AUF Blower Size

[TomorrowRiverMapler]

Looking for ideas on what others are using for blower size and how many on their evaporators. I have a home made oil tank arch that has a 2x3 fire box with an extended 2x6 flue pan and 8 inch flue pipe. Currently I have a small blower that has an output of 50 to 75 cfm. I saw a formula that said I need much more like 700 to 800 cfm which seemed pretty high especially from where I am today. I plan to upgrade to a larger blower I have with a 140 cfm output and was wondering if I should add a second one of the same size for 280 cfm? I'm thinking two fans are better than one for a more uniform air distribution under the fire and can throttle back if they are too much.
Thanks
Brent

[pobryan]

Brent, I have a 2x6 with a 10" flue. I added auf by taking the oil pump off a Beckett oil burner and ducting it into the back of my firebox with a piece of 4" exhaust pipe. It creates enough flow to make the cast iron ash door move and really makes the fire roar.
Pat


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[DocsMapleSyrup]

Brent:
I have a 550rpm Dayton blower that I bought from Smoky Lake Maple when I bought my pans $100-150 last year. It is on my homebuilt 2x8 arch. I have AOF as well and have a separate high pressure blower for that. If I were to do it again, I would feed both AUF and AOF with a bouncy house blower like a Koala KP-1200 and use a blast gate to control the pressurized air for the AUF. That way, if you ever decide to add AOF, you already have the motor. Just a thought. Here's my setup.

15077

[JeffB]

Brent..
Base your blower size on the size of stove pipe if blower is for air underfire. Just do the math and go from there


3.14 x radius x radius.
This will give you the area of your stack then use 5cfm per square inch.
This will give you approximate minimum blower size to go with.
If you go bigger it's easier to restrict air flow then it is to make more air flow .
Hope this helps !

[lpakiz]

Chad, from Docs,
If I were to do it again, I would use 2 blowers.
In order to keep stack temps reasonable, (and keep the sap in the pan), I need to adjust the air under fire (grate air) several times per charge of wood. Every time I adjust the under fire grate air, I am affecting my over fire air.
If I had a dedicated over fire blower, it would run constant, regardless of where the grate air was set.
Th Intensofire has 3 levers to adjust all the different air nozzles. With 2 blowers, 2 of these levers could be deleted. All I would need is a grate air adjuster.

[maple flats]

I use one HP blower for both and once I found the right balance I have not changed the settings in years. I do not even shut off the blower when I add wood. I found it not necessary when my grandson forgot to shut it down to fuel once and have not ever since.
For the CFM needed for just AUF you will do best at 250-300 CFM.
If you eventually go with AOF, you must have a high pressure blower (HP), a squirrel cage is not high pressure, it is low pressure high volume.

[RileySugarbush]

Funny, lpakiz, i had a two blower setup with HP Dayton and LP squirrel with individual inlet dampers. I'm much happier with a single HP ( Koala ) a blast gate on the under that is only tweaked occasionally, and single inlet flapper stop for firing. Much happier, though I am balancing stack temps with nozzle size this year plus a new longer arch and SmokyLake pans. More than one way to skin a cat!

[jrm]

With all the recent threads discussing blowers and audio, I'm thinking this might be the year to try that to increase my gph. I'm running a homemade barrel evaporator using a kit door and with an air flow opening below it. I have raised the height of my interior grate to be higher than it had been in the past, to ensure that the air from the air flow opening is getting under the fire.

I'm evaporating outside, I do have access to electrical by running an extension cord. I'm wondering if anyone has used carpet drying style blowers, such as http://www.homedepot.com/p/B-Air-1-4-HP-900-CFM-9-in-Air-Mover-Carpet-Dryer-Floor-Fan-for-Home-Retail-Plumbing-and-Water-Damage-in-Red-Vent-VP-25-Red/207012955. This one is outdoor rated, and I've seen others that are cheaper, also outdoor rated, could be used. I'm not sure about setting up with just a blower itself, in terms of kitting that out to be protected from the elements,

Thanks,
Janet

[mspina14]

Here's the blower I installed on my barrel stove I used to have:

15475 15476

I think the blower was 135 CFM. I connected it to the bung hole in the lid of the barrel with a piece of black pipe, a PVC adaptor, and some dryer venting duct.

Worked great. Made for a very hot fire.

Mark

[jrm]

Thanks for the pics, Mark. Those are helpful, including the blower brand. Being young (not really!) and unaware when I made the evaporator, I have the bung hole at the top of the door, not under the vent, the way yours was set up. After my second boil, I realized the error of my way. I do thing about finding another barrel lid and recutting. But, as I was thinking of adding the blower, I thought I could connect with a rectangular duct adapter. Seeing how you made it work is quite helpful.

On a different note, can you tell me what the piece is you are using to cap your stack? Having lived in Colorado for many years, I have put a "tent" of hardware mesh at the top of my stack to help control any possible embers, but that gets smashed, and of course, does nothing to help with snow/rain.

[mspina14]

I used a galvanized stove pipe cap on the barrel stove evaporator:

15478

Less than $10 on Ebay but will rust from the heat in a couple of seasons.

Currently, on my Mason 2X4 evaporator, I use this:

15479

It's stainless steel and costs about $40, also on Ebay. But it will last much longer.

Hope this helps.

Mark

[Ghs57]

I went with a bounce house blower I bought used off of eBay. It runs both my AUF/AOF. There is a damper on both pipelines. The air made a world of difference. Stack temp is low, fire is turbulent and very hot. Right now I'm moving the fan outside due to the noise level.

[jrm]

Looks like it's time for more eBay/online shopping. Thanks for the tips on the stove cap, even if I went with the galvanized model, much nicer and easier, I'm sure, that mine mesh method.

I didn't think to look for bouncy house, or other blowers on eBay. I sell there, but I don't think about the wealth of stuff I could find for this. Thanks for the suggestion.

[newmod]

I am using a 2x5 smoky lake hybrid pan. Homemade airtite arch. 6 inch fule about 10 ft tall. the blower i use is from and old power vent furnace, running AUF. it works extremely well. I know some HVAC guys and he just gave me a couple fans from his scrap pile. IT WORKS GREAT. I wouldnt change a thing