Under Pressured AOF - Help!

[Tuckeradams2012]

Good Morning Everyone,

I have had quite the stroke of luck over the past 4 months, I had originally gotten an knee surgery to repair my ACL from a skiing accident, then lo and behold just as I was feeling better, decided to slip on some ice in the woods and pull my knee cap in half and had to have that re-repaired. It has hung me up but I finally got my evaporator finished. So into the bush my family went, without me, tapping on my first season while I sat on the sidelines on a snowmobile, while my father and I test fired the evaporator with my new pan. All the seals were done nice, no smoke billowing out and the fire didn't even die out.

However, then I felt the AOF/AUF. I had bought this bounce house blower, and I hate to say, IT WAS TERRIBLE.

https://www.amazon.com/PicassoTiles-Certified-Inflatable-Bounce-Top-Mounted/dp/B074T1258F (https://www.amazon.com/PicassoTiles-Certified-Inflatable-Bounce-Top-Mounted/dp/B074T1258F)

The CFM flowing through it was laughable at best. Nothing like the rigid shop-vac that I stuck in the end to see how it would perform when I built it, which exhausted plenty of high pressure and CFM for what I think was needed. My question is, is this just a junk amazon purchase? I already have on order a Koala 1200 which has 7.25 max static pressure, but will this still not be enough? I thought these bounce house blowers were my answer to a cheap AOF/AUF dual setup. Gah. I have attached pictures, to give everyone some insight i have reduced the blower to 2" then a tee to 1.5 inch pvc to 1.5 inch conduit. 2" square tubing for the AOF, and as you can see, a bunch of holes in the AUF. I tried playing around with the ball valves, but even with with the AUF completely closed, its terrible.

Hoping I didn't mess up entirely, or maybe just thinking I am gonna run a loud shop-vac the rest of my time and lose my hearing. I don't know. Thoughts are appreciated.

2199721997

21998

21999

[Robert K]

The AOF looks good with what looks like the 10-12 degree turn down, the AUF looks small however, I have more tubes and I believe mine are 2 and 5/8 diameter. Also you may have to much restriction from the blower to the manifold. I matched the outside diameter of my blower and it only necks down at the manifolds. Perhaps remove the restriction and try again. Nice build.

[DocsMapleSyrup]

You are on the right track. I used a 1hp bounce house blower on my 2'x8' AUF/AOF arch. I mounted it in a box to reduce noise but have an opening in the back of the box to allow all of the air needed for the blower to perform. I did the same as tucker adams and brought the same size inlet as the bounce house blower into the manifold. I used 4"x2"tubing across the back of the firebox and 2"x2" going up the size. It looks to me like you are using too small of intake tubing as well as not having enough AUF outlet tubing. I built mine based on a thread from Rileysugarbush. You might want to search for that thread. Good luck.

[RileySugarbush]

Chad and Robert got it right. You want the feed from the blower to be at least as big as the blower outlet until it splits for the sides. Then each branch should be about half the area of the feed, with no restrictions until the nozzles. Looks like you have 12 nozzles with straight pipes of about 3/8ID " Those are too big in my opinion. Once you remove the inlet restriction, you will get too much AOF volume and blow all your heart up the stack. I would plug those down to 1/4 or smaller for this size rig. High pressure at the nozzles equals high velocity jets for good mixing. Small jets keep the volume flow within reason.

Sharing a blower with the AUF can be tricky too. Too much AUF opening and you lose all the pressure of the HP blower.

