Fluorescent light fittings earth leakage

[zolee]

Hi everyone, I have measured an earth leakage on twin Flo light fittings (2x58W fittings) in open plan office. Office has 18x twin Flo light fittings which are divided into 3 separate circuits, and 3x (10A) RCBOs for each circuit. I have reading of 3mA at each light fitting. 2x circuits are with 7 light fittings and 1x circuit has 4 light fittings. Circuits with 7 light fittings have 21mA earth leakage in tottal, which is not enough to trip 30mA RCBO. I had fault on one of the 7 light circuits (wire was burnt out in block connector and block connector was melted). I have rectified the fault and lights are working perfectly, but I am not sure if the earth leakage is okay if its there!?

 

[Vortigern]

Is it a suspended ceiling of plasterboard? Maybe the connectors are goosed and need a better insulated connection.

 

[zolee]

Is it a suspended ceiling of plasterboard? Maybe the connectors are goosed and need a better insulated connection.

Its a plasterboard. But building is quite old and wiring was done 30-40 years ago. Cables and wires are pretty stiff, but insulation resistance is >99MOhms. I am assuming it's because of old ballast and old capacitors. Plastic body of the capacitors is crumbling and we often have to tape it around with electrical tape.
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Its a plasterboard. But building is quite old and wiring was done 30-40 years ago. Cables and wires are pretty stiff, but insulation resistance is >99MOhms. I am assuming it's because of old ballast and old capacitors. Plastic body of the capacitors is crumbling and we often have to tape it around with electrical tape.

Unfortunately I cannot say which company I am working for, but they don't want to invest in new LED light fittings - they want me to find the fault ?

 

[Lucien Nunes]

You mention capacitors, so I presume these fittings have wirewound ballasts, not electronic, correct? Do they have starters (either glow or electronic)? Are the capacitors ordinary 2-wire PFC capacitors connected across L & N?

There might not be a fault as such. Fluorescent fittings can leak a milliamp each without being non-compliant, some fittings might leak more. Also, the measurement might be in error because of the high harmonic content of the lamp current, which can fool some test instruments. 3mA per fitting does sound high though. What I would do is this:

Find a fitting that produces the typical leakage current. IR test it L+N -> E at 250V. This will not damage a standard choke-ballasted fluorescent or its PFC capacitor. If the IR is good (megohms) then we know the leakage reading is either an error or capacitive. If there is any suspicion about the IR, the ballast can be tested to earth / its casing by itself at 500V and again should be many megohms.

Assuming the IR is good, confirm that the ballast is connected to the line rather than the neutral. Now take a leakage measurement with the fitting live and the tube in, but the starter out so that the tube does not start. In this condition, the same parts of the fitting are live as when the tube is working normally. If the leakage is present, then there is still an insulation fault somewhere.

If the leakage is low, insert the starter and re-check the leakage. If the leakage is now present, it is the result of the high-frequency harmonics caused by the lamp characteristics a) causing the leakage and b) interfering with the tester. If you wanted confirmation of the exact leakage current, you might need to use an analogue meter.

 

[zolee]

You mention capacitors, so I presume these fittings have wirewound ballasts, not electronic, correct? Do they have starters (either glow or electronic)? Are the capacitors ordinary 2-wire PFC capacitors connected across L & N?

There might not be a fault as such. Fluorescent fittings can leak a milliamp each without being non-compliant, some fittings might leak more. Also, the measurement might be in error because of the high harmonic content of the lamp current, which can fool some test instruments. 3mA per fitting does sound high though. What I would do is this:

Find a fitting that produces the typical leakage current. IR test it L+N -> E at 250V. This will not damage a standard choke-ballasted fluorescent or its PFC capacitor. If the IR is good (megohms) then we know the leakage reading is either an error or capacitive. If there is any suspicion about the IR, the ballast can be tested to earth / its casing by itself at 500V and again should be many megohms.

Assuming the IR is good, confirm that the ballast is connected to the line rather than the neutral. Now take a leakage measurement with the fitting live and the tube in, but the starter out so that the tube does not start. In this condition, the same parts of the fitting are live as when the tube is working normally. If the leakage is present, then there is still an insulation fault somewhere.

If the leakage is low, insert the starter and re-check the leakage. If the leakage is now present, it is the result of the high-frequency harmonics caused by the lamp characteristics a) causing the leakage and b) interfering with the tester. If you wanted confirmation of the exact leakage current, you might need to use an analogue meter.

Thank you Lucien ? I will do testing as you are suggesting, but next month probably (I have a lot of PPMs at the moment). To answer your questions, yes, there are wirewound ballasts and starters. Capacitors are 2 wire PFC capacitors.

 

[zolee]

Thank you Lucien ? I will do testing as you are suggesting, but next month probably (I have a lot of PPMs at the moment). To answer your questions, yes, there are wirewound ballasts and starters. Capacitors are 2 wire PFC capacitors.

Hi Lucien! Sorry, I have an follow up question

The regs state 531.3.2(ii) that earth leakage should be no more than 30% of the rating of the rcd/rcbo.

I am a bit confused. if regs are stating that earth leakage can`t be more than 30%, it means it cannot be more than 9mA (30mA RCBO) - am I right!?

If this is right, light fitings in office should to be replaced with new (LED) light fittings, because 21mA can cause nasty experience!??
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Hi Lucien! Sorry, I have an follow-up question

The regs state 531.3.2(ii) that earth leakage should be no more than 30% of the rating of the rcd/rcbo.

I am confused. if regs state that earth leakage can`t be more than 30%, it means it cannot be more than 9mA (30mA RCBO) - am I right!?

If this is right, light fittings in the office should be replaced with new (LED) light fittings, because 21mA can cause nasty experience!??

What code would it be on EICR? C2? or C1 because it does not comply with regs?

I would really like to hear your opinion regarding this case.

Have a great day.

Best wishes, Zoltan.

 

[Lucien Nunes]

Since the lower trip threshold of an EN61008 or similar 30mA RCD is 15mA, making the maximum leakage 10mA gives a margin against nuisance tripping. I am genuinely skeptical as to whether these fittings are actually lekaing 3mA each, I reckon there might be some error in the reading as the tester might not be correctly interpreting the harmonic-rich waveform. An interesting test, as well as the ones I already suggested, would be to run a ramp test with the light on, to see how much extra leakage the breaker takes before it trips. That might shed some light on whether the 3mA per fitting is accurate.

 

[zolee]

Since the lower trip threshold of an EN61008 or similar 30mA RCD is 15mA, making the maximum leakage 10mA gives a margin against nuisance tripping. I am genuinely skeptical as to whether these fittings are actually lekaing 3mA each, I reckon there might be some error in the reading as the tester might not be correctly interpreting the harmonic-rich waveform. An interesting test, as well as the ones I already suggested, would be to run a ramp test with the light on, to see how much extra leakage the breaker takes before it trips. That might shed some light on whether the 3mA per fitting is accurate.

I will test those lights again as you suggested it and I will do ramp test as well. I will be going back to that job beginning of the next month and I will let you know what readings I had.

Thank you so much for your time and help ?

Have a great rest of the day ?

P.S.
I am using Megger DCM305E Earth leakage meter.