Mason 2x3 - Stack Temp Questions

[ducxsterdoo]

Hi.. been searching the forum on stack temp and stacks glowing red, and not 100% sure what I should change, if anything.

Did my second boil today. I'm getting right around 7.5 GPH rate. Today I noticed that my stack temp (magnetic external thermometer) was pushing 800, and the tee out of the back of my evaporator was starting to glow red (see pic).

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I do have AUF and have been running it nearly at the lowest setting. If I run without the blower, the boil definitely is not as hard as when the blower is on, but it's still boiling at a decent rate.

I'm not necessarily unhappy with my current boil rate, but want to make sure I'm running as efficiently as possible and not sending too much heat up the chimney, and worst yet, causing it to overheat.

I'm burning mostly wrist sized maple and cherry, with some scraps of rough cut hemlock siding thrown in each time I fire.

Thoughts?

-craig

[Chickenman]

Mine looked like that the first 2 years boiling on it. I redid the bricks at the back of my fire box and started adding wood less often. I'm still getting 8+ gallons boil rate and with the same type of thermometer and I'm running in the 4 to 600 range now.
I could only get 1 season out of my stack as I know I was over firing the unit when my entire 10 foot stack would be cherry red and a 3 foot flame shooting out of the stack like a jet engine with an after burner.
Now, I split my wood smaller and add it less often and everything seems to be running more smoothly. I can open the door to add wood without having to turn the blower down and I'm not eating flames when I do.

[ducxsterdoo]

What did you do to change the bricks in the fire box?

[ecolbeck]

If you google “bricking mason arch maple” and look under images you will find some pictures of a wall in the middle of the arch which pushes the fire/flue gasses up against the bottom of the pan. That may help improve the heat transfer to the pan and keep your evaporation rate high while keeping flue temperatures moderated. However, with such a short arch, high flue temperatures may be hard to avoid.

[Chickenman]

What did you do to change the bricks in the fire box?

I will try to get you a pic tonight when I get home from work.

[ducxsterdoo]

This is how I bricked mine... The wall is less than 3" from the pan and I raised up the floor behind the wall.

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[ecolbeck]

That looks great. Perhaps you could shrink the gap to the pan down to 2" and extend the wall towards the flue exit. I think the idea is to keep flue gasses in close contact with the bottom of the pan for as long as possible. You could even extend the wall towards the firebox door. This would mean covering up some of the grating (not a problem) and would depend on the length of wood you are using. This would give even more contact time with the bottom of the pan. As mentioned before, short pans are not terribly efficient.

[eustis22]

for the cavity behind the wall, I bricked my Mason 1/2 way up the stack hole so its the same height as the wall. I have an XL so the preheater pan sits over the flame as well and my preheater achieves regular boiling too.

[Chickenman]

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This is mine. Little different, but it works.

[ducxsterdoo]

Thanks... Blocking the stack opening partly is interesting. That doesn't affect the draft at all?

[Chickenman]

hard to see it in the picture but there is a split brick width gap in front of the hole allowing full draft.

[eustis22]

I have not noticed any issues with my draft

[steve J]

I have the 2x4 with blower and once I have built a fair amount of coals in fire box I can not run blower on high as It gets cherry red big time. If my mixture of wood is 1/2 softwood I dont seem to have a problem.

[ducxsterdoo]

I've boiled a couple more times... I did add another row of fire bricks to the wall behind the firebox,that brings the wall within about 1 1/2" from the bottom of the pan. I'm also playing with the frequency of fueling, the mixture of softwoods, and blower speed. I've been able to keep the stack temps between 500 and 600 most of the time ( a couple unexpected temp spikes here and there), but my boil rate has dropped to about 6 1/2 GPH. So, I still need to figure out how to get more heat to the pan and less to the flue.

I think I will try adding some bricks behind the firewall as some of you have posted, to just shy of the flue exit, but still not sure how to balance boil rate and stack temp.

Probably something I just need to figure out, but if there are any other suggestions of things to try to get the best efficiency out of my 2x3 setup, I'm open.

THX...

-craig

[ducxsterdoo]

Well...after a bunch of trial and error, including adding brick behind the firewall, using the blower and keeping stack temp in check, my boil rate has been pretty much stuck in the mid 6 GPH range.

The other day I experimented without using the blower and got much better results and was able to keep the stack temp in the 500-600 range more reliably (again, with the occasional spike where it hit 650)...but I can get my boil rate well into the mid 8 GPH range.

Not sure what I'm doing wrong when using the blower, but for now, if I can get those kinds of results without using it, I'm OK with that, and it's a lot less to worry about in the process. I just feed it every 8 minutes and watch it boil.

[eustis22]

are you preheating the sap? My 2X3 does about 12 GPH and I can only run the blower on a low setting.

[Chickenman]

silly question but is your blower rotating the correct direction? Some are polarity sensitive to rotation.

[berkshires]

are you preheating the sap? My 2X3 does about 12 GPH and I can only run the blower on a low setting.

Wow, that's fantastic! Do you have any pics of your bricking? Do you have it bricked up the whole way back behind the wall?

I've got all my bricks cut for my 2x3 XL, putting them in this weekend. So I'm anxious to do it right. :)

GO

[ducxsterdoo]

are you preheating the sap? My 2X3 does about 12 GPH and I can only run the blower on a low setting.

Yep, preheating sap... My challenge is that if the blower is anything higher than a super low setting or if the firebox is loaded dup more than half full, anytime I stray from that the boil does seem to increase, the stack quickly overheats. I can easily increase the boil rate...but the stack gets cherry red.


silly question but is your blower rotating the correct direction? Some are polarity sensitive to rotation.

Yep... it's bowing the right way....

[eustis22]

can you send another pick of your bricking? It sounds like too much heat is going up the stack

[ducxsterdoo]

can you send another pick of your bricking? It sounds like too much heat is going up the stack

I don't have a current pic...but from the pic I show here, I added another row of splits to the dividing wall, bringing it to under 2" to the pan... then I filled in behind the wall to within a couple inches of the stack opening, also to within a couple inches of the pan. It looks very much like you're setup that you posted.

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