Power Supplies / Transformers

I need one of you electronics experts to set me strait.
I've had someone offer me a 110 Pri 24V Sec Transformer at 100 Volt-amps.
Isn't Amps at 24V allot different than Va? I always thought Va was Source
voltage + Amperage. Wouldn't a 110 - 24v 1A transformer be 111Va? This guy
is trying to convince me this or a 20va transformer is what I need. If I
want 15 amps shouldn't it be like 110+15 or 125Va?


John R