Tuesday night, I got to study first hand the loss of heating ability at various parts of my kitchen range, verses at the pipe.
My range is basically a firebox inside a big cast iron box (over 45 square feet) that I can channel the heat to different parts before it gets to the stove pipe. In affect, I can change the size of my range, to three different heat radiating areas, by simply moving two internal dampers.
The other night the girl friend had to work late so I made dinner (and we survived it too !
It was still 50 degrees outside and standing at all that hot cast iron up at cooking temps was getting a bit much. The kitchen thermometer said it was in the low 80 degrees.
I always use the IR gun to check the temps of the various parts of the stove top while I'm cooking to see if they are hot enough, or too hot, for what I'm cooking. Much more accurate than using the old time spit-gauge !
To cool the kitchen a bit, I left the stove in indirect mode and reached down and shut the dampers to the water reservoir jacket. That reduces the heat radiating area of the stove's outside surface by about 7-1/2 square feet. With those dampers closed, that sends all the flue gas heat around the oven, then on to the stove pipe instead of splitting it between the oven and the reservoir jacket.
To keep the stove top cooking temps up where I had them, I didn't make any change in the primary air damper, or the MPD setting.
As I was cooking I noticed the stove top temps stayed the same, but within about a half hour the kitchen had dropped back to 75 degrees. I thought maybe it was getting colder outside. Checked the outdoor thermometer and nope, still holding at 50 degrees.
The mano reading went up from .04 to .05 as the draft got a bit stronger from higher heat going to the stove pipe. The pipe temp only went about 10-15 degrees.
So, without changing primary or MPD settings, if adding heat radiating area away from the hottest parts of the stove should take heat from there making those hottest areas colder, why didn't the stove top temps drop ?
And if the heat went up the pipe instead, why, with the loss of that extra 7-1/2 square feet of stove heat radiating area of the water reservoir jacket, did the pipe temp go up such a small amount , yet the kitchen got cooler ?