Sophie, I find it an interesting juxtaposition that you tout the "idiot proof" nature of a single voltage system in a residential setting only to follow up with a paragraph extolling the virtues of a system where each individual device requires correctly sized local fusing instead of simply sizing the entirety of a branch circuit to handle the rating of the source overcurrent device. Not to mention, this arrangement of "ring mains" leaves me questioning its safety with respect to short circuit/ground fault protection. What is the gauge/size of the "spur" wires that lead to the outlets? And is equipment grounding sizing at least continuous with respect to the 32A supply main?
A 120v standard for residential use may in fact trace its origins to a historical design for the first incandescent lamps, however I think it's quite justified considering the many millions of man hours and pieces of equipment it would take to retrofit the entire North American grid with a 230v to ground two-wire service. I think any negligible gain in efficiency would be far offset with this endeavor. The task would have been further complicated in years past when the grounded or "neutral" conductor was also effectively the short-circuit/ground fault protection for the circuit as well as the equipment ground in some cases. In fact a somehwat disturbing number of these installations are still in use today. Also a limit of 120v is currently imposed by code, which does not allow luminaires (light fixtures) or loads under 1440kW (1/4HP) to be connected to a branch circuit over 120v line to line in a space defined as a dwelling unit or similar occupancy.
There is a very valid argument that twice the system voltage simply means double the potential current passing through a human body should one inadvertently find oneself part of an electrical circuit. You can idiot proof all you want, but even in an age where GFI protection for personnel is widely available and affordable people are still killed in the home by electricity. And in such situations where a grounded conductor is connected in place of an equipment ground it's twice the current that is going to try to flow through you instead of the system grounding point should you give it a favorable path. Higher voltages also equal greater arcing potential, higher fault current potentials, and overall greater associated risk.
Higher system voltages are commonplace when you start talking about buildings with hundreds of kW of lighting and several tens of thousands of kW motor loads. In these cases the (many times) cost of installing 480Y/277 or even higher voltage systems is eventually offset by the gains in efficiency; heavy industry often uses 4160v for internal distribution and to feed 100s+ HP motors. And with the growing use of extremely low power equipment such as solid-state and LEDs it is becoming more common to find lighting tracks, emergency lighting, and other hard-wired power and control systems operating at 24v, 12v or even lower, carrying only a handful of amps for tens of feet with building wire sizes that are already common. Greater voltage does not neccessarily equal greater benefit these days even taken from a standpoint of pure efficiency.
While the line of conversation has divereged somewhat it can be brought back to the main point of the OP that in his situation the concern over too high a voltage can probably be considered splitting hairs, just as Sophie, myself, and others could split hairs all day on the advantages of midpoint grounded (note: we still call it single phase over here) versus single voltage systems in residential settings. No matter how great the quality of grid power there is always the chance of transient surges, acts of nature ect, which is why electrical equipment is usually tested and certified some degree beyond what it should ever experience even in likely scenarios of improper use. From a safety standpoint there probably isn't much that has a margin of only a hundred or two volts between normal range and significantly unsafe operation. Much more prevalent are the dangers of currents in excess of what is safe or tolerable; excess volts usually lead to an immediate pop or bang while excess currents fester and lay in wait, until just the right circumstances can cause their revalation in far more destructive ways.
jim hardy said:
Observe that National Electrical Code is published not by the academic IEEE, but by the National Fire Prevention Association.
Yes. And I'm comfortable standing on this. We don't have 230v plugins cause my code says you can't, Sophie!
