Question: how many amps can a 40va 120 volt transformer with a 24 volt secondary carry?
Answer: Knowing that a 40VA transformer will produce 24 volts, Ohms law can be used to determine what amperage the transformer can operate at before burning up. 40 Watts / 24 Volts = 1.66 Amps. This 1.66 Amps is the amount of current that can safely be drawn on the 24volt R or C control circuit wire.