Very carefully confirming polarity

[BackwoodsEE]

I did not want to get my fingers anywhere near that loose wire before shutting off the disconnect and screwing it down to the charge controller input.

IMG_2580.PNG

[BackwoodsEE]

This was Voc from a string of 12 panels under cloudy skies. Probably more like 430-440 V under full sun. These aren't voltages you can just shrug off.

[max2k]

This was Voc from a string of 12 panels under cloudy skies. Probably more like 430-440 V under full sun. These aren't voltages you can just shrug off.

if you're scared don't go near it. Otherwise it's just that- high voltage with supposedly good amps to make sure you won't make it. I especially like 10uV resolution, nice touch . I'm a little confused with that negative kOhmV - what is that?

[NukeEngineer]

Do polarity checks at night under moonlight. Or have someone shine a flashlight on them. You'll get volts, but no real amps. Still wouldn't recommend carelessness, though.

My 72c panels read 25Voc in my garage at night, with just a 13W CFL above them.

[BackwoodsEE]

I kept one hand in my pocket like the old days of poking around in tube Heathkit radios as a kid, got my polarity confirmed, shut off the disconnect, and finished wiring it up. I've had a healthy respect for voltage ever since getting hit with a lot of it during an unauthorized high school lab experiment involving all the coils from all the workbenches hooked up in series with a sturdy D.C. power supply and some big sparks.

[max2k]

Do polarity checks at night under moonlight. Or have someone shine a flashlight on them. You'll get volts, but no real amps. Still wouldn't recommend carelessness, though.

My 72c panels read 25Voc in my garage at night, with just a 13W CFL above them.

for source which normally produces 8-10 A to produce 0.03A is nothing and that is deadly current level for a human. At this voltage you can be assured it will pass through your body at that level: 400V / 10,000 Ohm = 40mA Since they're deadly pretty much any time I prefer to work on my system during day light hours .

In reality I was shocked from DC power supplies (not proud of it / high school / tube amplifiers) in the range of 400V-600V DC so it is not immediate death sentence but it is also a lottery, any time can be the last. OTOH the color of blue glow changing in synch with music can't be beat: https://robrobinette.com/How_Tubes_Work.htm

[inetdog]

FWIW 40ma of DC is not an enormous shock hazard, since it does not have the same ability to disrupt the heart rhythm that 50-60 Hz AC does. It still would not be comfortable and should be avoided. There is always a risk of responding to the shock by jumping back or falling and injuring yourself that way.

[SunEagle]

I kept one hand in my pocket like the old days of poking around in tube Heathkit radios as a kid, got my polarity confirmed, shut off the disconnect, and finished wiring it up. I've had a healthy respect for voltage ever since getting hit with a lot of it during an unauthorized high school lab experiment involving all the coils from all the workbenches hooked up in series with a sturdy D.C. power supply and some big sparks.

I can relate to that "one hand in the pocket" strategy since I also built electronic kits in the late 60's while in high school. It doesn't take much voltage to hurt you but keeping the path from going through the chest by not using both hands is good way to stay safe.

[max2k]

I can relate to that "one hand in the pocket" strategy since I also built electronic kits in the late 60's while in high school. It doesn't take much voltage to hurt you but keeping the path from going through the chest by not using both hands is good way to stay safe.

even better way is to turn the damn thing off and discharge all the capacitors

[max2k]

FWIW 40ma of DC is not an enormous shock hazard, since it does not have the same ability to disrupt the heart rhythm that 50-60 Hz AC does. It still would not be comfortable and should be avoided. There is always a risk of responding to the shock by jumping back or falling and injuring yourself that way.

I know it doesn't sound much but in my university safety course the fatal level was stated at 30mA and human body resistance at 1kOhm giving highest conservative safe voltage of 30V. Anything higher requires caution/warnings. This page somewhat states the same: https://www.physics.ohio-state.edu/~...l_current.html 400V is way over any safe level.

[SunEagle]

I know it doesn't sound much but in my university safety course the fatal level was stated at 30mA and human body resistance at 1kOhm giving highest conservative safe voltage of 30V. Anything higher requires caution/warnings. This page somewhat states the same: https://www.physics.ohio-state.edu/~...l_current.html 400V is way over any safe level.

OSHA states that anything over 50volts can be hazardous to a human. That 50v value is due to the average body resistance which of course can vary per individual.

The problem is really the amount of current that can kill you which is very small probably in that 30ma range.

It is always best to wear PPE or rubber gloves when touching live electrical circuits. Most people get killed from standard 120v lines in the home. Sad and scary.

[inetdog]

I know it doesn't sound much but in my university safety course the fatal level was stated at 30mA and human body resistance at 1kOhm giving highest conservative safe voltage of 30V. Anything higher requires caution/warnings. This page somewhat states the same: https://www.physics.ohio-state.edu/~...l_current.html 400V is way over any safe level.

And this gives higher thresholds for DC: http://www.brighthubengineering.com/...ck-comparison/

[max2k]

And this gives higher thresholds for DC: http://www.brighthubengineering.com/...ck-comparison/

88 mA DC? Good luck 'letting go' that. I'm not sure what is that page authors are smoking but it is lethal level based on many other sources.

[sensij]

88 mA DC? Good luck 'letting go' that. I'm not sure what is that page authors are smoking but it is lethal level based on many other sources.

If by "lethal" you mean ventricular fibrillation, IEC 60479-1 must not be one of the sources you are referring to.

Chart.JPG

[max2k]

If by "lethal" you mean ventricular fibrillation, IEC 60479-1 must not be one of the sources you are referring to.

my bad, enjoy your shocks