Maybe 3.7amps is the vacuum's draw. Just looking at the diameter of the power cord leads me to believe it can handle 20 amps. My CT33 has a 20amp plug and is plugged into a 20amp circuit and has not problem power any tool.
Also, considering the tool and vacuum packages that Festool sells, you would have to assume they can be used together. I have a wide variety of their tools including the OF2200 and they all work fine with the vacuums. I am not going to look it up to confirm, but I am guessing the OF2200 draws higher amperage that any of their other tools.