Fusing solar panel cables

[Nickhlx]

Shock ..... horror, not 3 or 4 amps ? and DC !!! .... well ....

 

 

 

....Amps don't kill you ( a few tens of mAmps are enough) - it's the volts that push them !! If you put a hand on each battery terminal, you survive, and there's hundreds of them amps in there, waiting to escape...

 

 

Any volts over about 50V, and you start to feel it, depending on what bit of your anatomy you are applying it to (!) and how dry your skin is... For dry hands, with no cuts, this is a reasonable average. However, you can feel a PP3 on your tongue and even less voltages...

 

Nick

Edited December 12, 2015 by Nickhlx

[Graham.m]

Shock ..... horror, not 3 or 4 amps ? and DC !!! .... well ....

 

 

 

....Amps don't kill you ( a few tens of mAmps are enough) - its the volts that push them !! If you put a hand on each battery terminal, you survive, and there's hundreds of them amps in there, waiting to escape...

 

Nick

 

 

mmmm While volts has a part it is the level of current that kills. So you can have 1000volts at say 1 pico picoA you may feel it but I doubt unless you have a weakness that it will kill you. I think you will find that 250V at 300mA has a very good chance of causing your demise.

Edited December 12, 2015 by Graham.m

[Graham.m]

Shock ..... horror, not 3 or 4 amps ? and DC !!! .... well ....

 

 

 

....Amps don't kill you ( a few tens of mAmps are enough) - it's the volts that push them !! If you put a hand on each battery terminal, you survive, and there's hundreds of them amps in there, waiting to escape...

 

 

Any volts over about 50V, and you start to feel it, depending on what bit of your anatomy you are applying it to (!) and how dry your skin is... For dry hands, with no cuts, this is a reasonable average. However, you can feel a PP3 on your tongue and even less voltages...

 

Nick

 

I know and have know many people who get a tingle from a 12V battery as I have known many who got across 250 volts at nominal 30mA for mS and don't even know about it. Up to about 50V there is not generally enough volts, Over about 100V it does not take many mAs to say bye bye, order of a 100 or 200mA

Edited December 12, 2015 by Graham.m

[cuthound]

Shock ..... horror, not 3 or 4 amps ? and DC !!! .... well ....

 

 

 

....Amps don't kill you ( a few tens of mAmps are enough) - it's the volts that push them !! If you put a hand on each battery terminal, you survive, and there's hundreds of them amps in there, waiting to escape...

 

 

Any volts over about 50V, and you start to feel it, depending on what bit of your anatomy you are applying it to (!) and how dry your skin is... For dry hands, with no cuts, this is a reasonable average. However, you can feel a PP3 on your tongue and even less voltages...

 

Nick

Depends upon the resistance of the body, a little over 30mA across the heart will kill you.

 

Static electricity is often at many thousands of volts, yet people survive static shocks without I'll effect every day.

[BMC problems]

 

Graham you have become a very disruptive influence on this forum. You hit every electrical thread with foolish advice written authoritatively, which then has to be endlessly refuted by people who actually know what they are talking about. You obviously enjoy the banter but I wish you could spare a thought for those who are asking the questions - they just get very confused.

 

Clearly the forum is your plaything but you are using it very selfishly for your own fun and disregarding the detrimental effect your contribution has to anyone with limited knowledge. As I said, very very selfish.

 

This. It's getting quite irritating. It's so obvious to me when he's wrong.

 

He will never even think about what he's saying. The confusion engendered amongst those trying to learn is mean and spiteful.

 

 

Perhaps you could explain why you think my assumptions are incorrect?

 

Your assumptions are incorrect because that is not what the BSS regulations say. You simply made it up.

[BMC problems]

I fear that there is now a significant new area of risk with self installed boat PV. From my brief reading it appears that 120VDC is regarded as a safe upper limit for human contact. It would be very easy for me to order a set of panels with which I could easily exceed this figure and, if not made aware of the risk, wire them in the usual low voltage (12/24V) manner with exposed connections etc.

 

 

 

Yes, if using the connectors to isolate it is wise to do it with care and with dry hands in the dry. 100V or 150V is neither here not there. The precautions are sensible whenever it's done.

 

Most panels I've ever seen say "don't disconnect under load" implying that such disconnection is best done in the dark or after covering the panels. Having said that it's essential, as has been said, to disconnect the panels before the controller and so sometimes it's difficult to follow that instruction. I would guess the precaution is to protect the internal diodes against current spikes.

 

One of the nice things about the more upmarket controllers, Morningstar and Outback particularly is that they enable you to isolate the solar feed, presumably in a way that is safe both to panel and controller.

[nicknorman]

This. It's getting quite irritating. It's so obvious to me when he's wrong.

 

He will never even think about what he's saying. The confusion engendered amongst those trying to learn is mean and spiteful.

 

Your assumptions are incorrect because that is not what the BSS regulations say. You simply made it up.

 

I know. I've raised the matter with Dan - he's yet to get back to me. But whilst it is easy to set forum rules and guidelines to keep posts "polite", it is much harder to set rules and guidelines to require responsible posting on technical matters. The forum is already in danger of becoming a political talking shop only - the vast majority of posts are in VP and the like - and this sort of cary-on just perpetuates that gradual slide into mush.

 

A number of people have left due to constantly having their correct views on the likes of gas installations under attack from ignorant people and I'm starting to feel the same about electrics at the moment. It is sad but true that one person can ruin a forum for everyone else.

 

But he obviously gets a kick out of it so I guess we are just feeding him oxygen.

