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Outdoor Lighting Transformer InstructionsTransformer Instructions
On the secondary side (low voltage taps) of the transformer, each circuit has its own magnetic circuit breaker (toggle switch) that is connected to a Common Tap (marked with label, "COM"). These Common Taps can accommodate up to 300W (25A). The exception to that is when the transformer capacity is less than 300W; in that case, the capacity will be equal to the transformer capacity.
Even though the capacity of each Common Tap is 300W (or transformer capacity if less than 300W), the National Electric Code specifies that a circuit can only be loaded up to 80% of its maximum. That means that the working capacity is 240W (or 80% of the transformer capacity is smaller than 300W). Additionally, to account for loss of current through wire, reduce the 80% by another 10% - that makes 70% of capacity a better working number.
As a good general practice, as you connect each of your home run wires to the transformer, spread them among all the available commons. Ideally, if 2 or more home run wires share a voltage tap, then connect them to the same common.
Connecting lighting runs to the transformer:
The home run cable (e.g. 10/2 or 12/2) has two wires. One wire gets connected to the Common Terminal (labeled "COM"), the other wire connects to a Voltage Terminal (the colored labels that say 12, 13, 14, etc). The correct Voltage Terminal is the one that results in an optimal voltage at the fixtures connected to that run. This is a Multi-Tap transformer, which means you can output at a variety of voltages to compensate for Voltage Drop (see our learning area for more information on layouts and voltage drop). For example, if you have a long run of 100 feet you may need to use the 15v Voltage Terminal in order to have 12v of power all the way out at the far away fixtures.
You can hook up multiple home runs to each and any of the terminals. For example you may have 6 home runs, in which case you would have 6 wires in the same COM terminal and the other half of the 10-2 wires go into the colored terminals. The Voltage Terminals can have multiple runs/wires in each tap as well. To connect a home run wire to the terminals, split the paired wire down the middle to separate the two wires and strip half an inch of insulation off each wire. One end goes in the COM terminal, the other into a voltage terminal. Loosen the terminal screws (small flat head screw driver) and insert the wire into the terminal opening which is located at the bottom (90 degrees from the terminal screw facing the bottom of the transformer). Tighten screw to secure wire(s).
Low voltage wire does not have polarity, it does not matter which of the 2 wire connects to the Common Terminal and which to the Voltage Terminal, as long as one wire goes to each. Optional timers and photocells plug right into the transformer ports labeled and located inside the cabinet. It is easier to see and insert the wires into their terminals when the transformer is lying on the ground. Affix all your wires BEFORE mounting the transformer.
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