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Whats up with these Different BTU ratings ?

Post in 'The Hearth Room - Wood Stoves and Fireplaces' started by HDRock, Jan 18, 2013.

  1. ddahlgren

    ddahlgren Feeling the Heat

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    I am going to start with some data to compare stack temp and stove temp in various places to get an idea of heat transfer to the stove . If I know the temperature of the surface and the surface area along with the value of steel in my case I think I should get a pretty good idea of the btu output. Another idea I had is to record the heat rise in the room with a stable stove and stack temps. If i take xxx number of cubic feet of air and raise it 5 degrees in xx number of minutes I should be able to calculate the number of btus it would take to do that then just correct for one hour. These are ideas I am thinking about and may present a problem but might make some sense in the end also. I am also making the assumption that if the stack and skin temperature stays the same then the btu output from the fire is the same, again with a fully warmed up stove. My biggest problem is the wood quality But have a couple of dozen splits I know are premo seasoned 3 years oak and was saving for next week as we are going to have some nights in single digits though will intentionally run the furnace some to make sure I don't freeze any pipes in the walkout part of my basement. Oh and i can close off the room the stove is is and it is small at 11X17.

    Any ideas to make a better starting point fire away!

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  2. rideau

    rideau Minister of Fire

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    When was that article written? Canada (at least Ontario, but I think all of Canada) does have separate testing requirements and does not accept UL listing anymore. They can require you to have a csa certified stove, and some manufacturers do not spend the money to get their stoves tested to csa standards, even though they easily meet the standards. Typically, Canadian installations require ICC pipe (or equivalent) and larger hearth pad protection. UL?ePA tests performed in Canada for US UL ratings are not acceptable in Canada.

    So, maybe the EPA testing is the same...maybe only UL/CSA different. Anyway, the testing that establishes acceptable installation metrics is NOT intertchangable between the two countries, and DOES restrict stove installation. PROBABLY a typical Canadian isolationist act. Lots of things done here to "protect" Canada from American competition, despite treaties to the contrary...different tax rates on property capital gains for americans and canadians, limit to amount of non-Canadian music/tv programming permitted, etc.
  3. Jags

    Jags Moderate Moderator Staff Member

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    Are you going to use a specific base temp for btu output, or just run the stove under an "overfire" temp. Btu output is not linear with temps (i.e. 500F is not simply double 250F in heating ability). Maybe using a specific weight of wood so that you can calculate input (available) btu's to actual output?? Just throwing stuff out there.
  4. ddahlgren

    ddahlgren Feeling the Heat

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    I only have one stove to test mine but I know the wood is oak and know well seasoned as CSS for well over 2 1/2 years and dry enough if you put a good sized for my stove at least split probably 16 inches long and 5 inches on a side it will go to flames in 10 to 15 seconds yest still burn long and slow.. Two of these will run for 3 hours at mid heat. I will weigh it before loading though good idea. I think it will take 10 to 15 minutes for stack and stove temp to stablize and will record those then close the door and time a 5 degree temperature rise. Make sense so far?
  5. Jags

    Jags Moderate Moderator Staff Member

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    Sure. There are a dozen ways that this could be looked at. If measuring BTU output of the stove is the only variable sought, this is an easy test. But again, much of this can be manipulated by the operator. Are you gonna run 500F or 650F (or even 750F). That alone will skew the numbers by a huge margin.
  6. ddahlgren

    ddahlgren Feeling the Heat

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    Maybe at low around 500 and high around 700 as I think you only care about how low you can go to not overheat the house and high when it is bitter cold and you want to see if you can actually heat it. Make sense? I think for me next week is the perfect time as for the next few days we will be in the mid to high 40's but next week 20s to single numbers starting on Monday and a fun thing to play with after work. No sense cranking the stove hard and making the house 80 degrees on a 48 degree day but Monday through Thursday nights will warrant cranking it good in single numbers outside. Plus give me time to play a little and get some initial numbers and work out a sensible test procedure..
  7. Jags

    Jags Moderate Moderator Staff Member

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    Sounds like a plan.
  8. rideau

    rideau Minister of Fire

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    Do you use a moisture meter? Weight of wood - moisture present - BTU's lost to combustion of H2O = BTUs available: good to know as your starting point, or the experiement isn't too reliable....Might be a plan to run at a higher burn rate during the day, and a lower burn rate at night, to see if there is a difference in heating ability at the different rates? You'll need to take into account rise/fall of outfoor temp over the period, and also change in wind...fun and games. So, maybe one day high burn rate, one night high burn rate, one day low burn rate, one night low burn rate? Be interesting to see what you get with your stove compared to EPA testing. You can calculate the volume of air you are heating, and figure out your heat loss, and your temperature rise....Fun and Games.

