There is a company that makes the product you need right out of the box.
The company is called Hoyme.
The part number is F2. You can get them in 4-8" round duct.
Very easy to install and prewired.
Wired in series with W on both furnaces, motor fails open to allow heat if something goes wrong.
Im a bit confused the previous threat of wiring it to the w-c would be correct to have it open for heating. It sounds like you are talking about combustion air and dampers if this is the case this is a life safty issue and you would really have to look at manufacturers suggestions. For makeup air in the boiler it is not unusual to have a tie in to the burner contact point on each boiler to open the dampers.
My boss ask if two furnaces can control one damper independantly. I have not seen the job but was told there is one fresh air inlet that is piped into two seperate furnaces via the return duct. This air damper is to open, only when at least one of the two furnaces are running, does not matter which, and to be open when both are running. The furnaces are not twined, each have a seperate T-Stat and control different rooms. How can I control this damper with two furnaces, but not to back-feed to the furnace that is off?
I'm an HVAC/R service Tech! Just have not got enough post to be pro yet.
As previously suggested last year when this thread was created (2) current sensing relays in series with actuator. An independent power source would be preferred in this application due to one or the other being shut down for what ever reason.
For all those that have suggested that it might be a combustion air damper and that you cannot use an actuator with a combustion damper, well you are wrong on both counts.
The combustion air wither provided from an outside air damper or a combustion air fan must be proven before the pre-purge takes place, during the run cycle and during any post purge cycle.
"The bitterness of poor quality remains long after the sweetness of low price is forgotten". --Benjamin Franklin
"Don't argue with an idiot, they will drag you down to their level and beat you with experience". --Mark Twain http://www.campbellmechanical.com