Hi Lucian. I hope you see this post that I said I was going to put up in response to your information.
After what you said about being surprised about such a low resistance with equipment and because I hadn't given this too much thought, I had only assumed that some equipment had very low IR I have tested some over that last 2 weeks.
After testing various bits of equipment L+N->E I found that a lot were >999MΩ.
Many were lower than that but still in the hundreds.
The same type of equipment can have different result. Fridges 550MΩ, 250MΩ and the lowest 2.5MΩ
Same make of hand dryers next to each other; one at >999MΩ, the other 8.7MΩ
Frogeye emergency light at 11MΩ
The lowest one was an Andrews movable air conditioner at 1.75MΩ. It is a very old one with mechanical controls so no electronics, only 2 fan motors, a compressor and a condensate pump. The pump and condenser motors are shaded pole and the compressor is capacitor start. Not sure about the evaporator fan but i think it's shaded pole as well.
However, this has not been run for a while and it's possible the windings have some damp. When I get a chance I will put it in a warm room for a few days and test again. Then run it for a while and test.
An emergilite fitting which normally has >999MΩ had 0MΩ. However, this one was faulty.
I found a few bits of equipment took longer than you said for charging capacitors although still less than 4 seconds.
RCBOs 0.11Ω
RCDS N-E is 0.33 MΩL-E is 0,17MΩ.
However, an RCBO/RCDS capacitor (a ceramic one) is not on a filter circuit. It functions to provide the electronics with an alternative neutral in case the neutral is lost. I have read that this is not really necessary as the the chance that the neutral is lost at the same time as a fault on the circuit is negligible, hence, some RCBOs don't have an earth tail.
I don't agree with that. If you loose the neutral the circuit will appear dead. Someone can then touch the line conductor when investigating a piece of equipment forgetting to unplug it.
I tested various capacitors directly and found electrolytic are very leaky at DC. However, you did say that they are not used across L-E and N-E so that wouldn't be an issue.
In conclusion, it could only have been faulty equipment or a fault in the circuit under test that could have caused very low IR readings.
However, a circuit that should have a high IR reading but has one that is 1 to 100 just because of equipment doesn't really show the real condition of the circuit itself.
Therefore, as far as I'm concerned, all circuits that has plugable items should really be unplugged and 2 pole switches (as in FCUs) should be switched off.
As far as lighting is concerned there is no choice but to accept a lower reading if this is caused by any equipment. Switching the single pole light switch off won't help as when you connect L+N to test you are still connected to the L through the load.
So you were absolutely correct. Your information was invaluable and had got me thinking more about the circuit and things connected to the circuit.
Thanks.
After what you said about being surprised about such a low resistance with equipment and because I hadn't given this too much thought, I had only assumed that some equipment had very low IR I have tested some over that last 2 weeks.
After testing various bits of equipment L+N->E I found that a lot were >999MΩ.
Many were lower than that but still in the hundreds.
The same type of equipment can have different result. Fridges 550MΩ, 250MΩ and the lowest 2.5MΩ
Same make of hand dryers next to each other; one at >999MΩ, the other 8.7MΩ
Frogeye emergency light at 11MΩ
The lowest one was an Andrews movable air conditioner at 1.75MΩ. It is a very old one with mechanical controls so no electronics, only 2 fan motors, a compressor and a condensate pump. The pump and condenser motors are shaded pole and the compressor is capacitor start. Not sure about the evaporator fan but i think it's shaded pole as well.
However, this has not been run for a while and it's possible the windings have some damp. When I get a chance I will put it in a warm room for a few days and test again. Then run it for a while and test.
An emergilite fitting which normally has >999MΩ had 0MΩ. However, this one was faulty.
I found a few bits of equipment took longer than you said for charging capacitors although still less than 4 seconds.
RCBOs 0.11Ω
RCDS N-E is 0.33 MΩL-E is 0,17MΩ.
However, an RCBO/RCDS capacitor (a ceramic one) is not on a filter circuit. It functions to provide the electronics with an alternative neutral in case the neutral is lost. I have read that this is not really necessary as the the chance that the neutral is lost at the same time as a fault on the circuit is negligible, hence, some RCBOs don't have an earth tail.
I don't agree with that. If you loose the neutral the circuit will appear dead. Someone can then touch the line conductor when investigating a piece of equipment forgetting to unplug it.
I tested various capacitors directly and found electrolytic are very leaky at DC. However, you did say that they are not used across L-E and N-E so that wouldn't be an issue.
In conclusion, it could only have been faulty equipment or a fault in the circuit under test that could have caused very low IR readings.
However, a circuit that should have a high IR reading but has one that is 1 to 100 just because of equipment doesn't really show the real condition of the circuit itself.
Therefore, as far as I'm concerned, all circuits that has plugable items should really be unplugged and 2 pole switches (as in FCUs) should be switched off.
As far as lighting is concerned there is no choice but to accept a lower reading if this is caused by any equipment. Switching the single pole light switch off won't help as when you connect L+N to test you are still connected to the L through the load.
So you were absolutely correct. Your information was invaluable and had got me thinking more about the circuit and things connected to the circuit.
Thanks.