The british regulations do not consider anything over 50V DC to be "safe" - even then, Extra Low Voltage wiring in bathrooms (even at 12V) has to be seperated from ground as an extra precation.
We have 100-120V [1] in the same band as 220-240V and both systems have to meet the same wiring standards.
[1] Not common but 110V tools exist for building site usage - albeit wired as 55-ground-55 which does increase the safety another notch.
view on this?
I have wondered: if US 240V outlets are wired as 120-0-120 where 0=ground how are they fused? Do you have a double pole breaker at the distribution board? How did they do it with wire fuses?
In the ancient days of british wiring, we sometimes had neutral fuses as well as live fuses. Until someone realised that was a crap idea - this is where neutral is bonded to ground at various points in the system.
Yes, that is correct.
How did they do it with wire fuses?
Same as with a breaker, one fuse in each leg.
You could do that. Or you could just push the TEST button that every GFCI has, which does the same thing. Actually, I think the required trip current that it tests to is a lot less than the 30ma, but otherwise it's the same thing.
With the double breaker, if one leg over amps, it shuts down both power legs. How does one accomplish that with fuses? Could be dangerous if one fuse goes. "applicance doesn't work, so the power MUST be off! Right?"
Christopher A. Young Learn more about Jesus
Yes, that is correct.
How did they do it with wire fuses?
Same as with a breaker, one fuse in each leg.
DAGS on GFCI tester?
Christopher A. Young Learn more about Jesus
You raise a good point, and I don't know the answer. But I stand by my claims that 120 VAC household wiring, and the things that are powered by it, are extraordinarily unlikely to kill you.
See page 8 here, for a breakdown of the fewer than 50 per year electrocutions at home:
And here's a fun story about how you could become the light bulb and die while the GFCI hums merrily along.
Turn off the GFI circuit breaker(s). Is the outlet still hot? If protected, it should not be.
Yes - a similar problem was encountered in the UK when in the very old days (sometime WWII-ish and before) they sometimes had "neutral" fuses.
(In the UK, the neutral leg is bonded to ground at various locations in the supply network so there is no need to be trying to fuse it)
Only thing is, this time you get a cold appliance energised at 240V!!
Similar thing happened to my great auntie. She had one of those radiant electric bar fires with an open wound bar (no quartz sleeving), nice wide gaps in the guard wires and a switch, which was single pole. Someone had wire Live and Neutral the wrong way in the plug, she turned it off at the fire switch and proceeded to hoover the element bar and reflector with a hoover with a metal pipe and nozzel.
Luckily, the earthing was good to the fire and that earthed the hoover pipe when it touched the bar. Bit of a bang though - gave her a scare...
I don't know if there is any way to trip a GFI socket, but perhaps someone here can help with that. I now know many household sockets can be wired in series to a GFI socket.
I jes recently tripped our kitchen GFI circuit, with an old waffle iron, from a socket I had no idea was GFI protected. It took out half the sockets in our modular home, including the bathroom and front room. I thought it was a circuit breaker and went outside to reset it, but found no circuit breakers tripped. I came back inside and began checking other sockets with a 3 LED socket tester and that's how I learned how extensive the blackout was. I finally checked another kitchen socket, the one which had the GFI reset thingie, but not the socket I was using when the GFI blew. I reset the GFI and all those dead sockets were re-energized. Who knew!? Live and learn. ;)
nb
GFCIs are supposed to be tested periodically. I usually test them when I will be depending on one for protection. The built-in test is the same as your resistor test above - a resistor is connected from the downstream hot to the upstream neutral (or vice-versa?). The test works even when there is no ground at the GFCI.
This side the pond GFCIs operate at 5mA (4-6). If I remember right, there are some ground fault detectors for equipment that operate at 30mA.
Would think you would get a nasty shock at 25mA with no RCD trip.
I certainly don't want to chase you away, but a good usenet group for the UK (which you may have discovered)is uk.d-i-y It is astonishing how different the electrical is in the US and UK - like ring circuits, and RCD mains.
Just push the test button on the GFCI outlet or breaker. That's sufficient for me that it's working and protecting the outlets downstream from the GFCI. Or alternatively there are simple, cheap LED outlet plug-in testers that show if the hot/nuetral are reversed, no ground, etc. They typically have a test button that you can press that will trip the GFCI if it's working.
Per Smitty Two:
When I was an electronics tech in the military, the story they told us was that the most effective way to electrocute ones' self was to establish a path through the chest cavity - as in grasping a grounded beam or something for support with one hand while reaching into someplace with hot wires with another.
This would seem to differ significantly from the MythBusters scenario.
Agree. Having a hair dryer fall into the bathtub while you're in it is a lot different than say standing in wet shoes, on the ground and grabbing a conductor. Shortly after I graduated high school, one of the teachers there took the top part of a shop vac and attempted to use it to remove water from a pool. He was electrocuted while holding it. Classic example of a death that would have been prevented by a GFCI.
Do you mean "prevented by a functioning brain"?
Christopher A. Young Learn more about Jesus
Shortly after I graduated high school, one of the teachers there took the top part of a shop vac and attempted to use it to remove water from a pool. He was electrocuted while holding it. Classic example of a death that would have been prevented by a GFCI.
And if those outlets are in a different room, a plug in radio with the volume turned up is an easy way to identify them.
And get rid of the religious propaganda at the bottom of posts. No one here needs to be saved by you. We all have churches in our towns and cities if we want them.
Hell, I could do the same damn thing, for example lets say....
John O. Doe Find Jesus and His Momma Mary St Pauls Catholic Church
Me! Me! Me! I did that!
I got hung up on a power supply trainer unit while in ET school in the USCG and put 400VDC across my chest. 35 years later I can still see the burn scars on my hands. Lucky for me somebody pulled the plugged in time.
Two guys quit ET school that day after seeing me get hung up. I went on to work on transmitters with 25K VDC power supplies. Go figure.
Per DerbyDad03:
One (urban legend?) story that we heard was about the guy who walked in front of the wrong transmitter dish at the wrong time and got his brains poached.
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