Background:
I live in Metro Manila, Philippines where the electric distribution company, Meralco, delivers split-phase power to residential buildings. Our old (1980s) Meralco service drop consists only of 2 conductors, both phase conductors, and no neutral conductor. Phase-to-phase voltage is 240V, while phase-to-ground (measured with the help of an existing ground rod) is 120V.
We recently started the construction of a new house and wired it according to the Philippine Electrical Code (PEC). Based on my research, the PEC is very similar to the NEC. That said, the new house uses three-prong receptacles: 2 for the phases and one for ground. The grounding conductor is connected to a ground rod.
Since Meralco still hasn't energized the new house, it is temporarily connected to the old two-wire service drop, leaving the grounding conductor connected to the ground rod only (i.e. no connection to the load-side neutral yet).
Problem:
The heater in question is a Panasonic Shower Heater DH-3JL2P (rated at 3.5 kW). Its terminals are labeled Line (L), Neutral (N), and Ground (G). When I tested this heater initially, I had no idea that Meralco's supply is split-phase, not single phase. So I just operated it under the assumption that the line and neutral conductors are connected correctly at the receptacle (which actually doesn't matter now knowing that the supply is split-phase, i.e. both are line conductors, there's no neutral conductor).
Upon testing, the heater functioned properly as far as heating the water is concerned. However, I felt a significant electric shock when I touched the shower head where the heated water was coming from.
What could cause this shock to happen? I have a couple of ideas on why this happened, but can't really say for sure:
- Grounding conductor is disconnected to the load-size neutral (of the transformer).
- Heater is expecting a single-phase supply, not split-phase.
I can post a picture of the heater internals later.
Best Answer
Filipino electrical service is a morass. There is some Euro 230V single leg service, and there is some American style 120/240 split phase service. And if those services are wired to Euro or USA standard, they'll be as safe.
However, in actual practice, weird things get done in the Philippines. And there is a high rate of electrocutions. This is one of those weird deals. They are providing you North American style service, but not providing you a neutral.
In the top 2 diagrams, note where ground is bonded in the transformer, which wire that ties to, and how that same wire is bonded to ground in the service panel/consumer unit/breaker box. Then compare with the third diagram where something "ain't quite right".
The problem is, as you can see, this modified North American scheme gives you no place to bond ground in your panel. Ground is dangling there. It's not an isolated system, because the pole grounding pegs ground at the halfway mark. What do you do with it? Not this:
Neutral Is Not Ground.
You can't force one of them to be a neutral. Look what happens if you do.
Earth is a very unreliable conductor. It cannot flow enough current to be a reliable current return, as you may have discovered. However, under wet conditions, it can -- it can flow so much current to trip a -- Oh wait. Neutrals aren't on circuit breakers! So it'll just spin your electric meter madly until it heats up wires enough to burn your house down! Also imagine you have a fence between house and pole, and the fence wires are grounded at the house. At the pole, they're 120V above ground.
So... reality... You can't tie anything to ground, so you don't have a neutral. Both legs are "hots". And that means both legs need to have circuit breakers. Because a fault from either one of them to ground could potentially flow a lot of current in rainy conditions. (in dry conditions it would only electrify your grounds.)
The purposes of equipment safety ground
Grounds provide several important safety functions. Your grounding system is going to struggle to do its job under this setup.
What to do?
Given the service you have, your only option is to wire it like a NEMA 6 receptacle in the US - two hots, ground, no neutral.
First, you must remove any bonding inside your service panel between ground and any wire.
I would strongly recommend you use a split-phase or 3-phase panel, and wire this connection with a 2-pole breaker, so that both "hots" have overcurrent protection. Normally you don't need overcurrent protection on a neutral, but you don't have a neutral.
Ideally, the ground is simply a safety shield and the appliance should not connect with it at all. It's probably not a problem, but you need to consult with the manufacturer and make sure they can be powered with ground in between two hots (NEMA 6 style).
Ground is too weak to effectively assure breaker trip on a hot-ground fault. So it could sit there running 24x7 with a 10-15 amp ground fault - creating dangerous voltages in unexpected places (like your shower!), spinning your electric meter and running up your bill. Therefore I would strongly recommend you use a 2-pole ground fault detection breaker (GFCI or RCD). This would be your only protection against a ground fault in the appliance, since ground-as-high-current-path is not working.
The nuclear option
Sometimes the power company just can't provision a safe, proper service. In that case, the ultimate defense is to obtain a large service transformer of your own. Get one with a 240V primary (that goes to the utility) and a 120/240V split phase secondary (this is your main service). Since a transformer fully isolates the supply, you can configure the phase(s) and grounding as you please, i.e. correctly.
A 120/240 split phase transformer can be jumpered in either North American or Euro standard, with no compromises - exactly as you see in the first diagram. Which one would work best for you, would be a function of what electrical parts are available at sane prices, and what appliances are available at sane prices. This does not limit you. You can easily get 240V from a N.Am. configuration via NEMA 6. You can't get 120V out of a Euro panel, but you could add a parallel panel which gets 120V between neutral and the center tap.