Adjust baro draft for different coal sizes?

 
jschaefer7406
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Post by jschaefer7406 » Thu. Jan. 04, 2018 6:24 pm

Hello all,

Have a hand-fired warm air furnace, and have a question about chimney draft.

Know hand fired are recommended to run .04 to .06. I used to run mine at .04 when I burned nut exclusively. Switched to Direnzo pea a couple years back though, and found the recovery time to be pretty long (as expected with pea), also had a few puff-backs early on with learning pea. So, I’ve been running at .06 with the pea size and it helps a lot.

Picked up a load of Direnzo nut yesterday, and here are my questions. First and foremost, would you all go back to .04, or stick with the .06? I like how quickly it recovers, and the heat is great with it set to .06.

What I’m wondering is, will burn times be noticeably longer dropping .02” wc, or not enough to bother messing with it? Seems like it burns down more with it set higher, but not sure if it’s a significant difference or all in my head...

Thanks in advance,

Joe


 
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Post by jschaefer7406 » Thu. Jan. 04, 2018 6:35 pm

Don’t know how I put this here, can a mod please move this to the furnace board?

Thanks,

Joe

 
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Post by windyhill4.2 » Thu. Jan. 04, 2018 6:55 pm

Best way to get a moderator is to hit the exclamation mark in the upper right corner of your post box.

As far as setting the baro so draft is stronger....the higher the draft,the more heat is going up the stack. If you want quick recovery,cover the baro while you are tending the unit. You will need to remember to uncover b4 walking away.

 
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lsayre
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Post by lsayre » Thu. Jan. 04, 2018 7:02 pm

Pea coal may need a bit more draft than nut. Experimentation will tell.

 
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Post by Hambden Bob » Thu. Jan. 04, 2018 7:06 pm

Well Schaef, Ya' gotta figure that Your Coal Bed is sewed up alot tighter trying to push air through the Pea Coal compared to the Nut. I don't know where Your located per Your avatar info,so I'm guessing that You're tied up in the same Howler that most of Us are in. If Your Baro's Klinking it's butt off,It's just gonna be that kind of night. If it was me,and I was burning all nut with no Pea in the Coal Bed,I'd dial it back a touch......

There are other Mad Scientists here that may Counsel You otherwise due to their much better defined reasoning. I just hate seeing You suck a ton of heat up the flu while burning through Your Coal Load. In this weather,with Killer Diller Cold Temps coupled with the high winds doing a real Whammy on trying to violate Your House's Warm Core,You're going to want to be alot more vigilant at keeping that stove generating 'Der Inside Heat to push back against it all......

 
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Post by Lightning » Thu. Jan. 04, 2018 7:18 pm

Hey Joe, how is your furnace controlled for regulating heat output? Do you manually control the primary combustion air or does it have some kind of thermostat? Also, does your unit have independent secondary air control or is it fixed, or no secondary air at all?

 
jschaefer7406
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Post by jschaefer7406 » Thu. Jan. 04, 2018 7:25 pm

Thanks guys for the replies :)

Lee, has a manual slider for primary draft, and one for secondary (which I rarely use).

I did try lowering the setting from .06 to .05 when burning the same pea last week, just for giggles. Didn’t notice any difference in flue temp with my magnetic gauge, though.

Joe


 
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Post by michaelanthony » Thu. Jan. 04, 2018 7:50 pm

I can tell you many things about what I've done and how it has worked...you need to do the same in regards to writing down a log with pipe and stove temps, indoor-outdoor temp, coal size, primary and secondary air settings, draft reading-adjusting etc.
I'm not being a wise ass, just that our situations are probably NOT the same. You seem to know what you like and that's being warm, me too and I really don't care if I burn more coal or less coal as long as the wife is happy :yes:

 
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Post by jschaefer7406 » Thu. Jan. 04, 2018 7:59 pm

Hahaha, excellent points! :)

Everyone says lower chimney draft holds more heat in the furnace, but to me, what makes it different than adjusting the primary air? I mean, you’re essentially limiting the same airflow (just on different sides of the fire), no?

