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Liner Size

duh
duh Member Posts: 16
I have a five year old Buderus G115/WS4 oil boiler with a Riello burner. The vent pipe from the boiler is 5". The chimney liner is 5" diameter and goes up the chimney about 30-32'.

A chimney guy who came at my request to clean the liner told me the liner should be 6", not 5", and that it needed to be replaced for about $4,000. He didn't go up on the roof to look at it or clean it because there's no sense if it needs to be changed, he said.

I spoke with Buderus who originally told me the liner should be 5", then changed their minds to 6" because he said there was a "redesign which increased the BTU output." I called a guy who sells liners and he said, "No way a 6-inch! It should be the same size as the vent coming out of the boiler, which is 5-inches."

BTU output is 109,000 per the brochure with my purchase. When I asked the Buderus guy what the new BTU output is, he told me 109,000. "Huh?", you ask. Me, too.

In addition, neither the Buderus certified company who sold and installed the boiler, the guy who installed the liner, nor the fire department who inspected it, said anything about going from a 5" boiler vent to a 6" liner.

Is it true that the liner should be the same size as the vent going out the boiler? I can't believe it would have been installed with the wrong size liner to begin with.

What say you guys who know about this stuff? I know nothing.

Thanks so much,
duh

Comments

  • MikeL_2
    MikeL_2 Member Posts: 371
    Liner manufacturers will help you correctly size their products. I'm certain that chimney height is a factor; taller chimneys / liners have more capacity........
  • STEVEusaPA
    STEVEusaPA Member Posts: 5,689
    I say your fine. @Bob Harper is the expert, maybe he can weigh in.
    BTW, with that boiler/burner, you shouldn't need to clean the liner.
    Properly set up and tuned, you should never see soot.
    Regardless of what size liner you need, tell that chimney guy to go pound sand.
    steve
    HVACNUT
  • duh
    duh Member Posts: 16
    To SteveusaPA...The liner company requires cleaning to keep the warranty in force, but thank you for the comment. Good to know.
  • duh
    duh Member Posts: 16
    To MikeL_2...That's what got me wondering. When I called a liner company and gave him the information, he was adamant that it should be the same size as the vent pipe from the boiler, which is 5". Thank you.
  • HVACNUT
    HVACNUT Member Posts: 4,591
    That boiler wants to see 0 to slightly positive over fire and -.02 breach. If it can achieve that while maintaining a 0 smoke and good combustion numbers, then you're good.
    SuperTech
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 11,992
    Agree with @MikeL_2 the supplier can size the liner either 5" or 6" should be fine. You go by the boiler input not the output. 5" is probably right especially up 32 ft . The taller the chimney the more draft you get
  • Bob Harper
    Bob Harper Member Posts: 914
    Wow. My last house had almost the exact same setup: boiler, Riello, stack height and it ran through an existing 6" corrugated 316Ti liner. I inspected it several times a year and never once needed to sweep it. I had a barometric damper installed set to -0.02 wci and it usually ran wide open during firing. The stack draft usually held around that level except when it got very cold when it could hit -0.06 wci with the 5" baro. I changed it out to a 6" baro. and that settled it down.

    As for the sizing, mfrs. call for the same size as the appliance collar because they have no way of knowing what you're going to run it into. The point is, their 'size' is expressed as smooth round pipe--not corrugated, no offsets and no ovalization or rectilinear shapes. The gas code sizing charts call for a 20% derating for corrugated liners with additional deratings for offsets, long tortuous vent connector runs. NFPA 31 is a little goofy but especially on venting. They call for about or at least 10-15% as a suggestion on corrugated liners.

    A corrugated liner will clog up faster if the burner is not properly set up burning dirty. If you have a cleanout tee or wye at the base, a smoothewall liner makes more sense. FYI, you can get 5". 5.5", 6", etc in corrugated or smoothewall. The advantages of smoothewall are exemption of the initial derating, better performance, and self-cleaning to some degree. If it was me, I'd run a 5.5" smoothwall in 316ss with a baro. tuned using combustion analysis and a draft gauge. FYI, I used all rigid ss for the chimney connector because I can.

    The annual sweeping requirement is actually expressed as annual inspection and sweep as needed by most liner mfrs. Having said that, some sweep's insurance requires they run a brush on every job regardless if needed.

    Keep in mind the sizing charts in the gas codes are based off empirical calculations figured on an interior chimney. They leave it to you to figger it out with exterior chimneys.

