how to size a 120VAC to 24VAC transformer

[Saint Germain]

Hello All,

I need to size a step down transformer for a CCTV system. Until now I have only worked with DC circuits and power supplies so I am not familiar with the VA or KVA ratings of the transformers. I have some cameras that are specified with a wattage and some that are specified with VA, all operate on 24VAC. How do I perform that math to figure out what size transformer I should supply?

I have the following:
7 cameras that are 24VAC, Max 60W (120VA)
4 cameras that are 24VAC 73VA nominal

Is it as simple as this?
7 x 120VA = 840VA
4 x 73VA = 292VA
840VA + 292VA = 1,132VA
1,132VA x 1.25 (room for expansion) = 1,415VA or (1.5KVA Transformer)

 

[charlie b]

I am closing this thread, in accordance with forum rules. This forum is limited to electricians, electrical contractors, electrical inspectors, electrical engineers, and other members of the electrical profession. We are not allowed to assist persons who are not members of the profession. If I have misread the situation, if for example you are licensed as an electrician, then send me a Private Message to explain the circumstances, and I will reopen the thread, with an apology for the delay and inconvenience.