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Incredible Shrinking Chimney

gmcinnesgmcinnes Posts: 52Member
My mother-in-law has a 3 storey Brooklyn brownstone. The steam boiler was replaced this winter in an emergency job. They replaced the boiler with the same model, but at inspection time they were told that their masonry chimney needed to be lined. Unfortunately the 8" vent pipe on the boiler is too big to be carried up through the masonry chimney. Apparently a liner can be installed, but only at the cost of breaking the interior wall into the chimney on each floor.

I'm sure you Wallies must have run into this situation before. Are there any creative approaches for dealing with a situation like this?

FWIW, it's a Weil-McLain EG-75 Steam boiler, and it was a straight replacement for the one that was in there previously, which had blown a section, I think.

Comments

  • Bob HarperBob Harper Posts: 813Member
    I am a Certified Chimney inspector and my company relines for a living. Have the boiler sized properly for the house then see if it can accept the largest liner that will fit. Note smoothwall liners buy back the 20% derating penalty for corrugated liners. 8" means that boiler could probably heat several buildings at once.
  • FredFred Posts: 7,862Member
    The best approach would have been to calculate the total Radiator EDR before buying a matching replacement. Most steam boilers are well over sized for the connected radiation and if properly matched to the EDR, you probably could have used a smaller boiler and probably a smaller vent pipe.
  • HVACNUTHVACNUT Posts: 2,172Member
    All the rules are fine but what is the OP supposed to do now?
    Is the installer responsible to make it right? The specs do say 8" I.D. chimney x 20 ft.
  • Jamie HallJamie Hall Posts: 10,455Member
    HVACNUT said:

    All the rules are fine but what is the OP supposed to do now?

    Is the installer responsible to make it right? The specs do say 8" I.D. chimney x 20 ft.

    That's one of those questions which usually leads to a he said she said back and forth. Depends a lot on what the contract if any to replace the boiler said. And what a lawyer can make of it.

    The fact of the matter is that you either need to replace the boiler (again) with a smaller one, if that would be adequate, or line the chimney. As to who is responsible... wouldn't care to say.
    Jamie



    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.



    Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
  • gmcinnesgmcinnes Posts: 52Member
    Thanks guys. The boiler is certainly over-sized for the heat loss of the building. I'm going to tell them to get an EDR calculation done. I'll do a ballpark one for them next time I'm down there. A smaller boiler is the route they'd like to go, rather than tearing down walls in tenant apartments to reline the chimney for the current one.

    In the event the boiler is the right size, for the EDR, what are the options. Here are my ideas:

    Is there any type of fan-assisted vent for a steam boiler of this size? If so, would it allow a smaller vent?

    If the building heat loss is half the connected EDR, typically can some of the connected EDR be removed / bypassed easily?

    If the boiler comes with a 8" vent connector, is it permissible to reduce that to 7"? I'm looking at the NYC Fuel Gas Code Table 504.2 for a double wall Type B vent, and it seems there's plenty of headroom even in a 7" vent to accommodate the 299 MBTU boiler?
  • Bob HarperBob Harper Posts: 813Member
    It is negligence to install an oversized heating appliance attached to a chimney that cannot possibly vent it. Just because there is a hole to the sky doesn't mean you can attach anything you want. This insanity has got to stop. If the chimney isn't big enough, get a smaller unit, install a factory chimney elsewhere that is large enough or multiple heaters through multiple chimneys but each chimney has its limits! You put 10lbs of 'stuff' into a 5lb box! Yes, the installer of the boiler is responsible. Absolutely. Also, just because the guy before you did something stupid doesn't give you license to be irresponsible, too.
  • FredFred Posts: 7,862Member
    @gmcinnes , it's not a heat loss calculation that you want, at this point. You want to measure and calculate the total EDR of all the connected radiators. It doesn't make sense to remove radiators to try and reduce the size of the boiler you need. All that will do is cause you to have cold areas in the structure. Do the EDR calculation and compare that number to the Sq. Ft. of steam on the boiler plate. If you use that direct comparison, the piping and pick-up factors are already built in, by the manufacturer. Don't add any additional BTU's. I can almost assure you a smaller boiler will likely work.
  • gmcinnesgmcinnes Posts: 52Member
    @Fred That's plan A for sure. When I did a ballpark EDR for my place, I used this cheat sheet to estimate the EDR for each radiator. Is that accurate enough, or do I need to get a professional in?

