Question concerning the portage and main secondary air

Long time reader first time writer.
I have been looking into the portage and main 250 and I have a question concerning the primary and secondary air system. There is a motor that opens/closes a damper to the opening of the secondary air (the air that goes into the gasification chamber). How is this motor controlled? Is it by a thermostat and if so, where is it or is it by a timer?
I imagine that the primary air is controlled by the water thermostat and the fan turns on when the water is calling for heat. The motor keeps the damper shut until the heat in the chamber reaches X or a timer that times out and the motor opens the damper to allow the air into the chamber thus igniting the gases.
Can anyone help me out with this?

I bought a P&M 250 this summer and the motor opens the damper to both the primary and secondary air. This motor turns on with the fan. The primary and secondary air both flow at the same time, but there are separate adjustments for each.

Did you end up purchasing this unit?

I did not purchase one. I was in the process of building one but I have heard so many negative things about the gasification models that I have turned my attention to improving the stove I already have, a Taylor 450. It has been a great stove and I know how to work it. So my intentions are to improve it some with different additions and go from there. Thanks for the response.