New boiler to allow chimney removal

Discussion in 'Boiler Forum' started by rjvking, Sep 10, 2018.

  1. rjvking

    rjvking New Member

    Joined:
    Sep 10, 2018
    Location:
    CHICAGO
    Hi
    I have a 100' sf 1923 frame bungalow in Chicago, with cast iron radiators running off a 30+ year old natural gas boiler. I would like to get a new boiler and water heater to change the venting so I can eliminate the chimney and expand the kitchen.

    My brother is a union pipefitter, and my cousin is a union plumber, and I would like to do the install with their help. My brother has already shut down and drained the system to facilitate removing the radiators for rehab work in the house.

    I'm not really concerned with a complete revamp of the heating system as much as changing the venting. I am adding rockwool + Membrain on the outside walls as I redo things, and at some point in the future I'll redo the windows, as they are original with storms added later. I guess the house will be a little tighter.

    I have read a lot of posts here, but I'm not exactly sure what my options are. If anything, I would just like to keep things simple and go like for like, just changing the way it vents. Thanks!
     

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  2. Dana

    Dana In the trades

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    I'm not sure what the "...100' sf..." dimension is intended to mean. Are you talking about "equivalent direct radiation" square feet of all the radiators?

    Replacing like for like is usually a mistake. Typical oversizing of 3x or more has efficiency, comfort, and maintenance/longevity consequences. If you can't size the boiler to the design heat load, at least size it to where it won't short-cycle on the existing radiation. Errors on both are common, especially when (as is likely) the boiler has been replaced at least twice since the house was first built. The original house was probably a lot leakier, with less insulation, single pane windows/no-storms, and the original boiler was typical at least 2x oversized for the actual design load of the house in the pre-tightened pre-insulated condition, and 3x or more oversized for it's current condition.

    With any replacement boiler it's important to know the square feet EDR of radiator you'll be hooking up to. Take a look at the document in the above link, then measure up your radiation to estimate the EDR'. If you can come up with the EDR' it's possible to put an upper bound on the size of the boiler. If your current 83K-output boiler is tied to radiation than only emit 40K into the room doesn't heat the place any better or faster than a 40K-output boiler. The EDR' also tells you how small a cast iron boiler can be without running into potentially destructive too-cool condensing return-water temperature problems.

    The DOE output of the boiler nameplate in the picture is enough to heat a ~2500' of floor area in 2x4 /R13 bungalow about twice over, maybe 3x if it's an efficient shape (= basically a square or rectangular footprint, not a lot of corners, without a gazillion tiny dormers up top). With enough square feet EDR of radiator you may be able to heat the whole thing at domestic hot water temps with a condensing gas water heater (for both heat & hot water.)

    Assuming you have a heating history on the place, start by running a fuel use heat load calculation on last winter's gas billing, using the existing boiler with it's 83% nameplate efficiency as the measuring instrument.

    Replacing the existing 83K BTU-output boiler with an 80-100K-in modulating condensing boiler and an indirect fired tank would certainly work. HTP's UFT-080W and UFT-100W fire-tube modulating condensing boilers can almost always work as a drop-in replacement for a 100 KBTU-in cast iron system without substantially changing the system design. Unlike most other mod-con boiler vendors they advertise these as being able to pump direct just like a cast-iron beastie, no need for primary/secondary plumbing sculptures, and they have a purpose-made pre-plumbed secondary output to support an indirect water heater. They are also inexpensive, no more expensive to install (and usually less) than a power vented mid-efficiency cast iron boiler. The venting of the mod-con is plastic. Given that the old Utica is probably ridiculously oversized, and you're tightening up the place, the UFT-080W would be the better choice, even though it's DOE output is ~10KBTU/hr less than the old boiler.

    But if you can't wrap your head around a cheap mod-con, a Burnham ESC3 or ESC4 direct-vented boiler would drop right in, and can be side-vented. Just as with a mod-con the fact that it is direct-vented/sealed combustion it also means it won't depressurize the basement when running or provide an infiltration point- you can seal up the basement as tight as you like without concern or consequences. Even though the DOE output of the ESC3 is "only" 52,000 BTU/hr it's almost surely big enough for a reasonably house smaller than 3000 square feet, or even a fairly leaky 2000 square footer. With the lower output for the size of the radiation the return water to the boiler will be cooler, possibly cool enough to condense (TBD), but unlike most cast iron, the ESC boilers are self-protected internally to entering water temperatures as low as 110F, so dropping the size by 40% is not really much of a concern the way it might be with another vendor's line of cast iron boiler. If you have the EDR numbers the return water temps are fairly easy to predict.