    Also, there's some weird stuff in the basement apartment in that building - it's something that looks like slant fin tubing on 3/4" copper pipe. Never seen that attached to steam. No idea what the EDR would be.
  • gmcinnesgmcinnes Posts: 52Member
    @Bob Harper Amen. It's amazing how much time we spend cleaning up after the last guy :)

    To be fair, in this case, boiler venting into the unlined masonry chimney has enough capacity. I think the issue is getting an 8" liner down the chimney.
  • FredFred Posts: 7,862Member
    edited June 25
    gmcinnes said:

    @Fred That's plan A for sure. When I did a ballpark EDR for my place, I used this cheat sheet to estimate the EDR for each radiator. Is that accurate enough, or do I need to get a professional in?

    Also, there's some weird stuff in the basement apartment in that building - it's something that looks like slant fin tubing on 3/4" copper pipe. Never seen that attached to steam. No idea what the EDR would be.

    The Cheat Sheet isn't attached but, yes, there are tables that you will want to use to calculate each Radiator EDR. If you measure each radiator, the height, width, number of tubes/sections (depending on the style of radiator) you will get a very accurate EDR number. It sounds like the basement unit has a hot water loop on it. If it is, it can be a separate zone and you likely will not have to add any capacity for that. There will likely be plenty of capacity in the built in piping and pick-up factor to cover that requirement. If it is Steam, it will need to be calculated too but 3/4" copper on fin tube is likely how water, especially if it is below the boiler water line.
  • Bob HarperBob Harper Posts: 813Member
    gmcinnes said:

    @Bob Harper Amen. It's amazing how much time we spend cleaning up after the last guy :)

    To be fair, in this case, boiler venting into the unlined masonry chimney has enough capacity. I think the issue is getting an 8" liner down the chimney.

    Venting into an unlined chimney has been illegal since 1927.
  • gmcinnesgmcinnes Posts: 52Member
    @Bob Harper Yikes. I hope there's a misunderstanding and that the issue is something like an existing vitreous lining failing that's failing, rather than being totally unlined.
  • gmcinnesgmcinnes Posts: 52Member
    @Fred Attached the cheat sheet this time. I didn't know you could run a hot water loop from a steam boiler. You learn something every day.

    It almost certainly is below the water line, so that's probably what it is. I'll just count it as pick-up, as you say. I think most of that floor is heated from jacket / standby loss from the boiler room anyway... It's hotter than 1000 suns in the boiler room :)
  • gmcinnesgmcinnes Posts: 52Member
    Thanks guys. You're super helpful and generous, as always.
  • HVACNUTHVACNUT Posts: 2,172Member
    > @Bob Harper said:
    > Venting into an unlined chimney has been illegal since 1927.

    Probably has terracotta.
  • FredFred Posts: 7,862Member
    @gmcinnes , here is another chart that is pretty accurate.
  • STEVEusaPASTEVEusaPA Posts: 2,908Member
    Could this unit get power vented thru the wall? I'd doubt with a Brownstone there would be a legal place to go thru the 2-3' wall, unless there is a basement window you'd like to put out of service.
    steve
  • Bob HarperBob Harper Posts: 813Member
    I video scan terra cotta flue tiles every day. I haven't found a single one intact in my 35 yrs. of doing this, nor has any member of the National Chimney Sweep Guild. The TC is an obsolete material that fails laid in Ordinary Portland Cement-based mortars or lime mortars 99.99% of the time and they fail. I have never seen a flue tile bedded in the medium duty refractory mortar that's been required since 1980 much less the medium duty non-water soluble calcium aluminate refractory cement mixture that been required by NFPA 211 for over 20 years. Also, the chimney must be a minimum 4" nominal solid masonry unit with a 2" clearance to combustibles for interior chimneys/ 1" for exterior with firestops at the ceiling and attic. Never seen that. I have seen plenty constructed of hollow CMU blocks, which, if >4" do NOT meet the code since they're not '75%'ers'. When we break out flue tiles to reline, virtually 100% have soot stains on the surrounding masonry indicating leakage of flue gases. Also, just as my morning inspection today, all the gaps between tiles were air-washed clear of soot indicating air from the building or outdoors was getting entrained into the flue, just like a draft hood killing the draft.

    If the chimney is lined with TC tile but the tiles themselves are damaged, misaligned, etc. or laid in the wrong mortar or the mortar has gaps, protrusion or has not been able to resist softening, cracking or corrosion up to 1,800°F it is an automatic fail and must be relined or rebuilt.

    Seeing a TC tile sticking up out of a chimney means NOTHING as to whether it can be considered 'lined' or not.

    Power venting is tough, esp. in close quarters. IF the AHJ wanted to go by ASHRAE you'd have to terminate min. 25 LF from each lot line. Try that in a row home.

