Will this draft inducer work for the Jorgensen Wood Gasifier?

[deerefanatic]

Well, through an electrical mishap, I managed to fry the draft fans on my stove today.... Being I wasn't entirely happy with the control options afforded me by these fans, I'm again seriously wanting to go with a negative draft system using a draft inducer......

I found this unit here: http://www.draftinducers.com/ad1.htm

I talked to the folks there and they said that the unit is rated at 220 cfm on an 8" stove pipe (which is what I have). I asked them if that was free-flow or with a stove attached. They said was with a stove attached. I then described my stove a little and the guy said that they sell alot of them to Greenwood owners....

Anyhow, does this look like it would do the trick? I plan to put it in and then adjust primary and secondary air mixtures using damper sliders on the inlets.

Thanks!

 

[deerefanatic]

I see Northern Tool sells it as well for less money: http://www.northerntool.com/webapp/wcs/stores/servlet/product_6970_21928_21928

 

[steam man]

Matt-I have to say I am impressed with your tenacity in working on this project. I will say I think the salesman is a bit off. Fans are designed for a rating at a specific backpressure which then determines the power required to run it. That said I am wondering how much you varied from the gas nozzle sizing through the ceramic refractory. Gas flow though a nozzle is not linear so if you varied it from nofossils boiler you would need to calculate the size fan needed at the new nozzle size to achieve the same gas velocity taking into account the flow restriction through the boiler. Obviously you need some oversizing. If you could somehow add a duct to the inlet of the forced draft fan a relatively cheap flow monitor could be installed to help calibrate your flow rate.

I need more coffee...........

Mike

 

[pybyr]

here's my suggestion

picture a jet pump and how it uses a little primary pump to send some small volume high velocity flow through a bigger venturi to push a much larger volume of overall flow

make a pneumatic "jet pump" in the exhaust stack of your unit.

by doing that, the high-velocity low volume fan that "makes it go" can actually be entirely out of the hot area, and feed its air flow into the venturi via a metal tube

 

[deerefanatic]

True, I understand that. And that is where I run into problems. The EKO's don't have the CFM listed on their fans. Well, they may, but it's all in Polish! So I'm left making a large guess and working from there.......

As for the salesman, I know that he's hopeful on that fan, but where else do I go for info? thats the only wood-rated draft inducer I've seen. I'd much prefer the Tjernlund I series as it will move close to 560 cfm through an 8" stove pipe attached to an oil boiler.......

Nofossil says that he figures for his EKO with an output of 80,000 btu/hr, that he's moving 23cfm total through his stove.... So, being my design goal is 320,000 btu/hr, I should need around 100 cfm to combust properly.

So, back to the original question, will this type of fan work?

 

[pybyr]

here's my suggestion

picture a jet pump and how it uses a little primary pump to send some small volume high velocity flow through a bigger venturi to push a much larger volume of overall flow

make a pneumatic "jet pump" in the exhaust stack of your unit.

by doing that, the high-velocity low volume fan that "makes it go" can actually be entirely out of the hot area, and feed its air flow into the venturi via a metal tube

would that dillute & cool off the gases?

with a gasifier, you should have no creosote worries, and I'm suggesting on the flue side, so you've already captured all the heat that you are going to--- and the forced draft on the flue side of the unit means you arent' dependent upon natural draft/ rising gases to pull things up your chimney -- so, to me, cooling or dilution seems irrelevant

 

[deerefanatic]

Hmm.... Well Pybyr, It sounds like a great idea, but I wonder how well it would actually work as these gasifiers place a fair amount of load on the draft because they don't flow air well due to the convoluted path the air must take.......

Interesting thought though.....

At this point, I'm either going to go with forced positive or forced negative draft... I'd rather do negative, but if I can't find a fan that will do the trick for a reasonable amount of money, I'll go with another set of positive draft fans.......

 

[deerefanatic]

OK, I just got off the phone with Tjernlund and their tech told me that the paddle-wheel style draft inducers will not work for what I want.... They can flow alot of air, but they can't overcome very much in terms of static pressure.

So, that leaves me with no choice but to continue with the positive draft setup I had before....