Make yourself a manometer out of some clear tubing and see what you get at one of the nozzles. You want at least 6" H20. My Koala puts out 8"

[maple flats]

If you want to draw both AOF and AUF from the same blower, you likely have at least 2 issues. That blower is too small, and your plumbing is too small.
I use one HP blower for both, the outlet on my blower is 3", I then have a 4" pvc pipe with 3 long sweep elbows and likely about 12' of pipe before it goes under the arch. There it splits into 2 pipes using a Y. In the 3" going to the AOF I have a ball valve which is open about 65-70%, then the 3" turns upward and the AOF enters the 2x2 tubing which distributes the air. The AUF goes thru a second ball valve and then connects to a 4" heavy gauge stove pipe which enters thru the back wall of the firebox on the floor. That 4" pipe has a cap on the end, about 6" from the front of the firebox. In the pipe I drilled 3 rows of 5/16 holes spaced about every 2". One row points straight up, the other 2 each point toward the outside grates. The ball valve for AUF is only open about 30-35%. The first year I tried several setting for the valves, those seemed to work best and I've not adjusted them in over 8 years or so.
I think you have choked the air flow way too much.

[Tuckeradams2012]

Chad and Robert got it right. You want the feed from the blower to be at least as big as the blower outlet until it splits for the sides. Then each branch should be about half the area of the feed, with no restrictions until the nozzles. Looks like you have 12 nozzles with straight pipes of about 3/8ID " Those are too big in my opinion. Once you remove the inlet restriction, you will get too much AOF volume and blow all your heart up the stack. I would plug those down to 1/4 or smaller for this size rig. High pressure at the nozzles equals high velocity jets for good mixing. Small jets keep the volume flow within reason.

Sharing a blower with the AUF can be tricky too. Too much AUF opening and you lose all the pressure of the HP blower.

Make yourself a manometer out of some clear tubing and see what you get at one of the nozzles. You want at least 6" H20. My Koala puts out 8"

So are you suggesting that I only have a few nozzles instead of 12? I tried to follow the 6" guideline that was put out in the combustion article by the vermont extension, also trying to somewhat account for not doing it at the front of the arch. I can work on beefing up the pipe from the blower itself to the 2 inlets, and I could potentially figure out a way to add a second line into the AOF to give it more flow. That would have to wait until the season was done, because I welded that 2' square pipe to the wall of the evaporator.

[Tuckeradams2012]

If you want to draw both AOF and AUF from the same blower, you likely have at least 2 issues. That blower is too small, and your plumbing is too small.
I use one HP blower for both, the outlet on my blower is 3", I then have a 4" pvc pipe with 3 long sweep elbows and likely about 12' of pipe before it goes under the arch. There it splits into 2 pipes using a Y. In the 3" going to the AOF I have a ball valve which is open about 65-70%, then the 3" turns upward and the AOF enters the 2x2 tubing which distributes the air. The AUF goes thru a second ball valve and then connects to a 4" heavy gauge stove pipe which enters thru the back wall of the firebox on the floor. That 4" pipe has a cap on the end, about 6" from the front of the firebox. In the pipe I drilled 3 rows of 5/16 holes spaced about every 2". One row points straight up, the other 2 each point toward the outside grates. The ball valve for AUF is only open about 30-35%. The first year I tried several setting for the valves, those seemed to work best and I've not adjusted them in over 8 years or so.
I think you have choked the air flow way too much.

I agree to the extent that I have choked off some airflow, but was hoping a stronger pump might overcome it. I've ordered the Koala 1200 which should give me more air and pressure than the one I currently have. I will work on getting it better piped, maybe with more sweeps instead of a 90 degree angle and will look around for a Y instead because as of right now, everything is honestly just pushed together without pvc cement.

Good thing is at the very least that I can still use the evaporator without either if absolutely needed, just a much reduced boil rate.

[Pdiamond]

won't using what you have now at least help the boil rate a little

[Tuckeradams2012]

won't using what you have now at least help the boil rate a little Oh I am sure it will, especially if I direct everything to AUF. New Blower came in today but is being held at UPS. We shall see how much force that has got going for it.

[RileySugarbush]

So are you suggesting that I only have a few nozzles instead of 12? I tried to follow the 6" guideline that was put out in the combustion article by the vermont extension, also trying to somewhat account for not doing it at the front of the arch. I can work on beefing up the pipe from the blower itself to the 2 inlets, and I could potentially figure out a way to add a second line into the AOF to give it more flow. That would have to wait until the season was done, because I welded that 2' square pipe to the wall of the evaporator.

