Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length

[TJ (Tom) Cornish]

Welcome to the United States, where every plug is designed to expose live conductors when only partially inserted.

Why can't some portion (5 mm maybe) of the prongs closest to the plug body be insulated, like they are in Europe? Maybe because the prongs are already as thin as they can be without overloading them or weakening them, so there's no way to effectively insulate them without seriously derating the plug. Nothing like living on the edge.

Europe's decision to use 230v single-ended distribution is the reason insulated prongs are mandated, as touching a 230v current-carrying wire is significantly more dangerous than 120v in the US.  The UK mandates that power tools and some other devices be 120v and powered by a step-down transformer as the shock hazard is so much worse.

[Jonathan Johnson]

Europe's decision to use 230v single-ended distribution is the reason insulated prongs are mandated, as touching a 230v current-carrying wire is significantly more dangerous than 120v in the US.  The UK mandates that power tools and some other devices be 120v and powered by a step-down transformer as the shock hazard is so much worse.

I think that the suggestion that 230V is more dangerous than 120V is misguided. I think the danger is very much the same. You could say that "230V is no more dangerous than 120V" but I think a better way of saying it would be that "120V is no less dangerous than 230V."

Both voltages are capable of delivering deadly shocks. People have survived shocks from either voltage with no physiological effects. There are so many other factors to consider: the impedance of the source, the dryness of the skin, the current path through the body, the medical condition of the victim, etc.

Yes, 230V *can* deliver greater current through the body. But 120V also can deliver deadly current.

Saying that 120V is safer than 230V is like saying that getting hit by a 20-ton truck is safer than getting hit by a 40-ton truck. When you say 120V is safer (or 230V is more dangerous) than the other, you mislead people into casting off safety when dealing with the lower voltage. 120V circuits are no less deserving of safety measures than 240V circuits.

[Stephen Swaffer]

Keep in mind that most shock injuries and electrocutions are caused by a hot-ground fault.  In the US, 120 and 240 volt residential circuits present exctly the same hazard in this regard.  If I am understanding "single ended 230 volt" properly, this would create a hazard closer to what exist in the US on 480 volt "Y" connected systems.

Depending on how a home is wired (most of the time I used dedicated lighting circuits), there would be no need to rewire (especially not if wired in conduit) to go to low voltage lighting.  Most building wire is rated for 600 V max-there is no reason it can't be used for low voltage.  I agree that low voltage light fixtures may well happen before other distribution given a known load-and I think the path to retrofit might be doable in many cases.

POE also has in its favor a fairly large installed base as a lot of homes already include CAT 5 cabling to many rooms.

[Jonathan Johnson]

POE also has in its favor a fairly large installed base as a lot of homes already include CAT 5 cabling to many rooms.

PoE to USB charging adapters already exist

https://www.amazon.com/802-3af-Splitter-MicroUSB-Devices-WT-AF-5v10w-microUSB/dp/B019BMFCH8

https://fsrinc.com/fsr-products-listing/product/it-chrg-p2u-series

No endorsement of the above products. Just some I found searching for "PoE to USB."

[Daniel Levi]

Just an addendum worksite 110v in Britain is via an isolating transformer and is wired as 55-55 so only 55v if connected between 1 line and ground.

Sent from my Lumia 625 using Tapatalk

[TJ (Tom) Cornish]

I think that the suggestion that 230V is more dangerous than 120V is misguided. I think the danger is very much the same. You could say that "230V is no more dangerous than 120V" but I think a better way of saying it would be that "120V is no less dangerous than 230V."

Both voltages are capable of delivering deadly shocks. People have survived shocks from either voltage with no physiological effects. There are so many other factors to consider: the impedance of the source, the dryness of the skin, the current path through the body, the medical condition of the victim, etc.

Yes, 230V *can* deliver greater current through the body. But 120V also can deliver deadly current.

Saying that 120V is safer than 230V is like saying that getting hit by a 20-ton truck is safer than getting hit by a 40-ton truck. When you say 120V is safer (or 230V is more dangerous) than the other, you mislead people into casting off safety when dealing with the lower voltage. 120V circuits are no less deserving of safety measures than 240V circuits.

