Insulation resistance

[Regs]

Surely with the 2391 under your belt this is stuff you should know !

Yeah i know that of course. But if you add an RCD you are making the safety alot better you can't be held liable for a fault already in place. You could advise the customer and charge to correct it, surely?

 

[Regs]

a reading over 1Meg. is acceptable, but it's good practice to investigate anything under 2 Meg. the pond pump could just be moisture in an adaptable box or outdoor socket.

Yeah cheers, there is no adaptable box, i checked the socket. Insulation res. went up when i pulled the plug to the pump.

 

[telectrix]

Yeah i know that of course. But if you add an RCD you are making the safety alot better you can't be held liable for a fault already in place. You could advise the customer and charge to correct it, surely?

before adding an RCD you should test to see if there are any faults that will cause problems, along with earthing and bonding. you then factor the cost of fixing these faults as part of your quote.

 

[Marvo]

Any pumps but especially submersible types are prone to low insulation. Even slight wear on the shaft or seal coupled with the heating and cooling during normal operation and it's all over for the IR. If it's a small domestic pond pump then it's probably better to replace with new rather than attempt repairs.

 

[Octopus]

Doing an IR test with loads still connected is always going to end in tears.

 

[44ALLAN]

Hot motor /cold motor............summer /winter ambient temp lol.
Appliances just switched off or been standing for several hours.

The inexperienced will see faults that aren't there if their comparing results from previous tests

 

[Regs]

Doing an IR test with loads still connected is always going to end in tears.

Yeah i thought the load was removed so you don't fire 500v down your line and neutral and destroy items. Didn't realise, to be honest that items not in use but still plugged in would also still be a problem.

 

[LittleHelper]

Test between all conductors seperatley!! Probably a load!

 

[Brightspark2]

Check for more loads that are connected...or neons...FCU's etc etc

 

[Guest111]

Instead of disconnecting the main earth to the board,try disconnecting the L N E of the circuit you are working on and test them,it's just possible that even though you have disconnected the main earth that the bonds to gas and water may be affecting your readings.

 

[Regs]

O.k. forgot in 1 bed room there was surge protector under the bed, removed this and instantly gained from 0.36 to 1.6 M.O. Also found that unplugging my monitor for my mac gained another 1 meg to total 2.6 M.O. I'm happy for now with that, guess the rest could be the dishwasher or washing machine.
Again would this imply monitor or lead on way out?

 

[telectrix]

a lot of electronic gear has earth leakage. always disconnect before testing. as cpl. jones famously said " they don't like it up'em".

 

[Regs]

a lot of electronic gear has earth leakage. always disconnect before testing. as cpl. jones famously said " they don't like it up'em".

So as long as the cause of low insulation r. is not the cable insulation, then it doesn't matter if the insulation reading drops right down to 0.1M.O. The reason has been investigated and would still be acceptable of course then?

I take it some items of equipment are more prone to leakage than others then

 

[Marvo]

What you've discovered is that the earth is functional as well as protective. Depending what test voltage you use to mega test all surge arrestors will show as low insulation.

 

[Regs]

What you've discovered is that the earth is functional as well as protective. Depending what test voltage you use to mega test all surge arrestors will show as low insulation.

Now you mention it at 250v reading was 0.9 Mohm and 500v it read 0.36 if i remember correctly.