd do is to measure the resistance with an ordinary ohmmeter. This will eliminate neons nd other voltage related possibilities from the equation, or give an indication that the problem is along these lines.

 

[Sparkingmad]

There must be something still connected that isn’t isolated, transformer/driver, fan, boiler? Can you make safe what you have disconnected and turn power back on to that circuit? You may find fridge, microwave, or some kitchen appliance plugged in and not on a switch fuse spur?

 

[Pete999]

USB Socket has already been disconnected (downstream).

There are several neon double pole switches for the appliances which I already turned off (not disconnected).

I've disconnected the sockets downstream of the neons and still getting the low reading.

It's the Neons', causing the low IR reading

 

[westward10]

Are you doing an EICR as generally the line to neutral test isn't required.

 

[pc1966]

0.01M is pretty low for most IR tester's resolution so it could well be anything that is less than 20k ohm but not a total short.

As above, neon indicators are obvious culprits, but then I would expect a lone neon to be in the 0.1-0.5M region as they often have series resistors of the order of 220k. Surge protected electronics can also indicate low, but normally if you test at 250V it is in the tens or hundreds of M region.

It could be something really wrong with the cable/accessories so you ought to pin down what is still connected and if not look for rodent damage, really wet bits, or just possibly dodgy cable. Unfortunately home wiring can have studiedly added spurs, etc, so finding out exactly where all of the circuit is connected to is not a fun job.

 

[telectrix]

neons should not affect readings if the FCU/D/P switch is Off, as they are (should be) on the outgoing terminals.

 

[davidjtown]

Thanks for all the replies.

It ended up being a mixture. I split the ring and had the low reading at both ends. I totally disconnected the neons and tested each leg and it was normal (>999M).

On the other side of the ring I discovered a dishwasher that was plugged in under the plinth. When disconnected, again normal readings.

Thanks for the advice ?

 

[Pete999]

neons should not affect readings if the FCU/D/P switch is Off, as they are (should be) on the outgoing terminals.

Some only have SP switches though Tel