I'm not claiming that getting shocked by 120v is fun - I've had that experience several times in the course of my life.  I am very confident, however, that the data bears out significantly greater injury and damage from 230v shocks compared to 120v shocks.  The worst shock I've ever had in my life was from a battery powered camera I was attempting to fix that somehow I ended up coming in contact with the flash capacitor, putting about 300v DC through my fingers.  That was REALLY not fun.

I think your truck comparison is a straw man argument; the converse would be suggesting that we should use 2000v as a standard since 120v kills people, too.

In any case, my point was that Europe is thinking about their distribution system as well, and they are moving lower because they perceive their current voltage standard to be excessively dangerous in some situations. Unless you need that much power for your application, lower voltages are better - less insulation needed, less energy available for starting a fire or causing an arc flash event, smaller lamp filaments, etc. 

[Lyle Williams]

The rate of electrocutions is much lower in the UK, compared with the US.

Whatever it is that makes 120v safer, all the other stuff you do (or don't do) makes electricity 4x more dangerous in US workplaces:

http://foundation.asse.org/docs/study_rand2011.pdf

[TJ (Tom) Cornish]

The rate of electrocutions is much lower in the UK, compared with the US.

Whatever it is that makes 120v safer, all the other stuff you do (or don't do) makes electricity 4x more dangerous in US workplaces:

http://foundation.asse.org/docs/study_rand2011.pdf

Maybe less "Here, hold my beer..." in the UK...

In the US it's mandated that the neutral side of the power system be bonded to earth ground.  In some other countries, both the supply and return conductors are allowed to float.  There are pros and cons to both approaches.

[Rob Spence]

Keep in mind that most shock injuries and electrocutions are caused by a hot-ground fault.  In the US, 120 and 240 volt residential circuits present exctly the same hazard in this regard.  If I am understanding "single ended 230 volt" properly, this would create a hazard closer to what exist in the US on 480 volt "Y" connected systems.

Depending on how a home is wired (most of the time I used dedicated lighting circuits), there would be no need to rewire (especially not if wired in conduit) to go to low voltage lighting.  Most building wire is rated for 600 V max-there is no reason it can't be used for low voltage.  I agree that low voltage light fixtures may well happen before other distribution given a known load-and I think the path to retrofit might be doable in many cases.

POE also has in its favor a fairly large installed base as a lot of homes already include CAT 5 cabling to many rooms.

I recently repurposed a set of 14-2(w/ground) that was put in my kitchen for under cabinet lighting. There was a junction box in the basement under the kitchen where all the wires to the lights were planned to connect to a pair of dimmers near the kitchen.
I pulled the two dimmer circuits out to their own box, then clearly labeled the original box as 12v dc. I then connected a 12v power supply between the lighting wires and a wire from the upstairs dimmer. I then connected the 14-2 to the LED strip lights.

This worked because my 14-2 runs were kinda short (less than 20' mostly) so the voltage drop was not an issue. 75 watts at 12v is 6 amps.

At another site, the electrician (same guy as did my house) was adding 6 low voltage lighting circuits to an outside porch (ok, a big porch at a wealthy persons house).
In this case the wire runs from where dimmers (remote controlled) would normally be located would exceed 50'. Six low voltage 150 watt supplies would require #10 wire for the little led lights 😳 given the long runs. So, the solution was to locate 12 75w supplies close to lights and run 120v from the dimmers.

The moral of the story is that just cause you have low voltage lighting doesn't mean you can save on wire.



Sent from my iPad using Tapatalk HD

[Stephen Swaffer]

An LED requiring 75 watts is a big light-roughly equivalent to at least a 400 MH wall pack.  I am guessing the lights were also running on 12 volts.  Personally, I would argue for 24 volt LV distribution-there is a ton of 24 VDC stuff already on the market as that is a standard for industrial uses.  That would halve the current-also most in home circuits are less than 100'.  The other savings is that you would get by with 2 wires vs 3 and still have a safe setup.

I don't think the savings would be as much on wire size as on insulation-insulation rated for 50 volts would be cost savings.  Outdoor low voltage wire costs more than indoor LV.  In any case there are indeed trade offs-just as there are in any engineering problem.  This particular one will be driven by a combination of the market and engineering solutions-heavily influenced by the installed base.

[ProSoundWeb Community]