    So, measure up your radiators and check back. If you have a heating history sufficient for running the load calculation numbers I can help with that if it looks too complicated. Alternatively you can use an online Manual-J tool such as loadcalc to come up with the whole house number, but the online load calculators usually take more time and is prone to oversizing error (which can be minimized by using the most aggressive assumptions about air tightness & R-values.)
     
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  4. rjvking

    rjvking New Member

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    Hi Dana thanks for your reply...

    That should have read 1000' square feet in reference to the house. Living space is 1000' s.f. with an unfinished basement and unfinished walkup attic.

    I went through the calculation for EDR' and I came up with 53,380 as the total on existing radiators.

    I closed on the house last April, so I don't have any real billing history. The gas company was only able to give me an average wintertime bill for the previous owner, without specifics.

    Thanks for this information and recommendations, this is extremely helpful to me. At some point in the future, I'd like to finish or dormer the attic to add another bedroom and bath. Would the HTP might be the better choice with the future in mind?
     
  5. Dana

    Dana In the trades

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    53,380' EDR is a LOT of radiator. Sure this isn't another order of magnitude (or two) error?

    A 1000' of 2x4/R13 house with R20 fluff in the attic (5-6) and clear glass storms over wood sash single panes above a 1000' of uninsulated basement will typically come in under 25,000 BTU/hr @ 0F outside. With an insulted basement walls (careful how you do that) it'll usually be under 20,000 BTU/hr. That makes the Utica more than 3x oversized for the load which has pretty severe efficiency consequences.

    As a sanity check, what did the gas company say the typical winter gas use numbers were (per month, or season)?

    [edited to add] Was the 53,380 number the BTU/hr at 170F average water temp from the nomograph? That number would imply exactly 314' EDR total for the radiation, something that could reasonably fit in a 1000' house. If that's the case, at condensing temps low enough for 95%+ efficiency 314' EDR of radiator could deliver about 16,000 BTU/hr. At somewhat higher temperatures that would run 90-92% efficiency it would deliver 20-21,000 BTU/hr. With either a condensing water heater solution or modulating condensing boiler that could modulate down to under 10,000 BTU/hr it would work pretty well. The HTP UFT-080W can drop back to ~7500 BTU/hr at 95% efficiency, and would be easier to install than most and would pretty much just drop in. A water heater solution would require a bit more design work, but could be about as efficient, but probably a bit cheaper than a UFT-80w + indirect water heater. There are other mod-con boilers that could work well with 314' EDR of radiation, if that's what it is. The Lochinvar KHN055 can drop back to about 8000 BTU/hr at min-fire and wouldn't short cycle, but it's more expensive than the HTP with a few more bells & whistles to program. With verification of the EDR numbers I can go into it a bit further, but for a K.I.S.S. approach to a higher efficiency boiler it's hard to beat the UFT-080. (The exact same boiler is sold under the Westinghouse label as the WBRUNG 080W, recently seen at Home Depot.)
     
    Last edited: Sep 11, 2018
  6. mage182

    mage182 Member

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    Feb 17, 2011
    Location:
    New York
    I removed my chimney and replaced with a Burnham Alpine model which is direct vent. Everything works great except for the fact that I got some bad advice on sizing and have had to fight my unit to work efficiently. Putting in the extra time up front to do research into the best brand to purchase in your area (when support is needed), and the correct sizing will yield great results in the future.

    Not that I am advocating Burnham since I don't have much experience with other brands. But their new revisions including the smart zone boxes paired with some smart pumps would be an exciting install. Things have come a long way since I made the switch in 2011.
     
  7. rjvking

    rjvking New Member

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    CHICAGO
    Dana-
    314' EDR was the exact number I used with @ 170* F on the chart. The gas company gave me an average of $197 in the winter months, and $79 otherwise, so $118 difference.

    Mage - interesting, did you have problems because it was oversized?
     
  8. mage182

    mage182 Member

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    Feb 17, 2011
    Location:
    New York
    In the beginning yes. But I started with fintube due to time constraints and didn't move to CI baseboard until my second heating season. Now with all of my radiators being CI or CI baseboard and the boiler set to pretty much minimum fire for all zone calls except for the indirect tank, everything works pretty well. My 150k unit has 5-to-1 downturn so the minimum fire is about 30k. If both zone are calling for heat it works satisfactorily; if there is also a hot water call (I don't have the indirect priority turned on), it works very well.

