Wood Furnace Backdraft Damper Fabrication - Sheet Metal Hack

A pair of interlocking dampers are fabbed and installed inside a short length of duct in preparation for installation between a new wood furnace and an electric air handler. When the job is complete, this set and the set of dampers previously installed above the electric air handler will be fully automatic in operation. This set in the wood furnace duct should power to the closed position so any time electric heat or air conditioning is in operation, the supply air pressure will be blocked from blowing backwards to and through the wood furnace. We want them 'powered' in the 'closed' position for the simple reason that we want them to spring to the open position during a power failure to the home. IF there happens to be a large fire going during a power failure, there will still be excessive temperature reached in the supply air plenum without the blower running...BUT... if the dampers are open at that point, the heat can slowly raise into and through the ducts via radiation and natural occurring thermal currents due simply to the difference in temperature from one space to another.
That's getting ahead of what we are doing in the video though. This is a difficult build but at the same time a simple build. Simple in concept, but difficult in application because of the adjustments required for smooth operation. The bigger issue however will the the control scheme. Without a programmable digital controller it will have to be done electro-mechanically through relays.
Yes, you will see a little leakage around the ends of the dampers, but no worry....compared to what is normally installed in these applications this is a very good way to block the backwards airflow.
No, I don't get the actuator installed in this video. I haven't even checked the stock pile yet to see if I have a used one in stock.....There's about 3 or 300 reasons why I hope I DO have a used one. If I do have to buy a new one it will probably be a 24vac Belimo spring return actuator. The worst case scenario is to have to purchase TWO of the actuators, but we are going to attempt to be successful with only one. I've fabbed both dampers to operate in the same direction and that is clockwise to open. Hopefully the correct linkages can be connected together to cause simultaneous rotation with one actuator.
Stay tuned, the whole project will be coming up soon, but in the mean time there will be a ton of videos highlighting some serious 'fitting' work. This was a challenging project from start to finish !!
This is not intended to be for any explicit reason other than to show you what I've done with the project and not in any way is it suggested that you do the same thing for yourself. But you may find an idea or two to expand upon to improve for yourself. Enjoy.....