    My stove room has good air flow to the entire house...good for heating, awful for running this type of test.

    Good luck. It'll be interesting to observe your experiment.
  9. Huntindog1

    Huntindog1 Minister of Fire

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    Machria, Good Info.

    I was thinking also a stove could have a higher BTU per hour rating as the design of the stove has a higher air flow thru the stove when the input air control is wide open.

    Or like my Vogelzang stove I have noticed since it has a high BTU rating that for around a 2 cubic foot box size it has an extra secondary air tube in the top. Most stoves I have seen in that size range only has 3 tubes in the top , mine has 4.

    Another aspect is how preheated is the secondary air before it mixes into the smoke path. As a hotter secondary air from a air pathways in the stove takes a longer path making for more time for the air to heat up along its journey to be expelled out those burn tubes. The hotter the air the more efficient the burning of smoke gases. I seen the European stove called the Burly actually specs the temp of its secondary air. Most stoves do not spec that temp.
  10. rideau

    rideau Minister of Fire

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    And along the same lines, two identical stoves at the same air opening will provide different amounts of oxygen to the fire, and for differnt lengths of time, depending on draft. A high draft, moving air in and out of the firebox quickly, provides more oxygen to the wood, but turns the air over more quickly. I would think this would tend to keep the flue cooler, as more cold air is going through it and the air is not staying as long in the firebox to heat, , and also at the same time would allow more complete burning of combustion gas; further, one should be able to burn at lower draft rate but same oxygen rate (more rapid turnover of air), thus keeping hot air in stove longer and giving stove more time to transfer heat to room. resulting in a more efficient burn AND more of the heat staying in the firebox and home, less heat left in the emission gas/
  11. Machria

    Machria Minister of Fire

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    Thanks! And the problem with that is, they don't even as much as make a mention of the word "temperature" in the procudures.
  12. Machria

    Machria Minister of Fire

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    Yep, all good points. In the woodstock thread, I talked about the huge difference it can make with the amount of oxygen and how it is introduced. Remember, the wood is NOT the only fuel we are burning in these things. Oxygen is a big part of the burn. So stoves adding alot of oxygen to the burn can put out alot more heat than a same size stove burning the same amount of wood. Even though they both burned the same amount of wood BTU's, one may have added alot more BTU's to the mix via the other fuel, oxygen.

    Of course, we also didn't get into the whole "what/how is the stove designed to heat?" questions! Is it designed to put all the BTU's out at once, burn as fast and hot as possible to have a very high BTU output, for a very short period? OR is it designed to burn slow and long, and put out jsut a little heat for a very long time (like a BK would at low settings)?

    The one interesting thing from the begreen link is, it does say they do the tests using 4 different methods, and then average them out. High burn (air opened up), low burn, air closed and two in between those at med-high and med-low. That was good to see.


    I would like to see them do a safety test. That is, load the stove packed to the brim, with all very dry, small but high BTU wood. Like splintered up 2x4's or something. Light it up, and leave it wide open, stand back and see if there is a "meltdown", or does te stove handle that safely?
  13. ddahlgren

    ddahlgren Feeling the Heat

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    That is why I am going to record flue temp and stove temp. I would think with the same species of wood at the same moisture content in the same time the flue temp would describe the fire box / flame temperature and airflow through the stove.. Does that make some sense? Lowes has a moisture meter so will pick one up this weekend as I need one anyway. I need one and soon as I have a load of wood coming in claiming to be seasoned and before they dump it I am going to stick the meter on it and if something like 35% percent tell him to go home unless that is unreasonable and should be expected stored outside with no cover but another subject.

    I had another thought that comes from personal experience. I live in a 1870s house that was originally heated with pot belly stoves. My grand parents had a Holland gravity hot air furnace installed that burned coal and operated in may respects like a wood stove in that it heated a very large pile of cast iron and the natural heat flow from the cold air return allowed the hot air to circulate the same as a wood stove cold air in hot air out with no help. At some point it got converted to oil heat but still gravity hot air. Fast forward to 1976 and i bought the house from the estate and I installed a used blower assembly the second year I owned it mid winter. I ran it fairly slow as the duct work was very large around 10 inches for feeds and 2 floor joist bays for cold air returns. The upside is the oil bill went down 35% and the heat input the same because i did not change the nozzle in the burner. To me that indicates with the same heat in the thermal efficiency went up by the same amount as the oil bill went down with very similar weather. To me this says a wood stove that does not have something to help move the air is wasting wood. It does not have to be a blast of air but enough to help the convection and will help keep stove temps down when cranking it up hard. I hope i explained this well if not ask away as to what is not clear.

