"1. The risk of electrocution is significantly lower at 110-120V than at 220-240V."
Agreed, although those who are unfortunate enough to be electrocuted by 120V end up just as dead as those killed by 240V.
"2. The voltage is the most important factor when determining the risks with electricity"
I think the voltage level involved clearly is one
of the factors involved, but I would hesitate to say it's the most
important. Once somebody has found himself across the line with current passing through his body, then obviously the lower voltage level will result in a less severe shock, but surely the idea is to reduce the risk of getting connected across the line in the first place?
"1. Fire risk is far more important than shock risk. More people die from electrical fires than from electrocution."
Considering the fairly low electrocution figures in most Western countries, I wouldn't be surprised if it's true. That said, however, how often have there been discussions in ECN over whether a fire blamed on electrical causes was really electrical in nature? So are the electricity-related fire statistics reliable enough to even make a valid comparison?
"2. Currents are lower for the same power, leading to less cable heating and reduced fire risk."
True, but is it significant?
No argument with the first part of the statement obviously, but surely the degree of cable heating is down to I^2*R, and is thus dependent upon the size of the cable?
So long as the cable size is correctly chosen for the current concerned, I don't see this as a significant problem.
"3. As currents are lower, protective device ratings may be lower."
Well, in Britain there's the lower ratings of plug fuses for the protection of appliance cords, but if we're considering only the fixed wiring of the building, then that's discounted anyway.
So long as the OCPD is rated correctly for the cables, is this significant anyway?
"4. Arcing risk. As the voltage is higher, the prospective fault current is higher, making the protective device more likely to trip during a fault."
Maybe true if everything else is equal, but in practice the prospective fault current depends very much on the sorce impedance of the supply transformer, the feeder cables, and so on. Looking at some of the statistics around ECN, I'd say that on average the American supplyis probably capable of supplying a greater short-circuit current than many European supplies.
"5. Users of 110-120V systems believe them to be safer so don't take precautions
against shock, unlike users of 220V-240V systems."
I think this may be down to what people have grown-up with. The average North American might take 120V as "pretty harmless," but because 240V is used for the heavy-dity stuff like ranges and dryers will treat it with a little more respect.
The average Brit/European is used to having 220-240V everywhere, and I've seen plenty of people treat it with very little respect. Yet those same folk would probably be very wary of dealing with 380-415V 3-phase.
"6. The lower insulation requirements lead to nasty cheap low quality wiring
Not true. The voltages are too low to influence the insulation requirements.
I'm inclined to agree there. Although devices such as NEMA 5-15 receptacles may be rated at 125V, the construction and insulation materials are pretty much the same as a 6-15 device rated at 250V max.
Besides, I've seen some very cheap-and-nasty 240V devices as well.