Hi back again,
In the project house I wanted to have an old classic looking cast iron stove, but we have a HRV system (Heat Recovery Ventilation). So to have an open chimney with this type of system would not really work. Plus open to the elements & probably a 20% heat loss up the chimney.
So I wanted a sealed chimney, that I could open & close when needed. I did the typical search on the internet and came up with 3 solutions that did not suit my situation.
The 3 solutions that I found, both had the same method of opening the sealed chimney cap. It is a wire dropped down the chimney flue and is pulled and locked into position to open the chimney cap. This is an adequate method for an open fireplace, but will not work for a stove.
So we had to build our own solution. First we welded a flange to a twin lined insulated stainless steel flue and installed this in the opening for the chimney. This was purposely keep below the roof line. We then built a mechanism that would hold the cap. This moves up and down to seal the chimney. It is spring assisted up open. This mechanism is controlled by a 6mm rod that goes from the mechanism to a wall mounted control handle next to the stove. This handle is on a toggle arrangement, so locks in the up position or down position. In the opening for the chimney a steel flue with a weather sealing flange welded to it was installed. The diameter of this pipe was apx. 20mm larger than the twin wall flue. When installed the twin flue lapped the steel flue apx. 50mm. (See Diagram Below)
This was caulked with high temp silicone to seal the flue. This also provides a thermal break in the flue. The cap has 2 steel bands welded under it to hold the chimney seal in place.
Job finished, the mechanism works great, just life the handle to open the chimney cap. Your hands stay clean, they are independent of the stove.
That’s it, all the best,