Oregon began testing wood heaters in 1984 with a method OM7. OM7 was developed with the cooperative efforts of industry, test labs and regulators. The method they all worked to develop was intended to allow regulators the chance to compare one wood heater to another in terms of emissions results.
In 1988, EPA began testing and certifying wood heaters, using Method 28, a variant of OM7. This method uses dimensional lumber. Mostly 2 x 4’s and 4 x 4’s. The number of each or the actual size of pieces used is based upon firebox volume (FV).
NEITHER OM7 OR METHOD 28 WERE INTENDED TO PROVIDE REAL WORLD DATA. BOTH METHODS WERE INTENDED TO PROVIDE A STOVE TO STOVE EMISSIONS COMPARISON.
In 2015, EPA promulgates the NSPS (New Source Performance Standards) and sets new limits and revises Method 28, now called Method 28R. During the period EPA promulgated the 2015 NSPS, state regulators started pushing EPA to find out how wood stoves performed in the real world….meaning when burning cordwood. The problem was and still is, there is NO Federal test method, called an FRM (Federal Reference Method). In the absence of an FRM, EPA wrote into the 2015 NSPS the option to test with an Alternative Test Method (ATM).
A few manufacturers began testing using an approved ATM, which had to be approved by EPA each time and each time EPA slightly modified the test method. EPA was warned their actions would create “confusion in the marketplace”. So EPA agreed to allow all manufacturers to test with a cordwood method developed by ASTM. This method, allows for different types (species) of fuels so long as they fall within a field of specific gravity (density). Methods OM7, 28 and 28R only allowed Doug Fir because the regulators wanted stove to stove comparisons.
The irony of this entire matter is, using the current ASTM Cordwood method removes the ability to compare stoves to one another because the ASTM Method has a great deal more variability in the method. What is even more ironic is some manufacturers compare their cordwood (ASTM) results to competitor test results that were obtained on crib fuel testing.
Nobody should compare a cordwood tested stove results to crib fuel tested results. They are not the same. Btu results are calculated using one standard (B415.1-10) for crib fuel testing and the ASTM method for stoves tested with cordwood.
Want proof? The data below is accurate for an EPA certified wood stove.
Model: XXXXX Year Tested Emissions (% Change) Efficiency Btu’s
Crib Fuel 2014 .45 gr/hr 80% 10,800-39,400
Cordwood 2019 1.9 gr/hr 77% 11,322-62,623
Same stove is 322% dirtier burning on cordwood, 3.9% less efficient and produces 37% more Btu’s on the top end. This is why you cannot and should not compare stoves tested with different methods!
An EPA certifiying laboratory explained in their words why the two cannot be compared.
“BTU output for both crib and cordwood tests are calculated in a similar manner using B415.1-10. But the wood burning methodology and test endpoint (for high burns) are so drastically different that they do in fact produce similarly different results. A cordwood high fire test ends when 90% of the fuel had been consumed, eliminating a portion of the tail of the burn, which artificially makes the burn rate (and thus, heat output) higher. But also just the fuel load itself, you are putting in significantly more fuel (10lb/ft3 instead of 7 lb/ft3) with no spacers. I have never done a side by side comparison of the two methods on a given stove, but cordwood high burns are typically 3.5 kg/hr or higher, whereas crib wood high burns are typically down in the 2s.”
EPA is working on an FRM. Once completed, it will become the new test method. When the FRM is introduced by EPA, the rule states they (EPA) can require all wood heaters, both crib fuel and ASTM tested wood heaters to be retested when the certificates expire. Certificates are valid for 5 years from issuance.
The fact is, a stove produces more Btu’s on cordwood than when using crib fuel. Here is a quick list of reminders when discussing this topic with customers…they count on you for the knowledge!
|
