jay3000 said:
Thanks. I also notice a lot of different efficiency ratings but the particulate ratings are similar..
How can two stoves have nearly equivalent particlate rating but their overall efficiency rating are 15% different??
the "overall efficiency rating" is "default" in order to maintain a "true" efficiency rating the manufacturer must pay a pretty significant sum , and recertify (paying that significant sum each time) at a much more frequent rate. this translates to a higher manufacturing cost which would end up being passed to the customer through higher prices (which helps no one except maybe the testing facility who have to earn a living as well) if you take a peek at the epa site (broken link removed to http://www.epa.gov/woodstoves/index.html) look up the listing of epa certified stoves sold in the us you will find that virtually all will list the default number for the category they fall under , cat, non-cat , pellet, they all have identical ratings as they accept default.
now, if you understand the criteria the units have to meet to be epa certified, the combustion efficiency they hit at testing is going to be much higher than default or they will not burn clean enough to pass. thermal efficiency (heat transfer efficiency) varies greatly in testing when you look at a timed test , and think , well steel conducts faster than soapstone, so the transfer rate would be higher, this isnt necessarily so , faster yes , higher maybe not , soapstone absorbs heat and releases it over a longer period, testing which would reflect transfer efficiency would not be fair to them when compared to steel or cast iron even though the heat stored and released by the soapstone stove would conduct into the room eventually.
personally i put a lot of stock into the PM readings.(understand im industry) granted this is not done under real world conditions with john q. public's wood, but consider this , if a stove hits 1.6 (to use the 30-nc as an example) in testing , and another brand (im not going to name an example , but say stove "x" hits 3.2 GPH(or twice the PM) in testing with the exact same criteria, it stands to reason that in real world use , the stove with the lower GPA is still burning cleaner, and cleaner in my mind is a higher percentage of the actual log is consumed rather than being dragged up the flue , so the more of the actual wood is burned (PM is small pieces of solids in smoke which is really unburnt fuel) the more efficient the stove is, and the more BTU's per log you garner. (not to mention the cleaner your flue should be split for split)
all that said , in the world of EPA cert stoves , the difference is minor in heat output for units of similar firebox size and construction. the real litmus tests are "looks" , "price" and "support" the combination of the above should be the deciding factor in what you are looking for in the firebox size you require to heat the space you wish to heat.
there are many fine brands of stoves out there, any one of these brands ofEPA rated stoves will perform far better than a pre phase 2 non-epa stove of the same size will as far as BTU in the house per log. search for the look you like, the size you need, and with features you like and in your price range. which ever one you pick will very likely make you happy.
