How Critical Is .04-.06 on the Manometer?

Coming back to the well for another drink of the knowledge of the experienced here.

The Harman has been doing a fine job keep the house warm. I have been using a good 50 pounds a day, maybe just a little more. The baro has been set on 5 or so until now. The fires have been running between 500 and 550 generally speaking with 200-210 stack Finally got the namometer set up and need to know if I am headed in the proper direction.

With the fire good and banked, and fully lit, with the temps running around 500-550 with a stack right around 200, it is almost impossible to get down in the .04-.06 range. To get there the baro is open at about a 45 degree angle with the weight set around the 4 mark. This seems like rather excessive amount of heated air going up the chimney. This is a new chimney. It has a good 28' of 8x8 liner, is 28" above the roof line at the peak, and draws very very well.

Did I do the right thing here. What I am doing now is I set the weight back to six or even just a little higher, and I have cut the damper down on the stove from 1.25 turns to just a little over 3/4's. The manometer is reading generally .08, the stove is still 450-550 and now the stack is 175-190, running just a little cooler. I seem to be getting a little more heat or at least the same, and consume the same amount of coal as before this change in operating perameters. Not concerned about the amount of coal, that seems about right with temps low 20's at night and just above freezing during day or even a little colder over all. Does this seem like a reasonable setting for a chimney that draws pretty strong?

My other question is if I do need to open the baro up to get the manomerter down, is it advisable to route colder air to the baro with a small ducting system. I will agroengineer this with now problem. All I want to do is get it to pick up colder air from near the window, but not an open outside source. Currently the baro points to the front of the stove. Would it be okay just to turn it to the side where not as much heat is rising straight up or would the duct be better?

Thanks in advance for all the help.

I think "critical" is a relative term. Your critical may not be the same as my critical. It sounds like you are happy with your stove temperature performance and not unhappy with the coal consumption and burn time you are getting so I don't think getting your draft down to .04 is "critical".

You may want to tweak your setting a little to try to lower coal consumption a bit, but that falls under the category of "not being able to leave it alone" of which I am a proud member!!

Your idea of turning the baro so that it is pulling air from the side and not directly over the stove has merit. But you have to promise to record the temp differences you see on the flu pipe from one config to the other so us temperature geeks can get our fix! I don't think pulling air from closer to a window would do much more than just turning the baro unless there is a large temp difference near the window.

If your baro doesn't open enough by pegging the weight and there is still room for it to open, some have added a washer to the weight to get it to open further. If it is already open as far as it can go and you can't get below .08 others have installed a larger (7" or 8") baro onto the 6" pipe with adapters or installed a second baro to cut down on draft through the firebox. I think you are on the good side of the problem, though...too much draft rather than not enough draft.

Have fun experimenting!!

Harman recommends -.06" to -.10" WC, I found that my stack temps were running too high at that setting. I run it at -.04" to -.05" WC.
I wouldn't be too concerned about how much room air you lose through the baro, the benefit of the baro damper in the amount of coal saved and efficient stove operation far outweighs any room air sucked into the baro. Unless your house is very air-tight you don't need to vent any air into the house. As a matter of fact the barometric damper does a balancing act between the air pressure inside your house and conditions inside the smoke pipe. Ducting any outside air to or towards it will disturb it's operation.
It sounds like your chimney drafts like mine, my baro on the Harman is always way open, sometimes it hits the stop.
I'd set the draft to around -.05" WC and enjoy the heat.

The Baro is pulling 70* air from the room, the hot air in the flue pipe is ~200*,, so which one do you want going up the chimney?? Without the baro, I'd guess the flue temp would rise to 300+*.

You can use the baro to 'fine tune' your burn.. If you reduce your draft to .05 with the spinner still at 3/4, does the stove temp drop? or only the flue temp?

I think you are 'in the ballpark' with your settings.. When the wind starts to blow strong, your baro will do it's job and keep your draft and your heat output from the stove stable.

Greg L

[You can use the baro to 'fine tune' your burn.. If you reduce your draft to .05 with the spinner still at 3/4, does the stove temp drop? or only the flue temp?

Greg,

If I set for .05 and 3/4 turn I am lucky to keep above 300 in the stove. To get that low a setting the baro is open almost completely, and then I seem to loose the draw of the chimney almost all together. Stack drops below 150 at the .05 also. I thought it was just the reading coal giving me these temp drops at the above settings, but it is doing it on the blaschak also. It seems like this chimney really likes to draw very strong!! Better than having the problem the other way with not enough draw. Today is an extremely windy day here so it is not a good day to play with settings. In the current wind around 20 or so, the baro is completely open and it still holds .1 to .12, I just cannot get it any lower in this wind.

