I have a VOLT 150 watt transformer with 20 VOLT MR16 5 watt LED bulbs on three runs all from the 12V taps. When I add a 21st fixture, the breaker in the transformer trips usually after an hour or two. Once it trips, it will trip again right away when I reset it. The total watts is well below the capacity of the transformer and VOLT gave me a brand new transformer under warranty and it's still happening so it's not a transformer problem. I checked and am getting 11 volts to the last fixture on each run. I do not know what to try next. I called VOLT and Richard told me it sounded like an overload issue. He also said that some of the bulbs may be drawing more than 5 volts but even if all 21 were drawing 6 volts, this transformer should not trip. Anybody have any ideas?
You can't use every watt because of line losses. My Volt transformer guide recommends a power factor of .7. Twenty at five watts each totals 142 and change ((20 x 5)/.7). It wouldn't take much difference in wattage at a few bulbs to put you over the top. Twenty one puts you at exactly 150 watts. If possible, I'd consider replacing some of those bulbs with three or four watt bulbs. I'm using three watt bulbs in my path lights and it's more than sufficient to see to walk. If that doesn't work, you may want to consider going to a 300 watt transformer. Edited to add that you could also try a heavier gauge cable, but I'm going to be that would be quite a bit more work than replacing a few bulbs or even a transformer.
I read the same info but everyone I talked to at Volt said I should be able to use 80% of the transformer or 24 fixtures. My question is IF it is not a transformer size issue, how do I locate the problem?
It's always a good idea to check the amperage load on the output side of your transformer. Get a basic ammeter (cheap at Harbor Freight) and check one side of each wire separately coming out off the terminal block, then add up the amount of amps. With a 12v 150w transformer you should be at 10 amps or less ((150 / 12) x .8 ).
