Puzzled

I set up a 15-inch pedestal fan about two feet diagonally off the back corner of my stove. The fan was centered on the bi-metal thermostat housing on the back of the stove, but of course the air also blew across most of the back of the stove and across some of one side. My theory was, the fan would cool the thermostat and cause the air inlet to open further and accelerate the fire. A secondary effect would be to wash more heat off the stove.

Now here's the odd thing. The air inlet DID open up considerably, but the stove didn't get any hotter. It didn't seem to matter what my starting stove temperature was -- 250, 350, 450 -- the temperature would not change significantly. It wasn't like the fan was extracting extra heat; when I started at 250 degrees the room just got colder and colder over the next hour and the stove was still at 250. Some air was washing over the stove pipe, but the baro was still quite a bit open so it's not like I was killing the draft by chilling the flue.

So what the heck is going on? Why didn't the stove heat up when the air inlet opened more?
Anyone else with a DS Machine circulator want to try this and see if you get different results?

This is an interesting observation... Maybe the air blowing over the inlet on the stove is interrupting air flow into the stove? Maybe you could try shielding the air inlet from the direct air from the fan and see if that makes any difference.

Creating a vacuume or venturi effect over the air inlet?
Turn off the fan and prop open the door to the same amount and see if the stove heats up...
Do not leave the stove while it is propped open...

LDPosse wrote:This is an interesting observation... Maybe the air blowing over the inlet on the stove is interrupting air flow into the stove? Maybe you could try shielding the air inlet from the direct air from the fan and see if that makes any difference.

CapeCoaler wrote:Creating a vacuume or venturi effect over the air inlet?
Turn off the fan and prop open the door to the same amount and see if the stove heats up...

I kind of wondered the same thing but thought I was being silly.
However, I raised the fan so there was no air blowing around the air inlet, and now it behaves as expected. Thanks for the suggestions!

rberq wrote:I kind of wondered the same thing but thought I was being silly.
However, I raised the fan so there was no air blowing around the air inlet, and now it behaves as expected. Thanks for the suggestions!

So how effective is the fan in washing some heat from the DS Circulator?

My thermo controlled hopper fed Surdiac stove responded the opposite of yours. i used to have the fan on the floor off the back blowing across the heat exchanger to extract more heat, but at the same time was blowing "directly" into the intake valve. It kind of "supercharged" the coals and they would burn hotter, (and faster).I now have a pedestal fan up higher that blows across the top of the stove, (and not "into" it) and it works great for moving the hot air into the other rooms.

joeq wrote:i used to have the fan on the floor off the back blowing across the heat exchanger to extract more heat, but at the same time was blowing "directly" into the intake valve. It kind of "supercharged" the coals and they would burn hotter

Makes sense. My fan was blowing across the intake, like the wind blowing across the top of your chimney, so perhaps accounts for the difference.

LDPosse wrote:So how effective is the fan in washing some heat from the DS Circulator?

I'm not really sure. Needs more experimenting. Definitely a heat boost in the first few minutes, but also the air inlet opens more as the heat is washed off. So, is the extra heat over the longer term just the result of burning more coal because of more combustion air? Stack temperature is a bit lower with the fan running, but not a lot, so that says to me I am maybe getting slightly better efficiency? Might be just as well off to shut off the noisy fan and crank the bi-metal thermostat up a little.