Lets talk 35:1 woodstoves

[Gunner]

What exactly is a 35:1 woodstove?

Are they EPA exempt?...why?

What kind of emissions do they produce?

 

[webbie]

This is a stove that has it's air control fixed open to a certain degree and therefore is not classified as an "airtight".
Being so, it is not subject to EPA standards.

In other words, these EPA standards apply only to stoves that can be choked down past a certain point.

As far as emissions, it depends on the model. 35:1 models that are similar to EPA models in looks and construction are fairly clean burning, but models like Elks favorites - the cast box stoves by Vogelzang - these are probably less efficient. I'd give a range of 30-50% depending on model....

Even though these - in theory - do not burn as long as EPA stoves, they can often be choked down by using a stack damper and other similar methods with the result being satisfactory performance.

The 35:1 specifies the Air to Fuel ratio - not exactly certain how they figure that (whether the wood is converted to gas form to figure the cubic feet, etc.)

 

[BrotherBart]

They are stoves that don't allow you to cut the primary air supply back lower than a 35:1 air to fuel ratio. Essentially the air fuel ratio of an open fireplace. So the EPA treats them as exempt just like open fireplaces.

There is a lot of discussion going on about them at the EPA level.

 

[webbie]

3.1 Air-to-fuel ratio means the ratio of the mass of
dry combustion air introduced into the firebox to the mass
of dry fuel consumed (grams of dry air per gram of dry wood
burned).

 

[Gunner]

Ahhh, I see.

A damper must be manditory then to avoid overfiring?

 

[Gunner]

There is a lot of discussion going on about them at the EPA level.

The government must have them in the crosshairs

 

[BrotherBart]

There is a lot of discussion going on about them at the EPA level.

The government must have them in the crosshairs

Nah. They are government. They discuss a lot. They are interested in OWBs too and you don't see much happening with them.

 

[webbie]

Basically, the Bush Doctrine, meaning industry always can police itself - has taken hold at the EPA. Therefore they have now have passed a "Voluntary Compliance" programs for Outdoor Wood Boilers and also for many other similar products in our industry and others. What that means is NOTHING. Manufacturers can make and sell units which burn dirty.

As far as dampers, etc. - since these exempt stoves are probably tested with oven-dry wood as per EPA, they will generally burn hardwood firewood at a much lower rate - although the damper in the pipe is needed to get 'em down really low.

 

[stoveguy2esw]

englander 12-fp series, only draft controlled 35-1 A/F ratio freestanding wood fueled room heater on the market, look to the left , thats it


most are "fixed" air input units that are only able to be controlled with a damper in the chimney. furnaces are actually listed as epa exempt ,(personally i'd like to see that changed) especially OWB's as they waste huge amounts of wood and are IMHO an eyesore when in operation biggest problem behind them is they are literally un-regulated, so no emmissions standards, efficiency ratings????? yeah right , show me. and gawd they cost a fortune compared to what a good (even top of the line) epa woodstove costs, insurance companies actually like em cause they are not inside of the house, thats the only advantage (if you call having to go outside, trudge through the snow, load the OWB an advantage) now if they were efficient clean burning units , maybe i wouldnt bash them so hard, but gee whiz , they aint! i think they should be put through the same testing standards that indoor units are as far as epa standards are concerned, just because of this... answer honestly , does having the firebox outside the house make it as clean as a unit designed to go in a house has to be?????? of course not, so why do indoor units have to meet clean air standards when OWB's do not????

 

[webbie]

The reason that the EPA gives is the Big Picture. That there are millions of stoves sold, but not enough of the other products to make a big difference in the national air quality. So there is a method to their madness, but it does not help those who live in a valley with an OWB.

My thinking has always been a relaxed standard for central heaters and OWB, perhaps a max of 15 grams per hour, and also that they would not have to burn as low as stoves (maybe 20K minimum instead of 10K).....at least that would be a good first step and then it can be revisited if the units become more popular - which gives the makers plenty of time for R&D.

BTW, Europe does have standards for these - and has had clean burning central heaters for over 15 years. So it is not in any way an impossible task.

 

[BrotherBart]

The reason that the EPA gives is the Big Picture. That there are millions of stoves sold, but not enough of the other products to make a big difference in the national air quality. So there is a method to their madness, but it does not help those who live in a valley with an OWB.

My thinking has always been a relaxed standard for central heaters and OWB, perhaps a max of 15 grams per hour, and also that they would not have to burn as low as stoves (maybe 20K minimum instead of 10K).....at least that would be a good first step and then it can be revisited if the units become more popular - which gives the makers plenty of time for R&D.

BTW, Europe does have standards for these - and has had clean burning central heaters for over 15 years. So it is not in any way an impossible task.

How do they measure BTU output for stoves Craig?

 

[elkimmeg]

a little off topic but still dealing with exemptions if a stove like the death box I hate has a cook plate a loop hole in the EPA reconsies it as a cook stove and it becomes exempt
that same manufacturer list some stoves as woo/coal coal again is exempt but when onr reads it manual the disclaim coal usage wood only

then as mentioned is the air fuel exemption