    While I'm at it, most liner mfrs. recommend insulation. Note that if you block it off tightly top & bottom in a chimney that is relatively intact, you create a Dewars Flask, aka Thermos bottle, which insulates better than a cementitious insulation. The cementitious mix is good where the chimney is full of gaps such as missing mortar.

    Some mfrs., such as Energy Kinetics, strongly advise against using a baro.. Buderus says you can use one on tall chimneys.

    Last item: Inspection. NFPA 211 calls for a level II inspection on sale or transfer of property, change of fuel or efficiency or in the event of operational problems. The IRC refers you to 211 for heater chimneys.

    Thx Steve, HTH
    duh
  • Big Ed_4
    Big Ed_4 Member Posts: 1,882

    I have enough experience to know , that I dont know it all
  • duh
    duh Member Posts: 16
    HVACNUT...I'm not sure what you mean with all you wrote because I'm an old lady who knows nothing. I'm thinking it has something to do with the numbers the maintenance people check with annual cleanings. If so, these are the numbers:

    SMOKE TEMP CO2% DRAFT EFF

    10-17-19 0 326 12% -0.04% 86%
    11-26-18 0 X 11.50% -0.03% X
    10-10-18 0 340 10.50% -0.02% 87%
    9-4-18 0 344 10.50% -0.02% 87%
    8-30-17 0 260 10% -0.02% 88%
    11-3-16 X X X X X
    9-18-15 0 300 11% -0.02% 85.75%


    The X's are noted because the cleaning was done but the findings were not noted on the cleaning notice.

    Because I see 0's with "smoke" and .02 with "draft" (if "draft" is the same as "breach"?), I'm thinking it's ok.

    Thanks for your input, HVACNUT.







  • duh
    duh Member Posts: 16
    Big Ed 4...Thank you for posting that chart. I saw it online, too, but I didn't know if it applied to me and got confused because the Single Appliance, 5" @ 30', is more BTUs than Multiple Appliances. That seemed backwards to me, but, again, I don't know much.

    I have a SuperStore SSU45 water heater attached to my system. Does that mean I have "Multiple Appliances?"

    Also, with 109,000 BTUs according to Buderus folks, I'm well within the limits with a 5" liner. (By the way, is the BTU number the maximum thermal unit output?)

    Thanks for your comment and the chart!
  • duh
    duh Member Posts: 16
    Bob Harper...Wow, thanks for all your comments!

    Yes, you're right...the annuals required by the liner manufacturer are inspections, not cleanings, specifically.

    Also, the guy who installed the liner noted 35' but I assumed there was a bit extra for the bend near the end, and for ease of installation. It is a M-Flex, 316L, smooth wall. Originally he noted a 316Ti but changed it to the 316L. I don't know why or if it made a difference. They had difficulty getting it in at the end near the boiler and had to break out some time. It made a mess and more problems than I started with, but that's another topic for another time, perhaps. They could not fit an insulated liner in the chimney, which is about the normal 8x8, as I understand it. Don't know why they couldn't fir it except they were inept in many aspects.

    You refer to the NFPA 211...I assume that is a federal code, or something like that? If so, do the federal or state regs supersede Buderus recommendations? I think the chimney guy who is recommending replacing the 5" with a 6" liner mentioned something about that, so I'm concerned. Concerned because first, because I know there will be trouble getting a 6" to fit; second, because the liner-company-guy I spoke with on the phone said 5" because that's the output vent; third, the certified Buderus retailer installed it with a 5" and the fire department approved it; and fourth, because I don't want to spend $4,000 to replace it.

    So, whose recommendations come first and should be the ones I follow?

    Thank you for your lengthy comments, Bob Harper, The Expert.

  • duh
    duh Member Posts: 16
    Sorry, HVACNUT...That chart I wrote looked pretty darn good when I posted it! Hope you can figure it out by imagining spaces between the numbers!
  • duh
    duh Member Posts: 16
    I found the original Installation and Service Instructions for my Buderus G115 WS installed 9-18-15.

    Can someone tell, please, if the last sentence indicates a 5" flue liner? My understanding is that the company may have, at a later date, removed that last sentence.


    MINIMUM SIZE OF CHIMNEY
    The minimum recommended chimney size is 8" x 8 " (6 3/4" x 6 3/4" inside liner) or 6" diameter with a minimum height of 15 feet. Use a 5" flue pipe for connection to an existing chimney.