 

[deerefanatic]

Alright, I'm looking at positive blowers from Grainger...... Anybody care to throw a wild guess at the static pressure presented by one of our stoves to the fan? If I know that, I can select a blower to move the air I want from the derating curves.......

 

[pybyr]

Hmm.... Well Pybyr, It sounds like a great idea, but I wonder how well it would actually work as these gasifiers place a fair amount of load on the draft because they don't flow air well due to the convoluted path the air must take.......

Interesting thought though.....

At this point, I'm either going to go with forced positive or forced negative draft... I'd rather do negative, but if I can't find a fan that will do the trick for a reasonable amount of money, I'll go with another set of positive draft fans.......

for fans- whatever approach you try try looking at

www.surpluscenter.com
and.or
www.surplussales.com

for the "jet pump" idea, try a "Y" fitting with the smoke flowing straight through, and the branch feeding in. insert a smaller pipe, via entry through the branch, into the center of the main flow, with a final 45 degree fitting so that its outlet is pointing straight in the direction that you want the smoke to go. aim some extreme high velocity air down that tube and into the middle and see what happens. better still, set it up with a venturi shape, just like a carburetor, except in this case you're injecting the high velocity air in where a carb would be drawing the fuel out

 

[deerefanatic]

I got my original fans at surplus center.... They just don't seem to have anything that fits the bill for what I'm after.. I'm thinking I want to stay with a currently manufactured fan just for the ability to quickly get parts when needed......

As for the venturi idea, I think it would take a bigger fan to create enough draft that way than to just hook it straight to the stove...

 

[deerefanatic]

So, nobody can venture a guess as to the back pressure that a downdraft stove presents to the fans?

I suppose I can go big and throttle them down with a restrictor baffle.....

 

[pybyr]

So, nobody can venture a guess as to the back pressure that a downdraft stove presents to the fans?

I suppose I can go big and throttle them down with a restrictor baffle.....

what if you run some experiments with no fire and a vacuum or draft gauge and use some sort of suction at the flue.

then you could see the readings at the flue and then at the air feed, so as to get some kind of educated guesses of how much drop there is in between?

 

[deerefanatic]

THAT is a good idea... I have a shop vac that the motor is removable for use as a leaf blower..... should be able to duct tape it to the chimney and measure the draft.......

Brilliant, absolutely brilliant!!

 

[TCaldwell]

matt in the end you might need a 3 phase motor that you can modulate, 1 for experimentation at different hz rates to calculate flow with a inexpensive anemometer at the top of the flue stack, rather than guessing on the sweet spot that IS a moving target throught the burn process, also find somebody with a testo portable flue gas analyser to determine what cfm at what point offers the best effiency based on 02 percentage. without this process you are chasing a moving target, espically if you want to take this market. I applaud your ability and tenacity, keep it up. read jbatty's boiler resources thread for a little more info on my above thoughts .

 

[deerefanatic]

Yes, a flue gas analyzer would be the ticket........

I'm thinking at this point I'll test the static pressure with my little shop vac/leaf blower thingy... It will be a high reading due to the raw CFM that the blower will be trying to shove. Then I can get a worst-case pressure and can get a blower ordered from Grainger. My top priority right now is get it working again so I have heat for myself.... Then I can start messing around with the unit to get it dialed in using inlet restricters for the blowers.. Maybe next spring or summer I can get down to the O2 calibration and stuff..

Heck, maybe by spring I'll have the money to pick up a Testo for myself... Looks like the go fairly reasonable on eBay in working condition.

 

[WoodNotOil]

Here is a link that show some info on the fan that is in my Tarm Solo 40: http://ebm-papst.industrialpartner.com/centrifugal/g2e108-aa05-44.htm

It lists it at 91cfm for my 140,000 BTU boiler. It is manufactored by EBM and made in Germany.

The Froling boiler that Tarm USA is now selling uses a negative draft fan. Perhaps getting a "replacement" fan from a company like that for a similar sized boiler would put you on the right track. http://www.woodboilers.com/product-detail.aspx?id=50

I hope that info is helpful in some way. Great job so far on your boiler!

