Wood stove clearances?

Brucek1$ Posted By Brucek1$, Nov 30, 2017 at 7:13 AM

  1. coaly

    coaly
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    NFPA 211 is the standard for solid fuel burning appliances and venting. That is then adopted into codes. The standard is where you'll find the decreasing up to one inch allowance. I don't believe anything is mentioned about increasing. It is just detrimental to the efficiency and will cause rapid creosote build up by decreasing flue gas temperatures as the gasses expand. When temps goes below 250*f. the water vapor condenses on the flue walls allowing smoke particles to stick creating creosote. So increasing certainly becomes a safety factor if the operator isn't aware of it. You also need to leave much more heat up to create the same draft you would have with the smaller diameter. A waste of fuel.

    One line in the entire book of the safety standard states all appliances must also be installed as per manufacturers installation instructions. That way if the board that writes and approves the standard isn't aware of something a manufacture proves safe through testing, they are covered. That is where the wording in the correct manual comes into play since the manual is part of the UL listing. For instance when a manufacturer changes something in a manual there is paperwork involved to approve the change with U.L. Since yours isn't a listed appliance without a tag, this doesn't pertain to yours, but if you had a listed stove, to maintain the listing, it would technically be required to have "ONLY 7 inch C.S.A. or U.L.C. Listed factory built, residential type and building heating appliance chimney." that is the words from page 6 of the Canadian manual and notice the listed parts are tested to Canadian specs. This is why I'd like to find a manual for the U.S. market. They are then uploaded to the manual section for others free of charge. Installing as per instructions guarantees the appliance is installed "as tested".

    Sometimes specifications given in manuals are for different reasons. Such as being tested with a 15 foot chimney. The manual then must state to use "15 foot minimum" which many fear the stove will not work correctly if they have a shorter chimney. It has nothing to do with the operation or safety being shorter, it was just tested with that standard height and needs to be that minimum to be installed "as tested".

    Once you understand where codes come from and read them yourself it will come together. I always stated "no reduction in flue diameter was allowed" until bholler corrected me that the standard states reduction of up to one inch is allowed. I have the paperwork from Fisher and most of the stoves, others here have details about codes that affect their business and experience from what they specialize in working in the heating industry. I'm retired from the heating industry so my information is outdated compared to the newer appliances, but it puts me in a good position for collector and antique stoves before the information is lost forever.

    The reason for safe clearances is due to drying of building materials over time at elevated temperatures. The lower the moisture content, the lower the ignition temperature. When someone says "but it has been fine for xx years that way", that is time to be concerned.
     
  2. Brucek1$

    Brucek1$
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    Yeah thats what everyone has told me, its been like that since the house was built but the way my mind works is if I know something is done wrong i wanna fix it. I also want it fixed incase somethinh does happen( knock on wood) i want it to code for insurance purposes. You have any recommendations on heat shields? Been looking at the imperial ones some and any brands of chimney pipe to use/stay away from
     
  3. coaly

    coaly
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    For connector pipe I like Dura Black made by Dura Vent available at Home Depot. Heavy stuff and it comes in 4 foot lengths. They used to reduce all stove accessories to extremely low prices at season end, but now our local store puts it in a trailer to store until the next season. All chimney is pretty much rated the same, so it's price and brand preference. Two types of chimney sections are triple wall and "pack" type. Triple wall has stainless inner flue with thin insulation wrap around it, then a second wall with an air space to the outer wall. It is lighter weight and a bit cheaper than the double wall pack type which has a dense insulation packed between the inner and outer stainless walls. To see the two, Home Depot stocks Dura-Vent triple wall as a seasonal item here - that makes summer installs dificult (Dura Vent makes the pack type called Dura Tech available at many suppliers on line) and Lowe's stocks the pack type by Supervent. (stocked all year here) Both are rated the same, but the pack type has more insulation and stays hotter inside staying cleaner. Then you purchase a ceiling support kit that comes with necessary parts. You would need a through the roof kit, not the more expensive through the wall kit. The difference in looks and installation is the pack type is only 2 inches larger outside than the inside diameter and the triple wall is 4 inches larger than inside diameter. You can go either way even though your roof is cut larger than required for the 6 inch pack with 8 inch OD. Go exactly by the instructions and they are not a complicated do it yourself install. The chimney is more important than the stove. Most any stove will work with a good chimney, no stove will work with a poor one. You'll be amazed how much more heat you'll get from that stove since it will radiate inside instead of sending it up the chimney. Don't forget a damper in the first section of pipe above the stove.
     