    Also, I'm inferring the "...6-inch diameter with a minimum height of 15 feet" is still referring to CHIMNEY size because it's in the same sentence. It's not the liner size, but the chimney size. The last line refers to liner or flue pipe size. Am I correct?

    Thanks, again, HVAC folks.

    duh
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 3,190
    edited June 2020
    I believe there are situations that are subject to interpretation. Your most recent inspection/service technician may have recommended the larger liner because of his level of education or interpretation of a code, rule, or company policy. It may be an honest mistake. It may also be a calculated plan to get consumers to purchase unnecessary repairs. Either case, I'm positive that you do not need a new liner based upon the detailed info you have provided. Don't
    sell your self short because I'm an old lady who knows nothing. You have provided more details than many of the professionals who ask for help here. :/

    In order to maintain warranty by having the annual inspection/cleaning, call the warranty provider. Is that the installing company, the liner manufacturer, or a third party? The actual warranty paperwork should have contact information.

    Once you have contacted them with your concern, they should be happy to provide a second opinion or alternate inspection company.

    Regarding your question about more than one appliance; that means two fired appliances with 2 connections to the chimney, for example, if you have a water heater with a burner and a house heating furnace with a separate burner. That is not the case in your situation since both the heat and hot water come from the same oil burner. So use the single appliance chart.

    The minimum chimney of 6" diameter x 15 ft high refers to the verticle portion of your chimney. You indicated that you have a 5" by something more the 30 ft high. That is actually a greater capacity chimney than the minimum specified in your Buderus instruction booklet. And the 5" connector is the size of the horizontal(ish) section of pipe between the base of the chimney and the back of the Buderus boiler. Technically that is the connector, but in the trade, many of us call it the smoke pipe. That connector has the barometric draft control attached to it. It may also have elbows and a cleanout or inspection opening.

    The connector in this picture is more verticle than horizontal.
    Edward Young
    Retired HVAC Contractor from So. Jersey.
    Services first oil burner at age 16
    P/T trainer for EH-CC.org
    SuperTechduh
  • Bob Harper
    Bob Harper Member Posts: 914
    edited June 2020
    I'm laughing at the "chimney length" in the charts. We don't need to know how long it is, just how tall it is! Ok, I'll try to behave.

    They went with 316L because that mfr. doesn't make smoothwall in 316Ti. 316L is softer and easier to fabricate that the Ti variant. Ti is exotic and cool but it's main benefit is stabilizing the ss at high temps so you don't get intergranular corrosion from chromium carbides forming at the grain boundaries.

    When sizing a liner it's worse to go too small than too big. A lot has been made about oversized liners being a problem. You also have the other side of that argument from Jim Davis who feels no chimney could be too big. I like properly sized, installed and maintained liners. A lot has been made about using liners to improve performance. I see it everyday but again, there are those who don't believe it. The main reason to reline is to protect the patency of the flue. When you have an unlined chimney or one that once was lined but has failed, it can no longer perform its intended function and therefore, by code, must be relined or rebuilt. That's what an NFPA 211 level 2 inspection tells you- the condition.

    NFPA is a separate entity that has promulgated various safety codes. Many, such as 211, have been adopted as an industry standard--not by local ordinance at first but through litigation. Where local codes don't provide an answer the "trier of fact" (court) will look for the most appropriate industry std. to measure the case. This is what happened with 211. It has been adopted directly in some jurisdictions into the building code. In Delaware, it was adopted by the State Fire Marshal's office and held up in the Superior Court as applying to the full std. Now, if your jurisdiction has not adopted 211 but has adopted the IRC, then you have adopted 211 for heating chimneys. The IRC refers you to 211 for heating chimneys so you get to it in a roundabout way.

    If you have a mfrs. instructions that expressly goes against the codes and stds. the proper move is to present your info. to your Authority Having Jurisdiction (AHJ) to rule on acceptance of which method and get it in writing.

