Hi -- electrical newbie here. I used a mix of old fixtures (that were set up when we moved in) and new ones to reinvigorate our garden landscape lighting. Now I seem to be burning out bulbs way too quickly, and I assume it's my setup.

On each side of the yard, I'm running a low-voltage transformer with an out of 12V 300W Max, with about 75' of 14G wire, and -- on the north side of the yard -- the following lights (totaling up to 117W):

• 12V-11W
• 12V-11W
• 120V-50W (this seems weird, but was one of the pre-existing lights)
• 12V-20W
• 12V/24V-5W
• 12V-20W

Any idea why they'd (especially the 12V-11W and the 20W/12V bulbs) be burning out so quickly? I'm attaching a sketch showing the full setup. Note that there are two transformers (the boxes at the start of the wire), and the problems are happening on both sides.

 

Do those transformers have multi tap voltage selection for output voltage ?

Some high wattage transformers run at an exceptionally high voltage until loaded to at least half their rated wattage. Many of those bigger transformer have a selectable output voltage means where you can lower the output voltage.

You could check the voltage at the transformers with the lights connected to see what the actual voltage is with the lights connected.

 

I don't think so... it seems to be fixed. Attached is a shot of the back of the transformer if this helps.

 

Check the area where the low voltage wiring connects.

 

That 50w 120 volt should not be on that system. Are you sure you are correct?

Looking at your diagram it looks like you have a loop. Is that correct? Are you running the lights in series?

With low voltage lighting, voltage drop can be an issue. Many cases manufactures recommend #12 or #10 wires. Can you measure the voltage at each light?

 

I took that as a misprint for 12v. A 120v bulb on a 12v transformer won't even light up.

 

Whoops -- you're right. Not even sure how I mis-recorded that one. It's actually 12V-20W, so the total is 87W on the line. The wire isn't a loop, and the individual lights are connected directly to it.

• 12V-11W
• 12V-11W
• 12V-20W
• 12V-20W
• 12V/24V-5W
• 12V-20W

PJMax, below is a photo of the bottom of the transformer, which is the only thing that I identified that could have given me any choice (re. the multi tap voltage selection question.). I tied the new wires into the same spots the old wires were in. The lack of a label made it hard for me to know what it was...

I'll pick up a voltage meter this weekend to check that answer... (And thanks guys!)

 

That may be a dual output transformer where the center is the common. Without a model number.. a meter would be needed to check the voltage. A basic analog meter from a home improvement store is fine. They run $15 or so.

It may be ideal to put all the lights on one transformer.
I see they're on opposite sides of a sidewalk.

 

Looking around, I think this is what I have -- http://intermaticstore.com/~/media/i...s/ml300rtw.pdf -- the Malibu 300RTW. But I'll get a meter. The lights are run on two sides of the tile path from the sidewalk up to the house.

 

That looks like it. This is them describing an overvoltage problem. Unfortunately they don't mention what the transformer should be loaded to for minimum operation.

NOTE: This lighting system is designed to last many years under normal
conditions. However, lamps eventually burn out and operating with one
lamp out can shorten the life of the others. IT IS IMPORTANT TO
REPLACE BURNED OUT LAMPS PROMPTLY.

They tell you in the instructions to use a larger cable size and keep no slack at the transformer end. This is to reduce voltage drop. At this point.... you want some voltage drop. Adding a small coil of wire.... maybe #16.... will introduce a voltage drop.