The death rate of around 6 a year in UK from appliance electrocution demonstrates that they are safe. One of the safest things we interact with in fact. Thus your imagination is incorrect.
Usually yes. Not always.
not the most effective position.
NT
Because if the switch fails the motor is hot when the user *expects* it to be off. Light switches can only be single pole, for the same reason. Sure, you're welcome to have no switch at all, if the EPA doesn't get its nose bent. ;-)/2
See above.
o t
** Having the metal case of a hand held appliance connected to supply groun d can be very dangerous to anyone working with electrical wiring. Touching a live wire with one hand while holding an earthed drill in the other could be the last thing they ever do.
However, the MAJOR hazard to anyone using any earthed appliance happens whe n the appliance plug, supply outlet or extension cable in use has been misw ired.
For example: if an appliance plug has Neutral and Earth swapped, it will ge nerally continue to work and is not a hazard * UNTIL * the user comes acros s an outlet that has Active and Neutral swapped. The appliance will no long er work in that outlet but the metal case is now live and lethal!!
Obviously, any safety advantage is lost if the earth connection is missing
- due to a loose wire in the appliance plug, the AC outlet or an ill fittin g connection. Again, this is invisible to the user until a potentially leth al fault develops in the appliance.
Clearly, it is MUCH SAFER to use appliances that do NOT rely on grounding f or safety and have NO connection to the AC supply ground to go missing or b ecome live as a consequence of a wiring error.
It follows from the above that a Class II appliance must NOT be connected t o supply ground or else it looses most of its added safety.
Also, the two insulation layers in a class II appliance are separate and IN DEPENDANT - meaning that an event that causes the functional layer to fail at particular point will not also cause the protective layer to follow, whe ther immediately or at some later time.
Class II appliances are however not perfect, they may become dangerous to u se if physically damaged or contaminated with liquids or conductive particl es and not all appliances are suitable candidates for class II constructio n.
... Phil
two
it
nd
et
und can be very dangerous to anyone working with electrical wiring. Touchin g a live wire with one hand while holding an earthed drill in the other cou ld be the last thing they ever do.
It happens, like most potential scenarios, but seldom. The risk is tiny, be low 1 in 10 million.
hen the appliance plug, supply outlet or extension cable in use has been mi swired.
generally continue to work and is not a hazard * UNTIL * the user comes acr oss an outlet that has Active and Neutral swapped. The appliance will no lo nger work in that outlet but the metal case is now live and lethal!!
About 50% of UK houses have RCDs, meaning the power will cut immediately if the 1st wiring error occurs. All new installs are required to have RCDs no w. All new appliances & extension leads have prewired plugs. So that scenar io can still happen, but the risk is in the process of gradually disappeari ng.
g - due to a loose wire in the appliance plug, the AC outlet or an ill fitt ing connection. Again, this is invisible to the user until a potentially le thal fault develops in the appliance.
for safety and have NO connection to the AC supply ground to go missing or become live as a consequence of a wiring error.
A bit of a nonsequitor there. In some situations class 2 is safer, in some class 1 is safer.
to
It's not that simple. There are lots of appliances out there in daily use t hat don't meet current class 1 or class 2 safety standards, some old, most imported from China etc. Such things are widespread. Those are plugged into other appliances at times, and the resulting combination is much safer if class 1 is used than class 2.
INDEPENDANT - meaning that an event that causes the functional layer to fai l at particular point will not also cause the protective layer to follow, w hether immediately or at some later time.
That's the basic concept of class 2, but the reality is there are plenty of appliances marked as class 2 [[]] where one solder joint coming adrift can easily result in live touching a metal case.
use if physically damaged or contaminated with liquids or conductive parti cles and not all appliances are suitable candidates for class II construct ion.
Indeed, both have their merits & downsides. If using a metal drill that can occasionally drill into an unseen live wire, I'd be a lot happier for it t o be earthed.
NT
Seems to me there are 6 who would disagree with you if they could.
-- Rick C
No, it had mains parts also. We did eventually find a solution to the problem and get it passed. That product has been superceded by now anyway.
Get real. There is no such thing as absolute safety.
Yep. Moons back, one of the engineers in our group was responsible for testing power devices (as in MG sets, power supplies, and electrical components). OSHA required that my employer build a grounded cage around his work area. He said that wasn't for his safety, rather ours. When he got across one of the test units and the grounded cage, his body wouldn't fly across the room and hurt one of us.
They did, years ago. A pair of windings on two separate plastic rods, with the windings spaced about 1/16" apart provided the isolation. If there was a nearby Lightning strike, they windings would vaporize. I repaired some TV tuners back in the '60s and '70s that needed one or both sets replaced. I may even have one set of new coils in a box of TV parts, buried in the back of my storage building.
Some AA5 radios had a Bakelite chassis, and some others didn't use their steel chassis for neutral. They used terminal strips, and ran a wire from one end to the other for neutral. The tuning capacitor was mounted on rubber grommets, or on a piece of fiber board. The knobs on these radios were push on, and no set screws.
-- Subject: Spelling Lesson The last four letters in American.........I Can The last four letters in Republican.......I Can The last four letters in Democrats.........Rats End of lesson. Test to follow in November, 2016 Remember, November is to be set aside as rodent extermination month.
One side of the tuning capacitor was still connected to the shaft, no?
Sure but don't grab a pair of pliers if you lose the knob.
Yes, but a lot of the knobs went through the front of the cabinet, to the recessed tuning capacitor. The worst were the steel case shortwave radios, that needed an external antenna.
Or when you jerk a cord out of an outlet and leave a pin behind. I had a teacher do that in elementary school. The fool was hold in a bare pair of pliers in one hand and had the EMT conduit in her other hand. I yelled to warn her not to. She called me a $#%^&* fool, and damn near killed herself.
-- Subject: Spelling Lesson The last four letters in American.........I Can The last four letters in Republican.......I Can The last four letters in Democrats.........Rats End of lesson. Test to follow in November, 2016 Remember, November is to be set aside as rodent extermination month.
ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.