My old attic fan finally broke and I replaced it with a smaller model that was properly sized for the exhaust opening.
The problem is that now the louvers which used to be blown open by the grossly oversized fan only open a little.
I can open them manually, so I'd like to find something to help me open the louvers when the fan comes on and close them when the fan turns off.
I thought of trying to use a zone valve assembly, because when the valve is powered up it turns about 1/3 and them stops. I've looked around at actuators which open and close dampers, etc. but I'm hoping someone has done this already to short-cut the whole research aspect of this project.
If the dampers are, or can be, connected to a common shaft that turns one way to open them, and the other way to close them, then a fire damper actuator would be one solution.
This is a small motor that turns a shaft one way when energized, and when de-energized turns it the other way via a self contained spring. Typically they're connected to the fire alarm system in commercial buildings. When the system is normal, the actuators are energized, and air can flow through the heating ducts. Upon fire detection, the actuators are de-energized, and the fire dampers close, thus preventing the spread of fire and smoke from room to room through the ducts.
They can be connected in any configuration, in your case, simply connect the electric part of the actuator to the fan motor (downstream of the thermostat), and the mechanical part so it opens the damper when it is energized. I've connected many of these this way where an emergency generator is installed inside of a building and a damper is installed between the radiator and the outside.
Any commercial heating guy would know what these are, and where to get them.