Paul,
Even though the lighting you have is wired directly to a 120v dimmer, there is probably a small in-line transformer to run the Xenon lamps. This small in-line transformer is either magnetic (core & coil) or electronic (circuit board). Electronic is more then likely what you have. The way they dim is different and in turn require a dimmer that works properly with the type of transformer/ballast.
Standard dimmer = good for 120v incadescent lamps up to its stated wattage (600w) Humming can be an issue with low quality lamps when dimming.
Magnetic Low Voltage Dimmer = good for incandescent loads that are "low voltage" (12 or 24V) and use a magnetic transformer (large and heavy) up to its VA rating. Humming can be an issue with both lamps and transformer if low in quality.
Electronic Low Voltage Dimmer = good for incandescent (xenon and other inc.) loads that are low voltage (12 or 24v) using an electronic transformer. Wattage capacity of the dimmer is usually restricted to smaller loads, 450w or less. Humming is usually not an issue with transformer do to its solid state nature. Larger combined electronic loads should be on their own circuit to address nuetral overload issues.
Fluorescent Dimmer = Used in conjuction with special dimming ballast to dim fluorscent loads. Flickering on start up and at low level dimming can be an issue if not on seperate circuit.
LED Dimmer= This one can get tricky depending on the type of driver the LED's are using and the amount of load. Dimming down to 20% is about the most you will achieve. Consult with the LED manufacture as to what type of dimmer they recommend. Most dimmer manufacture will not recommend you dim LED at this time as they can not achieve full range dimming.
You are probably now really confused.
