Reasonable/Acceptable GPH boil rate on a 2 x 5.5 with a steam hood?

[Old County Road]

This past weekend I was finally able to fire up my used Lapierre/Waterloo/Small 2' x 5.5' evaporator. The back pan is 2' x 4' and is a drop flue design. The front pan is 1.5' deep by 2'. The stack is 10" and runs up through the roof with a total height of probably 15'. The evaporator has a 2' x 6' steam hood with a 10" stack that also has a total height of probably 15'. I have a squirrel cage blower installed under the arch doors.

I boiled this past weekend for 23 hours total and averaged about 13gph which seems low to me but wanted to check with others on that. My wood is a mix of split up hemlock slab wood that is mostly dry and fist size hardwood that is very dry.

I expected to be boiling in the upper 20s low 30s vs the low teens. Any thoughts on what I shoud be getting for gph evaporation?

Thanks!

[fisheatingbagel]

I have a Smoky Lake 2x5 hybrid, also a 5" drop flue design. I average 25 gph with small dry wood. I have a blower, but it's too small to make much difference. No hood or preheater. I have an 8" stack. I think you should be able to get 30 gph with a blower.

How does the boil look in the flue pan? It should be boiling "vigorously". What is your sap level in the flue pan? How often are you firing?

I wonder about your Hemlock that is "mostly" dry. Have you tried boiling with just the dry hardwood?

[Mead Maple]

I borrowed a neighbors 2x4 divided mason flat pan last year. With my 275 oil barrel arch and a blower I could cook that at 13gph but never a drop more


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[Old County Road]

Hey Dave - the boil in the back pan was pretty vigorous but I don't have much to compare it to as this was my first boil on the rig. I will try your suggestion of just burning hardwood for a coupe hours and see if that makes a difference. I am pretty sure the previous owner told me he could get low to mid thirties out of the rig.

In terms of firing times I was trying different times between 10 and 20 plus minutes. I found that if I kept the firing times closer to 10 minutes the front pan wasn't boiling well as it cooled off quickly when I opened the doors to load wood. When I went 20 minutes or so the front pan boiled much better but the back pan died off toward the end.

I ordered a stack thermometer so I am going to keep an eye on that and see if I can find the sweet spot on when to fire.

[maple flats]

When I use some hemlock (I have a sawmill) slab wood my boil rate drops a little. You say the hemlock is "mostly dry", that might be part of the issue too. I would think you should be able to get over 20 gph, maybe 25, not likely 30 unless the wood is dry, and split "wrist size" not fist size. Also, if the hemlock still has the bark on, surprisingly that can slow it some too. Hemlock like most evergreens actually have a natural fire retardent in the bark, to help them survive a forest fire.

[gbeneke]

Your evaporator has about 30 maybe 35 square foot of surface with those flues. With the steam hood and stack heights you should be getting at least twice your rates or better. Use your hard wood and keep it stoked more often. Your pants should get hot after 15 seconds when the door is open.

[Old County Road]

Thanks Paul - I used to boil on a 2 x 4 flat pan for years and usually averaged 10 gph - so only getting 13 gph on the 2 x 5.5 is a bummer. I am going to tweak a few things and hopefully make a better showing. I am assuming the hood helps - but I was also wondering if in some ways it could hurt. The steam seemed to be pretty good though when it was going.

[Old County Road]

Thanks for the input and advice Dave K and Wood Loader. I did not know that evergreens bark has a natural fire resistance - good to know! My slab wood (from my Wood Mizer) was really dry - but then got snowed on in an early storm before I could cut it to size and get it under cover. Some pieces are fine and some not so much so I am trying to mix them up when I load, but I plan on trying to boil with just dry & split small hardwood this coming weekend. I knew my wood situation was going to be the weak link this season as I didn't put the time in last summer and fall when I should have! On the plus side my 3/16" tubing is working great and I was finally able to get back to maple sugaring after a 5 year break.

I have attached a screen shot of steam exiting my stack - seems like a pretty good plume to me but I don't have much to compare it to.

[Pdiamond]

You might be better off installing the blower on the back side of the arch firebox blowing towards the front. this would improve the boil on your syrup pan and fire. Then it would follow the ramp thru the flues and out the stack. That is how my SL 2 x 4 raised flue evaporator is set up, and I boiled off 325 gallons last Sunday in 6.5 hrs, straight sap no RO. Made 6 gallons of syrup. Used wrist size hardwood, beech, ash, and maple. We fired every 6 to 8 minutes.

[Old County Road]

Thanks for the suggestion PDiamond - I will have to explore that option. It would be nice to not have the blower in the front as it is kind of in the way.

I imagine you shut your blower down when you fire so as to avoid a face full of flame?

I boiled for 23 hours on unsweetened pans to make 6 gallons. I would much rather do that in 6.5 hours like you did.

My woods have a nice mix of maple, ash, birch, and beech which is what I burn at home - I will have to put in the extra time this spring to prep the sugar house for next winter.