LED Landscape Lighting: Troubleshooting and Circuit Sizing Guide
LED fixtures dominate current landscape lighting installations for straightforward reasons: lower energy draw, longer service life and more consistent color output than halogen alternatives. In California, updated Title 24 building energy standards now require high-efficacy lighting — including LEDs — in all residential new construction hardscape applications.
Diagnosing and Fixing LED Fixture Problems
LED failures in low voltage landscape lighting almost always fall into one of three patterns: all fixtures out, some fixtures out or a section of fixtures out.
All Fixtures Out. Start at the transformer. Check and reset the circuit breaker inside the transformer housing. If the breaker resets but the fixtures remain off, check the GFCI outlet on the circuit supplying the transformer. If the outlet is live but the transformer still does not produce output, measure voltage and amperage at the transformer terminals. A transformer that receives power but produces no output on the low voltage side has likely failed and needs replacement. Verify that all wires entering the transformer are fully seated inside the terminal lugs and that the lug screws are tight. If the transformer has a built-in photocell, bypass it and test manually.
Some Fixtures Out. Individual fixture failure typically indicates lamp burnout. Replace the LED lamp first. If the fixture remains out after lamp replacement, check the connector at that fixture. Loose or corroded connections should be replaced with copper crimp or heat-shrink connections. If the lamp and connection are both sound, inspect the socket itself — a compromised socket seal allows moisture to reach the contacts.
A Section of Fixtures Out. When a consecutive run of fixtures goes out, the run has been disconnected from the circuit — either through a broken wire, a failed splice or a connection that has pulled apart underground. If systematically checking lamps, connectors and sockets does not restore function, the wire itself may need to be traced and tested for continuity.
Circuit Sizing: How Many Fixtures Per Run
The number of fixtures on a circuit is determined by the fixture load and the acceptable voltage at the last fixture on the run. The National Electrical Code limits circuit loading to 80 percent of the transformer's rated output. A 150-watt transformer can support a maximum of 120 watts of connected load.
Do not design runs as a daisy chain — run wire from the transformer to a central point in the zone and split the circuit from there. This T-feed or home run configuration maintains more consistent voltage across all fixtures.
For longer runs or systems with high fixture counts, multi-tap transformers are the appropriate solution. These transformers offer output taps at multiple voltage levels (typically 12V, 13V, 14V, and 15V), allowing the installer to compensate for voltage drop on longer runs by selecting a higher starting voltage.
After installation, verify voltage at each fixture with a voltmeter. LED drivers tolerate a range of input voltage, but operating consistently at the low end of the range reduces lumen output and can shorten driver life.
