Let's talk for a moment, if we may, about voltage drop. Not your everyday ordinary Garden variety low voltage, voltage drop but the kind that happens when undersized wire is used on your power source(plug, house wiring, etc). Some tract home builders are wiring their homes with 15 amp breakers which means they are probably using 14 gauge wiring. I'm going to tell you why you should always leave your homerun wire connections open (to test voltage) until every fixture has been installed on every transformer and/ or other electrical load turned on that is normally operating along with your lights that is powered by the same breaker in the electrical panel. Have I lost you yet? Consider this scenario-You have just closed the door on your transformer and are high fiving with your foreman because everyone of your fixtures is operating between 11-12 volts . Yeah we did it it's gonna look great , this is the life. We really have this voltage drop thing conquered you're thinking. Not so fast, you still have another 600 watt transformer to install on that same 15 amp breaker protected 14 gauge wired circuit. You get through that one and you say to your foreman - "Gee, Felix we got 11-12 volts to each fixture on this one too but we had to use heavier cable and higher taps to do it. The runs Didn't seem to be any different or the loads any greater than the last transformer we did I wonder why. what these two gentleman don't know is transformer #1 has lost somewhere in the vacinity of 1 or more volts (varies by transformer)on each of it's secondary outputs as a result of the additional load placed on the primary voltage of their 14 gauge wired circuit. So when the power goes on at night and the 70 foot sycamore tree has light at 40 feet and no higher from transformer #1 both business owner and foreman are scratching their heads and wondering why? what's going on. The moral of the story is this- never close your homerun connections and quit testing voltages until you have turned on the full load that will be on when those lights are operating at night to the circuit that your transformers are operating from. Does this make sense?