Where are the dangers in a solar system?

[pr3nt]

Disclaimer - complete newbie here!

I've watched a ton of Will's YouTube videos and I'm also just about done reading his book on solar, and while he does a great job reminding us the correct order to connect the various components so we don't damage any equipment, there isn't any information on how not to damage ourselves!

Please let me know, and if Will sees this, please consider a video showing us beginners which parts of a solar system we can and can't touch and where the dangers are for getting shocked or causing a fire or explosion, etc.

Thanks!

 

[Rider]

If you follow the beginner's guides in the Learning and Beginner's sections, pretty tough to get to catastrophic conditions. Use the sizing guidelines and tools.

Probably the biggest single thing you could do wrong is underestimate and under-size the wires.

With output from an inverter, treat it just as you would in your house; if you don't grab 120VAC plugs in your house, you don't do it here either.

 

[pr3nt]

Hi Rider, thanks for the response. I totally get how undersizing wires can cause issues, and I apologize for not being more clear initially, so I'll give an example. I saw this video on YouTube where this guy is touching both terminals of a car battery while the car is running. Looks crazy to me but I really have no idea what is safe to touch and what isn't. Other than damaging equipment, is there no way to "shock" yourself? Let's keep it simple for now and not consider how an inverter changes things.

 

[Rider]

Ok. A couple of things: 1st, 12VDC is pretty harmless. I test 9VDC batteries on my tongue to see how fresh they are.

2nd, "path of least resistance". Electrons will follow the path of least resistance. Since the wires are connected to the battery and there is some kind of circuit there, the electrons will follow the wires and not you. Basic electrical 101.

As the DC voltage increases, it can become dangerous, but you're talking in excess of 50VDC. Might get a tingle from 24 or 48VDC.

A single solar panel with an output of 12-24VDC in itself is not dangerous. However, if you put a bunch in series and the total goes to 70, 80, 90, over 100V, yeah, then you've got a shock condition. If you've got open wires that are not connected to anything, you can become the path of least resistance and get a good jolt. Someone posted different levels of volt and amps, AC v DC and what constitutes dangerous levels.

 

[offgriddle]

Safety First. ~ It is difficult to write a book and include specific electrical safety precautions without the author risking personal liability. ~ Under the right conditions, ie if the person is standing on a puddle and has a heart condition, even 12 volts can be dangerous. When working with electricity, work one hand as much as possible with the other behind your back, you want to avoid electrical current going from on arm to the other across your chest and heart. Before working on wiring, always use a known working electrical meter to test the circuit that you think is shut off and remember that circuit breakers can fail. Never completely trust a non contact voltage testor, (like the pocket kind that lights up and beeps when you hold it near wires, [aka a wiggy]). Electricity starts to increase in danger above 40 volts. PV systems are capable of exceeding 40 volts.

 

[SCClockDr]

Being on a ladder or roof is high on the hazard scale. 120VAC (house power) requires some caution as it can kick. The usual injury is cuts, abrasions, & bruising when you react to the kick. 240VAC is indeed a dangerous shock hazard. All metal jewelry (rings, chains, neck wear, etc.) should be removed & stowed safely, not in a pocket.

DC
While low voltage DC (9-48 VDC) is quite safe shock hazard wise, contact with a ring, etc. that creates a current path will cause severe burns & can produce molten shrapnel. Higher voltages will also pose a shock hazard as well.

 

[dmcdonough]

starting a fire is the real danger here

 

[pr3nt]

Thanks for the replies, guys! Rider's comment got me on the right path and I found the following which clarifies things a lot more:

What is the safe limit of DC voltage for humans to touch?

Answer (1 of 25): Back in the 1970’s, there was a known electrocution at about 42 VDC. There may be a lower case since then. However, the phone company has used 48 VDC (it was really closer to 52V and could meander up to 56 V) for over a century without losing too many workers.

www.quora.com

 

[A J]

Or "when you least expect it".
A while back I was rotating my battery bank and not having a ratchet, but a wrench, you can only guess what happened.

 

[dmcdonough]

Yeah I set up a little tool kit by my battery bank! taped up wrenches/sockets etc... man that can be terrifying not to mention expensive!

 

[pr3nt]

So, AJ, I assume that the wrench touched both terminals simultaneously and resulted in a bunch of sparks, and while potentially the wrench could get hot enough to burn you, there was still no risk of shock (assuming a 12v battery). Is that true?

 

[MrNatural22]

There’s enough amperage in a car battery during a dead short to weld with. Old off-roader repair trick. ️️️

 

[Supervstech]

So, AJ, I assume that the wrench touched both terminals simultaneously and resulted in a bunch of sparks, and while potentially the wrench could get hot enough to burn you, there was still no risk of shock (assuming a 12v battery). Is that true?

There is always risk.
Conditions vary between weather, and individual skin conditions...
if you ALWAYS treat voltage potential as dangerous, you won’t be surprised and hurt or kill yourself.
Work with one side at a time, and don’t put yourself between a closed circuit. Always have a fuse or breaker open when working on PV current.

I have been seriously shocked with 24v. But the worst part is often the fright, resulting in uncontrolled motions causing injury.
Believe me... you move A LOT when you get a spark or shock and you aren’t prepared for it. If that motion puts your head or hand into a sharp object... yeah... time for a hospital visit.

 

[A J]

Yeah I set up a little tool kit by my battery bank! taped up wrenches/sockets etc... man that can be terrifying not to mention expensive!

So, AJ, I assume that the wrench touched both terminals simultaneously and resulted in a bunch of sparks, and while potentially the wrench could get hot enough to burn you, there was still no risk of shock (assuming a 12v battery). Is that true?

Thankfully I had the system disconnected before I even touched the wrench.

The bang, spark and the felling was indescribable, my first 1200A experience, did't phase the battery just a scar on the terminal bolt.
No burn, to quick for the thermal reaction and yes 12V system, at the time X3 FT-165Ah bank (FT - Front terminal).

 

[A J]

There is always risk.
Conditions vary between weather, and individual skin conditions...
if you ALWAYS treat voltage potential as dangerous, you won’t be surprised and hurt or kill yourself.
Work with one side at a time, and don’t put yourself between a closed circuit. Always have a fuse or breaker open when working on PV current.

I have been seriously shocked with 24v. But the worst part is often the fright, resulting in uncontrolled motions causing injury.
Believe me... you move A LOT when you get a spark or shock and you aren’t prepared for it. If that motion puts your head or hand into a sharp object... yeah... time for a hospital visit.

Too right Dangerous, that's why I have that picture HAZARDOUS VOLTAGE avatar, I look at it as dangerous given the right environment.... (ALWAYS)
I had one batt disconnected, I was working on the middle one, in a tight space.
From what I remember it was the after that was the shock, bit hard to explain, all calm and casual, then I went in to shock, if you understand that!