How does Water Column (draft) work? Just measured my M55 insert.

[steveg_nh]

I just measured the damper/draft on my M55 insert after the stove ran for 3-4 hours on setting 5. She was good and hot. I assume that's not a problem, the manual just said wait one hr, not "only 1 hr", so I assume they just wanted to be sure it was hot enough inside to get a good measurement.

Anyway, it was pretty close to where it should be (between neg 0.15-0.17 WC), I tweaked it just a bit, and it's hovering right around the middle of the range, at 0.16. By the way, whoever recommended just using a ball inflation needle on the end of the hose as the best way to access the vent access hole is genius! That worked fantastic.

Anyway, I got it dialed in, and then turned the stove down right after. Within only a minute or so of turning it down the flame had quickly died off, so I took another measurement, and now was seeing WC of around 0.19-0.20. So does that mean draft is weaker when the flame is smaller? I'm not sure I understand how this works, and I'm curious to learn. Why measure only at high heat? Is that always the best measurement?

I also assume that the fact that the WC did in fact change once the stove was turned down, is totally to be expected.

Anyway, thanks for the lesson ion advance. I like learning new stuff!

 

[F4jock]

I just measured the damper/draft on my M55 insert after the stove ran for 3-4 hours on setting 5. She was good and hot. I assume that's not a problem, the manual just said wait one hr, not "only 1 hr", so I assume they just wanted to be sure it was hot enough inside to get a good measurement.

Anyway, it was pretty close to where it should be (between neg 0.15-0.17 WC), I tweaked it just a bit, and it's hovering right around the middle of the range, at 0.16. By the way, whoever recommended just using a ball inflation needle on the end of the hose as the best way to access the vent access hole is genius! That worked fantastic.

Anyway, I got it dialed in, and then turned the stove down right after. Within only a minute or so of turning it down the flame had quickly died off, so I took another measurement, and now was seeing WC of around 0.19-0.20. So does that mean draft is weaker when the flame is smaller? I'm not sure I understand how this works, and I'm curious to learn. Why measure only at high heat? Is that always the best measurement?

I also assume that the fact that the WC did in fact change once the stove was turned down, is totally to be expected.

Anyway, thanks for the lesson ion advance. I like learning new stuff!

Not exactly sure what you are asking but yes, draft decreases as firing rate does. Also. Did you go from negative inches of WC to positive? If so you should have had mucho smoke in the room if you were measuring in the right place.

Suggest you search measuring chimney draft for more detailed explanations.

 

[steveg_nh]

It went from negative 0.16 to negative 0.20 (I rounded) as fire size decreased.

 

[F4jock]

It went from negative 0.16 to negative 0.20 (I rounded) as fire size decreased.

Something is screwy then. The hotter the gasses produced by the fire the stronger the draft should be. Due to the heated air and airflow the chimney should have less pressure than the surrounding atmosphere thus a larger negative number means a stronger draft. If I read your data correctly your draft seems to have increased as the flame died. If this is true it appears to me that perhaps your measurement point is incorrect.

 

[steveg_nh]

But if the flame has died off but the fans/blowers are running at the same speed, draft would be higher no? I guess my question is that it is normal to have different readings and different temps/operating levels?

 

[F4jock]

But if the flame has died off but the fans/blowers are running at the same speed, draft would be higher no? I guess my question is that it is normal to have different readings and different temps/operating levels?

Yes it's normal to see operating differences but given the decrease in flue gas temperature as the fire decreases and assuming constant fan and blower speed the draft should decrease. Whatever. If it works well be happy.

 

[steveg_nh]

Interesting. So no idea what was happening.

 

[F4jock]

Interesting. So no idea what was happening.

What you need to do is research chimney draft to undetstand. I'm an Engineer. I work on hard data. When the conclusions of an experiment seem wrong the first thing to do is to question the conditions under which the data was obtained. Unless you didn't describe them completely you've defied a few laws of physics and thermodynamics.

 

[ohbix]

Did you wait long enough to allow the stove to equilibrate at the lower setting? It would have a smaller flame, and the exh fan would be at a slower speed. I too am curious as to your readings at different heat levels.

 

[railfanron]

Good call Chickenman!
Ron

 

[steveg_nh]

Did you wait long enough to allow the stove to equilibrate at the lower setting? It would have a smaller flame, and the exh fan would be at a slower speed. I too am curious as to your readings at different heat levels.

No, I don't think I did. I will read again today.

 

[steveg_nh]

Ok I feel silly. I think I just didn't wait for things to settle down when reading it before. I just rechecked and on low (it had been on low for a while), my reading is still 0.16-0.17 WC. It didn't increase.Sorry. I feel like a dope.

 

[F4jock]

Ok I feel silly. I think I just didn't wait for things to settle down when reading it before. I just rechecked and on low (it had been on low for a while), my reading is still 0.16-0.17 WC. It didn't increase.Sorry. I feel like a dope.

Don't feel bad, just learn as we all have and still do.

 

[Doug Doty]

My ussc stove will raise from .22 to .28 going from high to low. I am going from memory but I have my Dwyer meter mounted on the wall behind the stove and monitor it all the time. Hotter or larger fire lowers my W.C. readings. In fact it draws .5 before the fire lights and will get as low as .22 when at the hottest.

 

[steveg_nh]

Interesting...Hey I just read your signature...what are you not impressed about, on your stove? Not to sidetrack my own thread.

 

[Doug Doty]

It has been pellet finikey and as a result I have had to work on it a good bit and found poor fit and finish inside and out. Other than the auger being rough and covered with burrs that were grinding on the pellets nothing functional. The motors on the combustion and circ. look very cheap compared to all other brands but that is just impression and they will hopefully prove me wrong. Very open and easy to work on though. It is throwing great heat and doing 1900 sq. feet at 10 degrees last week so not over all disappointed for the price of it. some sour grapes since I would if either bought used or paid the extra and got a P68 in the beginning.