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[mlappin]

Still haven't decided on a design yet. I followed jackel440's thread after I found it on a google search.  http://outdoorwoodfurnaceinfo.com/forum/index.php?topic=642.0

Then I stumbled on peacmar's build here and read it with great interest: http://outdoorwoodfurnaceinfo.com/forum/index.php?topic=2132.30

Then read his collection of information here: http://outdoorwoodfurnaceinfo.com/forum/index.php?topic=1182.0

Question is this, is peacmar's research flawed? When running my numbers for tube diameter and length for the secondary heat exchanger, every commercial unit I've compared my numbers to are undersized according to the formulas in peacmar's thread.

When comparing how much area I would need on just a vertical heat exchanger for easier cleaning (like Central Boiler or Heatmaster) I come up with a incredibly large number of vertical tubes required or do the turbolaters work that well? According to the formulas in his thread I would depending on the size of the tube need up to 28 vertical tubes, or basically enough to take the place of the horizontal tubes in a P&M design. Vertical tubes are only half as efficient at transferring heat compared to a horizontal tube, unless of course using turbolaters doubles the efficiency of a vertical tube, if so then I'm back to a quite reasonable number of vertical tubes only which would greatly simplify cleaning. Vertical tubes only also greatly simplify adding a bypass.

Fan size, for the 8 hour btu's I'm looking at I need about 63 CFM, or according to peacmar's thread would need 150% of that or roughly 95 CFM. I see some use up to a 500 CFM fan. From looking at some videos of the newer Optimizer I'm guessing from the dimensions of the fan (narrow but large diameter) and the sound of it running that they use a higher speed blower that is capable of producing the required air flow but at higher static pressure than most squirrel cage fans can produce. A standard squirrel cage fan when the static pressure starts getting much over one half inch the performance drops off drastically. The one thing that's not mentioned anywhere in the thread is what kind of static pressure if any to expect.

Going with a scotch design and the required cleaning doesn't really bother me that much, but the wife and I both like to travel in the winter. Normally if I cleaned it before I left it would be fine till I got back. However, about every other or every third year we travel to the UK to visit the wife's mothers side of the family. She doesn't have hardly any family left on her side here, but over their she has aunt's, an uncle, and a metric ton of cousins. When traveling that far it's not worth the hassle to stay for less than three weeks. When we travel Dad tends the boiler now as he has to come out every day to check the cattle anyways and I'm sure I can get him retrained to load a gasifier properly, but actually convincing him that it might need cleaned before we get home is something else entirely.

[mlappin]

I can say this, we have some extremely polite members on this site.

I've belonged to a few other forums that by now at least a few would have pointed out I'm being so anal retentive that I squish when I walk.

[BoilerHouse]

Miappin,  I have been meaning to respond I am just not sure I have a lot to add.  I wouldn't get too hung up on some theoretical calculations, I think your best bet might be to use some of the builds that have been posted here as a template and do as they do.  Also perhaps you could get out your tape measure and a sketch pad and have a good look at some commercial units.  Imitation is the sincerest form of flattery.  Also have you been over to hearth.com?  Most of these guys eat, breathe and sleep gassifiers.  They could likely help out with the tubulator question.  I know it will allow for shorter tubes and/or fewer of them but they are bound to be a bit of a maintenance nuisance. 
If you have a forced air system in your house you could simply shut the boiler down, keep the pump running, and go on holidays and allow heat to back-flow from the plenum heat exchanger into the boiler system.  I have done this for a week in the dead winter with no ill effects.  If the boiler has to be fired, my guess is that the tubes would stay relatively clean for three weeks.  My unit is not a gassifier, and I brush the tubes (6 x 2.250" x 30") every week (about 10 minutes), I am sure a clean burning gassifier would last much longer.

[mlappin]

Does it effect my extreme manliness in any way if lets say someone sent me some info on a 2 year old Eclassic that's selling for about what I expect it to cost me to build my own and I bought that instead of building my own?

Also thought if I bought it, then I could devote my time to other things this summer, and have more time to properly build mine. The other thing, I hate taking on major welding jobs in the summer. I hate the heat and found it painful to weld while wearing shorts and sandals for some reason.

[BoilerHouse]

Manliness is in serious jeopardy unless new found leisure time is spent drinking beer and watching UFC.

[jtepn87]

Manliness is not lost when intelligence and monetary reasons are used, using saved time and money to do other manly things. Such as in said example. However if used for laziness, or to do non-manly things; then manliness is lost, and a strike is placed against ones man card.

[mlappin]

May be moot anyways, sent em a email yesterday morning, still haven't got a reply. Could have sold as fast as they listed it.

[Sprinter]

I don't think you can be anal enough when planning a project like this. It eliminates a lot of shoulda coulda woulda's in the end.  I think if your capable, I would just copy the most efficient proven design that you can. I like the fact that this is the direction your headed.
Are you familiar with a Sampson loading valve like the use on natural draft indoor wood boilers? They sense the water temp and open and close the draft door by means of a lever and chain. So it's actually a variable rate draft which adjust the firing rate. It could be used in conjunction with the fan inlet to provide variable cfm rates.

[mlappin]

I don't think you can be anal enough when planning a project like this. It eliminates a lot of shoulda coulda woulda's in the end.  I think if your capable, I would just copy the most efficient proven design that you can. I like the fact that this is the direction your headed.
Are you familiar with a Sampson loading valve like the use on natural draft indoor wood boilers? They sense the water temp and open and close the draft door by means of a lever and chain. So it's actually a variable rate draft which adjust the firing rate. It could be used in conjunction with the fan inlet to provide variable cfm rates.

Yup, a friend is in the plumbing/heating/hvac business and he used one on his boiler.

I was going to use a PID controller to run a VFD that would run a three phase squirrel cage fan. Most of the affordable fans I can find the motors won't take running at a slower speed and I'm doubting the fans are balanced enough for overspeed.

A fan from Cincinatti Blower can be had new with a VFD suitable motor, for 600 bucks.

I've found some Ametek Nautilar combustion blowers on Ebay cheap enough, hook em to line voltage then supply a PWM signal or a 0-10 volt signal to control speed, problem is this, all are used, if it takes a dump and I can't find another you're looking at close to a 1000 bucks for a replacement from Ametek and a 8-10 week lead time.

Seriously thinking of using a off the shelf 110 volt squirrel cage fan, then having a Belimo damper actuator controlling  a baffle plate over the intake of the fan.

After some experimenting an absolute low setting could be found that would allow for the longest possible burn times under low heat demands without getting exhaust temps too low.