Possible X10 Stumbling Blocks

As with any technology, there are some warnings and possible stumbling points:

Two phase power:

In the USA, homes are typically supplied power on 2 separate 110 volt lines called phases.  One half of the circuits in your house are on one phase, the other half is on the other.  220 volt appliances, like an electric range, or an electric clothes dryer use both phases.  The only place these phases connect is at the street transformer, either on the pole or in one of those large green boxes on your lawn.  If your transmitter is on one phase and your receiver(s) is/are on the other phase, the X10 signal has to travel from the transmitter all the way out to the street and then back into your house to the receiver.  To make matters worse, transformers actually degrade the signal.  So what does all that mean?  Some modules may only work intermittently or not at all - a very frustrating experience!

To solve this problem, you need an X10 active coupler/repeater.  While there are some that can be wired in to your load center (breaker panel), the easiest to install plug into your electric dryer's outlet.  You simply unplug your dryer, plug in the module, and then plug your dryer into the module.  If you go this route, be sure to look at your dryer outlet BEFORE you order the module.  Some dryers are 3 wire, while others are 4, and you'll need to order the correct one.  If you don't have an electric dryer, plan on hiring an electrician to install a hard-wired repeater.  Unless you have the experience and knowledge to work safely inside a load center, it's a job best left to the pros.

Also be sure that the coupler you order is an ACTIVE coupler/repeater, and not just a simple coupler.  Couplers look very similar to repeaters but are nearly worthless.  A coupler will take whatever X10-like signal it sees on one phase and electrically tie it to the other.  While this will shorten the trip the X10 signal needs to take (it won't need to go all the way out to the street and back), it doesn't amplify the signal or filter out any X10 signal noise.

Repeaters on the other hand actively listen for X10 signals.  When they are heard, the module amplifies the signal and re-sends it out on both phases at higher power.  Unlike passive couplers, active couplers can reject any signal noise they may hear.

Plan on spending $60-$70 for a dryer coupler/repeater or $15 (plus installation) for a hard wired one from the start.  While you can try to do without one, I've found that installing a repeater takes care of 90% of the problems you may have.

Electronic devices impact the signal:

Since the X10 signals travel along your home's power lines, things plugged into any outlet can adversely affect the signal.  The biggest culprits are electronics and uninterruptible power supplies (battery backups).  Things like TV's, computers, laptops, stereo systems, and other devices act like vampires and actually 'eat' the X10 signal as it goes by on your homes wires. 

Again, there is a simple solution: X10 filter modules.  You simply plug the filter module into the wall, and then the device into it.  These modules block the X10 signal from being eaten by the electronics allowing it to pass by undisturbed.  Plan on purchasing 1 for every piece of electronics you have.  Typically you shouldn't need more than 4 or 5.  I have several computers and TV's and use 4. 

If your devices are plugged into a power strip, you only need to buy 1 filter to protect them all:  Plug the module into the wall, and then plug the power strip into the module.  Anything you plug into the strip is then filtered.

Typically filter modules can be had for $4-$8 each.  Like repeaters, plan on purchasing these from the start.  Nothing is more frustrating than having a working X10 setup and then suddenly it stops working because someone turned on a computer or TV somewhere in the house. 

Avoid multiple transmitters:

Multiple transmitters should be avoided.  If you have an absolute need to have 2 or more transmitters, for instance you have a computer controlled transmitter and want to add motion detectors which require a radio transceiver, keep them on separate house codes.  NEVER use 2 or more radio transceivers on the SAME house code!  Multiple transmitters hurt the X10 network in 2 ways: 

  1. Many X10 transmitters do not have 'collision detection'.  That means that as soon as a transmitter gets a signal it will begin transmitting the X10 signal onto the power lines regardless if there are other X10 commands currently being broadcast.  If you only have 1 transmitter then you will only have 1 source of X10 commands (and thus no collisions).
  2. Most radio transceivers (IE, the TM751) have a bug in them which locks them up if they hear an X10 signal (either on the powerline or via a remote) for the house code they are set to.

Just remember:  NEVER have 2 or more radio (TM751, RR501) transceivers on the same house code, and you should be safe.