    When it comes to worrying about oversizing don't pick fly poop out of black pepper. Get the biggest liner down that fits (for oil) up to about 8". Once you get bigger and you have a setback T'stat, you may find the chimney not to 'prime' or be 'self-starting'. It's full of cold dense air that must be pushed out the top like a giant push pop. Units with a pre-purge can negate this effect. FYI, once you get over 6" diameter connector you need to drop to 24 ga. galvy, which is getting hard to find. An easy substitute is to use 26Ga. ss rigid chimney liner as your chimney connector (oil)/ vent connector (gas) aka, 'smoke pipe'. Min 3 screws per joint but best practices call for a screw every 6" of circumference of pipe with no screws or seams from 5-7 O'clock. You never want condensate sitting in seams or bathing crummy screws. If you didn't incorporate a tee, eye or other condensate trap (shame on you) then use ss connector with ss screws. They're 400 series but hold up well enough and are magnetic, unlike 300 series. HTH,

    PS, when sizing rectilinear shaped chimney liners, don't count the cold corners. Draw a circle or oval within and that's your max. effective flue area.
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 3,190
    edited June 2020
    @Bob Harper All good information and I get it. But the question is: Should @duh spend the money on a new liner? I think not. The one that's there is just fine. It's been working for over 7 years and has been checked annually. What has changed between last year and now? The physics of barometric pressure, air pressure, air temperature, and weight of the air per volume at a given temperature has not changed. Not in any of my books anyway.

    The original installer of the system selected an adequate liner, there was difficulty installing it. Now she needs a larger diameter liner? this job has "Extra Charge" written all over it. "Since the larger pipe won't fit inside the flue, we need to do this, that, and the other thing to finish the job. Oh, by the way, it's gonna cost $$$ more for unforeseen additional work."

    My advice is to get the warranty provider on the case. Have them solve it. Get it in writing before you spend another dime. Your Combustion Test readings show the chimney is drafting. That is the bottom line. The safety of the system is proven by the test results.

    P.S. The "how tall it is not how long it is" quote is for painting flagpoles! But I also use it when teaching about Circulator Pump Head. :D
    Edward Young
    Retired HVAC Contractor from So. Jersey.
    Services first oil burner at age 16
    P/T trainer for EH-CC.org
  • Bob Harper
    Bob Harper Member Posts: 914
    If the liner was video inspected by someone certified then it can be considered intact. The question of sizing then is the $64 question. If it's burning clean and working fine with no backpuffing or CO spillage then it must be ok. If you're getting any operational problems then yes, it must be considered. A manometer can measure draft pressure but not mass flow. That's the prize. If you're gunking up a corrugated liner then what was working fine after sweeping may puke and backpuff later. If the chimney was lined with tile its relatively easy to break out the tile and install a bigger liner if need be. Yes, it adds to the cost but sometimes you gotta do what you gotta do. However, with this boiler I don't see it. A 30-35ft. liner will probably suck like crazy, which itself can be another problem, hence the baro. damper option.
    No O2 given on combustion analysis numbers or stack CO. Really need these. Forget bogus eff. and calculated CO2.
    EdTheHeaterManHVACNUT
  • duh
    duh Member Posts: 16
    EdTheHeaterMan...Thank you for your especially helpful comments on June 5, and for hitting the nail on the head with your June 7 comment. Yes, it is indeed "should I spend the money on a new liner?!"

    I will contact the liner warranty company but I suspect they will just be concerned with the integrity of their liner and leave the sizing issues up to the installers. At some point I could contact the Certified Buderus Installer and ask him why he allowed a 5" liner to be used with this boiler if a 6" is required.

    I personally believe at least some of the issue is with Buderus. According to a tech I've emailed, the redesign of the GS115/WS was made in 2011 and they changed the Installation and Service Instruction manual to reflect the "new" BTU output. This is a bit convoluted but here goes... The tech says the original manual had this phrasing, verbatim:

    Minimum size of chimney
    The minimum recommended chimney size is 8" x 8" (6 3/4" x 6 3/4" inside liner) or 6" diameter with a minimum height of 15 feet. Use a 5" flue pipe for connection to an existing chimney.

    I'm interpreting this to mean the chimney must be at least 8" x 8" OD with 6 3/4" x 6 3/4" ID, unless it is a round chimney, and then it must be 6" in diameter with a 15' minimum chimney height.

    The tech told me when the redesign was done in 2011, and I'm quoting now, "the last line in the paragraph is the text that was removed." That means the reference to use a 5" flue pipe for connection to an existing chimney is no longer in the manual. The problem is, my manual has that sentence still in it, and my unit was installed 9-18-15.

