Observation, Commentary. Notes, Tips, Humor and Resources


VA in equals VA out.

A simple calculation for electrical current draw in appliances and air conditioners

VA's are VA's. VA in equals VA out. For the purposes of the technician in the field, just remember the VA's going into a transformer are equal to the VA's coming out.

For example: How much current does a standard 40 VA transformer pull? The answer can be determined by determining how much current it provides. The primary voltage is 120 and the secondary voltage of a standard air conditioner transformer is 24 volts, and the max rated output is 40 VA. It could provide less than 40 VA but will burn up if asked to provide more than 40 VA

So, using 40 VA in this example, the primary amperage maximum is 0.33 amps (120V times 0.33A = 40VA) and the secondary amperage maximum is 1.75 amps (24V times 1.75A = 40VA). A technician could safely wire up to 36 of these 40VA transformers on a single 15 amp 120 volt circuit - allowing for an 80% load factor

Yes, the term 'VA' stands for Volts times Amps. Volts multiplied by Amps is also the classic definition of a Watt.