Manometer Readings

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Woodcutter Tom

Burning Hunk
Apr 28, 2019
169
Northern Illinois
I got my manometer today. Dwyer Mark II 25. Filled reservoir and zeroed out gauge. Installed it on wall and connected 10 inches of rubber tubing to 4 feet of 1/4 copper tubing. Connection is shrink wrapped since I have not located a 1/4 compression by 3/16 barb fitting yet. Stuck other end of copper tube into stove pipe about 9 inches above stove top. My stove top to chimney cap length is 14 feet straight up. ----I can drop this to 12 feet.
Today is quite windy. I do not have a fire going. At times the reading is .03 - .05. Then the wind get howling and I have seen the reading as high as .15.
Should I wait for a calmer day to be concerned about the readings?
Should I start a fire anyway and see what happens? (Or should I be on my way to the store to buy a damper?)
I saw FixedGearFlyer's video with his Magnehelic that displays .06 with his furnace running.
I expect more draft with fire burning.

SBI states that I should look for .03 - .05. A reading of .08 would be excessive draft.

Manometer Reading.jpg
 

begreen

Mooderator
Staff member
Nov 18, 2005
90,555
South Puget Sound, WA
A more accurate test will be during a calmer time, but go ahead and start the fire and see what it reads and note the outdoor temp when testing. This will factor in. The results will be more meaningful when it is colder outside. Maybe start a fire around 8pm when the winds have died down and it is colder outside?
 

Woodcutter Tom

Burning Hunk
Apr 28, 2019
169
Northern Illinois
A more accurate test will be during a calmer time, but go ahead and start the fire and see what it reads and note the outdoor temp when testing. This will factor in. The results will be more meaningful when it is colder outside. Maybe start a fire around 8pm when the winds have died down and it is colder outside?
I think I will do that. It is 60 degrees outside now. 14 MPH winds; gust to 25 mph. Forecast calls for 50 degrees at 8:00pm. Same wind though.
Or maybe I'll wait till morning when it should be in the low 30's.
 

JRHAWK9

Minister of Fire
Jan 8, 2014
1,728
Wisconsin Dells, WI
I think I will do that. It is 60 degrees outside now. 14 MPH winds; gust to 25 mph. Forecast calls for 50 degrees at 8:00pm. Same wind though.
Or maybe I'll wait till morning when it should be in the low 30's.

You are not far from us....it's supposed to get cooler the next couple of nights. Calling for teens tomorrow night and low 20's Thursday night by us. May be a couple of good nights to test it out.
 
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MongoMongoson

Member
Feb 6, 2021
213
Wisconsin
Hey Tom, I'm in Kenosha County, WI... working from home watching the laundry trying to blow off the clothesline.

I have been through a similar exercise with my stove setup. I had readings of 0.03 - 0.05 on a calm, cold night with no fire going, but I have a lot more stack above my stove. You should be able to give it a go without much concern, but if this is your first time burning that stove you might not want to fill it all the way... If it is new you should start slow, anyway. At least that's what I do. I like to dry out the firebrick before having a rip roaring fire. Maybe that's an old wive's tale but that's what I always do for the first fire in the fall every year to prevent cracking the brick.

I'm no expert on draft measurement, having only just recently done it... but my understanding is that you should take your draft measurement upstream (so, below, in the case of stovepipe) any draft limiting devices like a damper. If you do run and get a damper, remember that your draft measurement might not be accurate if you put the damper on the outlet of the device and the manometer tube above it.
 
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Woodcutter Tom

Burning Hunk
Apr 28, 2019
169
Northern Illinois
Here are my test results.
Outside temp: 30 F
Wind 4 - 8 mph -- with gusts to over 17 later in test.
Stove top to chimney cap: 12 FT.
Manometer probe was in stove pipe temp probe hole; therefore no flue temps.

Verified calibration.
Started with small fire to get heat in stove.
With no fire the reading was .01
Within 2 minutes of staring, reading was .025.
About 10 minutes in, reading was .06
For next 45 minutes reading was steady about .06 - 065. I did see a spike to .075.
I then raked the coals a bit and added 4 pieces of 4 1/2 " splits N - S.
Once wood started to burn, reading was .07.
It rose to .09 but back to .075 when I slightly closed Primary air.
It stayed around .07 but there was not much fire, so I opened primary all the way.
I adjusted the primary air as I felt was needed.
During this time I saw between .10 and .13. The spikes to .13 were during wind gusts.
Even when coaling, there was spikes to .13.
The STT only got to 440 during this time.