    I originally thought that last sentence only referred to the 5" flue pipe coming out the back of the unit, but I'm not so sure now. I asked the tech the BTU output of my current unit and he told me 109,000. I asked him the BTU output of the unit prior to the redesign and he told me 98,000. So Buderus, according to the tech, removed that reference to a 5" flue pipe because the BTUs increased by 11,000. So now I think that last sentence is also referring to a 5" flue pipe accepting a 5" liner because the tech is using the deletion of that sentence as a reason to use a 6" liner. But my unit was installed years ago by a Certified Buderus Installer using a 5" liner. How come the installer didn't know?

    I've looked online at BTU stuff, and Big Ed_4 in an earlier post was kind enough to send me a chart showing I could have 146,400 BTUs and still be okay with a 5" liner going 30' up. And you, EdTheHeaterMan, was kind enough to answer my question about having the SSU45 water heater not being a factor in the BTU calculation. So why would they change the manual after the redesign? And why should I change the liner if the 5" liner is handling the BTUs?

    I should add, the reference to Chimney Venting in the Buderus manual says to "connect boiler to vertical chimney with a 5" vent pipe" and to comply with local codes and regulations. If no local codes, then use NFPA 31 and NFPA 211. It also says, "NFPA 211 requires chimney to be lined before connecting boiler," which doesn't make sense to me, but let that go. I don't have access to the NFPA documents, though I tried online. I think the new chimney liner guy who is recommending the change also mentioned those codes, but I don't know what they say in regard to my liner.

    I think I'm going to ask the Buderus tech why I would need a 6" liner is my BTU output is only 109,000. But maybe I'm missing something and the additional 1" diameter offers something else I don't know.

    EdTheHeaterMan, are you currently a heater man in the NH or MA area? If so, I may be interested in hiring you. And thank you for your kind comment about not selling myself short. I now know more than I care to about this boiler stuff. I just want to turn up the heat and have it warm! I'll let you experts handle the rest, though I do love to investigate and solve problems. I do love to ask, "why?"

    Thank you for your help, EdTheHeaterMan. You're so kind.

    duh
  • Bob Harper
    Bob Harper Member Posts: 914
    https://www.nfpa.org/codes-and-standards/all-codes-and-standards/list-of-codes-and-standards/detail?code=211
    Create a simple profile to get free read only access
    The flue pipe they are referring to is the chimney connector, aka "stovepipe" can be 5". Liner sizing is by BTU/hr. input-not output. You can't just go by the nozzle size because almost everything runs at a much higher pressure than the 100 psi nozzles are stated at. Double check the charts in the manual. Again, if its working at 5" corrugated and its burning clean then you're probably ok. If its burning dirty then a 6" corrugated can quickly become a 5", which means fix it so it burns cleanly. The manual referenced a 6" round inside a standard "8x8" flue tile because you can't get a 7" round down without breaking out the flue tile. Note that very few flue tiles are properly aligned without offsets, overhangs or mortar protrusion all of which effectively reduce the area for a liner to fit. This is a major reason most pros leave this work to a chimney pro. It can take special tools, experience and patience to get a liner down sometimes.
    HVACNUTduh
  • duh
    duh Member Posts: 16
    Bob Harper...Thank you for that link. I was able to manage my way through it to see the NFPA 211 code but I'm not sure where I should look for liner requirements applicable to me. I'll have to spend more time to find it.

    So you're saying the BTUs to which the Buderus tech referred are INPUT BTUs? I thought it was OUTPUT all this time. But maybe it doesn't matter because if they were 98,000 in the old G115/WS units, and now they're 109,000 in the redesigned units, isn't the 5" liner enough to handle it if the 5" capacity is 146,400?

    By the way, the liner is 5" smooth wall 316L. You mentioned corrugated and "burning clean" in your last post. What is "burning clean" and how can I tell? Is that from the diagnostics the boiler folks do annually? Like the smoke, CO2, etc? Or is that from the chimney cleaner going up on the roof to clean my liner, which is where I started with all this.

    I'm curious as to what you and EdTheHeaterMan might think is what Buderus is recommending in their manual? Is it where the manual says "...0r 6" diameter with a height of 15 feet?" Again there only reference as to liner size is under the heading Minimum Size of Chimney in my last post. That's the only time the word 'liner' is used in the document. There ARE references to venting, which again point to the NFPA 211, so now I'm left trying to figure out what the requirements are in my state of NH for my boiler.

