Different power distribution systems
There are except for voltages basically five different power distribution systems in the world:
1. Single phase systems. X10 was designed for this and works fine. I have personally 220V 50A, single phase so I don't have any problems.
2. American split 220V Volt which should perhaps be called a two phase system but many Americans incorrectly call this a "three phase" system. This is basically a 220V supply with a centertap called neutral, giving two different 110V lines relative to the neutral. This means that the two phases are 180 degrees out of phase. This is important because it means that the phases have their zero crossing at the same time and X10 is using the zero crossing to synchronize the communication. X10, is BTW. using a subcarrier or a radio signal at 120Khz on the power lines. This subcarrier is turned on and off to create bits in a digital data transmission. It is a little bit more complicated than this but it is not really important here.
If you would connect an X10 transmitter between one phase and neutral and a receiver to an outlet on the other phase with the same neutral, this would normally not work unless there is some kind of path between the two phases. This path could be a water heater, an electric cooker or an air-conditioning unit connected to what they call a "three phase" or a 220V outlet creating a path between the two phases. Of course this path would work while this appliance is operating meaning that the X10 receiver would perhaps stop working when the thermostat switched off the water heater!
A common solution to this problem is a small capacitor around 0.1uF - 0.22uF / 600V over the phases. Note, that that will cause the X10 signal to be equal and of almost equal phase so a 220V X10 module connected between the two phases will not see the X10 signal! Other solutions consist of tuned LC circuits or even active repeaters. If the LC circuits are well designed, they can introduce a controlled phase shift and therfore solve the problem also with 220V modules. An active repeater will also solve that problem. Usually the capacitor solution is good enough if you don't have any real 220V modules.
In some areas they have also what they call "industrial three phase" which is a real three phase, star or "Y" configuration. I don't think they use delta distribution in the States.
3. Star or "Y" configurations like 220/380V or 240/415V. They have three phases 120 degrees out of phase. They use three phases and one neutral which in the first case will give 220V from any phase to neutral and 380V between any two phases.
Why should you worry about this technical stuff? Simply because these three phases are 120 degrees apart and their zero crossing do not occur at the same time. As I said earlier, X10 is using the zero crossover to synchronize the communication and the solution above with a capacitor will normally not work.
However, all or at least almost all X10 transmitters for the US market have a feature they call "three phase transmit". This means that every data bit is repeated three times. The first time at the zerocrossing, the second time 2.75 ms later and the third time 5.5 ms after the first zerocrossing. This corresponds to the time difference between the zerocrossing of the three phases (real 3phase) at 60Hz. If you would have 60Hz three phase, you could at least in some cases, use capacitors between the three phases to redistribute the X10 data onto all three phases.
The timing for the "three phase transmit" is, as far as I know, hardcoded in the control IC, also called the PIC. It might be possible that some version have a control pin that should be grounded or lifted up to change the timing between 50 and 60Hz. I have no information about this. The bad news is that US, 60Hz "three phase transmit" timing will not work on 50Hz three phase.
I am not even sure that all transmitting modules sold for 50Hz have their "three phase transmit" timing adjusted for 50Hz. In Chile I bought some modules marked 220V 50Hz with the three phase transmit adapted to 60 Hz. I believe that these modules were modified here in Chile. However, this is not very serious in Chile since three phase is very uncommon here, at least in private houses.
So, if you have three phase 50Hz and want to use US 60Hz modules, you would either have to put all your X10 devices on one phase or accept that the X10 controller in the bedroom can control the lights in the bedroom but might not be able to control the light in the living room. The opposite could also be true.
There are active repeaters that can overcome this problem but expect them to be around for a couple of hundred dollars. They are a lot more complex than the active repeaters one would use on an American "three phase" (two phase!) system. These repeaters receive data, synchronous with zero crossing, and retransmits it on the other two phases synchronous with their zero crossing. It is in fact a little bit more complicated than this, because a good repeater should be able to retransmit data from any phase to all other phases and this without retransmitting it's own retransmitted data and ending up in infinite loop.
I know that ACT in the US and perhaps some other companies manufacture these kind of repeaters for 220/380V and also for some other voltages. Celtel in the U.K, is also supposed to sell at least one type of repeater. This is probably one of the reasons why X10 is not very popular in Europe and other countries with three phase systems. Well, price policy and approvals are also important.
4. Triangle or delta configurations like (127)/220V. They also use three phases 120 degrees out of phase but they don't distribute the neutral to the consumers. The voltage between any two phases is the nominal voltage, usually 220V. Sometimes, one phase is connected to the ground at the transformer, sometimes so is the neutral, which is not distributed, connected to the ground at the transformer. This system is not very common but it is (was?) used in, some but not all places, in among other countries, Norway, Belgium and Argentina.
The same problems here as in case three but it is more difficult or perhaps impossible to find active repeaters. In fact, I don't know but I have neither heard about them nor looked for them. Anyway, ask your friendly local X10 dealer or ACT in the States.
5. DC. X10 will not work on DC systems!
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