Ground problem or defective GFI.
Landscape lighting transformer keeps tripping. Try resetting the breaker. If any of the transformerstimers have 120 V extension cords check the extension cords as well. If so clean it off with a clean dry rag and try again.
The GFCI Outlet must be wired from the wiring of the same circuit therefore the wiring must be contiguous and not connected to other circuit wires because this could cause the GFI Outlet to trip but there is more to this problem as described below. Transformer is cycling on off at night. After I reset the the breaker the breaker on the transformer would trip after 5 minutes.
GFIs are notorious for nuisance tripping. GFCIs are notorious for nuisance tripping. If this is the case then it may be best to contact your outdoor lighting professional to find out what can be done.
In some circles some electricians and homeowners will also refer to these outlets as just a GFI. Now whenever the lights come on they will stay on for a little while than the transformer will trip its circuit breaker. Use a high grade model such as the Hubbell GF5252I.
Home What causes the breaker to trip on a low-voltage landscape lighting transformer. It could be many things but in general if your wiring plan is uneven you may need to balance the load better among the available circuits at the commons or upgrade your transformer. Reduce lamp wattage fixture quantity or increase size of Transformer.
See shorting solution below. If all of the landscape lights in a system stop working typically there is a problem with the power to the low voltage lighting transformer. The breaker on the transformer would trip about 1-2 seconds after the timer turned the lights on.