    I understand well the difficulty in fitting liners and breaking tile. I'm pretty confident I cannot fit a 6" liner in my chimney. That's another issue for another time...

    Thanks for your input, Bob Harper, and for the link.
  • duh
    duh Member Posts: 16
    Is it okay to put a 5" flue pipe into a 6" liner? Any drawbacks in doing that?
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 11,992
    @duh

    all flue, chimney and smoke pipe, vent connectors always go by BTU input to the appliance. Btu out put means nothing as far as venting goes.

    Yes, a 5" connector can be used with a 6" liner
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 3,190
    @duh, I am retired now, and when I was working it was in Southern New Jersey. As I mentioned in my original post, your chimney inspection person may be making an honest mistake due to a lack of experience. You may be getting worried over nothing.

    For peace of mind, you can get a second opinion, Does your fuel supplier have a service technician that can perform the annual maintenance on your oil burner? He may be able to perform the annual inspection of the liner to meet the requirements of the warranty.

    Checking the base of a chimney and cleaning the 5" connector pipe was part of my annual tune-up. I would use a mirror on a stick to look at the chimney liners to see if there were any reason the have a Chimney Sweep make a call. 99 and 44/100 of the time the liners were clear. I would state that on my work order. That inspection was good enough for the Township Fire Marshal that required such inspections for rental units.

    Your local officials may or may not require such inspections, but the warranty you referred to should be happy with the annual tune-up, as long as you ask the technician to mark that he looked at it, on the work order.
    Edward Young
    Retired HVAC Contractor from So. Jersey.
    Services first oil burner at age 16
    P/T trainer for EH-CC.org
  • duh
    duh Member Posts: 16
    EdTheHeaterMan...You said they always go by BTU input into the appliance and BTU output means nothing. When you say "the appliance" do you mean the BTU input into the liner or the boiler? My boiler says right on it Gross BTU Output = 109,000 MBTU/h and Net IBR Rating = 95,000 MBTU/h.
  • duh
    duh Member Posts: 16
    Bob Harper...You recently wrote,
    "If you have a mfrs. instructions that expressly goes against the codes and stds. the proper move is to present your info. to your Authority Having Jurisdiction (AHJ) to rule on acceptance of which method and get it in writing."

    Who is the AHJ? Is their a hierarchy? How do I find out?
  • Bob Harper
    Bob Harper Member Posts: 914
    AHJ= building code official. Call your local bldg. dept. as things vary all over. I have over 1300 various jurisdictions within PA.
  • duh
    duh Member Posts: 16
    EdTheHeaterMan suggested going to the liner manufacturer, which I did. I gave them the measurements and they agreed the 5" is ok so they will put it in writing to the chimney guy.

    Bob Harper suggested getting the AHJ's ruling in writing which I will do once I get a copy of the liner manufacturer's written ok.

    I'm not having the 5" liner removed and replaced with the 6" liner.

    Thanks for all your help and for saving me $4,000, one and all!

    duh
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 3,190
    edited June 2020
    EdTheHeaterMan Said...You said they always go by BTU input into the appliance and BTU output means nothing. When you say "the appliance" do you mean the BTU input into the liner or the boiler? My boiler says right on it Gross BTU Output = 109,000 MBTU/h and Net IBR Rating = 95,000 MBTU/h.

    @duh APPLIANCE MEANS THE FURNACE OR BOILER.

    With those numbers, you have a 130,000 input, and it is expressed in GPH or (gallons per hour ) It should also say 0.90 GPH firing rate or Max input or something similar.

    THE FOLLOWING IS FOR THE NEWBIES IN THE INDUSTRY. Slightly off original topic but it seems that everyone else is teaching here so...

    There are 2 ratings on furnaces and 3 ratings on boilers that are measured in BTUs

    There are reasons for the different ratings

    You need to think about the reason for the rating to determine which one to use.

    Input is how much fuel is going in to make the flame. and also how much exhaust is being generated. If the reason you need to know the BTU is how much fuel is being used, then you use the input rating. This would be for things like firing rate or gas pipe size

    If the reason you need the BTU rating is to know how much heat will be generated by the furnace or boiler to put into your house (or water heater or other use) then you use the output.

