I have low voltage landscape lighting plugged into an outside outlet. The total watts is about 500 and I am using a 600 watt transformer. The outlet is a GFI outlet and has a dedicated 20 amp breaker. Nothing else is on this breaker. Sometimes the breaker will trip. I have replaced the landscape wire recently. It kept tripping before I replaced the wire. The house is 1 year old. What do you suggest to keep the breaker from tripping? Replace the 20 amp with the next step higher? Replace the GFI outlet? (which I think is odd that the breaker trips but the GFI doesn't, but I am no electrician)

My guess is that you have an InterMatic(Malibu) Low Voltage Power Pack #ML600TW combo transformer/timer, or something similar, and I cannot see by their instructions you have caused any problem.

The GFI will only trip if there is a ground fault in the cord or the power pack.

The breaker will trip due to an overload or a short in the circuit from the breaker to the transformer. Even if you had 600 watts on the transformer, at 120 volts, is a draw of 5 amps on the 20 amp breaker, so overload should not be the problem.

Either there is an intermittent short between the breaker and transformer, or in the transformer, or it is possible for the breaker to be defective. There is a chance that the breaker is fine, but the wire terminal is loose, which will create heat at the terminal on the breaker, and this heat will migrate into the breaker, causing the CB to trip.

The breaker may also be affected by heat being created in an adjacent breaker.

Check the breaker itself for tightness into the panel, check the wire terminal for tightness, try another breaker, or check the circuit, and in the GFI outlet box for a possible intermittent short.

Check these items, and get back with more questions, along with more details, and we can go from there.

Thank you for your reply. Correct on the Malibu transformer. Normal one that I bought at Home Depot. Here is something else I just thought about... could there be a problem with the landscape wire? For example, where one of the lights is connected to the wire, it could get moist with water and trip the breaker? Again, I am no electrician. But it can be raining cats and dogs and it doesn't trip.

I will replace the breaker with the same amp tomorrow. Could there be a problem with the GFI? It being a bad one?

Could be a defective breaker, or GFI. I would like to think the short is in the GFI outlet box, popular location for shorted wires because of the size of the GFI and how little room is usually left in the box for the wires.

I need to kick myself for not responding to your idea of changing the 20 amp breaker with a larger rated breaker, and the answer is absolutely not.

The low voltage wiring is protected by a automatic resetting device in the transfomer, and any fault in the LV wiring should stop there.

Thank you for the help. I'll replace the GFI (I have a new one that they left me when the house was built last year) and the breaker. I'll update in a couple days.

I replaced the GFI and the breaker. Been working great for the past week so I guess that fixed it. Thanks!