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John,
My side and end pipes are not insulated. I do have insulation on the cross pipe right in front of the flues. I was taking comments from other traders on the need for insulation, considered it and chose to try it without. I have boiled for 3 hours with the angles and they seem to hold the AOF pipes in correct position.
I like your set up too!
So how does it boil? Are you pleased with the addition of AOF to your rig?
Chris
Well Chris, I wish I could tell you. We just had 19 inches of snow and not a drop of sap yet. I'm anxious to find out if it was worth the trouble, and I'll report results as soon as I have them.
On the issue of insulation on your pipes, it is probably fine as long as the air is going through them. If you shut it off, the inside and bottom walls will get very hot and expand. The top will be at sap temp and the outside maybe a little cooler. That means it is really going to want to curl on you.
I like you idea of the spa blower, BTW.
John,
Man I hope you get some sap soon too. We are in a lull also. Gives us time to work the first bugs out of the add ons this year.
I think these spa blowers do a real nice job in both the WRU and the AOF. If I had it to do again I think I would have got 220V units and used less power and ran easier. They make some noise about 54 decibels. But a lot of the noise is in the actual evaporator from the bubbling in the WRU and thru the air nozzels too. Air out put is about 120 CFM. They run about $150, install easily, are weather proof, and could be mounted under the evaporator. Just run 2 inch PVC.
I think this was Dave 3% solutions idea. I will give him credit.
SM
Well I made some progress on ther AOF system. After the first boil I was having trouble with getting the outer syrup pan partitions to boil. I changed the 1/4" pipe AOF nozzles out to 3/16 drilled pipe plugs. This should keep cool air to a minimum and hopfully cause more turbulence. I also reworked how the air enters the dampers. Hope to test boil this weekend so I am 100% when we get the next run.
I finally got enough sap yesterday to do a 4+ hour boil and with 280 gallons of sap, I was able to get about 65 gph including startup and shutdown. Forgot to brush the flue pan before starting and it was third boil since it was brushed or I could have possibly done a little better. Running the under fire air wide open and the top wide open too definitely uses more wood in an hour but I can also get 20 more gph vs running with 80% top air and 20% bottom air. Not sure how much wood if any I would be saving running 20 less gph if any by the end of the day because of the much slower boil rate. I am firing every ten minutes running it wide open. Was running stack temps staying between 1400 and 1600+ after a couple of hours of boiling and it was eating sap if it stayed in those temps probably during best hour was well over 70 gallons.
WVM, I checked out your rig construction pics, and the thought that comes to mind is the higher stack temps to get it really going well. Is this a symptom of the slope back of the fire box transitioning lower than optimal for the drop flues? An idea that comes to mind is placing a row of fire bricks flat across the area at the transition just aft of the AOF tubes. This might function like a "trip strip" on an airplanes wing. Perhaps think nascar and wind tunnel testing, but in this case it's inside of the firebox. Might help mix the burning gases better, and get them higher up into the flues. The flames might go up over, and back down though, so it might boil even harder in the front of the drop flue pan, and behave similar aft. 5 gal/ hr improvement?
WVM, I think Len is on to something. Even though mine is a small flat pan rig, I made a change today. I was firing ever 7 minutes and I could get my stainless stack to glow red the first foot or so. Daryl suggested I put small pieces of brick in my flue area at the back of the pan. I'm boiling now. I've increased my firing to at least 9 minutes. No red stack. Haven't check GPH but full pan boil so it should be the same. What it comes do to is that I'm keeping more heat in the rig longer. I think every rig is just a little different. When adding the AOF we need to find that optimal set up.
Well I made some changes to the AOF system. I tried it out today and had alot better results. First thing I changed was the hole size, I changed from 1/4" pipe nipples to pipe plugs drilled out to 3/16". I also changed how my air dampers attach to the blower. The results were encouraging I boiled for about 45mins to heat up some water to clean the pans. The syrup pan was boiling the entire width of the pan and the flue pan was boiling very hard in the first 2ft the stack temp was about 650*. I am anxious to see how everything will work if I get a stack temp around 900*
Keep in mind, and I'll have to check my notes, but I believe the rule of thumb is every 100°F you raise your stack temp you are reducing the overall efficiency of to the tune of 5%.
I guess it depends on if you're after more GPH or more GPC (gallons per cord).
We just picked up a furnace blower, and we want to hook it up to our 2x6 leader drop flue evap. Does anyone have any pics. to give us a feel on how to do it?
Also I'm not understanding what it means to have a % going over the fire and a % under the fire. Under the fire I get but I don't get what over the fire means?