Archive for the ‘Transformer Load’ category

Calculate the Load

March 5th, 2010

These multiple tap landscape lighting transformers have built in secondary circuit breakers connected to the commons (COM). Each circuit or COM can handle up to 25 Amp or roughly 300 watts each. If a circuit exceeds 25 Amps you will likely overload the circuit and trip the breaker.

To illustrate:

A) 300W transformer has one COM and can handle up to 300 watts

B) 600W transformer has two COMs and each COM can handle 300 Watt (2×300=600)

C) 900W transformer has three COMs and each COM can handle 300W (3×300 = 900)


  • Add up your fixture’s total wattage and divide into 300 Watts (25amp) maximum per circuit
    • 40 fixtures @ 20 watts each = 800 watts. Requires 2.6 circuits or 900 watt (3 circuit) transformer
    • Select your cable/wire