    Dave
  14. rideau

    rideau Minister of Fire

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    WHY? That is a bit much. One can't and shouldn't build to protect against every possible idiotic thing a person can do. Accidents happen. Big problem in the USA that we have developed an attitude that accidents can't happen and are always the result of negligence. Don't get me started.
  15. rideau

    rideau Minister of Fire

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    Yes, I think anything that gets a bit of air moving past the stove will take some of the heat away from the stove as it passes and cary it whereever it goes. How much air flow is desirable probably depends on the speed with which the stove is pshing out the heat. The slowly radiating heat of a soapstone stove probably needs less air and benefits from slower air, so the air has more time to pick up heat as it passes. A highly convective stove probably benefits from much more air being pushed past it. A fan in the home is likely adequate for most people, and can be adjusted both in terms of placement and speed (and size) according to ones needs and the temp at which the stove is being run. On a warm day one might want to not have a fan, or conversely, one might want a fan on hign t quickly push the air to the far reaches of the home nad keep the stove room moderate. My instinct is that this air movement is well managed with an axcillary fan that gives the home owner many options, in use, placement, volume and speed.
  16. clemsonfor

    clemsonfor Minister of Fire

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    This would be scary and disturbing to me!!!
  17. ddahlgren

    ddahlgren Feeling the Heat

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    My thought is if you lower the stove temp with a fan and keep the flame temp the same the flame / fire will transfer more heat to the stove as it tries to reach equilibrium. Flue temp should go down as well as more heat gets transfered as stove temp goes down, it is all about temperature differential. If you took it to an extreme if the house was on fire and the house hotter that the stove the stove would be a heat sink heated by the house fire.
  18. rideau

    rideau Minister of Fire

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    OK, Don't go overboard. Don't try that test. :rolleyes:
  19. Huntindog1

    Huntindog1 Minister of Fire

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    UL test for Wood Stoves. My stove is UL approved.
    http://www.ul.com/global/eng/pages/...ndards/catalogofstandards/standard/?id=737_10

    [​IMG]
    Browse the Catalog of Standards
    UL 737

    Standard for Fireplace Stoves
    Scope Table of Contents
    • Cover
    • Transmittal
    • Table of Contents
    • Body
      • INTRODUCTION
        • 1 Scope
        • 2 Glossary
        • 3 Components
          • 3.1 General
          • 3.2 Attachment plugs, receptacles, connectors, and terminals
          • 3.3 Boxes and raceways
          • 3.4 Capacitors and filters
          • 3.5 Controls
          • 3.6 Cords, cables, and internal wiring
          • 3.7 Overcurrent protection
          • 3.8 Polymeric materials and enclosures
          • 3.9 Power supplies
          • 3.10 Printed wiring boards
          • 3.11 Switches
          • 3.12 Transformers
        • 4 Undated References
        • 5 General
        • 6 Materials
        • 7 Assembly
          • 7.1 General
          • 7.2 Flue damper
          • 7.3 Fire screen
          • 7.4 Flue collar
          • 7.5 Radiation shield and baffle
          • 7.6 Thermostatic control
          • 7.7 Grate
          • 7.8 Separable handle
          • 7.9 Barometric draft regulator
          • 7.10 Combustion air duct system
      • PERFORMANCE
        • 8 General
        • 9 Test Installation
        • 10 Temperature Measurement
        • 11 Fire Tests
        • 12 Radiant Fire Test
        • 13 Brand Fire Test
        • 14 Flash Fire Test
        • 15 Glazing Test
          • 15.1 General
          • 15.2 Impact test
          • 15.3 Water shock test
        • 16 Strength Tests
          • 16.1 Fire chamber
          • 16.2 Chimney connector
        • 17 Stability Test
  20. Huntindog1

    Huntindog1 Minister of Fire

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    UL test Continued:

    • FIREPLACE STOVES FOR USE IN MOBILE HOMES
      • 18 Installation
      • 19 Chimney
      • 20 Spark Arrester
      • 21 Combustion Air Inlet
      • 22 Test Structure
      • 23 Test Method
      • 24 Drop Test
    • BLOWER ASSEMBLY
      • GENERAL
      • 25 General
      • CONSTRUCTION
      • 26 Enclosure
        • 26.1 General
        • 26.2 Mechanical protection
        • 26.3 Electrical protection
        • 26.4 Doors and covers
      • 27 Mounting of Electrical Components
      • 28 Field-Installed Blower Assemblies
      • 29 Field Supply Connections
        • 29.1 Permanently-connected units
        • 29.2 Cord-connected units
      • 30 Grounding
        • 30.1 General
        • 30.2 Permanently-connected units
        • 30.3 Cord-connected units
      • 31 Internal Wiring
        • 31.1 General
        • 31.2 Methods
      • 32 Separation of Circuits
      • 33 Bonding for Grounding
      • 34 Capacitors
      • 35 Insulating Material
      • 36 Motors and Motor Overcurrent
      • 37 Switches and Controllers
      • 38 Transformers
      • 39 Spacings
      • PERFORMANCE
      • 40 Test Voltages
      • 41 Temperature Measurements
        • 41.1 Thermocouple method
        • 41.2 Change-in-resistance method
      • 42 Input Test
      • 43 Temperature Test - Electrical Components
      • 44 Dielectric Voltage-Withstand Test
      • 45 Leakage Current Test
      • 46 Stalled Motor Test
      • 47 Strain Relief Test
        • 47.1 Power supply cord
        • 47.2 Field wiring leads
      • 48 Push-Back Relief Test
      • 49 Short-Circuit Test
      • 50 Knockout Test
      • MANUFACTURING AND PRODUCTION TESTS
      • 51 Production Line Dielectric Voltage-Withstand Test
      • 52 Production Line Grounding Continuity Test
    • MARKING
      • 53 General
      • 54 Marking Permanence Tests
        • 54.1 General
        • 54.2 Air oven-aging test
        • 54.3 Humidity test
        • 54.4 Unusual-condition exposure test
    • INSTALLATION INSTRUCTIONS
      • 55 Installation and Operating Instructions
        • 55.1 General
        • 55.2 Installation instructions
        • 55.3 Operating instructions
  21. Huntindog1

    Huntindog1 Minister of Fire

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    The Scope of UL test 737 for Wood Stoves:



    [​IMG]
    Browse the Catalog of Standards

    UL 737

    Standard for Fireplace Stoves

    Scope Table of Contents
    1.1 These requirements cover fireplace stoves that are freestanding assemblies having fire chambers intended to be operated open to the room or, when equipped with doors, to be operated with the doors either open or closed.
    1.2 Fireplace stoves covered by these requirements are intended for attachment to a residential chimney capable of being used for use with low heat appliances and intended for use with solid wood or coal fuels.
    1.3 Fireplace stoves are intended for installation in accordance with the Standard for Chimneys, Fireplaces, Vents, and Solid Fuel Burning Appliances, NFPA 211, and in accordance with codes such as the International Mechanical Code, International Residential Code, and the Uniform Mechanical Code.
    1.4 Fireplace stoves intended for use in mobile homes are to be installed in accordance with the Mobile Home Construction and Safety Standards published by the Department of Housing and Urban Development (HUD).
    1.5 The product shall include:
    a) A field-installed cord-connected or permanently-connected blower assembly; and
    b) Other field-installed electrical accessories, rated at 250 volts or less, and intended to be employed in locations in accordance with the National Electrical Code, NFPA 70.
  22. begreen

    begreen Mooderator Staff Member

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    EPA testing is for emissions, UL for safety. They test for entirely different parameters.
  23. rideau

    rideau Minister of Fire

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    Yes, I realized (remembered?) that half way through the post. Just saying, stoves are not automatically OK in Canada if they are tested here. They MAY accept EPA in Canada, they DONT accept UL in all of Canada. So the article's point that it is important to keep the stoves legal for install anywhere in NA is not met...UL/CSA testing is expensive...I think over $40,000 per stove...so some aren't tested both places.
  24. Machria

    Machria Minister of Fire

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    I would like to see that "over fire test" not to dis-allow a particular stove to be sold, but just as information to us consumers. 1, so we can make educated decisions whether we want the stove (maybe kids will be operating it...), and two so if we do own it, we know what to expect / watch for.

    Exactly, UL FOR SAFETY is the key here! The UL is NOT performing tests for quality or performance, strictly safety.
  25. ddahlgren

    ddahlgren Feeling the Heat

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    I think to make a simple analogy with using cars as an example. UL is the same as NTSB seeing if it is safe. EPA is still EPA to see if it is clean burning and we need what would be Car and Driver or Consumer Reports to show how useful it is and what good and bad points it has. Car and Driver type review as it has more performance stats and what you really need to know in the end. The Consumer Reports model works best as they do not take advertizing and that can be a problem as a high paying advertiser will never get a bad review if they make something that is just not all that good or does not meet advertized goals. I am a member of a Corvette owners user forum very much like this one for wood stoves but obviously for Corvettes and companies that supply parts and they have a rule that you can not speak poorly of a 'sponsor' not matter how bad you are treated by them or if the quality of what they sell is sorely lacking. It sort of making the forum useless. How does that work here? I have some interesting observations about a vendor that does advertize here but will keep them to myself rather than getting thrown off for the comment. i would rather have access to the accumulated knowledge and friendship than make the comment if off base.

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