Master Forge

[peakbagger]

When I totaled my Toyota Prime and bought another one for a total of $15,000 of tax credits I had to be darn sure I paid 15K in taxes that year, I sold off some mutual funds that had lots of capital gains on them just to make sure as the EV credits did not carry forward, it was use them or lose the amount above what was owed in taxes.

These days almost everyone has a IRA, if they need to pay more taxes to cover a credit, they can always do a conversion to Roth IRA.

 

[EbS-P]

As far as I can tell it's a new stove by a Taiwan grille maker. It is not listed on the EPA site for the tax credit, nor is the company. Actually, there is no record of it in the EPA database. I tried to get a manual and no luck so far. There is no company website and Lowes does not have the manual listed. They need to be careful here. This could be lawsuit territory if the claim is false. Caveat Emptor.

Here are the epa certs.

EPA Information

Our wood and pellet stoves are made to provide you comfort. Built by experienced heating professionals and backed by industry leading customer service.

www.cleveland-ironworks.com

Edit… way late to the party.

 

[begreen]

Enerco stoves also show up now in the EPA database. None of their woodstoves have an HHV that qualifies for the tax credit.

 

[gruesome]

Does anybody know (and could maybe post) how the efficiencies are computed in the Polytests wood stove tests, or similar tests in general? I see the combustion efficiency, heat transfer efficiency and overall efficiency columns in the spreadsheets in the report, but the procedures in the report seem to only specify the emissions calculations. I don't see anything about efficiency.
I'm guessing that the combustion efficiency (about 95%) might be computed from the CO content (incomplete combustion), but the heat transfer efficiency (about 75%) really dominates the overall result. The stove under test is not sitting in any kind of calorimeter (it is sitting on a scale to determine the fuel burn rate), and ambient temperature in the (rather large) room does not seem to change much. They do measure the stove surface temperatures on all sides. Are they just assuming some heat transfer coefficient to air? But how could they, as they apparently have the attached blower going (transfer coefficient is a strong function of air speed)? Flue gas temperature is monitored, but they are only monitoring the sampling volume flow, unless I misunderstand their setup (the flow meters are in the sampling lines, not the main flue). Even if they knew the flue gas flow, are they assuming all flue gas energy is lost?

Anyways, I would appreciate a comment, if anybody knows how the efficiency measurement is done.

 

[gruesome]

I found part of the answer: The EPA uses the Canadian standard CSA-BS415.10, which determines efficiency using the 'stack loss method'. Unfortunately I can't find BS415.10 (it's very annoying - and actually seems wrong - that standards that are part of the law still cost money to look at), but an older version BS415.1 has two prescriptions for calculating the efficiency. Since the Polytests spreadsheet (contained in the Enerco EPA certification file) contains the stove surface temperatures, but not CH4 measurements, I assume the alternative method in Appendix C is used? The description of the Polytests setup seems to contain only three of the four sampling trains described for the alternative method, though.
Maybe the method was simplified in later versions of BS415? In any case, it seems the full energy entering the flue (and not for example the energy leaving a stove pipe of some standard length) is considered lost, and in the alternative method also the heat energy stored in the stove mass.

If anybody here has looked into this before, I'd really appreciate comments and clarifications.

 

[EatenByLimestone]

@BKVP

Can you clarify a little?

 

[gruesome]

I don't see BKVP having posted in this thread. - Nevermind, now I get it. He must have stoves certified, so he would know how it works and what the underlying assumptions are. Yes, that would be great if he could comment.

To me that BS415.1 pdf is just confusing, and especially that second (alternative) method seems to have some assumptions and fudge factors (that factor 1.03 in equation 13 just seems to come out of nowhere) and subscripts replaced with commas so you have to guess what they mean; it's almost like the engineers went 'oh, it's only a standard, and just taxpayer money, no need to proofread this after typesetting, actually, let's run it through the combobulator and replace some random '2's and 'd's with commas'. Now if the actual certification filing had a real spreadsheet with the formulas, that would help, but it's just a pdf printout.

 

[begreen]

I couldn't find justification for the Master Forge woodstoves to be qualified for the tax credit certificate based on testing. Originally it was found that their pellet stove qualified, but not their woodstoves. I haven't looked at recent testing to see if there is an update.

