Low voltage landscaping transformer

Hi,

I will be purchasing two low voltage transformers for some landscape lighting, and will likely buy the VOLT brand transformers. Right now I plan to have 10 6 watt LED spotlights on one transformer and maybe 4 or 5 on the other. They sell 75, 150 and 300 watt (and higher) transformers; I have heard that using a transformer that is significantly bigger than the load it's supporting is not good, as the transformer can overheat and the lights can be overdriven, resulting in a shorter life for both. However, the VOLT customer rep. I spoke with indicated that that wouldn't be an issue with their transformers - he said I could use a 1200 watt transformer with one fixture on it and it wouldn't cause any problems. Does anyone have experience with the VOLT brand transformers and could speak to this? Right now I only need the 75 watt version but may want to put additional lights in the future, so maybe the 150 (or even 300) watt versions would be better. I wonder if it's because of the toroidal core that's used for their transformers? Here's a link to their website:
Multi-tap 150 watt Transformer 12 - 15 volt | Landscape Lighting | VOLT®

 

The problem mentioned has to do with some transformers delivering a higher output voltage than marked when the load is much smaller than the maximum load.

Also, a transformer with much more capacity than the load except that it may consume more energy powering the same load compared with a smaller transformer. You can think of a minimum power draw regardless of the load.

You mignt inquire about whether the transformer has multiple output terminals allowing a range of output voltages close to including slightly less than the rated voltage. The lights will draw the exact power they want regardless of the capacity of their power supply.

Sometimes two smaller transformers are preferable to one large transformer. This is only when the lights are quite spread out and there would be less voltage drop running the primary (120 volt) power to two separate locations from each of which shorter not-so-fat secondary (12-24 or so volts) lines are needed to reach the lights.

 

If the lights are rated for a range of voltages including what the transformer delivers at low load then no special treatment is needed.

 

The Volt transformer you linked to is a good choice. An ideal size for your requirements. It has multiple taps so that you can custom select and fine tune the lamp operating voltage.

However, since you're using LED lighting, the voltage is nowhere near as important.

 

Great, the feedback is much appreciated.

For the runs that will have 10 6 watt LEDs, I'm thinking two runs of 12/2 cable, daisy chained 5 lights apiece, and perhaps step up the voltage to 13 or so (on the longer run) after measuring with a voltmeter to keep things consistent. Would this sound reasonable? Might not need to even step up the voltage on the second run, distance from transformer to last fixture probably will be about 75 feet including leaving a little extra loop of cable at each fixture for future flexibility if I want to move the lights.

Also, since my wattage requirements on the transformer going in front of the house will be less (only 4 - 5 6 watt lights, total 24 - 30 watts) I'm debating whether to get the 75 watt unit for that part of the house. Not a big deal either way, will be able to hide the transformer behind a large shrub, and I have a hard time envisioning adding much more lighting to that transformer (maybe a couple moonlights up in the tree if I'm super ambitious some day?)

Thanks!

 

Sounds like a plan that should work well.

 

Thank you PJmax.

AllanJ, the VOLT transformers I am considering are all multi-tap, so I will be able to adjust voltage as needed, thanks!

 

I took a second look at the VOLT offerings...the 300 watt transformer is only $10 more than the 150 watt and the same transformer box is used (so it wouldn't be any bigger, just 1 pound heavier). Still like the 75 watt for the front yard but for the back / side of the house maybe the 300 would be best. Again, supposedly it's not an issue with their transformers to have a light wattage load, assuming that's true I'd rather just spend the extra $10 and have a lot more capacity, any thoughts?

 

The multi taps will take care of output voltage vs. system load.
The only issue may be a slight bit more AC line draw due to the bigger transformer primary.

 

Thank you PJmax, I think I'm gonna go with the 300w for the back yard and the 75 watt for the front.