 

[pybyr]

THAT is a good idea... I have a shop vac that the motor is removable for use as a leaf blower..... should be able to duct tape it to the chimney and measure the draft.......

Brilliant, absolutely brilliant!!

glad to help- I love the way we get to "collectively invent" around here

since about the time I exit-ed diapers, I've loved to repair things and scrounge and build things out of bits of cast off stuff, and half the fun is the puzzles of how to figure out different ways to ascertain and find ways to the right fit

 

[pybyr]

Yes, a flue gas analyzer would be the ticket........

Heck, maybe by spring I'll have the money to pick up a Testo for myself... Looks like the go fairly reasonable on eBay in working condition.

I keep thinking that for some things like combustion analyzers, and probably various other instrumentation it would be GREAT if someone were willing and able to set up and administer a medium-term rental program. You'd pay a deposit, and be liable if you returned it ruined, and then be able to rent it on a weekly or monthly basis.

I bought a Bacharach "Wet Kit" combustion analyzer NOS and find its instruments really handy, if a bit retro (although I like that in a way- never needs batteries), and I'd love to be able to use one of the electronic ones that lets you watch changes in readings in real time, but don't see how I could ever justify the purchase as something that'll really save me back the $$$.

With all the DIY-ing going on in alt-combustion circles (greasecar and grease furnace folks, wood, & etc) surely someone could make enough money to justify the overhead and labor of an on-line "Instruments-R-Us" service...

 

[deerefanatic]

Yah, really!

WoodNotOil: Thanks sooooo much for getting the info off your fan for me!! I found the spec sheet and derating curve on Papst's website: http://www.ebmpapst.us/allpdfs/G2E108.PDF

Now I've got somewhere to start. I'm going to make a homemade manometer tomorrow and take some pressure readings, then use those to plug into the derating curves and figure out a blower thats about 125% of what I need.......

This is starting to look better!

 

[pybyr]

matt in the end you might need a 3 phase motor that you can modulate, 1 for experimentation at different hz rates to calculate flow with a inexpensive anemometer at the top of the flue stack, rather than guessing on the sweet spot that IS a moving target throught the burn process

except you don't necessarily need a 3 speed fan, which might be hard to find in the sizes Matt is dealing with. It is possible to modulate the speeds of single phase AC motors with TRIAC based controls. I started looking into those for hopes of creating a variable speed circulator at lower cost than the permanent magnet ECM ones, but discovered that with the single phase/ TRIAC controllers, you slow the motor but don't really pick up advantages in (in fact have a net loss) of the relation between electrical input and mechanical output

for some concepts, see
powerelectronics.com/mag/506PET23.pdf

and for Matt's efforts to just "find the right amount of blower" it's the variability, not the efficiency, that's the focus

and if this is of interest, I think I still have some product brochures set aside that I could backtrack

I applaud your ability and tenacity, keep it up. read jbatty's boiler resources thread for a little more info on my above thoughts .

can you point me back to which thread by jebatty you're referencing? I think I found it once here, but sometimes get lost in all the good info that's awash in these parts

 

[deerefanatic]

pybyr: The thread jbatty is talking about is this one here: https://www.hearth.com/talk/threads/24164/

See post number 23 in that thread..... Very informative.

At this point, I don't think I'll do the variable speed thing. It's just easier to have a sliding block-off plate on the blower to throttle it back. And I can measure air flow with a simple manometer kit from Dwyer Instrument that can allow me to compute CFM's for when it comes time to determine the correct fan for the job......

 

[deerefanatic]

WoodNotOil: Is that the only draft fan in your stove? Or is it the same fan for both primary and secondary air? Or same, but two seperate ones?

Thanks!

 

[WoodNotOil]

There is one fan and separate places to adjust primary and secondary air flow. The primary is an adjustment where the fan mounts on top of the boiler on the front right when facing the front of the boiler. The secondary air is adjusted with a slider near the bottom door, however that lever could control an opening in some other location on the boiler. Here is the only inner image I could find online of it: http://www.cnypipeworx.com/Alternative_Fuel_files/3boilerad.jpg

 

[deerefanatic]

Ok, that helps me quite a bit... A single fan is a viable option then, which is a welcome thought.........