You definitely should measure the current drawn by the power supply at the job site. If there is a short in the wire, this will become obvious with a current measurement.

The Elan web site says the Z100 requires 50 mA at 12 volts. Your 200 mA supply should work perfectly, although I personally would be on the conservative side and use at least a 300 mA supply.

The Xantech blocks do indeed put the LEDs in parallel, but I think the LEDs draw about 15 mA each, maybe less. Also, since the signal is pulsed, and they are only drawing 15 mA when the pulse is high, the average current they will draw will be much less. That should rule out the Xantech approach as a problem.

You mention that the wire you used at home was the same as the wire you use on the job. I am a bit at a loss about this -- are you saying that you removed the piece of wire from the wall and took it home? If you mean you simply used the same type at home, you should have no problems as that piece at home has not had the opportunity to be a staple target, has not been pulled around corners (which can strip insulation if done very roughly)...in short :) you need to consider the actual length of wire connected at the job site.

Hey, while you are at the site with the voltmeter measuring the current draw, maybe you should FIRST measure the resistance across the wires in place. With your LEDs and keypad disconnected, all conductors should have infinite resistance from one to another. You may read a resistance in the tens or hundreds of thousands of ohms, which is the resistance from finger to finger if you are touching the metal of the wires and the probes.

Please let us know what you find.