Not quite. Everything is interrelated especially with one blower feeding over and under, so simple answers are not easy. Think of it this way.

AOF wants high pressure at the nozzles.
So no restrictions from the blower to the nozzles.
Pressure = velocity. 8" h20 at the nozzle will give about 80 mph jets.
If the nozzles are too big or too numerous, at 80 mph you get too much air over the fire, more than you need for secondary combustion, and that extra are just reduces the time the hot gasses are under your pans.
Also, if nozzles are too big or too numerous, you move down the performance curve of the blower and get less pressure and therefore less velocity for mixing.
If you open up the AUF too much, you get a fast burn and also pull down the AOF jet velocity.

So my recommendation was to close down the12 nozzles. Maybe reduce them to 3/6 by drilling through a stainless pipe plug and threading it in there.

And to check if you are getting full Static pressure at your nozzles do this:

Put some vinyl tubing tight over one nozzle. Make a loop in it and add water so you get a U of water at least 10" tall.
Turn on you blower and measure the difference in lights of the two water columns. That is your static pressure.
Open or close the AUF and see what affect it has. Plug all the nozzles ant the AOF and that is the Static Pressure at no flow. The best that blower can do.

Here is my first attempt from a decade ago. It worked but had some shortcomings: Nozzles too big, blower too weak. I have totally redesigned it with a bounce house blower, 8" h2o pressure, smaller nozzles, new controls for quick air shut off and quieter. But this old video will demonstrate the manometer at least.

https://www.youtube.com/watch?v=LhiEyMjVx5g

[maple flats]

Another thing that might help, run the AOF straight in from the blower and use at least a 1 or 2 size larger pipe until you branch off for the AUF and leave the AOF valve wide open, then throttle the air down for the AUF. Burning more wood is not your objective, burning the excess wood gases is the objective. Running less air under and getting more over will help. Also, 3/8" nozzles are too big, my 3x8 , as I said above uses 1 high pressure blower to run both and it works very well, my nozzles are only 1/4" black pipe. For best results you want velocity out of the AOF nozzles to create turbulance above the fire, not volume.
Just changing the air ducting that shows on the outside, to favor more pressure to the AOF will help.

[Tuckeradams2012]

Evening All!

So, I tried the Koala 1200, and truly it was still underpowered but an improvement. As suggested by Dave (mapleflats) I upped the output pipe to 3" (blower outlet is a little under 4") and then used a wye fitting to direct it down to the AUF with spaflex but it had a straight shot to the AOF. This helped but not a lot. Then I closed the AUF entirely, and still not that great even though it was a straight shot to the AOF outlets. Then I utilized John's (RileySugarbush) idea of blocking off some of the nozzles, 6 out of my 12 in fact to see if I could increase pressure and still with no AUF divergence and playing around with it, I still wasn't getting close to 80 velocity. Seems like I just have the wrong blowers, or I truly screwed my 1 blower for both AOF/AUF solution, I think my piping down to 1.5 inch for each just doesnt vut it for one blower for both.

My temporary solution for now is to separate out the two until the end of this season when I can bring up my welder without it being freezing.

1. AUF with my old underpowered cheap blower, which delivered a good amount of air underneath when it is by itself. I am guessing this will likely still get me the necessary bump in air I need to boil faster, but am likely risking a high temp in the stack without AOF if I cannot get it dialed in.
2. AOF utilizing a shop vac blower. It definitely got to a good velocity without any restriction, likely too much, so I can throttle it down. I will ask John to chime in on how many of the nozzles I should plug down from my 12, 3 on each side for a total of 9? I did confirm that i was utilizing 3/8 inch nozzles, so wondering if I can just clamp down hard on them with pliers and make them go down to 1/4"? Or should I find a 3/16 stainless plug (I wouldn't even know what section in home depot to find them! HA).

Thanks for all the insight everyone, as I still don't have a sugarhouse, just a huge evaporator on wheels, it is a challenge to set it up each time. Hopefully it won't be like this next season! First is always a doozie though I bet!

Tucker