I don’t have a stove temp gauge, only the flue gauge. So I can not compare to see if stove temp remains steady or also drops with chimney draft...

I’m not trying to be wise either, just something I’ve never fully grasped since I started coal in late ‘11.

Joe

 
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Lightning
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Post by Lightning » Thu. Jan. 04, 2018 8:10 pm

So let's keep the baro separate from the coal sizing for a minute. If you set the baro to a stronger draft pressure the result should be a hotter stove at the same primary air setting. This is because primary combustion air is driven by the negative pressure inside the fire chamber. So hypothetically let's say you set the primary air half open and the baro to hold -.04 which results 300 degrees over the load door after it stabilizes. Then, if you were to set the baro at -.06 and kept the primary air setting the same you would see the temperature of the stove increase.

A stronger set draft pressure will also make recovery faster since its forcing a higher volume air thru the fuel bed.

As for sizing, like mentioned a stronger draft may be needed to get the same heat output with smaller sized coal. Smaller sized coal packs more tightly and requires more pressure to force the same amount of combustion air thru it as bigger sized coal.

As for secondary air you have control of that. Some stoves have fixed secondary air which would need to be controlled by draft pressure.

 
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Post by michaelanthony » Thu. Jan. 04, 2018 8:14 pm

jschaefer7406 wrote:
Thu. Jan. 04, 2018 7:59 pm
Hahaha, excellent points! :)

Everyone says lower chimney draft holds more heat in the furnace, but to me, what makes it different than adjusting the primary air? I mean, you’re essentially limiting the same airflow (just on different sides of the fire), no?

I don’t have a stove temp gauge, only the flue gauge. So I can not compare to see if stove temp remains steady or also drops with chimney draft...

I’m not trying to be wise either, just something I’ve never fully grasped since I started coal in late ‘11.
https://smile.amazon.com/HOLDPEAK-Non-Contact-The ... ed+scanner

Get one of these my friend...have fun while you stay warm ;)

 
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Post by jschaefer7406 » Thu. Jan. 04, 2018 8:16 pm

Lee,

That makes perfect sense, and is as I thought. But to me then, you’re not really “keeping heat in the stove” as is often said, you’re just moving the available output range, yes?

So in the example, if you were to raise the baro setting, and close the primary to compensate, you’d get the same burn (both time and temperature). Right?

And M, that’s a great idea. Actually have one on my service van at work I can probably borrow. I’d get a magnetic one and leave it there, but was curious where to place it (being a furnace and not a stove). Door is cast (obviously), front is roughly 1/8” plate.

Thanks,

Joe

 
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Post by michaelanthony » Thu. Jan. 04, 2018 8:21 pm

jschaefer7406 wrote:
Thu. Jan. 04, 2018 8:16 pm
Lee,

That makes perfect sense, and is as I thought. But to me then, you’re not really “keeping heat in the stove” as is often said, you’re just moving the available output range, yes?

So in the example, if you were to raise the baro setting, and close the primary to compensate, you’d get the same burn (both time and temperature). Right?

And M, that’s a great idea. Actually have one on my service van at work I can probably borrow. I’d get a magnetic one and leave it there, but was curious where to place it (being a furnace and not a stove). Door is cast (obviously), front is roughly 1/8” plate.

Thanks,

Joe
Joe, I would put the mag gauge on the flue pipe...thats the money shot!

 
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Post by jschaefer7406 » Thu. Jan. 04, 2018 8:27 pm

Sorry for the confusion, have one on the flue pipe. Don’t currently have any way to measure actual stove temp though :)

Joe

 
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Post by Lightning » Thu. Jan. 04, 2018 8:28 pm

Personally I don't believe in the "hold heat in the stove" thing. Here's what it boils down to.... All else being equal, the stove will be most efficient with heat radiation when it uses as much of the oxygen that it can (that is provided) before the heated gases leave the stove to go up the pipe.


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