You will need a low voltage wiring guide when planning your outdoor lighting. This will help you decide what size wire, how many lights can be on each run of wire and how to run your wire.
Voltage drop explained
Voltage drop happens when your wire is too small to handle the number of lights or is too long. Having too long of a run will have the lights at the start of the run at 12 volts and the lights at the end having only around 8 volts. The lights will still work, but will not last as long if they are not running close to 12 volts.
Having too many lights on the same run will have the same effect. The lights at the start of the run will have more voltage than the lights at the end of the run.
To correct this problem, mapping your runs with a connection in the middle of the run going both ways will correct this problem.
How many watts of lights will be in the run
After you have mapped out where the lights will be you must include the wattage of each fixture. This will help in deciding how to run the wire from transformer. must have the number fo feet between each fixture and the wattage of the lights at each location. Try to limit each run to 100 to 150 watts of total output.
Divide the fixtures into areas for the best coverage and having the same number of watts in each run. Long runs can be split in the middle and the amount of lights will be cut in half. This will ensure that all lights get close to the same power.
How to use the chart to find out the size of the wire that you will need
After you have made all of your plans on where the lights will go and how the wire is laid out, use the chart to get the correct size wire for your lights to prevent a lot of voltage drop.
Getting the correct low voltage wire for your lights will give you the best performance for each light.
Don't forget to get the correct transformer and wire connectors for your lights best performance also.