Edited December 12, 2015 by nicknorman

[BMC problems]

I know. I've raised the matter with Dan - he's yet to get back to me. But whilst it is easy to set forum rules and guidelines to keep posts "polite", it is much harder to set rules and guidelines to require responsible posting on technical matters. The forum is already in danger of becoming a political talking shop only - the vast majority of posts are in VP and the like - and this sort of cary-on just perpetuates that gradual slide into mush.

 

A number of people have left due to constantly having their correct views on the likes of gas installations under attack from ignorant people and I'm starting to feel the same about electrics at the moment. It is sad but true that one person can ruin a forum for everyone else.

 

But he obviously gets a kick out of it so I guess we are just feeding him oxygen.

 

I think you are doing the right thing, calling him out each time.

 

Personally I really can't be bothered to argue.

[Loafer]

I once heard that a 12V car battery would kill you if you touched both terminals with two 'open wounds', i.e. no skin resistance.

 

What do you reckon chaps?

[Nickhlx]

No... (assuming an otherwise healthy person)

 

The voltage would not cause enough current to flow

[cuthound]

I once heard that a 12V car battery would kill you if you touched both terminals with two 'open wounds', i.e. no skin resistance.

 

What do you reckon chaps?

Dunno, probably not, but I got a shock as a lad, when I fell face first on a Scalextric track and "kissed" the conductors.

[Graham.m]

No... (assuming an otherwise healthy person)

 

The voltage would not cause enough current to flow

 

 

Sorry puzzled what voltage and what current?

[nicknorman]

I think you are doing the right thing, calling him out each time.

 

Personally I really can't be bothered to argue.

 

I'm finding it very tiresome too. Of course as soon as I get a bit grumpy with him he's straight off to Dan to complain, threatens to sue me for libel etc.

 

Anyway, I need support from someone so don't stop!

Edited December 12, 2015 by nicknorman

[Loafer]

I'm finding it very tiresome too. Of course as soon as I get a bit grumpy with him he's straight off to Dan to complain, threatens to sue me for libel etc.

 

Anyway, I need support from someone so don't stop!

 

 

You have mine!

 

[WotEver]

Going to the other extreme I once managed to get close to 1kV across my hands. I screamed like a girl and ended on my back. Fortunately I was young and healthy and suffered no heart problem. Apart from some nasty burns on my fingers I was fine.

 

In this instance the current was (obviously) very low, but it was pulsating DC.

 

I didn't like it much.

 

 

You have mine!

Mine too. I used the same word - "tiresome" - myself a day or two back.

[WotEver]

No... (assuming an otherwise healthy person)

 

The voltage would not cause enough current to flow

The human body 'inside the skin' is generally reckoned to be around 1kr. This would only result in a 14mA current flow @ 14V.

 

Tony

 

You might feel it (like a PP3 on the tongue) but it wouldn't kill you.

[cuthound]

I'm finding it very tiresome too. Of course as soon as I get a bit grumpy with him he's straight off to Dan to complain, threatens to sue me for libel etc.

Anyway, I need support from someone so don't stop!

You have my support too Nick.

 

We have already lost Gibbo,so I would be unhappy to see someone as genuinely helpful as you stop using the forum..

[Graham.m]

The human body 'inside the skin' is generally reckoned to be around 1kr. This would only result in a 14mA current flow @ 14V.

 

Tony

 

You might feel it (like a PP3 on the tongue) but it wouldn't kill you.

 

Somewhere in the back of my mind is 50V @ 50mA will kill. Probably came from some safety course I did years ago, can't confirm from that long ago.

 

Don't know how reliable this is but it ties up with a lot I am aware of http://www.mpoweruk.com/shock.htm

[Loafer]

 

Somewhere in the back of my mind is 50V @ 50mA will kill. Probably came from some safety course I did years ago, can't confirm from that long ago.

 

Don't know how reliable this is but it ties up with a lot I am aware of http://www.mpoweruk.com/shock.htm

 

That information states that there is 'no resistance' between two open wounds - which suggests to me that a 12V battery would deliver a fatal current. I haven't tried it though. Maybe we should use a few captured terrorists and try it out?

[WotEver]

 

That information states that there is 'no resistance' between two open wounds...

As opposed to NIOSH which states "Under dry conditions, the resistance offered by the human body may be as high as 100,000 Ohms. Wet or broken skin may drop the body's resistance to 1,000 Ohms," adding that "high-voltage electrical energy quickly breaks down human skin, reducing the human body's resistance to 500 Ohms."

 

NIOSH is the US National Institute for Occupational Safety and Health.

 

Obviously NIOSH is wrong...

[Loafer]

As opposed to NIOSH which states "Under dry conditions, the resistance offered by the human body may be as high as 100,000 Ohms. Wet or broken skin may drop the body's resistance to 1,000 Ohms," adding that "high-voltage electrical energy quickly breaks down human skin, reducing the human body's resistance to 500 Ohms."

 

NIOSH is the US National Institute for Occupational Safety and Health.

 

Obviously NIOSH is wrong...

 

Not necessarily. That information is assuming that the skin is still in place, even if a bit damaged. My suggestion assumes NO skin in the way, with a very salty electrolytic body underneath.

[WotEver]

The quote states "Wet or broken skin may reduce the resistance to 1kr"

[Loafer]

The quote states "Wet or broken skin may reduce the resistance to 1kr"

 

What's a 'kr'?

 

If it's 1000 ohms, then that 14mA could still kill someone with a heart condition, couldn't it?

Edited December 12, 2015 by Loafer

[WotEver]

1000 ohms

[Loafer]

Mind you, if you're messing about with a 12V battery with a heart condition and two open wounds, you probably deserve everything you get!