can any one tell me what the efficiency is on the Hearthstone Mansfield
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EPA default efficiency is 63% like all other non cats and the independent cordwood efficiency is 73%. Take those numbers with a grain of salt, lots of variables.
Well, the Mansfield burns hot and clean: keeps your house nice and warm for a good spell. That's practical efficiency. It seems to me that you can try to split hairs and compare efficiency ratings but the real test is what it actually does season to season for users. There must be some good reason why they just default to 63%....
I'll add that any manufacturer that claims a specific efficiency for their stoves is trying to trick the consumer into buying their stove. Far too many variables in fuel and operation and changes with time to set an efficiency that you could use to shop with.
The test labs only publish the presumed average efficiency rating on the EPA labels because the emissions test burns don't produce results from which efficiency data can be derived. For one thing, emissions testing must be done on a level playing field, so they use identical "charges" of stapled-together dimensional Pine, kiln-dried to the same moisture level (I think it's 18%).
Many of the same labs that do emissions testing also offer efficiency testing, but the manufacturer must schedule and pay for separate tests, with different protocols. Efficiency testing is also sometimes done "in house", and monitored by test lab personnel. During efficiency testing, it is necessary to monitor temprature differentials and other factors not part of the emissions testing procedure.
As I understand it, during efficiency testing, fuel species, dryness, size of load and refuel rate are all up to the manufacturer, who is basically allowed to show the product being tested in the best possible light (nobody is going to test for efficiency with kiln-dried Pine). Aside from these manufacturer-controlled factors, there are several other variables that can affect the outcome of a given test, such as atmospheric conditions, calibration of testing equipment and the human factor. As a result, test lab personnel have stated that a posted efficiency score might only be accurate to within 6 points one way or the other.
In other words, in a different lab on a different day, a stove that claims a 69% efficiency rating might have scored as low as 63% or as high as 75%.
As to the validity of manufacturers' published efficiency numbers, there is an obvious motivation to post the highest number a given model has ever scored, which at least affords the shopper some kind of basis for comparison shopping, if not an accurate representation of real-world performance.
Many of the same labs that do emissions testing also offer efficiency testing, but the manufacturer must schedule and pay for separate tests, with different protocols. Efficiency testing is also sometimes done "in house", and monitored by test lab personnel. During efficiency testing, it is necessary to monitor temprature differentials and other factors not part of the emissions testing procedure.
As I understand it, during efficiency testing, fuel species, dryness, size of load and refuel rate are all up to the manufacturer, who is basically allowed to show the product being tested in the best possible light (nobody is going to test for efficiency with kiln-dried Pine). Aside from these manufacturer-controlled factors, there are several other variables that can affect the outcome of a given test, such as atmospheric conditions, calibration of testing equipment and the human factor. As a result, test lab personnel have stated that a posted efficiency score might only be accurate to within 6 points one way or the other.
In other words, in a different lab on a different day, a stove that claims a 69% efficiency rating might have scored as low as 63% or as high as 75%.
As to the validity of manufacturers' published efficiency numbers, there is an obvious motivation to post the highest number a given model has ever scored, which at least affords the shopper some kind of basis for comparison shopping, if not an accurate representation of real-world performance.
The question might better be posed--how much heat and how long do you want it for? Nice and steady or hot and fast burning? Seems to me that if you can get continuous heat, you will feel more comfortable-no matter what your thermostat reads. Now, you can afford that with wood, but I doubt you can afford that will fossil fuels? Or electric?/
jman, measuring and quantifying the "efficiency" of a wood stove is next to impossible, considering all the variables involved. Any of the modern EPA approved woodstoves on the market is going to burn wood "efficiently", meaning that it will, through primary and secondary combustion produce all the heat inside the stove it can. What happens then, in terms of how much heat is actually made available and transferred into the space you want to heat, depends on a myriad of things. What's the stove installation configuration (insert, hearth, freestanding)? What's the stovepipe/chimney configuration? What type/quality (moisture content) of fuel are you burning? Are you using forced convection (blowers/fans), or relying soley on radiation? What's the configuration of the space you're hoping to heat? The stoves are comparable...the "systems" into which we install them and the ways in which we operate them are what really matters. Rick
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