    The difference is the amount of heat generated less the amount of heat used, which is the amount of heat that goes out the vent or up the chimney. (sometimes called stack loss)

    If you put 100,000 BTUs in the flame and you get 75,000 BTUs of usable heat out the pipes or ducts to heat the house, then there are 25,000 BTUs of heat wasted up the chimney or out the vent.
    In this example, the heater would be 75% efficient at the steady operating state. The efficiency rating, known as AFUE, makes allowance for on and off cycles so it might be 73.8% AFUE on this 75% efficient heater.
    (Just Guessing)

    Look at these ratings from different heaters.

    This rating shows the input and output is very close because the AFUE is over 90% very little loss up the vent


    This 80-85% AFUE Boiler rating has a larger difference between input and output. there is a third rating that boilers have called NET rating. This is a number that the dead men from long ago agreed upon for what you might lose in the piping between the boiler and the radiator. That number is 15%. No specific relation to any particular building or pipe design. Just a number everybody agreed upon.

    Finally, this shows an oil fired boiler with the Input, Output, NET and firing rate... the input and firing rate are the same thing expressed two ways


    Since #2 Heating oil has a BTU Value of 140,000 BTU per gallon the 1.00 GPH boiler has a 140,000 input. The 0.75 GPH boiler has the 105,000 BTU input. and so on...


    NOW, HERE IS YOUR TEST QUESTION...

    WHAT RATING DO YOU USE FOR SIZING A CHIMNEY LINER?

    A. GPH

    B. INPUT

    C. NET

    D. OUTPUT
    Edward Young
    Retired HVAC Contractor from So. Jersey.
    Services first oil burner at age 16
    P/T trainer for EH-CC.org
    SuperTechduh
  • duh
    duh Member Posts: 16
    EdTheHeaterMan...Ahhhh! You must have been ---or SHOULD have been---a teacher at some point!

    I only realized the importance of INPUT!! BTUs a few days ago, before you sent this last post! I initially thought the 109,000 output BTUs listed on my boiler was the important information. But I think Bob Harper had a little sentence in one of his earlier posts that mentioned input being the determining factor, so I started wondering about the 109,000.

    I began to think it's not what is noted on my boiler (109,000 BTUs) but, in snooping around some more, I figured it is what is noted on my Riello burner (126,000 BTUs). And after reading your last post, it makes sense! 109/126 = 86.5% AFUE, right? And that's about what I've got! It's not a high efficiency unit but the promotional materials try to make it sound close. I also assume a different burner might alter the AFUE a bit. No? And the difference between the input of 126K and the output of 109K is what is going up the chimney, correct?

    So, I called M-Flex and initially they were reluctant to give me any info because I'm "just a homeowner." I asked for a different service person, gave him the information, and he said the 5" is okay because with the length of the flue pipe to the chimney at about 3 feet (the hypotenuse-ish length) (what's that distance from the boiler to the chimney connection called again??), I have about 130,000 BTUs capacity. Also, the length of my chimney, according to the info on my M-Flex warranty, is 35', so it may be even better because he used 30'. I asked for the citation so I could tell my chimney guy, and it's the NFPA 54, 13.1(d) chart that he used. (I think it was good info from Bob Harper who told me about NFPA and I've been looking through a lot of it. Too much, actually!)

    This is all very enlightening and I think your lesson for newbies helped explain it much better. But I'm still wondering why the chart in the June 4 posting by Big Ed _4 is showing 146,400 for a 5" pipe? And though I know it's an estimate, that's still more than a 10% difference...

    Also, does having a smooth wall liner do anything to increase the limit, or is that already taken into consideration?

    Fabulous information for folks like me who have no clue, EdTheHeaterMan. Gotta keep it simple for us.

    Please tell me I'm on track with my thinking? I suspect I'll have to convince some folks who are in the industry that it doesn't need a 6" liner. Buderus being one of them! The tech actually yelled at me in an email and told me to install it the way they said (with a 6" liner) or not at all! Problem is, it's already installed! By a certified Buderus installer. And inspected by the fire department!

    Great help, Ed. Wish I could take you to lunch! We could discuss boilers and BTUS!

    duh
  • duh
    duh Member Posts: 16
    Just a short while ago I was so encouraged by EdTheHeaterMan's information and my understanding until I spoke with the chimney guy. Now I am disheartened and disgusted.

