Question on EPA OWB Sizing

[ecrane99]

Hi All,

I am now looking at outdoor gasification units. Is it true that you can oversize a gasification unit so that it only needs loading once per 24hrs. My house is well insulated 2500sf and am now looking into the greenwood aspen 175. I learned from this forum that the traditional OWB will idle and smoke if oversized but have seen some comments that the new gasification owb burn very hot and can be loaded up with wood for a 24hr burn, but not sure if that is true.

 

[webbie]

I would say, in general, that you should not oversize and you should not load every 24 hours. The Greenwood chart shows 8 hour burn cycles and that is probably the design burn time - although you may make it to 12 or so in more temperate weather. Turning a boiler down too low results in poor combustion and also premature failure of certain parts due to the buildup of corrosive acids.

 

[muncybob]

Soooooooooo, are you saying that no matter what type of boiler(OWB, gassifier, etc) that if you go "no storage" you should undersize the unit?? That seems to be what I understand from other posts...but I'm not certain I really undertand why!?

 

[webbie]

I'm saying you should properly size the unit.......exclusive of storage. Large storage does give the ability to EITHER oversize or undersize because you burn full boat - and can reload twice in 8 hours (for instance) and charge up the storage for 24 hours. But if you want the boiler output to more carefully match the home AND for the unit to burn relatively clean and efficiently, then a 4-9 hour burn time is probably optimal. Note that some OWB have a large water jacket which could be considered storage.

 

[ecrane99]

I just found that Sequoyah makes a smaller gasifier E3300 which is smaller than the greenwood aspen 175.
The Sequoyah E3300 is the smallest outdoor gasifier I have found so far. They have more info than greenwood has on their website including a video http://woodgasificationfurnace.com/ also http://wdheat.com/. Looks to me like the E3300 could be a nice fit for me. Can anyone comment on the Sequoyah company and their new outdoor gasifiers?

 

[greeninsulation]

The Green Gasification:
, sizing depends upon home size, btu , location etc. People should call and not go just by the specs online. Going larger is advantegous in that it takes longer log size etc. More thermal mass is always going to retain heat longer. these units are built out of 1/4" boiler plate and will get a true 18 + hour burn time out of them. These units have NO cataylic converters to burn out, long exhaust travel, Low emissions and burn 50% less wood to heat 100% of home,business, hot water. Demand is huge. see video at www.WoodGasificationFurnace.com

As a Seller of these, I will be Happy to answer any questions about either the E3300 or the E3400

 

[webbie]

Green,

do you have independent lab tests showing a clean 18 hour burn?

Also, in general, if you are the seller of these units we discourage direct commercialism here on the discussion forums - if you want to advertise on Hearth.com like other vendors, contact Eric Johnson (moderator) or myself using PM or email.

No problem with introducing us to the availability of the units once, but I notice you are relatively new and perhaps not familiar with our stance on that.

Welcome to the forums and boiler room!

 

[greeninsulation]

NO lab results but testimonials from satisfied customers. am not trying to advertise but trying to answer peoples questions straight from the "horses mouth" sorry

 

[webbie]

No problem with answering questions or right from the horses mouth....we welcome that, as long as we know who you are and your relationship with the company.

That web site crashed my browser twice - the video should certainly not automatically load and play!

Anyway, glad to see they are EPA passed. Large units.....even the smaller one is over 20 cubic feet of firebox. As a simple example, if a person loaded a 20 cubic foot firebox twice a day (every 12 hours), they would burn one cord in 3 days. Even if they loaded it 1/2 way (the minimum mentioned on the site), they would burn a cord in 6 days. So it would seem as if these units were for people with almost unlimited wood availability and large heat loads. As a for instance, one member here (nofossil) burns 4 cords a year to heat 3500 sq ft in Vermont....in a boiler with a firebox 1/3 or less the size. These units would burn that 4 cords in less than a month with 1/2 way filling twice a day.

I suspect these large units will be good for a subset of wood burners - those with their own woodlots and large buildings and heat load. At the same time, I have numerous concerns about massive fireboxes (over 10 cubic feet)......especially I have concerns about the buildup of corrosive liquids and premature burnout. I also have concerns about overall efficiency and amount of fuel burned. It took years before the original designers of downdraft units (Eshland, Tarm) discovered that using the units at lower capacities (long burns) ate the steel away prematurely. Will we see the same with a bunch of OWB downdraft units newly introduced to the market? Only time will tell.

Certainly don't mean to be negative or too nervous, but having seen with my own eyes what happened to the early Wood Guns and Tarms it is a question worth asking.

 

[ISeeDeadBTUs]

NO lab results but testimonials from satisfied customers. am not trying to advertise but trying to answer peoples questions straight from the "horses mouth" sorry

Um, Craig??? Just my two cents but Dudes like this should be labeled as "salesperson" or "Company Rep" or something similar, before some newbie ends up on this site and thinks he/she is getting some sort of unbiased observation.