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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:

  1. Grounding conductor is disconnected to the load-size neutral (of the transformer).
  2. Heater is expecting a single-phase supply, not split-phase.

I can post a picture of the heater internals later.

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  • 3
    If the heater was grounded properly, you would not get a shock. So obviously it is not grounded properly. – FakeMoustache Feb 27 '17 at 11:16
  • Turns out that the receptacle was wired wrong. One phase conductor and ground were switched. Now that I've fixed that, there's no obvious leakage current. However, there's still a minute shock (more like tingling) when touching the water inlet connector. It is properly grounded now, yet I still feel a bit of shock. Thoughts? Just saying that it's not properly grounded isn't helpful at all. – Darwin Bautista Feb 27 '17 at 14:23
  • So indeed the device was not properly grounded. Properly connected to a ground wire does not mean properly grounded. If the ground connection has some voltage on it compared to the house, then you could feel a tingle. Just saying that it's not properly grounded isn't helpful at all If you know it so well, why are you asking here then ? If you have a better explanation, please enlighten me. – FakeMoustache Feb 27 '17 at 14:34
  • @DarwinBautista There's always the possibility that something else isn't properly grounded. You could get a tingle when simultaneously touching something that was grounded and something that wasn't grounded. – Simon B Feb 27 '17 at 15:14
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    @StainlessSteelRat ROFL it's obvious that I wouldn't have asked if I wired the whole thing. I'm an electronics engineer myself and I know the difference between line and ground; I'm not an idiot. If you read the whole damn thing, you would see that I asked specific questions. How many ways can you ground something with an 8-ft. ground rod and ground it wrong? Nobody even thought about stray voltages, ground loops, inductance or whatnot. Just saying "hire an electrician" doesn't help because I already did that (they're not that reliable here). – Darwin Bautista Mar 2 '17 at 8:35
16

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.

enter image description here

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.

enter image description here

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.

enter image description here

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.

  • Provide a very high current path back to neutral for a hot-ground fault -- to assure a breaker will trip. This is a left-handed way of providing ground-fault protection. In this case, this setup Will Not Do That, and could create a dangerous situation. Your best bet to resolve this is use active/intelligent 2-pole ground-fault detecting breakers (GFCI aka RCD).
  • Keep metal appliances at a safe voltage relative to your water pipes etc. Your in-house earthing system would struggle to do that against a ground fault.
  • Protect equipment by giving static electricity and lightning a way to get to earth. Your earthing system can do that.
  • Ensure your conductors don't float at very high voltage. This will be handled by the power company's grounding back at the pole.

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.

  • 1
    ...yeah. In effect, what they have is a split-phase TT (as opposed to the TN-C-S that's assumed by the NEC) earthing system, with the earthing of the system performed at the power company transformer. Hence, there needs to be a RCD/GFCI in the system to protect people from shock. – ThreePhaseEel Mar 2 '17 at 2:03
  • I was surprised to read "Earth is a very unreliable conductor. It cannot flow enough current to be a reliable current return...". Isn't ground return a common way to save a wire? See en.wikipedia.org/wiki/… and en.wikipedia.org/wiki/Single-wire_earth_return. The issue is the grounding quality. Better: here and here. – Peter A. Schneider Mar 2 '17 at 9:54
  • @PeterA.Schneider As OP ran into while voltmeter testing, voltage is the same on both sides of a resistor until you flow any current through it. OP tested 120V from his local ground to each hot. Then when he put a load on it, it didn't hold up. Neutral Is Not Ground: intended current return is not safety shield. Single-wire-earth-return systems are oddballs: earth isn't ground, it's return. They are pumping the voltage crazy high to drive the current to near nil so the high earth resistance doesn't matter. It's still a pretty scary setup; I guess they don't have wire fences. – Harper Mar 2 '17 at 17:31
  • @PeterA.Schneider As far as "unreliable", I mean it varies by soil type, but it matters an awful lot if it's wet. So you could throw something together that seems to work under test conditions, and then moisture level changes and everything falls apart: what worked, doesn't; what was safe, isn't. – Harper Mar 2 '17 at 17:53
  • 1
    Are any wires at all connected to the neutral bus? None should be! No neutral wire should be connected at all, since you cannot provision neutral. Think about 3-phase delta, 3 corners of a triangle, none in the center where ground is. Yours is like that, but with only 2 sides. This is more like an isolated system and I would wire it just like that. Conductors to hots only (via breakers), grounds to ground, GFCI/RCD if possible. – Harper Mar 3 '17 at 5:58

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