I need help choosing a transformer and I believe the choice will come down to the 100 or 150 Watt Slim Line options. I do not plan more than 10 lights, but some runs may be quite long. How do I determine which voltage is necessary, choosing between 12 and 15 volts?
Hi, mbuck. My eyes glaze over when I have to think too hard about techie stuff like multi-testers and voltage drop but I’m sure Evan will weigh in). What’s “quite long”? 100 feet? 300 feet? I have an approximately 30 light plan (with the longest runs being about 65 feet long) on a multi tap transformer (non VOLT ). My shorter runs are connected to 12V taps and my longer runs are on 15V taps. Using 12 gauge home run wires (which could well be overkill) to address potential voltage drop and my system has worked flawlessly since installed last winter. Just my 2 cents.
mbuck: 12V vs. 15V is less important than the gauge of the main line wires and the sum total of the wattage of all of your lights, but as Meso asks, how long is long? The installation guide for the transformers is available on the Volt website under the downloads section of the transformer product description. There you will find a chart showing what gauge wire is needed for your main lines, depending on the length of the runs. Anything less than 300 feet will not be a problem for either the 100W or 150W Slim Lines so long as you use the recommended gauge wire, keep the sum total of the lights wattage at less than 80W or 120W (80% of 100W or 150W) and keep the lights per main line run at no more than 8-10. For my install, I used the 100W Slim Line and 12/2 gauge wire for the main line runs to 4 Pro Junction hubs. I got carried away and ended up installing 29 lights for a sum total of 75 watts. The photo of the 100W Slim Line on the Volt website is apparently of an older model transformer, showing a set of 3 clamp connectors. The current 100W Slim Line actually has 4 clamp connectors, which allowed me to run a separate main line to each of my hubs. My longest run was 130 feet, 90 feet to the hub and 40 feet of 5 daisy chained puck lights, all connected with 12/2 gauge wire. With everything on, the furthest light from the transformer measured 14.7 volts, an insignificant drop over the 130 feet of cable. If all you plan to install is 10 lights at 8 watts or less, the cheaper 100W Slim Line will do just fine, assuming you use the appropriate gauge wire. If you might some day go crazy as I did and want to install a whole bunch more lights, the 150W Slim Line would be a better choice, using the 12V circuits for the shorter/fewer lights runs, and 15V for longer/up to 10 lights runs. Have fun. Bob
Thank you for mentioning this Bob! I will bring this up to the team so we can update. @mbuck , Meso & Bob have hit the nail on the head! Essentially, a handy voltmeter will be your best friend for determining voltages after ensuring you're using the proper gauge of cable based on lengths of runs, and are within the range for power recommendations (no more than 8-10 fixtures or approx. 80W per individual run). With the proper cable and recommended amount of fixtures, you could then apply the volt meter to any of your longer runs that you may find questionable, or at any spots where you may notice a dim fixture and troubleshoot/determine from there if you possibly needed to increase the voltage to a higher tap within the transformer. Typically, you want to size the transformer you need based on the total wattage consumption of your system and not the voltage tap you need (12V & 15V are standard options within most of our units).
Thanks for the responses! It sounds like I may have been asking the wrong question. My longest run will be approximately 150 ft. I know now this means I should be looking at the 12 gauge wire. Followup question- It seems like all the discussion is about the decision to use 12 gauge or thicker. Why is the 14 gauge sold and when may this be preferred to the 12 gauge?
mbuck: If you go back to the transformer installation document and back up one page from the wire selection chart, you will find an equation for calculating maximum voltage loss across the length of a main line. I did a quick calculation for a 150 foot run of 14 gauge wire from a 100 watt Slim Line which uses 15 volt connectors. Assuming a line loss of 3 volts to an ideal of 12 volts feeding the final LED on the main line, the total maximum allowable bulb wattage on the line would be 35 watts. While you haven’t said what the wattages are for the 10 bulbs you plan to install, 14 gauge wire might be acceptable for your runs if you limit that bulb wattage. As an aside, while the chart doesn’t say what to use for runs under 100 feet, all of the Volt Easy-Install kits come with a 150 watt Slim Line and a 100 foot roll of 14 gauge wire, including the most expensive kit which has a sum of 42 watts worth of bulb wattage. So, obviously, 14 gauge wire will work just fine for runs of less than 100 feet. Evan can probably give a more exacting response, but it appears to me that you could use 14 gauge wire for your 150 foot runs if you limit the total bulb wattage on the line. The downside is that it will limit the addition of more lights to the main line, should you wish to expand in the future and thus should go with the 12 gauge wire as recommended by the chart.
