CSLB C-27 Landscaping ContractorHardscape and FeaturesMedium
A landscape contractor is designing a low-voltage lighting system for a client's backyard. The total wattage of all planned fixtures is 300 watts. The contractor plans to use a 12-volt system. What is the minimum amperage rating required for the transformer to safely power all the lights?
- A30 amps
- B15 amps
- C20 amps
- D25 amps
Show answer & explanationAnswer & explanation
Correct answer: D. 25 amps
To calculate the minimum amperage, use the formula Amps = Watts / Volts. For 300 watts at 12 volts, Amps = 300 / 12 = 25 amps. It's always good practice to size the transformer slightly higher than the exact calculated load to allow for future expansion or voltage drop, but 25 amps is the minimum required.
Why the other options are wrong
- A. 30 amps (30 * 12 = 360 watts) would provide a buffer, but 25 amps is the calculated minimum.
- B. 15 amps (15 * 12 = 180 watts) is insufficient for 300 watts.
- C. 20 amps (20 * 12 = 240 watts) is insufficient for 300 watts.
Ohm's Law for Low-Voltage Lighting
A fundamental electrical formula (Watts = Volts x Amps) used to size transformers and wires for low-voltage lighting systems.
- Watts (Power) = Volts (Voltage) x Amps (Current).
- Used to determine required transformer amperage.
- Ensures safe and efficient system operation.
Memory trick: Watts are the POWER, Volts is the PUSH, Amps is the FLOW. Power equals Push times Flow.