AC or DC 90V?

20Hz.
Max.

 

220V for ringer?? I thought it was around 75-100V AC @ 20Hz. Guess what the outcome will be if someone was fixing the telephone line and someone just called to that line.

You clearly didn't read and/or understand what I said.

The gas discharge protection devices are usually pitched somewhere around that voltage, but it isn't clear whether the equipment should still work that high or just survive it.

 

Did you know that some people have died from testing a 9 Volt battery on their tongue???

From the electric shock? Or from snapping their head back enough for loose their balance and fall from the ladder they were standing on to reach their smoke detector?

A 9V battery can definitely deliver enough current to kill someone if you get past the skin resistance and the current travels through the body along a critical path. Having needles or open sources on both wrists would be a good candidate. But through the tongue along a path that is about half an inch? I'd want to see decent documentation of such an event.

 

I'm glad you are fine. I too had a few bad experiences with 220V buts its much nasty compared to a 110V outlet. This one is capable of 2.5A at 120V so its bad right?

Almost anything that is run from a mains outlet, at either 110 VAC or 220 VAC, requires more than 50 mA to operate. Hence, virtually all power sources intended to power things that are normally powered from the mains are capable of delivering significantly more than 50 mA of current. Since 50 mA at 110 VAC is only 5.5 W, and since 50 mA is well into the potentially lethal range of currents, any power supply at this voltage rated at much over 1 W should be considered dangerous and potentially lethal.

Notice that use of the term "potentially". In order to kill you the resistance between the points of contact have to be low enough and the path actually taken by the current through the body has to be such as to actually cause death. That's why lots of people have gotten bit by 110 VAC or even 220 VAC and lived to tell the tale -- it's actually a bit difficult, particularly with 110 VAC -- to satisfy both criteria at the same time. So most people end up with a very unpleasant experience and perhaps some skin burns. But most any given entanglement has the potential to satisfy both and thus the potential to be fatal. It's a game where the only winning strategy is not to play.

 

My Dad worked in the power division for a railroad running 600 VDC at enough current to run a train. Literally. Several trains in fact.

He had a trick to quick check cartridge fuses by tapping the ends with his index and small fingers as his hand flew past it. The moving hand kept the contact brief and his insulated shoes kept him ungrounded. If he felt a tingle the fuse was bad.

I yelled at him for quite a long time when I saw him do this in front of me. I was in my late teens (young enough to know some not all) when this happened.

I do not know if he stopped the practice after our talk.

Treet ALL electric power as if it can kill you and it never will.

At my dad's shop they had a 13.8 kVAC to 440 VAC transformer go bad (I think this was early 1970's). Since the 13.8 kV side came from the street transformer that powered a few businesses on the street, the electrician had to wait for the city utility company to coordinate with the affected business and kill the transformer. Apparently the physical set up was such that they couldn't open that one transformer and they had to go to the nearby (as in across the street) substation and kill several transformers. It was taking hours to get everyone on board and so the electrician decided to change out the transformer while it was live. He insisted that everyone leave the area so that there was less change of someone saying something or doing something that would distract him even for a moment. Then he made sure he had on all of his protective gear, which included a glove for his left hand that was glued to the side of the suit and that fit his hand so tight that it was a struggle to get into or out of it, after inspecting it very carefully. He then made sure he has exactly the tools he would need and nothing more. He then crawled into the vault and proceeded to very slowly and methodically change out the transformer.

I've tried changing out simple stuff like wall switches and light fixtures with the one-hand-in-pocket approach and it was extremely difficult (for me) to do. I can just image the amount of practice it took to be able to change out a transformer like that (though, in some ways, it was probably easier since everything is big enough that it isn't wiggling around every time you touch it).

