Isn't this how the USA used to be, two live wires, one neutral. The neutral was off the central point of the transformer, thus giving 110v between the neutral and any live wire, but 220v between the two live wires.
That is still the standard supply system in the United States (and Canada) for residential properties, with 120V used for lighting and general-purpose receptacles and 240V for heavier loads such as dryers, electric ranges, larger heating and air-conditioning units, etc. The 120V loads in the house will be distributed as evenly as possible between the two sides of the supply.
However:
Thus, the neutral is not earthed, as it is in the UK and other countries.
The supply neutral is most certainly earthed (grounded) in America. There is also a requirement for a further earth electrode to be connected to the incoming neutral at each house as well, and as with PME in Britain, internal metallic pipework etc. is bonded to the same point.
Along these two wires we can get both 220 and 110. I assume it is three phase, haven't looked into it properly,
I'm a mechanic, not a sparky. icon_redface.gif
The 120/240V American system is not 3 phase, but
single-phase 3-wire.
In our current rental house we have 220 and 110 split outlets in all the sockets, and inside are three black wires. I forget exactly how they are connected, but they work, and give the right voltage.
The "all black" wiring scheme is unconventional, but the 1-phase 3-wire system provides for outlets at both voltages. 110-120V outlets are connected between one live on the supply and the neutral. 220-240V outlets are connected between the two live conductors. In the U.S., the 240V outlets are generally provided only for specific appliances where needed, e.g. for a fixed heating or air-conditioning unit. But as I believe most appliances in the Philippines are designed for 220-240V use, that would explain why if the house was U.S. military it was wired with 120 and 240V outlets throughout to allow the use of local Philippines appliances and American 120V devices.
Definitely a US thing, as this is ex-military accommodation, thus the dual voltage. I'm not sure if the single return line is the earth or neutral, and does it go to ground? It doesn't appear to be insulated, and is used more as a stress member as the wires are run across to the house from the power pole.
I cannot speak for what is common practice in the Philippines, or indeed how it is
supposed to be done there, assuming everything done to code. But as far as North American practice is concerned, it is not uncommon for aerial supplies to consist of two insulated conductors for the two "hot" legs of the supply plus a bare neutral, since the latter is grounded anyway.
I recall the electrician for our new house telling me we will be using dual-pole breakers in the main panel, so both sides of a circuit are isolated, unlike the UK, where you only shut off the 'live' side.
Again, it's a case of which, if any, side of the circuit is grounded. In North America, a 120V branch circuit is normally fed from a single-pole breaker, since one side of the circuit is connected to the neutral, which is grounded. A 240V branch circuit will be fed via a double-pole breaker, since both legs are live (each at 120V with respect to neutral/ground).
I'm curious why the UK is so adamant you connect the live wire to the correct place, and neutral too, whereas in the Philippines it makes no difference which way round they are connected.
The issue is exaggerated far too much these days. For a simple 2-wire (ignoring any grounding connection, if present) a.c. connection a lamp, motor, and so on will work perfectly well no matter which way round it's connected. The supposed "problem" which is often quoted is that a single-pole switch on the appliance (say the on/off switch on a blender) can end up opening the earthed side of the circuit if the connections are made the "wrong" way round, such as can happen with a reversible plug, leaving the motor or other operative part of the device live even when switched off. The fact is that this simply is not a problem in most cases. The argument about somebody "fiddling" with it and not realizing that it's still live really doesn't make a whole lot of sense, since anyone who knows enough to be fiddling around inside anyway should also know enough to realize that while the device is still plugged in there are going to be
some live parts inside (which will still be the case with the switch in the "correct" side of the supply).
Most of Continental Europe uses reversible plugs, as did the U.K. years ago. There are a few instances where it's desirable to ensure correct polarity of connections (e.g. a heater with semi-exposed elements which could remain live even though cold), but for the majority of portable appliances it really doesn't matter.