 

[gruesome]

I couldn't find justification for the Master Forge woodstoves to be qualified for the tax credit certificate based on testing. Originally it was found that their pellet stove qualified, but not their woodstoves. I haven't looked at recent testing to see if there is an update.

I don't think there has been an update to the Enerco wood stove efficiencies, at least I haven't found one for the June 2022 Polytests test report for the H100 (and similar) medium sized wood stove that I own. So it would still be at 73% weighted efficiency (using the high heating value for the wood), and thus does not qualify.
I found this thread by @Nofossil. If I read the numbers right, every percent of dry basis water content steals 0.15% of efficiency. To gain 2% efficiency (to pass the tax credit threshold of 75%), one would thus need to use wood that is 13% (dry basis) drier. Polytests used 22% MC (dry basis) = 18% MC (wet basis) wood, to reach 75% efficiency the wood used for the certification test would need to be at 8% MC (wet basis). For a lot of the US the equilibrium moisture content for wood exposed to outside ambient air is around 13% (I assume this is MC), but if you ran the test in Boise in late summer, you might get lucky...

One could argue that you don't need a tax credit as much for a $900 stove as you do for a $3000 stove, but you could also argue the opposite, i.e. that people who buy cheaper stoves need the money more... ;-)
In any case, I'm more interested in the reasons why the certification procedure and calculation is as it is. Moisture content is one issue, and flue losses due to excess air is another one. I think efficiency should be corrected to some standard moisture content, to put all tests on an equal footing.

 

[begreen]

My memory of moisture content reported in the tests I read for random stoves was more in the 19% range. I think some BK tests reported higher.

 

[gruesome]

My memory of moisture content reported in the tests I read for random stoves was more in the 19% range. I think some BK tests reported higher.

Thanks. So the 18% MC wood used for the Enerco stove tests is in the normal range then.

 

[BKVP]

Howdy from Syracuse NY. CSAB415.1-10 is correct. And you must pay to get a copy of the test methodology, that is how they are funded.

When the IRS issued the tax credit, they did state it would be based upon the HHV efficiency. In the 2008 tax credit they failed to be specific and many interpreted the tax credit to apply to the LHV (Low heat Value) efficiency. The IRS thought they had that covered with stating HHV this go round. However, the IRS did not stipulate whether or not the HHV would be the overall or any one test run. If you have four test runs (M28R) and 3 runs are 72% HHV and your fourth run is 75%, there are those that believe this makes units eligible. Well does it? I won't comment further on the practices of mfg's.

You can look at test reports (required by law to be posted to websites) and see the overall HHV efficiency.

Thank you,

BKVP

 

[gruesome]

Thanks, Vice President! I have a few more questions, not about what other manufacturers might be doing, but about the testing procedure(s) in general, and their influence on stove design. It would be great if you could find time to comment!

Does BS415.1-10 still contain the alternate method for determining efficiency? If yes, which of the two is more typically used, and what are the advantages and disadvantages of the two methods?
Do you get to pick the fuel moisture content, i.e. can you specify to the testing company what MC fuel to use?
Could you comment on the role excess air plays for the total efficiency? I assume you need some excess air to drive CO and HC flue gas content down, but beyond that I assume excess air increases flue losses?
Do the EPA regulations allow to add a flue gas heat exchanger to the stove, to improve efficiency? I think you are not allowed to run the flue below 115°C, but as long as you stay above that value, would you be allowed to add a flue heat exchanger as integral part of a stove?

 

[BKVP]

Thanks, Vice President! I have a few more questions, not about what other manufacturers might be doing, but about the testing procedure(s) in general, and their influence on stove design. It would be great if you could find time to comment!

Does BS415.1-10 still contain the alternate method for determining efficiency? If yes, which of the two is more typically used, and what are the advantages and disadvantages of the two methods?
Do you get to pick the fuel moisture content, i.e. can you specify to the testing company what MC fuel to use?
Could you comment on the role excess air plays for the total efficiency? I assume you need some excess air to drive CO and HC flue gas content down, but beyond that I assume excess air increases flue losses?
Do the EPA regulations allow to add a flue gas heat exchanger to the stove, to improve efficiency? I think you are not allowed to run the flue below 115°C, but as long as you stay above that value, would you be allowed to add a flue heat exchanger as integral part of a stove?