 

At my dad's shop they had a 13.8 kVAC to 440 VAC transformer go bad (I think this was early 1970's). Since the 13.8 kV side came from the street transformer that powered a few businesses on the street, the electrician had to wait for the city utility company to coordinate with the affected business and kill the transformer. Apparently the physical set up was such that they couldn't open that one transformer and they had to go to the nearby (as in across the street) substation and kill several transformers. It was taking hours to get everyone on board and so the electrician decided to change out the transformer while it was live. He insisted that everyone leave the area so that there was less change of someone saying something or doing something that would distract him even for a moment. Then he made sure he had on all of his protective gear, which included a glove for his left hand that was glued to the side of the suit and that fit his hand so tight that it was a struggle to get into or out of it, after inspecting it very carefully. He then made sure he has exactly the tools he would need and nothing more. He then crawled into the vault and proceeded to very slowly and methodically change out the transformer.

I've tried changing out simple stuff like wall switches and light fixtures with the one-hand-in-pocket approach and it was extremely difficult (for me) to do. I can just image the amount of practice it took to be able to change out a transformer like that (though, in some ways, it was probably easier since everything is big enough that it isn't wiggling around every time you touch it).

Working with one hand in your pocket is a good rule - but not always possible to get the job done, and a complete waste of effort if you're not wearing rubber soles.

 

Working with one hand in your pocket is a good rule - but not always possible to get the job done, and a complete waste of effort if you're not wearing rubber soles.

From the description my dad gave, this guy went to rather extreme measured. Not only did he have rubber-soled boots, but he taped his pants legs to the boots and then he put his feet into a couple of layers of trash bags and taped those to the pants legs too (I suspect, but don't know, that this might actually have been just protect the boots in order to extend their life). He also war a face mask that he taped to a rubber hood. Basically, he went out of his way to ensure that the only exposed skin anywhere to be seen was his right hand. For all I know, he might even have worn thin rubber/latex gloves on that hand. I've thought about whether doing that would be effective when working on household wiring that is live, but I've never researched it or done any tests.

 

From the description my dad gave, this guy went to rather extreme measured. Not only did he have rubber-soled boots, but he taped his pants legs to the boots and then he put his feet into a couple of layers of trash bags and taped those to the pants legs too (I suspect, but don't know, that this might actually have been just protect the boots in order to extend their life). He also war a face mask that he taped to a rubber hood. Basically, he went out of his way to ensure that the only exposed skin anywhere to be seen was his right hand. For all I know, he might even have worn thin rubber/latex gloves on that hand. I've thought about whether doing that would be effective when working on household wiring that is live, but I've never researched it or done any tests.

Sounds over the top - the best way is not working on live circuits. But I've had to once or twice.

 

...Or you can do it in a Faraday cage! As per linemen working with UHV!
Max.

 

Somehow I don't think a Fadaday cage was a viable option for someone changing out an emplaced transformer in a vault.

Whether it was overkill or not I'm certainly not in a position to judge. Messing around with 13.8 kV in a tight space where you are lying down and having to shift position quite a bit, I can see being concerned about accidentally making sufficient contact with inadvertently exposed pieces of the body to warrant a bit of paranoia.

 

I recall once being called into to a factory sub-station where the breaker had tripped.
The 4Kv bus bars were enclosed but not insulated, during the night evidently a rat had got inside and managed to jump on to one busbars, he was OK until apparently from the evidence, his tail flashed to the side of the enclosure.
There were what appeared to be burn marks in the buss bar copper for about 12"!
Max.

 

Somehow I don't think a Fadaday cage was a viable option for someone changing out an emplaced transformer in a vault.

Whether it was overkill or not I'm certainly not in a position to judge. Messing around with 13.8 kV in a tight space where you are lying down and having to shift position quite a bit, I can see being concerned about accidentally making sufficient contact with inadvertently exposed pieces of the body to warrant a bit of paranoia.

A Faraday cage provides lots of excellent earthing to complete your circuit to the grave - unless you're manipulating the work with a long insulated pole; forget it!

 

A Faraday cage provides lots of excellent earthing to complete your circuit to the grave - unless you're manipulating the work with a long insulated pole; forget it!

Agreed.