After the coals were burnt down, I raked them forward and to the sides so I had a tunnel down the middle of the fire box.
I added 5 pieces of 2 x 2 ash. E - W.
These pieces started quickly.
Within just a few minutes I closed the door. The reading was .11. STT 330.
Within 3 minutes I saw a spike to .16.
With the Primary air 3/4 shut I had a reading of .18.
The readings would fluctuate between .15 and .17. I did see spikes of .20. That was the highest I saw.

Since SBI states that ideal is .03 to .05, and that .08 is excessive draft, do you think I need a damper in my stove pipe?
Could this be the cause of my low stove heat problem?

 

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MongoMongoson

Member
Feb 6, 2021
213
Wisconsin
Here are my test results.
Outside temp: 30 F
Wind 4 - 8 mph -- with gusts to over 17 later in test.
Stove top to chimney cap: 12 FT.
Manometer probe was in stove pipe temp probe hole; therefore no flue temps.

Verified calibration.
Started with small fire to get heat in stove.
With no fire the reading was .01
Within 2 minutes of staring, reading was .025.
About 10 minutes in, reading was .06
For next 45 minutes reading was steady about .06 - 065. I did see a spike to .075.
I then raked the coals a bit and added 4 pieces of 4 1/2 " splits N - S.
Once wood started to burn, reading was .07.
It rose to .09 but back to .075 when I slightly closed Primary air.
It stayed around .07 but there was not much fire, so I opened primary all the way.
I adjusted the primary air as I felt was needed.
During this time I saw between .10 and .13. The spikes to .13 were during wind gusts.
Even when coaling, there was spikes to .13.
The STT only got to 440 during this time.

After the coals were burnt down, I raked them forward and to the sides so I had a tunnel down the middle of the fire box.
I added 5 pieces of 2 x 2 ash. E - W.
These pieces started quickly.
Within just a few minutes I closed the door. The reading was .11. STT 330.
Within 3 minutes I saw a spike to .16.
With the Primary air 3/4 shut I had a reading of .18.
The readings would fluctuate between .15 and .17. I did see spikes of .20. That was the highest I saw.

Since SBI states that ideal is .03 to .05, and that .08 is excessive draft, do you think I need a damper in my stove pipe?
Could this be the cause of my low stove heat problem?


When I had an overdraft condition I had NO problem getting my stove hot. It was just the opposite, it was a bit out of control when it was fully loaded. With a 12' stack it seems unlikely you'd have an overdraft condition.

Keep in mind that the accuracy of that manometer is +/- 3% of the full scale reading. Full scale is 3 WC. 3% of that is 0.09 WC, so when you are reading 0.17 you might only have 0.08... or you might have 0.26. Let's hope it isn't 0.26.
I don't know where you are in Northern Illinois, but I have a Magnehelic 2000-00 sitting around. If you want to use it to compare readings to your manometer you are welcome to borrow it if you are close by. The accuracy of the 2000-00 is +/- 0.01 WC.

Did SBI give you a procedure to follow, or at least recommend a point during the burn where the measurement is most meaningful? Pacific Energy recommended running it up to full operating temp and operating it there for an hour before taking the measurement. I think they wanted it to reach steady state, so it wasn't in the process of ramping up or down.
 

Woodcutter Tom

Burning Hunk
Apr 28, 2019
169
Northern Illinois
When I had an overdraft condition I had NO problem getting my stove hot. It was just the opposite, it was a bit out of control when it was fully loaded. With a 12' stack it seems unlikely you'd have an overdraft condition.

Keep in mind that the accuracy of that manometer is +/- 3% of the full scale reading. Full scale is 3 WC. 3% of that is 0.09 WC, so when you are reading 0.17 you might only have 0.08... or you might have 0.26. Let's hope it isn't 0.26.
I don't know where you are in Northern Illinois, but I have a Magnehelic 2000-00 sitting around. If you want to use it to compare readings to your manometer you are welcome to borrow it if you are close by. The accuracy of the 2000-00 is +/- 0.01 WC.

Did SBI give you a procedure to follow, or at least recommend a point during the burn where the measurement is most meaningful? Pacific Energy recommended running it up to full operating temp and operating it there for an hour before taking the measurement. I think they wanted it to reach steady state, so it wasn't in the process of ramping up or down.
My problem is that I never have got heat out of the stove. Plenty of heat up the flue, but not at the stove pipe. My house is high on a hill. I am about 100 feet higher than my mailbox at the road which is at the end of a 600 foot driveway.

