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Omni 3-way Switch Wiring Diagram.


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Somebody is thinking single-phase voltages while somebody else is thinking about three-phase voltages...even though with a delta secondary, you can still tap the center point on one phase and get 120/240 volt single-phase while still getting 240 volt three-phase. I can't think of a single instance where three-phase was used to hook up residential load. You may use a three-phase bank to get single-phase voltage as well (to use in the house), but the three-phase power would be used for something other than the residential load.



 

I assumed other companies supplied similar since the three-phase 127 v (or as my one-time boss called it, the 380 v supply) is almost a de facto international standard.

The defacto international standard is that there is no standard whatsoever.

While that is true, 127 volt secondary would be a real oddball voltage. However, if you had a three-phase grounded-wye configuration (secondary side) bank that was set up to give you 220 volts phase to phase, you would find that each phase to ground leg would be 127 volts. I have never seen this configuration...and if it was used, it was meant to supply 220 volt (which cannot be split to 120 volts due to the fact it is a wye congiration bank). In that system, you could NOT establish a neutral in the house. You could establish a ground (or earth), but only for protection...not for a current-carrying conductor (which is what a neutral is).

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Brilliant example of how to go off-topic in two posts. It can't be done any faster than that. 

Greetings! Forums are ment to be a place to have a casual conversation between intrested members discusing what we are doing with our time, and are not allways toeing the party line. Cave men, flying

Greetings! The "KEY" is "Three-ways are fairly easy to implement provided you have the right switches and you can follow the diagram." That is why I posted the diagram. Yes I do have dry wall, with

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The issue with even "correctly" wired PH circuits is for instance the shell of the lampholder being energized even when the switch is off. It should in fact always be at ground potential, even when ON. Translate this to other more complex appliances or devices and you start to see the problem. 

 

It's not that the PH is merely different, it's fundamentally wrong, as commonly implemented. 

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Somebody is thinking single-phase voltages while somebody else is thinking about three-phase voltages...even though with a delta secondary, you can still tap the center point on one phase and get 120/240 volt single-phase while still getting 240 volt three-phase. I can't think of a single instance where three-phase was used to hook up residential load. You may use a three-phase bank to get single-phase voltage as well (to use in the house), but the three-phase power would be used for something other than the residential load.

 

 

I assumed other companies supplied similar since the three-phase 127 v (or as my one-time boss called it, the 380 v supply) is almost a de facto international standard.

The defacto international standard is that there is no standard whatsoever.

While that is true, 127 volt secondary would be a real oddball voltage. However, if you had a three-phase grounded-wye configuration (secondary side) bank that was set up to give you 220 volts phase to phase, you would find that each phase to ground leg would be 127 volts. I have never seen this configuration...and if it was used, it was meant to supply 220 volt (which cannot be split to 120 volts due to the fact it is a wye congiration bank). In that system, you could NOT establish a neutral in the house. You could establish a ground (or earth), but only for protection...not for a current-carrying conductor (which is what a neutral is).

 

I had a 127v three-phase domestic supply in Saudi together with the neutral - not uncommon.

 

MERALCO here in Manila supplies two 127v phases with no neutral. 

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The issue with even "correctly" wired PH circuits is for instance the shell of the lampholder being energized even when the switch is off. It should in fact always be at ground potential, even when ON. Translate this to other more complex appliances or devices and you start to see the problem. 

 

It's not that the PH is merely different, it's fundamentally wrong, as commonly implemented. 

 

How do you do this with the MERALCO supply of two 127v phases?  Both sides are live and domestic switches only isolate one side, so the other side is always live which in the case of a screw type bulb holder may be the thread or the center pin.  (MERALCO do not provide a neutral.)

 

Many houses in the area install a ground - a length of rebar driven into the soil with a cable spot-welded to the exposed end.   This is not the best or safest set-up.  Initially the ground was for earthing metal cases, etc.  However a practice arose where people began to use 110v and 120v appliances across one phase and ground.  I don't know quite how this affects the meter reading with current flowing through one phase but no being returned through the other - especially the new digital meters, perhaps someone could comment.  With a perfect earth, that is a full 127v circuit, 110v appliances will be running 15% over the rated voltage and 120v appliances at 6%.  These are not especially dangerous overloads but people shold be aware.

 

Nowadays the stores in the Manila area sell only 220v appliances.  Some 110v and 120v appliances are available second-hand in the port area but people are tending to use voltage regulators for these rather than a grounding.

 

Sorry to go on at length about Manila in a Cebu forum but I suspect unification will eventually happen and as in other things the Luzon standard will be adopted.

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How do you do this with the MERALCO supply of two 127v phases? 

 

You can't, unless you use a DP switch, which no one does. This is why the whole concept is fundamentally flawed. 

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Sorry to go on at length about Manila in a Cebu forum but I suspect unification will eventually happen and as in other things the Luzon standard will be adopted.

 

I seriously doubt that you will ever see a consolidation of voltages here. You have no idea what the financial hit would be to change voltages for entire systems. There isn't even standardization of primary voltages in the US (even though secondary voltages are fairly standard...there are still numerous possibilities). There is no way the Philippines electric utilities (which are private companies BTW) will ever throw away the kind of money you would be talking about. And as voltages go...127 volt secondary IS a very oddball voltage. If it were not so, there would be all kinds of electrical stuff made just for that voltage...and there are not. There is no market, so there are no (or at least very few) products. Read the acceptible voltages for anything electrical BEFORE you plug it into a weird voltage like that...or you will shortly see magic smoke coming out of it. Many things don't have enough tolerance to take the variance. Again, though, as I said before, 127 volts is the leg voltage for a 220 volt grounded wye transformer bank. Therefore, you could easily use the phase-to-phase voltage (220 voltage) which is a common voltage around the world (especially in the Philippines)...and be just fine. Have you ever actually used a voltmeter on your outlets to find out what the true voltage is? On any voltage, there can be up to a 6% variance (up or down) possible (even more in poorly regulated systems). Therefore, the actual voltage for a supposed 127 volt circuit could be as little as 120 volts or as much as 134 volts in reality.

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