  4. Brucek1$

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    Anyone have any good recommendations on heat shield kits, or materials
     
  5. Brucek1$

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    How high up does the shield need to go uo past the top of my stove and how far on each side? I ordered a 36"x52" imperial wall shield.
     
  6. bholler

    bholler
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    How ever far it needs to go so it prtects everything within 36" even when measired doagonally
     
  7. Brucek1$

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    In theory since i know the clearance is suppose to be 22", so couldn't i go off that measurement
     
  8. bholler

    bholler
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    Not by code because you dont have the ul tag.
     
  9. coaly

    coaly
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    Post #19 in this thread has a diagram showing measurement diagonally to wall keeping 36 as the minimum above and around shield. Simply measure from any part of the stove to any combustible for the clearance. If you use a yard stick from the stove corner towards wall, angle it until it touches stove and wall. This gives you the perimeter of the shield required.
     
  10. Brucek1$

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    I see it now, i think im gonna stick with the 22" off the stove, biggest heat shield i could find was 36"x52" i think going off that it will make it
     
  11. coaly

    coaly
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    Yes, it's only from an insurance or code standpoint. I know that double shield design on the back of your stove passed with 12 inch reduced clearance on the Goldilocks, but that stove has 6 inch outlet and a different intake system, although the intake system actually allows more intake air into the Goldilocks! The Goldilocks requires double wall pipe for the reduced clearance, so maybe they didn't want to raise the installation cost of the stove requiring more expensive connector pipe to be used. Canadian clearance to single wall pipe is 24 inches compared to U.S. requiring 18. So that is where the 22 inches comes from. Here is page 8 in the Canadian manual. Notice diagram "figure 6" at bottom;

    upload_2017-12-7_12-18-27.png

    Notice the side clearance passed for 36, which is 48 for unlisted stoves in Canada.
    The 24 inch pipe clearance in bottom diagram is the Canadian requirement preventing the stove from being installed closer. Had it been tested with close clearance pipe, it very well could have passed for much less. That's how Goldilocks passed down to 12. (with the exact same stove back)

    Testing was done by any approved Lab using UL testing standards to become "listed".
    A thermocouple is a small tube with dissimilar metals inside that bend with heat and make contact inside. This generates a small electric current flow that can be calculated to temperature. They are used on turbine engines as sensors in the engines connected to gauges in cockpit as well as used on gas appliances to generate the current needed to hold pilot safety open to allow gas flow through appliance when the pilot remains lit properly. Thermocouples are mounted on movable walls placed around the stove with a specific testing wood charge inside and allowed to burn extremely hot. The temperature recorded can not exceed 117*f above room temperature on exposed surfaces. When a manufacturer tries for a certain clearance and that test shows the temperature is too high, the wall is moved away from appliance and retested until the "safe" clearance is given and allowed to be printed in manuals and tag. There are other reasons such as the pipe clearance example that may require more clearance.

    So in your case of no tag, the insurance company or building inspector doesn't want to hear some guy by the name of Coaly on the internet told you what stove you have. (It's the only documented Fisher Stove that uses 7 inch outlet so there is no doubt what you have)
    If you want a copy of the Canadian manual hit "start a conversation" with me by clicking on my screen name at left so I can email you a pdf of the entire manual. That satisfies some insurance co. and inspectors. Others go by the law that says no tag, no listing, period.
     
  12. Brucek1$

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    Yeah im not terribly worried on not having the tag, i know what the clearance is suppose to be so ill go off that, and this summer ill be changing out the stove pipe and chimney pipe to 6" inch to get my 18" clearance on the stove pipe. Its close right now at about 16.5" to 17" inches so ill let it slide this heating season since our roofs are covered in snow already
     
  13. bholler

    bholler
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    Yeah the only reason to go with the larger clearances is to meet code and insurance requirements. You know the tested clearances so as long as you honor them you will be safe. Now if something happens a nd you have asn insurance claim you may regret not meeting code though. You really dont need a premade heat sheild sheet metal or cement board works fine. You really should meet the pipe clearance. Or sheild the pipe.
     
  14. Brucek1$

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    Could steel roofing be used, having a hard time finding sheets of sheet metal made that long
     
  15. Brucek1$

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    I guess my specifically the corrugated roofing, and im guessing using galvanized steel is a no no?
     
  16. Brucek1$

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    So decided to just build my own heat shield, gonna go with durarock and just paint it with black stove paint but my question is, if i go from the floor to the ceiling what gap do i need at the ceiling, and i know 1" at the floor just dont know on the ceiling, and do i need the opening on the sides too or can i close them off(thinking of using metal studs on the sides instead of the spacers.
     

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