You can still generate both efficiency values with CSAB415.1-10. Simplidying, the LHV is not looked upon favorably because it is dry basis. 50lbs of fuel at 20% MC, means efficiency is calculated once the load gets to 40lbs. No one uses 0% MC, so HHV is preferred.

Yes, the method(s) do permit for a range in MC. This is absolutely necessary due to variably of MC within even a single piece of fuel. M28R is 19-25% MC.

Not all fireboxes are designed equally. What is too much air in one, maybe too little in another. In testing, we control the stack velocity and that is part of the control mechanisms of a firebox being tested. Too little air and combustion temperatures may not be high enough for complete combustion of PM. In catalytic units, history has taught us to warm the air before it enters the firebox.

As for flue gas heat exchangers, so long as any model can be tested with an FRM, you can test it. If a technology advancement is made but could be prohibited by the method, parties can request an ATM (Alternative test method). ATM requests receive extreme review by the agency.

BKVP

 

[gruesome]

Does anybody know (and could maybe post) how the efficiencies are computed in the Polytests wood stove tests, or similar tests in general? I see the combustion efficiency, heat transfer efficiency and overall efficiency columns in the spreadsheets in the report, but the procedures in the report seem to only specify the emissions calculations. I don't see anything about efficiency.
I'm guessing that the combustion efficiency (about 95%) might be computed from the CO content (incomplete combustion), but the heat transfer efficiency (about 75%) really dominates the overall result. The stove under test is not sitting in any kind of calorimeter (it is sitting on a scale to determine the fuel burn rate), and ambient temperature in the (rather large) room does not seem to change much. They do measure the stove surface temperatures on all sides. Are they just assuming some heat transfer coefficient to air? But how could they, as they apparently have the attached blower going (transfer coefficient is a strong function of air speed)? Flue gas temperature is monitored, but they are only monitoring the sampling volume flow, unless I misunderstand their setup (the flow meters are in the sampling lines, not the main flue). Even if they knew the flue gas flow, are they assuming all flue gas energy is lost?

Anyways, I would appreciate a comment, if anybody knows how the efficiency measurement is done.

Answering my own question, and posting, in case anybody besides me is interested... :

During the CSA BS415.1-10 test particulate emissions are sampled in a dilution tunnel, which does draw in additional air, but flue gas temperature, CO and CO2 content (as % of exhaust gas) are monitored in the flue (stove) pipe directly attached to the stove, without any additional admixture or dilution. Excess air is computed from the difference between measured CO & CO2 content and a theoretical CO2 number derived from complete burning of an assumed wood composition. From the continuously monitored weight of the stove + stove pipe + wood one knows the amount of fuel burned and thus the theoretical heat input, and from the exhaust gas temperature and composition and the excess air computed from the measured CO & CO2 content one computes the heat loss through the flue. I think the heat stored in the stove (from the surface temperatures and stove mass) is also computed, but that probably doesn't change much once the stove is running. From the computed heat loss through the flue (and the heat stored in the stove mass) and the weight of the burned wood the net efficiency is computed continuously.

This efficiency is summed/averaged over the burn time, averaged over different burn loads (maybe weighted according to observed North American wood stove heat use profiles?), and that is the HHV efficiency listed on the EPA web site.

In calculating the energy content of the wood the moisture content is subtracted (i.e. the energy is computed from the dry wood mass), but not subtracted is the heat loss due to vaporization of that water, and of the water resulting from the burning itself - this is what using the 'high heating value' HHV for the wood means. If I understand the measurement procedure correctly, condensation of water in the stove is not allowed, the flue gas has to be above 115°C, so this water vapor energy loss is an additional de facto loss for every stove measured according to this procedure.
Varying moisture content wood in the test load will therefore change the efficiency, but the effect is relatively small, 0.15% efficiency change per 1% moisture content change. There is no efficiency correction for that, but the fuel has to be in the range allowed by CSA BS415.1 (18% to 25% dry weight basis).

That's it, in a nutshell, or at least my understanding of it. Please post corrections and clarifications.

Added: an interesting paper online describing a 2016 research effort by chemical engineering undergrads to implement an EPA/CSA BS 415.1-10 equivalent alternative test setup: https://scholarworks.uark.edu/cgi/viewcontent.cgi?article=1083&context=cheguht . I think it nicely describes the essentials of the measurement method.