Insulation Resistance

[RF Lighting]

On a socket circuit

 

[thomo27]

Hi thanks for all help so far.

Ok so I had forgotten to unplug the Plasma on the wall and the dishwasher I have retested, all FCU were in the off position and appliances unplugged.

My new reading was 0.10Mohms , on all variations P-N , P-E and N-E Im no longer receiving my 4.96Mohms when testing between P-E & N-E.

Everthing OK at the CU no temp links left in ...

Does low battery life cause test equip to give bizarre readings ?

Cheers Again


Ste

 

[Space cat]

This might be a silly question but --

Does this ring actually work when the power is on? Or maybe you haven't dared try since you got that 0.97 ohm reading.

If it does still work, you must, as others have suggested, have a large inductive load out there somewhere. A bell transformer isn't big enough. How about a motor in a fridge or freezer?

Edit: Drat and double drat! I see you beat me to it - but I'm pleased you got it sorted.

 

[333rocky333]

500 volt through the plasma telly

 

[industryspark]

Thomo wrote

Ok so I had forgotten to unplug the Plasma

that could have been an expensive mistake!

what tester have you got? a lot will tell you when your batteries need replacing, i believe my megger will tell me the battery strength-cant remember how to do it off top of my head though! have a look in your testers manual.

i would be inclined to think you have missed something first. maybe you can half the ring and test or test sections at a time to try narrowing down the low IR.

 

[Space cat]

500 volt through the plasma telly

Fortunately, the 500 volts never reached the TV - unless his tester can push out the necessary 250 amps!

Edit: repeat after me; "I must not pist when possed!" - or quote other people's figures without taking the trouble to understand what they meant.

Having said that, it wasn't a good idea to try. Lots of electronic gadgets have line powered, switch mode PSUs in them - and electrolytic capacitors can go off with quite a bang!

 

[FingRinal]

The correct way to conduct insulation resitance testing is to first carry out a continuity test between conductors. This will identfy any funny low readings or loads before you zap them with 500V. When you are satisfied with this, then carry out insulation testing.

As a further precaution, it's sometimes worthwhile doing a 250V test first before getting onto the 500V test.

For PIRs, I mainly test beteen L+N together and earth for socket and light circuits. And I normally test the whole board on the load side of the main switch. Only if this throws up a poor result do I break things down further. If the client pays for full testing, then that is what they get. New installations are always fully tested.

 

[securespark]

The socket which FingRinal installed behind the fridge without an accesible isolator?

 

[thomo27]

Hi

I was practicing dead tests so Continuity was my first series of tests , my CPC continuity reading was 0.96 so if I multiply this by 0.25 (which is what I have been taught in order to reach my R2 result for ring circuits) I get 0.24
Have I gave the inpression my R2 was nearly 1 as I have stated 0.96

My tester is a Robin 3010 DL insulation-continuity tester

 

[Space cat]

RF Lighting wrote:
The socket which FingRinal installed behind the fridge without an accesible isolator?

Or the extension lead plugged into a socket behind a kitchen cupboard to provide power for a built-in fridge and freezer!

PS: I'm not suggesting that FingRinal had anything to do with that one.

 

[FingRinal]

The socket which FingRinal installed behind the fridge without an accesible isolator?

If only RF (and others) understood what an isolator was or could actually read what is written (including the Regs)

Edit: not to mention the portion of the fixed installation (btwn switch and socket) which would NEVER again be tested under RF's design and installation Regs

 

[Spark123]

Hi

I was practicing dead tests so Continuity was my first series of tests , my CPC continuity reading was 0.96 so if I multiply this by 0.25 (which is what I have been taught in order to reach my R2 result for ring circuits) I get 0.24
Have I gave the inpression my R2 was nearly 1 as I have stated 0.96

My tester is a Robin 3010 DL insulation-continuity tester

For sockets on a ring R1+R2 is (r1+r2)/4, (remember tho, R1+R2 for spurs will be higher .)

If you are wanting for some reason to know R2, at the mid point will be half of r2 (think resistors in parallel) - remember this may be higher for spurs too.