Incandescent System Layout


Once the transformer has been installed and all fixture locations determined, the next step is to run the correct size cable from the transformer to the fixtures while providing each fixture with between a 10.5 and 11.5 volt operating range. This is accomplished by:

  1. Grouping fixtures into distance zones as illustrated below. Do not have a fixture that is 10' away from the transformer on the same cable run as one that is 100' away.
  2. Use the proper cabling method for the application. Try to center load all cable runs when possible to minimize the voltage differential between fixtures. Maximum voltage differential between the first fixture and the last fixture on any given circuit should not exceed 1 volt with a 0.5 volt differential being optimum.
  3. Use the correct size cable to accommodate voltage drop. As a general rule of thumb, limit the wattage load per each cable run to no more than 100 to 160 watts.
  4. Choosing the correct voltage tap on the PX Transformer terminal block. The PX Series Transformer low voltage tap lugs are the biggest in the industry. If your system has 5 cable runs that all need to be installed into the 13 volt tap, multiple cables will easily fit into each of the lugs.


For maximum light output and lamp life, the goal when installing low voltage systems is to provide each lamp with between 10.5 and 11.5 volts. To stay within a 0.5 to 1.0 volt differential between the first light and the last light on a given circuit, you must group the fixtures into distance zones and not overload the cable with excessive wattage. As a rule of thumb, limit the distance between the first fixture and the last fixture on any given run to no more than 50 feet.

The FX PX Transformer allows you the opportunity to utilize the voltage tap that will provide each circuit with the proper voltage. For cable runs in the "distant zone" you would typically select the 13 or 14 volt tap. For cable runs in the "close zone," you would typically install the cable run into the 11 or 12 volt tap depending upon the wattage load and size of cable.