I see where you got the 3% at Full Scale info, but I can't believe you would apply the .09 to every reading. The unit would be a piece of junk, You could never confidently zero it out. Zero might be .09 or it might be -.09 ????

I live about 1/2 hour southwest of Rockford. I'll pass on the offer for now but maybe.....

SBI did not give procedure. I took readings throughout my test.
 

Woodcutter Tom

Burning Hunk
Apr 28, 2019
169
Northern Illinois
I purchased the damper today and installed it. It will take some learning on when to close the damper. I still had .15 reading on the manometer with the damper fully closed. I thought it was not working at all. But it does effect the draft. It is still quite windy today. I can see, feel, and hear how the wind effects the draft. I am cruising about .09 - .10 now. STT 410 F. I have not been able to get a .03 - .05 reading today.
There will be a learning curve to determine when to close the damper, how much to close it and it's relationship with the primary air.

Anyone that uses a damper have thoughts on the proper use of the damper?

My goal is to get heat from the stove. Tomorrow will be cold in the morning (high 20s F). I'll start a new top down fire and see what I can do to get heat.
 

ABMax24

Minister of Fire
Sep 18, 2019
1,202
Grande Prairie, Alberta, Canada
I purchased the damper today and installed it. It will take some learning on when to close the damper. I still had .15 reading on the manometer with the damper fully closed. I thought it was not working at all. But it does effect the draft. It is still quite windy today. I can see, feel, and hear how the wind effects the draft. I am cruising about .09 - .10 now. STT 410 F. I have not been able to get a .03 - .05 reading today.
There will be a learning curve to determine when to close the damper, how much to close it and it's relationship with the primary air.

Anyone that uses a damper have thoughts on the proper use of the damper?

My goal is to get heat from the stove. Tomorrow will be cold in the morning (high 20s F). I'll start a new top down fire and see what I can do to get heat.

Is the manometer on the stove side of the damper?
 

brenndatomu

Minister of Fire
Aug 21, 2013
6,567
NE Ohio
There will be a learning curve to determine when to close the damper, how much to close it and it's relationship with the primary air.
I'd just adjust the stove where you want it (sounds like primary closed is going to be common) then close the damper where you want it...if you need more/better control from the pipe damper, you can get some fender washers and clamp then over the holes in the damper plate with some through bolts.
 
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kennyp2339

Minister of Fire
Feb 16, 2014
6,103
07462
To establish a draft, the stove needs to be running at its highest setting with a full "seated" fire going. Most manufacturers will say .05"wc is a perfect draft at this setting, I would think that theres a little bit of play and say .05 - .08 is within the normal range, intervention after .1 is needed, When I tested my draft I was bouncing between .15 - .18 so nearly 3 times the recommended draft, installed a damper and effectivily lower my draft reading to .08 -. 1 and very, very happy with my stoves operation now. (This is the second full season with the damper and I have further reduced my wood consumption / have much better heat output)
 
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Woodcutter Tom

Burning Hunk
Apr 28, 2019
169
Northern Illinois
It does look like this will take some trail and error, and unfortunately the season seems nearly over. I ran a couple of tests last week when the temperature was 22 - 23 F in the morning. Now it is the high 40's - low 50's.
I can tell that the wind does affect my draft.
From what I have seen .07 - .08 seems a more realistic number than the .03 - .05. I cruised at that for over 3 hours on a day with no wind, and stove pipe temps of 700 - 800 F. But my stove top temp only got to 485 F. That is the frustrating part. I am creating a new post asking of this is normal.
Thanks for the help guys.
 

Hoytman

Feeling the Heat
Jan 6, 2020
360
Ohio
Remove your manometer tube from your stove pipe and suck through it with your mouth. Try to maintain any number around -.01. Let us know what you learn from this experiment. (Hint: I highly doubt you can maintain any number and you’ll see how little air it takes for -.01c.)


Most people that I know that use these Manometers regularly use coal stoves, as do I, and most of them agree the best place to take a reading from is over the fire in the firebox, and I agree. You know exactly what the fire is doing then.

However, it doesn’t really matter if it’s taken from the pipe. Most don’t want to drill a hole in their stove and I don’t blame them.

