I only have to think about the volt amp rating if there are many devices on the circuit. 50VA is what we carry around and its over kill for most applications. When I used to install XCI zoning systems I would have to calculate the volt amp draw if there were more than 4 zones. For instance each thermostat might be 2VA at most, and each damper actuator 3VA. So I would just add them all up and be sure I had more than enough VA.
How did you know to install a 50 VA transformer not a 70 or a 10 VA thanks .
I only have to think about the volt amp rating if there are many devices on the circuit. 50VA is what we carry around and its over kill for most applications. When I used to install XCI zoning systems I would have to calculate the volt amp draw if there were more than 4 zones. For instance each thermostat might be 2VA at most, and each damper actuator 3VA. So I would just add them all up and be sure I had more than enough VA.