A common mistake made by many is to replace existing lamps with lamps of higher wattage than those originally installed. As an example, Mr. Smith has a low volt system with a 600 watt transformer and 25 fixtures illuminating his landscape. All of the original fixtures had 20-watt lamps in them for a total load on the transformer of 500 watts.
When he went to replace the lamps, he added ten 50-watt lamps, and fifteen 20-watt lamps. What he has done is increase the wattage demand from 500 watts to 800 watts thus overloading the Transformer. Overloading the transformer will cause the Transformers Circuit Breakers to Trip thus shutting the system down!
Solution: Reinstall lamps with the same wattage as the originals.