It really doesn’t matter if the manometer tube is below the damper or above it either. Mine is actually in my pipe between a built in stove damper and a pipe damper that I put in about 12” off the stove top.

That is, my manometer tube is above one damper, but below the upper damper and I have seen zero difference in readings regardless of which damper I am using. Not to say someone else couldn’t experience something different, but I really have my doubts.

In low 70F outside air temps (OAT’s), running my stove at 170F...that measured under my thermostat box on the back of the stove using an IR gun...I can easily maintain -.005wc to -.01wc with zero reversals and CO detectors reading zero. Surface temps of my single wall stove pipe at the thimble can be as low as 85F surface temps. Folks, that is low!!

I can keep my hand on my stove pipe for as long as I want to, to about a pipe temp of 115F. Much hotter than that and I have to remove my hand after a few seconds. Try that burning wood. Ha! Unless it’s a catalyst wood stove with double wall pipe, you can’t get pipe temps much lower than 250F without putting creosote up your chimney.

When temps are below freezing and my stove is running normally at around 300F, pipe at thimble is 95F surface temp and manometer usually reads -.02wc.

That’s a 7” outlet stove, single wall stove pipe from stove top to thimble, and an inside the home masonry chimney, 8”x8” clay lined chimney that is just shy of 15ft from the firebox floor to the top of the chimney. It’s only 10ft from the top of my thimble to the top of the chimney.

Remember...I am burning coal.
My reason for sharing these numbers with you is that you should be able to have much lower pipe temps and still have plenty of draft. Pipe temps as high as 700F-800F are excessive and a sign you do need to use a damper...especially to increase your stove temps...which is the issue you said you were having

If I burn wood in my stove the numbers for pipe temps and draft will be much higher for any given stove top temperature. For my particular chimney and stove the pipe temps would be 250F-400F, but never as high as your temps, and my stove top temps from 400F-600F.

That said, I have yet to burn wood in my stove with the temps mentioned in the above paragraph WHILE using my manometer. I know for a fact though that the chimney will draft quite a bit higher than -.02wc that I get burning coal.

I would not be surprised to see manometer reading from anywhere between -.04 to -.08 knowing that it will draft without reversal to much lower...as low as when burning coal.

The only thing I would need to keep in mind while burning wood is to find my lowest pipe pipe temp to keep creosote from forming in the chimney and correlate that to my/your manometer reading. That’s your lowest running draft. It will vary some according to outside temps.

Hopefully some of my numbers for comparison you will find helpful.
 
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brenndatomu

Minister of Fire
Aug 21, 2013
6,567
NE Ohio
Try to maintain any number around -.01. Let us know what you learn from this experiment.
Nobody, but nobody specs a draft of -0.01" for a wood burner...that's just asking for trouble...the lowest I've seen was my Yukon Husky furnace which called for -0.03" WC. Did you mean -0.1"?
Most people that I know that use these Manometers regularly use coal stoves, as do I, and most of them agree the best place to take a reading from is over the fire in the firebox, and I agree. You know exactly what the fire is doing then.

However, it doesn’t really matter if it’s taken from the pipe. Most don’t want to drill a hole in their stove and I don’t blame them.
I've tested both ways, it was the same.
 

brenndatomu

Minister of Fire
Aug 21, 2013
6,567
NE Ohio
I can keep my hand on my stove pipe for as long as I want to, to about a pipe temp of 115F. Much hotter than that and I have to remove my hand after a few seconds. Try that burning wood.
140-150* external (single wall) pipe temp happens regularly on my Kuuma VF100 wood furnace...certainly cool enough to touch for a second or two with no consequences...
 
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Hoytman

Feeling the Heat
Jan 6, 2020
360
Ohio
The experiment I was referring to was actually sucking (I wrote blow and meant to say suck) through the tube with his mouth. That’s a far cry from telling someone to try and run their wood stove that low. In fact, that was the entire point of my post...wood burning draft by nature will be higher simply because in most wood stove cases they have to be in order to keep the chimney clean.

No typo written. I meant -.01, but trying to suck air and maintain -.1 is not much different. My point is it is hard to maintain either number and maintain that number with breath (or by sucking air) because it doesn’t take much breath to hit either number or exceed -.1 or higher. Try it! I have. It is so little air it is hard to believe when you try sucking on the manometer tube. No problem at all to bury the gauge...without even a hint of effort.

