KLook wrote:Yeah, I can accept that Paul, I have seen plugged exhausts. Happens in chainsaws also with the build up in the muffler of exhaust port. Still, If it can't get out, it can't get in. It can't be magic. If a wide open MPD equals a *500 fire, then shutting it down will equal less then that. It make take a little time, but it will happen. Briefly, you may see a temp spike as the heat is prevented from flowing out the pipe, but very soon the fire will quite down and loose temp.
I'm not talking "if", but "how much" ?
And yes, my little range will slow down with the MPD fully closed
. But I'm not talking about the MPD being on, or off. I'm talking about matching the MPD to whatever the primary damper setting is that I happen to be using.
With the MPD partially closed to get the draft to it's sweet spot of .04, for whatever the primary is set to, it does run hotter and the stack runs cooler. Open the MPD fully and the stack gets hotter, but farther down stream within the stove (my range is a base heater in disguise) the oven and water tank jacket run cooler, but the plates over the fire box stay the same temps.
I was put onto the idea of testing to see if it has a draft/MPD sweet spot when I was trying to find ways to get the oven temps higher. I read some old kitchen range operating instructions and one of the recommendations is to use an MPD and partially close it. Guess what? It works. The oven gained about 25 degrees without having to do any changes in the primary damper setting.
If I turn the MPD down more than .04, the stack temps stay down, but the stove starts to slows down until it reaches the point where it will burn at that air/flue gas flow rate. Open the MPD more than .04, and the temps climb in the stack more than in the stove, again without changing the primary damper.
In other words, there's a fine line between where I can choke the stove just using the primary, but heat more easily goes up the stack, . . . and the point where, if I match the MPD to how much the stove is choked by the primary. By matching the MPD to the primary I don't choke the fire, but I do slow the exhaust gas flow. The heated gases stay on the stove side of the MPD longer. The result is, my temp tests show my stove's (I'm not saying all stoves) temps go up more than they will with the MPD wide open.
Each system is unique, so it doesn't surprise me that others may be getting different results.