New Pans on my 2x6

[Waynehere]

So I have a home made arch and just bought some new pans. They have 9" raised flus in them. The previous pans were drop tube and was getting 25 gph. These are suppose to get 60-80, but only get 30-35. I think my firebox isn't large enough. Inside dimensions of the firebrick and ceramic blanket, I have 16"w x 16"t x 28"d. With the old pans I could get temps under the syrup pan of 18-1900 degrees, and the stack was running 600-900. With these new pans, I am still getting the same under my syrup pan, but struggle to get up to 350 degrees. I assume the sap pan is really sucking a lot of heat. I can make the firebox taller, but was wondering how large a firebox for a 2x6 with AUF and AOF should be?

[Bucket Head]

Wayne,

Did you do anything to modify the arch and insulation? If not, you need to raise the ramp- the arch floor from behind the grate leading up to the flue pan. The ramp needs to go past the front of the flue pan by about a foot and then follow the pan bottom to just shy of the rear of the pan. You need to get the flame/heat up into these flues and keep it there! You will have to figure in the thickness of the insulation so you have about a half an inch, give or take a little, beneath the pan. Leave a little space at the end of the pan for the heat/gases/smoke to drop down and head to the smoke stack.

Steve

[Waynehere]

Hi Steve,
Yeah, already did just what you mention. The flames and gases are making it up in through there, but I think I just don't have enough fire. As you notice, the difference between my front pan and the stack temp is huge. I raised my whole evaporator up about a foot so we don't always have to take a knee when we fire it. I can drop my firebox down then by a foot to gain some more height this summer, but I was wondering what these units typically have for a firebox size? Of course, with 11 9" raised flues, the guy that made it said it had the same surface area as a 3x8? I didn't calculate out the area myself, but that is more then the standard sap pan.

[brass maple]

Do you have a blower. If not that would help.

[Waynehere]

Yeah, that is what the AUF and AOF is. (air under fire and air over fire) :)

[brass maple]

Guess I missed that part of your post lol

[mellondome]

Do you have enough blower? Also what size Is the wood you are using? How dry? How often are you firing? Your dimensions sound right for the firebox.

[Big_Eddy]

So I have a home made arch and just bought some new pans. They have 9" raised flus in them. These are suppose to get 60-80, but only get 30-35.

What makes you think you should get 60-80 GPH? For a 2x6, even with AOF and AUF, I would think 40-45 GPH is a maximum number and 30-35GPH is reasonable, until you start adding a steam-away and hood etc.

Search the archives to see what others are getting.

[Waynehere]

Do you have enough blower? Also what size Is the wood you are using? How dry? How often are you firing? Your dimensions sound right for the firebox.

I believe I do. AOF is a pressure blower with a 3/4 hp motor. I have it blowing on 3 sides of the firebox. I was thinking I will add more if I modify it though. AUF I have a squirrel cage blower with a speed controller, that blows up through my firebrick floor that has holes drilled out. I was thinking about adding more holes again as well, although last season I always had to throttle it back to try and keep my stack temp below 1000. My wood is seasoned 10 months and 18" wrist size. With hard wood I fire every 15-20, pine usually 10 mins. Like I mention, I seem to have good temps under the front pan, but the sap pan is sucking up all the heat.

[Waynehere]

What makes you think you should get 60-80 GPH? For a 2x6, even with AOF and AUF, I would think 40-45 GPH is a maximum number and 30-35GPH is reasonable, until you start adding a steam-away and hood etc.

Search the archives to see what others are getting.

Well, I am going by the guy that built this and also one of his customers that I talked to on the phone. I reached out to this guy for some advice, but no reply yet. I have looked through these forums a lot and I agree with your findings. Once in a while I see the higher outputs, but usually associated with some help like you mention. I was just trying to see what the normal size of a 2 x 6 firebox is as mine is homemade. :)

[mellondome]

You may needes to get more air under and fire more often. With my 2x6 I fired every 5-7 min depending on weather. I had just regular grates with a squirle cage 465 cfm under... over was 1hp dust collector. I could make the stack glow if I turned the air over off with the air under full on.

[Waynehere]

You may needes to get more air under and fire more often. With my 2x6 I fired every 5-7 min depending on weather. I had just regular grates with a squirle cage 465 cfm under... over was 1hp dust collector. I could make the stack glow if I turned the air over off with the air under full on.

You might have a point there. I will have to try that before I get ready to tear my arch all apart. Thanks.

[Sugarmaker]

Couple of things come to mind.
First your temps sound right and you are checking things so that's great. You also know what the temps were on the other pans.
If you really have the area of a 3 x 8 on top of a 2 x 6. Then you could probably double your fire box to be about the same size as a 3 x 8 and it would boil at the suggested rate. Maybe? So like your thinking, maybe deeper fire box might work? More fire more often = more temp.
Yes the flue pan is going to draw out more heat reducing the stack temp. Mine did when I increased surface area with new pans.
My stack temps went down a lot. But rig went from 110 GPH to 140 GPH. So you should be seeing some increase in GPH with the new pans.
Try opening up the drafts, firing more often may work too.
Not sure you will get to 60 gph?
At some point you might have to much pan for the fire??? Not sure where that point is?
Regards,
Chris

[Waynehere]

I was thinking the same about having too much pan as well. I tried firing more often without much success. I did go from about 20 to 30-35 gph, so yes I did see some increase. I found a larger fan and am going to get it hooked up to see if I am just lacking auf. Thanks for all of your input guys.

[mellondome]

Drilled brick will really decrease air flow under the fire unless you are using a pressure blower there as well.

[Super Sapper]

I think that you are too restricted on your AUF with the drilled bricks. I have a V bottom flu pan on a 2 X 6 (surface area of a 2 X 8) and can get a fireball coming out of the stack when I add wood so it is over 1000 coming out of the stack. This is with a 260 cfm blower. I had unistut spaced 3/8" apart for a grate but have increased to 3/4" this year. If it is a restriction with the bricks you will not get any more air with a larger low pressure blower.

[Waynehere]

Interesting about the drilled brick. I had heard good things about them. I don't have time to change them out for some grates this year, but I should be able to put some more holes in them. Thanks for the heads up...

[Waynehere]

So we finally got to boil today. You guys were spot on. Not enough AUF. I was able to get the stack up to 400-430 and got the GPH up to 47. Only problem is my stack is 9" and I think I need to increase it to at least 12". I have fumes and a little flame coming out of the arch now, unless I turn it down. Was firing every 9 mins, twice as fast as the 15-20 mins.

I think I still have some modifications yet for this summer. More ceramic blanket to handle the extra heat and re-design the grates. Thanks for you help everyone.

[mellondome]

What do you put between your pans and the arch? Dont use the flat woven gasket. Use the thick fireblanket that is cut to 1in wide. It will seal up much beter

[Waynehere]

Yeah, next year I was thinking the same. The main leak I have it out the front as my frame on the top of my door has warped a little and leaking when under pressure.

[mellondome]

You may need to make the transition out of the flue pan a little larger. This will allow more air flow. You have plenty of stack size.

[Waynehere]

You know, I was looking at that the other night and was wondering if that was large enough. Will look into that too. Thanks