    He just told me it doesn't matter what the M-Flex tech calculates, or what the NFPA 54 13.1(d) states, or what the certified installer did, or if the fire department inspected it. The only thing that matters is what the manufacturer says, even if it went to court. And Buderus says this, the only references to 'liner' and 'venting' in the manual:

    MINIMUM SIZE OF CHIMNEY
    The minimum recommended chimney size is 8" x 8 " (6 3/4" x 6 3/4" inside liner) or 6" diameter with a minimum height of 15 feet. Use a 5" flue pipe for connection to an existing chimney.


    and this:

    5.1 Flue pipe installation
    5.1.1 Chimney venting
    Connect boiler to vertical chimney with a 5" vent pipe. Use only venting systems that comply with local codes and regulations.
    If local codes are not existent, refer the the following regulations:
    • NFPA 31, Installation of Oil-Burning Equipment,
    • NFPA 211, Standard for Chimneys, Fire Places and Solid Fuel
    Burning Appliances,
    • In Canada refer to CSA B139, Installation Code for Oil-Burning
    Equipment,
    • NFPA 211 requires chimney to be lined before connecting boiler.



    I am personally interpreting the 6" diameter reference with a minimum height of 15' as referring to direct venting because it's under the heading MINIMUM SIZE OF CHIMNEY. The original manual before the redesign of my unit had a sentence under MINIMUM SIZE OF CHIMNEY saying to connect to a 5" liner, but they removed that. The chimney guy and Buderus say the 6" means the liner size. I asked why they put a 5" flue pipe on the unit if they wanted a 6" liner; he said that's an 'engineer thing.'

    I told the chimney guy we can't fit a 6" but he said it can fit if the bricks and mortar are ground down to make room, I think??? I know they will have trouble in the smoke chamber area where it angles to the boiler because it caused trouble in the past. He said they use mirrors to do it. Is this where the expression "smoke and mirrors" comes from? Ha!

    I suspect this will cost way more that the $4,000 I'm quoted. I have a center chimney cape and I guarantee they will not be able to do it easily.

    Oh, for about an hour I thought we were okay.

    duh
  • STEVEusaPA
    STEVEusaPA Member Posts: 5,689
    Almost 2 weeks and still batting it around. I stand by my original post. I think you’re fine. Combustion numbers show it, liner sizing charts show it. The only person complaining about it is the guy trying to sell you a new liner.
    Check your original manual. I’m pretty sure you can direct vent it, which is a lot cheaper than a new liner.
    steve
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 3,190
    edited July 2020
    Do you have the original installation manual? Was the new information available at the time your equipment was installed? Finally, is there a Consumer product safety recall?
    I also agree with @STEVEusaPA
    Edward Young
    Retired HVAC Contractor from So. Jersey.
    Services first oil burner at age 16
    P/T trainer for EH-CC.org
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 3,190
    edited July 2020
    @duh
    The original installation manual says 5" and you followed the original manual when you installed it according to the installation instructions available at the time of installation. Unless there is some official recall on file with the Consumer Protection Agency that requires you to make a change from the original manufacturer instructions, then a good lawyer would win the case in your favor.

    That is only in the very rare case that you suffer a loss that requires the insurance company to pay for something, and that the insurance claims adjuster reads the details of the current installation instructions, (highly unlikely), and does not have access to the original instructions, (which you have) and that it ends up in court. and you neglect to do the proper maintenance on your heating equipment. (AND Your last name is Murphy the one they write those laws about)

    My advice is in no way legal advice, but I believe you should let this issue rest. This is not something that you go to jail for and you should have homeowners insurance in case of a monetary loss.

    Please let your mind go to another problem that is more helpful. Do you have a working sewing machine? There are thousands of people that could use a mask and can't afford the basics. Perhaps a few friends of yours can do your community a service in some way or another. Just get your mind off this Chimney. It is Just fine and Legal as it is.
    Edward Young
    Retired HVAC Contractor from So. Jersey.
    Services first oil burner at age 16
    P/T trainer for EH-CC.org
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 3,190
    In your original post, you said the change from 5" to 6" was because of a redesign. Your installation instructions are from before the redesign. So your boiler is from before the redesign. So your boiler does not need to follow the new instructions because the boiler is not redesigned. It is, as we might say "Grandfathered" and able to stay "as is."

    Your rating label shows the capacity based on the boiler before the redesign. Unless you get a new label and upgrade to the new design, (I don't recommend that) then you are just fine.
    Edward Young
    Retired HVAC Contractor from So. Jersey.
    Services first oil burner at age 16
    P/T trainer for EH-CC.org