Don't overload the modules:

Pay close attention to  the power ratings of the receivers you are using.  X10 receivers typically use 3 different types of relays to turn loads on and off:  Solid State, high power mechanical, and low power mechanical.  Each has different maximum loads they can handle.

Solid state receivers can typically handle 300 watts with no restrictions.

High power receivers can handle 1800 watts (15 amps), and have no restrictions.

Low power mechanical receivers are rated for 1800 watts (15 amps), BUT NOT FOR INCANDESCENT LIGHTS!  When used with incandescent lights, IE normal light bulbs, flood lights, C7/C9 & mini holiday lights, they are only rated for 500 watts (around 4.5 amps).

Both high and low power mechanical receivers make an audible clicking sound when turned on/off.  Solid state controllers make NO noise.

So why do low power mechanical receivers have a limit on lighting loads?  When you first turn on a normal light bulb there is a huge inrush of many amps of power until the lamp begins to glow.  This inrush only lasts a few hundredths of a second, and then the power consumed quickly returns to normal levels.  This initial inrush of power however creates a lot of heat within the receivers relay.  This heat will actually weld the contacts closed so they can no loner open.  Once this has happened your receiver is permanently ON and can not be turned back off.  Solid state receivers also tend to fail stuck on if you overload them.

In all cases, NEVER use a receiver marked as 'Indoor only' outdoors unless in a watertight enclosure.

Beware of Noise and the Neighbors:

At some point, you may witness your lights going on or off when they shouldn't be.  Typically, these problems can be traced back to two problems:  noise on your electrical lines, or neighboring homes that are also using X10. 

Noise is an insidious beast - it's hard to track down, and sometimes impossible to eliminate.  Properly using plug in filters will eliminate all the noise from inside your home, but it may also be coming from outside.  If you have a coupler/repeater installed (and you should), take a look at the LED(s).  Are they blinking when you aren't sending X10 commands?  If so, you may have a noise problem.  While there is X10 test equipment available, explicitly the XPTR and XPTT pair, the price for the pair is simply prohibitive for normal homeowners.

Every night around 11PM, I have a 'noise storm'.  By watching the LEDs on my dryer coupler, I can see them start to blink slowly on one phase for a few seconds until it becomes solid red and abruptly goes out.  This led will do this 3-5 times and then the led from the OTHER phase will start to do the same thing.  I've gone as far as shutting off every breaker in the house, except the dryer outlet obviously, and the same storm will happen.  Since it happens with such regularity, I think my electric company must be doing some kind of maintenance at that time every night which is being picked up as X10 noise.  Thankfully, even with all this noise I can still control my X10 receivers.

Typically, the electrical transformer at the pole blocks incoming X10 signals from other houses in your neighborhood.  However, there may be several houses on the same transformer that your house is on.  In those cases, it's possible for a neighbors X10 signal to start controlling the receivers in your house.  Using a repeater/coupler may actually make this condition worse;  Signals coming to your house may be too low to actually activate your receivers, but the whole function of a coupler is to take low-power signals and amplify them.

If you suspect that your neighbors also have X10, the easiest thing to do is ask them and come to an agreement on what house codes each of you will use.  Remember that in electrical terms, your neighbors may not be next door - they could be across the street, or even behind your house.

If you have a CM11A or CM15A computer interface, and have installed the 'Active Home' software, you can use the 'Tools/Find Other Computers' utility to confirm that other X10 signals are getting into your home.  Hook up your interface to the computer and disconnect all your other X10 modules.  Allow the utility to run for a day or 2.  Any red dots indicate a House/Unit code that is being picked up by your interface.
 
If you don't want to bother your neighbors with a sharing arrangement, or if you are sure you have a noise problem and are sure it's coming from outside your home, you can install a whole-house X10 filter (PZZ01) inside your load center.  The filter itself is inexpensive,, however it MUST be installed between the electric meter and your load center (breaker box).  Unless you have an external 'meter cut-off' you absolutely should NOT install this device yourself!  Even if you shut the main breaker off, there is still LINE VOLTAGE coming in from the meter to the panel.  You must install this device over the neutral coming in from the meter so the wires you would be working on are LIVE!  Hire someone to do this work for you and live another day.