Cooking breakfast with it 12 below zero outside, and a balmy 75F in the kitchen.
With such biter cold causing a very strong draft, I thought it would be a good time to experiment with letting more heat out of the range and see what that does to stack temps. Many of you with ranges know that propping the oven door open helps get more heat out of the range. But, ranges that also have a water reservoir are kinda rare.
For those without the adjustable oven door shelf like Kevin's Glenwood Model E has, that slides to hold the door open at any angle you choose, here's a picture below of the antique way to hold it. A small sad iron makes a very nice weight for that. With the door open part way to let out some of that heat before it gets to the chimney, that lowered the stack skin temp about 10F.
After that test, I closed the oven door and let it all come back up to temp. Then I tried leaving just the water reservoir tank lid open . Using the IR gun, when I first opened it, the inside surfaces of the tank were 380F (I don't use it for water heating). Just leaving the lid open lowered the stack skin temp 15 F.
Then I tried propping the oven door open again while the water tank lid was still open. That only dropped the pipe temp an additional 6 F.
So it looks like leaving the water tank open is better at heat extraction than the oven. The water tank is all copper and large enough to hold 4.5 gallons of water. All that copper is surrounded on all four sides and the bottom by hot flue gases. It is a really good, fast way to transfer heat out of those gases. So it would seem, even better than the much larger oven.
While all this was going on, I had my helper checking temps under the oven, too. Going by the relaxed position, the cat thought it was good.