[Sean]

Does it matter if ac or dc?
Thanks again

I'm not sure what you are asking about. If you are asking about the transformer voltage then it is AC. If you are asking about the capacitor voltage rating it should be rated for DC voltage. AC voltage is generally shown as the RMS value. To find the peak voltage that the capacitor would see which is what you would want to use to determine the voltage rating of the capacitor you multiply the RMS value by the square root of 2 or 1.414. For 24VAC RMS the peak voltage is 24VAC * 1.414 = 34V. Of course this is only applicable for a sinusoidal AC signal like you get from your wall outlet.