Split phase in an apartment

[timlight10]

My apartment is in the US and has split-phase power. Can I use two RF Transceivers, each on a different power phase, to control X10 modules on the two separate phases if I use an RF controller like the Firecracker?

[HA Dave]

My apartment is in the US and has split-phase power. Can I use two RF Transceivers, each on a different power phase, to control X10 modules on the two separate phases if I use an RF controller like the Firecracker?

Yes! I've done it. Although... it might be best to use one RR501 transceiver (instead of two TM751 Wireless Transceiver Modules) ... the RR501 is called the "polite" transceiver as it waits and listens to see if there is other traffic on the powerline.

Other usage in the building could cause the signal to cross phases from time to time..... which could be a problem. But a RR501 transceiver should resolve that concern.

[timlight10]

Yes sometimes my system works, other times not. I suspect that to be due to neighbors using their electric stoves, water heaters and dryers from time to time, thus coupling the phases for me. But this would be a nice way to solve the problem for good (I hope!)

[Brian H]

High power devices like electric stoves, dryers and water heaters. Many times act like a phase bridge. Most times improving the X10 signal on the other phase.

Do you know if your higher voltage is 220 Volts to 240 Volts or around 208 Volts?
Some condominiums and large buildings are three phase and alternate two of the three phases to each unit. 208 volts would indicate it was a three phase feed.

[dhouston]

If it is 208VAC 3-phase, some controllers designed for use with the TW523/PSC05 interfaces and some stand-alone controllers (e.g. Powerlinc) only supply PLC signals for the local ZC timing.

It might be helpful if you describe your current hardware in more detail.

[timlight10]

I have a TM751 transceiver and a Firecracker interface for my PC. Then I have various LM465 and AM466 modules throughout the apartment.

[dhouston]

OK.

The simplest course depends on whether you have 240VAC Split Single Phase or 208VAC 3-phase distribution. See Fig 2 and Fig 5 at...

• http://www.behlman.com/applications/AC%20basics.pdf

With Split Single Phase distribution, you can get by with another TM751 as long as both are relatively close to the Firecracker. Both will receive the RF at the same time and both will transmit at the same time since their ZC points coincide. There will not be any collisions should there be any incidental electrical coupling of phases.

With 3 phase distribution it gets more complicated. X10 PLC transmitters on different phases will always collide when there is incidental coupling. I've modified a graphic I used elsewhere to show why this is the case.

• http://davehouston.org/3-phase%20collisions.png

Whenever a '1' half-bit triplet is transmitted, it will be repeated at 60° or 120° intervals (I've only shown 60°) which will always corrupt the following '0' half bit.

So, with a 3-phase system the best course is to add a 3-phase coupler and use a single transceiver.