2x6 wood fired to propane conversion

[pwm]

We are converting our wood fired 2X6 CDL raised flue to run on propane this year. The burner assembly is a piece of 1.5" square tubing with the ends welded closed drilled and tapped 1/8"NPT for the three burners and 2 inlets with needle valves to connect two (we tried 1 tank and it would freeze up and reduce the flow) propane tanks. The burners are from HF and are rated at 500000 BTUs we bought the cheaper ones because all we used is the burner ends and the hose. We tried using 2 burners first but we didn't get a good boil the full width of the pans, with 3 burners it has a good boil the whole width of the pans. So far we have tested it 3 times with water it took a few times to get the burner angle right so that the front pan had a good boil and the flue pan had a good boil its full length. Over all it seems to boil at least as good as it did with wood, the first section in the front pan boils better than it ever did with wood so that should help lower the time between draw offs(about 45 minutes now) for us. I am not sure how the cost will be with this set up but we do have a small RO so we don't boil for the long hours like we did before the RO, but the test boils we did were encouraging because we didn't have to run it wide open to get a really good boil the entire length of the evaporator and the stack temperature was relatively cool, so we must be utilizing most of the flame. I will update this post after we know more.[/ATTACH]20180129_165105.jpg20180129_165135.jpg

[jerzeemaple]

I’m thinking about doing this if you can share any additional information on efficiency that’ll be great! Good luck this season

[pwm]

Just to update this post. WE did run on propane for 2018 we made 55 gallons of syrup and we used $700 dollars of propane. In January of 2019 the gas company installed a gas line to the sugar shack so we altered the burners to run on natural gas we also added 1 more burner for a total of 4. We ended the 2019 season making 150 gallons of syrup (we added taps on 3/16 tubing) and we used $235 dollars (265 X100 cubic feet) of natural gas. We did 5 or 6 test boils with water trying to improve the boil and in the end it was boiling about the same as it was with wood and slightly better than the propane. The syrup pan boils much better with the natural gas than it ever did, the flue pan boils great in the half towards the front (its a raised flue) and so so the other half. One reason for the poor rear boil I think is the stack is 10 inch diameter too big for the size of the burners so we will try and tweek it some more to improve the boil. Other than that we are very happy with the conversion and I would recommend it if you have natural gas but I don't think I would with propane.

[Mead Maple]

Just to update this post. WE did run on propane for 2018 we made 55 gallons of syrup and we used $700 dollars of propane. In January of 2019 the gas company installed a gas line to the sugar shack so we altered the burners to run on natural gas we also added 1 more burner for a total of 4. We ended the 2019 season making 150 gallons of syrup (we added taps on 3/16 tubing) and we used $235 dollars (265 X100 cubic feet) of natural gas. We did 5 or 6 test boils with water trying to improve the boil and in the end it was boiling about the same as it was with wood and slightly better than the propane. The syrup pan boils much better with the natural gas than it ever did, the flue pan boils great in the half towards the front (its a raised flue) and so so the other half. One reason for the poor rear boil I think is the stack is 10 inch diameter too big for the size of the burners so we will try and tweek it some more to improve the boil. Other than that we are very happy with the conversion and I would recommend it if you have natural gas but I don't think I would with propane.

PWM,
That is great to see the kind of savings and what seems like increased efficiency by going NG. I know most of Vermont does not have NG so that would never be an option and I think all would agree that propane is a bit out of reach. Glad your conversion worked out so well for you!


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[maple flats]

How much space do you have under the flues? I wonder if the issue is too big a stack or just too much space under the flues. I also wonder if NG fueled wants a barometric damper like oil does?

[pwm]

we have sand level with the top of the arch just like when we boiled with wood but we closed up the far end a few inches more than it was with the wood.there seems to be a lot of heat going up the stack more than when we ran the propane.

[n8hutch]

How far into the arch do your burners go? The reason I ask is I have found with my wood fires arch, 5' deep firebox, that in order to get the flue pan really boiling hard I need to get a log or 2 to the back of the firebox when I fire it.

Maybe you would do better if you had a burner closer to the back of your fire box.

[Willstrtr]

How did this work out for you? Putting a few numbers through my head at 1.5 million BTU's you would be burning about 16.5 GPH of propane? Seems like a ton of gas in a 2X6 for what you will get off of it for syrup.

[maple flats]

In regards to comparing NG to propane, NG is lower cost for sure, but I noticed the original propane looks like it was using 100# propane tanks. If those were not filled by a delivery truck the cost per # is far higher.
My old bottler used propane as did a little 1.3 gpm tankless HW heater and a small finisher and a 500,000 btu torch to light the fire and I spent far more on propane than I do now. I put in a bulk 50 gal tank and get it filled by a delivery truck. I now run a 2x6 finisher, a 3.1 gpm water heater and a wall furnace for my RO room and I use about 1/2 the $ / year as when I used bottles I took to get filled while using far more propane.