You've entered into the often misunderstood world of low voltage power wiring. Basically you have to treat the wiring just like 120V wiring with junction boxes UNLESS you use class 2 power limited transformers. This is what is required with typical low voltage puck light installation. Wiring must still be in wall rated to pass though the structure. Not all combinations of low voltage lighting installation parts by manufacturers are UL listed (and some will tell you that)so it is possible that you can't even connect what you have been given in a code approved way. For these parts to be compatible the transformer will have five 5 amp fuses or circuit breakers on it, each meant to supply up to 60 watts of lighting. So each fixture will have it's own run of cable back to its own connection point on the transformer. It's OK to lengthen runs using the manufacturer's voltage drop table and recommended wire size.

"I shouod see some voltage drop on a run like that as well. " Voltage drop only occurs is current is flowing. Most meters are high enough impedance you would see almost no drop over the distance you have. Voltage drop is the current (amps) times the resistance of the path (ohms). No current, no drop. An unloaded transformer ALWAYS measures higher than it rated voltage. There is no current flowing in the secondary that acts to lower the output voltage. Transformer outputs fall in voltage as the current they are supplying rises.

OK, everyone got me sufficiently paranoid to contact Juno. The tech rep responded as such to my question about using a dimmer designed for a magnetic transformer on a dedicated outlet for a magnetic transformer: "Electrically that arrangement would work. Since you state that the outlet is located in a remote location, and presumably will be dedicated to only provide dimmable power for the T550N transformer you should be OK. The only reservation I have about this type of setup, is the possibility of some other electrical device being plugged into a wall outlet wired off a dimmer. It might be a good idea to use a single receptacle instead of a duplex to minimize the chance of this happening. Perhaps even labeling the outlet "for low voltage lighting only" or something of that nature as an added precaution. You will have to install a cord and plug on the transformer. If you have not ordered the T550N already, you can order it with a 6 foot cord and plug option. You would order the transformer as catalog# T550N-BL-CP6. Otherwise you can attach your own cordset." I apoligize for not getting all the facts beforehand. Would those who recommended trashing the existing systems or felt there was imminent danger of fire consider this sufficient or are there still logical objections?

Volt, understood. I think it would be pretty cool if you did LV pier mounts though... They’re hard to find and more and more people are moving to LV systems. I think you could sell them for much more as well. Maybe a bit more challenging for DIY, but many folks, like me, are working with contractors on a bigger job and this type of install is no problem. My plan now is to buy a normal line voltage fixture, put in a low voltage bulb, and wire it up to my Volt slimline transformer. Fingers crossed. Lastly, I saw this from Cascade Lighting website: “Our customers often ask if we offer 12 volt post top or column mount lanterns. We are happy to answer that any post top or column mount lantern with a medium base (A19 – or Edison screw base) socket or the smaller candelabra base socket may be installed with a low voltage 12 volt system or simply alone. The secret is that the lantern socket solely depends on the voltage of the lamp installed and the voltage to the lamps. There is no need for a “conversion kit” to turn a 120v fixture into a 12 volt powered fixture. 12v Post Top and Column Mount Lantern Lamp Choices If you are installing a lantern and want it to operate as a 12 volt system, you would first choose a 12v incandescent or LED lamp to fit the lantern socket type (medium base or candelabra). There are various wattage output options available and in stock at Cascade. The next step is to connect the lantern wire leads to the proper direct burial low voltage cable size (to fit the job) and then connect the cable to a professional grade magnetic landscape transformer. “