As far as pipe temps go, I was talking about wood stoves, not a wood burning furnace with electrically controlled draft dampers etc. Pretty good, none-the-less. Shows how well they work. I have zero experience with them.
 
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MR. GLO

Member
Jan 26, 2021
156
Massachusetts
Here are my test results.
Outside temp: 30 F
Wind 4 - 8 mph -- with gusts to over 17 later in test.
Stove top to chimney cap: 12 FT.
Manometer probe was in stove pipe temp probe hole; therefore no flue temps.

Verified calibration.
Started with small fire to get heat in stove.
With no fire the reading was .01
Within 2 minutes of staring, reading was .025.
About 10 minutes in, reading was .06
For next 45 minutes reading was steady about .06 - 065. I did see a spike to .075.
I then raked the coals a bit and added 4 pieces of 4 1/2 " splits N - S.
Once wood started to burn, reading was .07.
It rose to .09 but back to .075 when I slightly closed Primary air.
It stayed around .07 but there was not much fire, so I opened primary all the way.
I adjusted the primary air as I felt was needed.
During this time I saw between .10 and .13. The spikes to .13 were during wind gusts.
Even when coaling, there was spikes to .13.
The STT only got to 440 during this time.

After the coals were burnt down, I raked them forward and to the sides so I had a tunnel down the middle of the fire box.
I added 5 pieces of 2 x 2 ash. E - W.
These pieces started quickly.
Within just a few minutes I closed the door. The reading was .11. STT 330.
Within 3 minutes I saw a spike to .16.
With the Primary air 3/4 shut I had a reading of .18.
The readings would fluctuate between .15 and .17. I did see spikes of .20. That was the highest I saw.

Since SBI states that ideal is .03 to .05, and that .08 is excessive draft, do you think I need a damper in my stove pipe?
Could this be the cause of my low stove heat problem?

What cap do you have on your chimney?
 

Hoytman

Feeling the Heat
Jan 6, 2020
360
Ohio
I mentioned that little test because it shows just how sensitive the Dwyer Mark II model 25 is. So, it’s more accurate than you think. It can be purchased “certified” as well, and for not much more money if you’re so inclined. Most guys I know say it’s not necessary.

I’m going to buy a magnahelic and borrow an idea from a guy and make a mantle “clock” type gauge. Something that looks a little better on the wall. The magnahelics are more sensitive, but the Dwyer Mark II model 25 is more than sensitive enough for my needs. I hook mine up in reverse so I can use the larger of the two scales.
 

Highbeam

Minister of Fire
Dec 28, 2006
19,308
Mt. Rainier Foothills, WA
It does look like this will take some trail and error, and unfortunately the season seems nearly over. I ran a couple of tests last week when the temperature was 22 - 23 F in the morning. Now it is the high 40's - low 50's.
I can tell that the wind does affect my draft.
From what I have seen .07 - .08 seems a more realistic number than the .03 - .05. I cruised at that for over 3 hours on a day with no wind, and stove pipe temps of 700 - 800 F. But my stove top temp only got to 485 F. That is the frustrating part. I am creating a new post asking of this is normal.
Thanks for the help guys.

I installed a pipe damper this winter and use a fancy digital probe meter in my pipe. Using it to maintain high stove temperature and low flue temperature while not smoking. Couple things I have learned are don’t open the loading door with the damper in any position except full open. The open damper offers some restriction compared to no damper, you can use any setting, mark the pipe with some references for angle of damper, you’ll need to adjust your setting based on conditions, adjust your pipe damper and then your stove intake. You can turn your epa stove into a smoke dragon and gunk up your chimney if you’re too aggressive. Long cool burns are not good for noncats.

I’ve only been able to lower flue temperatures slightly, maybe 100-200, but since there is a slower flow of those flue gasses there is much greater heat retention and efficiency. It’s not just about the temperature of the gasses but flow rate.
 
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Woodcutter Tom

Burning Hunk
Apr 28, 2019
169
Northern Illinois
Remove your manometer tube from your stove pipe and suck through it with your mouth. Try to maintain any number around -.01. Let us know what you learn from this experiment. (Hint: I highly doubt you can maintain any number and you’ll see how little air it takes for -.01c.)
It does take very little air to move the water/oil in the gauge. It is quite sensitive. And quite difficult to keep a constant number.......unless you cheat like I did and stick your tongue in the hole.
 
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Woodcutter Tom

Burning Hunk
Apr 28, 2019
169
Northern Illinois