Landscape Contractor
Prepping for Installation: Calculating Your Project Load Size
From transformer to fixture selection to calculating your voltage drop, we've laid out the steps to make sure your fixtures have the power they need to light the night right.
Selecting Lights
Determine the preferred color temperature, beam spread, and lumen level for each application.
Determine the type of light you would like to use: drop-in, integrated LED, or adjustable integrated LED (VLO).
List the wattage and VA* (volt amperage) for each fixture in the system.
Choosing a Transformer
Add the VA values of each fixture to determine total VA of the system.
The total VA value of the system should not exceed the wattage value of the transformer.
Example: A system totaling 300 VA should use a transformer rated with at least 300 Watts.
Location Considerations Landscape lighting transformers can be placed inside or outdoors, but always within 8 feet of a standard GFCI outlet. Ideally a transformer should be on its own breaker circuit to ensure consistent power is provided to the system. Another important consideration is that the installation be at least 12” above ground level and at least 10 feet away from any pool or pond. Use gray electrical conduit to run wires from the transformer down to the ground. Also ensure the conduit is buried 6 inches underground in compliance with national electrical code.
Transformer Control Options
Photo Cell – Sensor turns lights on when it gets dark and off when it gets bright outside.
Mechanical Timer – Uses traditional pin setting to automate on and off sequencing.
Digital Timer – Program on/off times for each day of the week and automatically adjusts for daylight savings time.
Smart Control (Wi-Fi) – Schedule and control your lights from your phone or another Wi-Fi enabled device.
Calculate Your Voltage Drop
Utilize the voltage drop calculation below to select the appropriate cable gauge and to determine the voltage that will be delivered to the last fixture on your wire run. This calculation should be done on each cable run to ensure safe and effective operation.
Voltage Drop = (2 x Length of Cable x Total VA on Run) / Cable Constant
End Fixture Voltage = Transformer Tap Voltage – Voltage Drop
Length of Cable – The length in feet of an individual wire run.
Total VA on Run – The total VA of all fixtures that will be installed on an individual cable run.
Cable Constant – Predetermined value (see chart to the right). We recommend starting with 12 gauge and adjusting to a larger cable if necessary.
End Fixture Voltage – The outcome of this equation (above) should be greater than 10V to ensure effective operation.
Transformer Tap Voltage – Varies by transformer and can be 12V, 13V, 14V or 15V.
Note: We don't accept responsibility for any misuses or misunderstandings of the wire size calculations. We always recommend utilizing a voltmeter to confirm your calculations.
What if your number is less than 10V?
If possible, select the next highest voltage tap and recalculate.
Decrease the load (eliminate fixtures) on the wire run and recalculate.
Increase the wire gauge and recalculate.
*The VA for each product or lamp is listed with the product specs.
Installation Process
Begin by removing the transformer door. Then measure 12” above the ground and mark where the bottom of the transformer should sit. Next, determine which knock-out you want to use on the bottom of the transformer. This is based on the best hole for the wire(s) to come through. If you had all wires going out to the right for example, you may want to use the right-hand side knock-out. There may also be obstacles that you are trying to avoid.
After you have determined the knock-out you want, mark the position at the top keyhole slot location followed by the slot location at the bottom and top of the transformer. Next, drill .125” pilot hole or .250 hole for anchors if installing into drywall. Secure the transformer by adding and tightening the screws. Once the transformer is secure, add any accessories. The last step in this part of the process is to install the wire and reinstall the transformer door.
Connecting Wires
If you have multiple wire runs, a helpful tip is to create a small “flag” with different colored electrical tape to make troubleshooting easier. Also document each run with the number or color of the tape, the location or zone of the wire run, and the total load of each run on the sticker inside the transformer.
Check to make sure all fixtures on each wire run are operating within the 9-15V range.
When inserting wire into the terminal blocks and common, be sure to unscrew the screw all the way to fully open the connection; then insert the wire and finish by tightening the screw to ensure a firm connection.
Helpful Tools
120V GFCI, AC outlet
Tape measure and pencil
Drill and drill bits (diamond tip if drilling concrete)
2 anchors provided with the transformer
Screwdriver
Wire strippers
Still Deciding Which Lights To Use For Your Project? View our entire portfolio of lighting options.