    HTH,
    Peace.
  • LanceLance Posts: 127Member
    One dimension for the flue means it is round? Consider square, rectangle liners. Convert to square inches to get a liner equal to 8" round if you have rectangular chimney. It just may make the difference. You can also downsize your btu input by properly reducing input to the burners. (smaller orifices or eliminate two burner inputs from either end by plugging the orifice. It will not compromise anything but will reduce the need for an 8" flue. Of course all the facts for steam side supply have to be met for the system.
    An 8" round is 3.14 * 4 squared. 16*3.14 = 50.24 sq. inches. A 7*7= 49 square inches. I'd say this would work. Room for a 7" squared? Nothing says the flue has to be round.
    Yes you can power vent, but why do it if you don't have too. A liner is needed. Just engineer it right and it work. By the way, if it is oversized, reducing input to right size makes it work better and cheaper. Too often even the oversized is oversized. Reduce load by eliminating unwanted, unneeded radiation.
  • jkempmtljkempmtl Posts: 1Member
    To answer one of your earlier questions, Enervex and Tjernlund make chimney top draft inducers for residential size boilers.
  • DickCDickC Posts: 15Member
    Liner manufacturers provide sizing charts which take into account the lateral connection from the appliance to the chimney, the height of the chimney and then the diameter of the liner providing a maximum Btu specification for their product. In a quick scan of a Selkirk liner chart, a 5' lateral connection in a 35' chimney would allow venting with 7" liner with Max. sizing of approximately 300 MBH dependent on the single or double wall model selected. I would determine whose liner was installed and take a look at their specifications and compare to application at this site first. Lateral connection and chimney height are the big variables.

    I have a friend in ME with an oil boiler 6" breech and a new stainless liner of 5". The code in ME states it cannot be connected unless the OEM manual specifically addresses it or an engineer deals with it specifically. On gas equipment, they allow down sizing based on the Btu input of the appliance.

    We have for years used charts in NFPA 54 to correctly size. OEM guidelines on many oil boilers have for years been totally out of line. I am told that W/M has addressed this on the oil side in their manual with their gold oil all breeched at 7" from 3 section up.
  • HEBHEB Posts: 3Member
    There are several side wall vent kits that we have used where the chimney was to small or in need of considerable repair. Field Controls has a SWG power venter that will work check out fieldcontrols.com there is also inline power venter that would allow you to down size the liner required.
  • October HomeOctober Home Posts: 72Member
    edited June 27
    I don't understand. What inspection? Do you mean a code enforcement official inspection? If there was an inspection then a permit was pulled. If there was a permit pulled, that would require the installer to install it correctly which means correct venting.

    No?
  • FredFred Posts: 7,862Member

    I don't understand. What inspection? Do you mean a code enforcement official inspection? If there was an inspection then a permit was pulled. If there was a permit pulled, that would require the installer to install it correctly which means correct venting.

    No?

    It sounds like they had a permit and a follow up inspection which it failed due to the venting issue. It will require proper venting but the boiler installer doesn't have to be the one to line the chimney although he/she should have advised the homeowner of the requirement.
  • Bob HarperBob Harper Posts: 813Member
    Details missing so here is one iteration: IRC Table 2428.2(2) Type B vent double walled gas vent ( the table you use for liners). Single appliance, CAT I, single walled vent connector.
    8" rd @ 30ft. high w/ 5Ft. lateral offset natural draft 521 MBH. @ 50 Ft. 602 MBH.
    Now, at 30ft/ 5ft. 6" rd NAT= 271 MBH bit derated 20% for corrugated liner = 217 MBH. Ok, so how about 7" rd.? 382 MBH x 0.8=305.6. MBH if no offsets and meets these parameters.
    FYI, the ubiquitous "8x8" flue usually measures about 6.25" square I.D. not including offset flue tiles misaligned or protruding mortar "schnotz" that reduce the effective flue further. Speaking of which, the cold corners really don't count. Take the circle or oval that fits inside rectilinear shapes and use that area. I'd ask your Authority Having Jurisdiction (code official) if you can substitute a 6" round smoothwall that does not require derating. Otherwise you're looking at tile removal. This normally does not require opening walls but it can, esp. in crazy older homes in cities. We have to do it most of the time on flues in Philly because the masons were on drugs or needed to be. Yes, you can use power vents as long as they are at the termination so the entire vent system is under negative pressure or you have listed pressure vent stack. The fan would have to be interlocked with the burner and incorporate a draft proving pressure switch. This doesn't guarantee flow but it is one layer of protection. Now, get someone NCI certified to block off that draft hood once the inspector's gone and install a barometric damper with a spill switch.
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