Wow, you have a really good chimney. Just to check, have you pulled the tube off the manometer and checked that it still reads 'zero' when unhooked?? The manometers need periodic 'zeroing'. I'm not sure if it's temperature changes or atmospheric pressure that causes the changes. but It helps to check the zero ocassionally.

If you your stove and coal likes .06-.08" and won't pull enough air through the fire to make heat on less draft, then that's what your stove likes !! Like 'Freetown Fred' likes to say, 'just like a woman, find out what she likes, and stay with it' . So if that's what your stove likes.. stay with it.

Enjoy the heat..

Greg L.

I have to agree with titleist.
Given the information you gave, I don't see any need to sweat what you are already doing.
I doubt you would ever see a measureable difference in droping your draft .01-.02..
500-550 with a stack a tick under 200.. that doesn't sound 'wasteful' at all..
Sounds pretty darn good to me!

You are going through around 50# a day...
I just don't see that to be horrible.

Dan

I have been tinkering with the stove again trying to tweek it out. I did not explain a few points as why I am concerned about loosing a lot of hot air up the baro. I have an extremely short hook up to my chimney. There is an 8" thimble through the stone wall, 6x8 adapter, 6" elbow, baro which is about 12' long which points to the front of the stove, 12' stove pipe, and then the stove. It seems that since the baro is so close and in the heat rising off the stove, I figured I was loosing a good bit of heat up the chimney. Most of the other set ups I have seen the baro was at least a reasonable distance way from the direct heat of the stove. I have turned the baro 90 degrees to the side, and sleeved a piece of 7" round over top of it. This does not interfer with the movement of the baro, but now it is not drawing out of the really nice warm air over the stove, but rather cooler air from near the window. BUT it is not drawing outside air. I can reach inside the 7" if needed to adjust the baro. I did check the manometer and it is still properly zeroed.

The stove was banked about an hour ago. Stove is running 500-550, stack before the baro is 300 plus, above the baro is under 200, mano is reading .08-.1 (windy day outside ). The baro inside the sleeve is cool to the touch ( it was not cool at all before this change, you could not keep your finger on it for very long), and the amount of air going through that baro, well WOW!!! At least I think I have tweeked it in a reasonable fasion for this particular chimney and stove. I will be anxious to see if I get more or less heat out of it this evening, calling for low of 20.

I have a keystoker 70,000 handfired stove running off a interior stainless steel (except for the last 6 feet. The chimney runs thru a older two story house and is 8 inch. I keep my draft set at .02 all the time and it gives off plenty of heat.
If I ran my stove at .05 to .06 my coal usage would increase alot and I wouldnt be able to sit in my living room it would roast you out.
I also have a manual damper which is 6 inches above my stove and after that in line is the baro.

The purpose of the barometric damper is to obtain uniform draft, not any particular number as long as it is high enough to supply the minimal requirements of the stove. Once draft is uniform over a wide range of outside conditions and stack temperatures, you can set the air input to the stove with confidence that a particular setting will result in the same output and not vary with outside conditions.

Yes my stove stays very consistent,as far as minimal requirements of stove wouldnt that change with every installation??

mina678 wrote:Yes my stove stays very consistent,as far as minimal requirements of stove wouldnt that change with every installation??

No. the requirements of the stove are set by its design and remain the same no matter where installed. A stove with a very deep bed of coal or with convoluted flue passages will need a higher draft to operate than a simpler stove, and that would be so no matter where installed.

I agree that every stove would be a different beast ,But again my consumption and heat output seem to be right on at .02. My bimetallic damper in the back of my stove responds to air temp and opens and closes to maintain a constant temp.

mina678 wrote:I agree that every stove would be a different beast ,
But again my consumption and heat output seem to be right on at .02.

Then that is where you should run it...

Most of the stuff in manuals, is printed for the 'average' consumer.
That doesn't mead that you cannot find a sweeter spot in there someplace
to make your own appliance work better.
Or at least make you happier...

If Harman for example says you should run your stove at .06,
that doesn't mean it won't run good for you at .04.
Or... .08.......

Dan

My Mark III stays at .04 most of the time, unless it's either in the single digits outside, or real windy. I set the baro on the oil boiler to .06 ... so if there's a big wind gust, the stove never gets hit with anything much over .06. Has been working fine for me for years.