    The new Burnham offering of an 80k modcon with a 10-to-1 downturn would be a perfect situation for my house. Maybe I'll get it right next time.
     
  9. Dana

    Dana In the trades

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    Retail gas energy is sold in therms, ccf, or decatherms, not dollars. The price per unit of energy varies quite a bit from year to year, market to market. There's no way for me to convert the dollar estimates into BTUs per heating degree day or BTU/hour based on the dollar figures, unless you know the fully-delivered full retail rates in $/CCF or $/therm, or however they are metering and billing it.

    So, with only enough radiator to emit 53,380 BTU/hr you don't need a boiler with more output than 53,380BTU/hr. The pre-existing 83,000 BTU/hr boiler doesn't heat the house any faster than 53,380 BTU/hr. The oversizing just causes it to cycle on/off during a continuous call for heat. At more than 1.5x oversizing it the burns would run at about a 60% duty cycle.

    A modulating condensing boiler won't cycle on/off at 170F- it would just throttle back the burner until the call for heat was over. But it also won't deliver more than 87% efficiency at that temperature. The odds are nearly certain that you could heat the place with 130F water and beat 90%, even running at a fixed temperature. If using an outdoor temperature sensor and some programming tweaks I'd expect it to hit mid to high 90s efficiency.

    That cheap HTP modulating condensing boiler should be about the same cost or cheaper to install than a new 82-87% efficiency power-vented cast iron beast, and reasonably sized for your radiation. It'll heat the place easily as well as the old boiler, but at higher efficiency. If you go that route and want to keep it simple, just set it up for 130F fixed temperature output and see if it keeps up during cold weather, bumping it up only if it loses ground. Don't use deep overnight setbacks on the thermostat- any savings from cooler temps overnight get erased by having to run it at a higher output temperature/lower efficiency to have reasonably short recovery ramps in the morning. If you want to squeak a few percent better efficiency installing the outdoor temperature sensor and programming the output temperature to change in response to outdoor temperatures can maximize efficiniecy with a bit of tweaking of the response curve.
     
  10. rjvking

    rjvking New Member

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    Awesome, thanks for all your help!! Definitely going the HTP route.

    And yes, I have no idea what the previous owners were paying per therm, and I'm sure there was enough variance to make that average kinda useless. None the less, thanks again!
     
  11. Dana

    Dana In the trades

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    If for some reason you can't find good local support or a local supplier for the HTP branded version at a reasonable price, the Westinghouse WBRUNG 080w is EXACTLY the same boiler under the label, but the support channels would then be through Westinghouse, not HTP.

    There's a floor mounted version too, if doing a wall-hung version isn't going to work. The floor mounted version ends with "F" (for "floor") instead of "W" (for "wall"). I believe it's a few hundred more expensive.

    If wall mounting on an uninsulated exterior foundation wall, put 3" of polyiso insulation and a sheet of 3/4" OSB or plywood to the foundation, or trap the sheet of polyiso & OSB/ply to the wall with a 2x4 wall, with a piece of OSB or plywood on the side facing the basement to mount the boiler on. The cut bottom edge of the polyiso should be off the floor- to above the high-tide mark if possible if the basement has a flooding history. That way you can still fully insulate the foundation at some later date without having to move the boiler.

    You'll still want to figure out what indirect water heater to hook up to the dedicated secondary port, and how to set it up. It's probably worth taking a hard look at the existing circulation pump and replacing it with a more efficient ECM drive "smart" version. When you drop the water temp to get condensing efficiency the pump runs longer- a LOT longer when using the outdoor sensor and "outdoor reset" control. It may set you back a couple hundred up front for a smart pump, but it gives you the flexibility to optimize the system flow. With heating loads as low as yours you may need/want to set the boiler to never fire at it's maximum rate too (a programmable feature with that boiler). A guy posting here as NY_Rob can probably fill you in on those details and give relevant installation & setup suggestions, having recently installed the same boiler in his house. (Your system looks like it's simpler than his.)

    If they're doing the work hopefully your brother or cousin has experience installing boilers, including condensing boilers(?). If not, perhaps they know somebody who can advise on how to set it all up. Hydronic heating systems are more than just a plumbing problem- it's not rocket science, but there are a number of things that need to be set up correctly for it to run problem-free.
     
    Last edited: Sep 12, 2018 at 2:45 PM
  12. rjvking

    rjvking New Member

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    Would the SuperStor line of water heaters be worth looking into, considering they are an HTP product as well?

    Mounting the boiler should not be a problem, I should be able to leave the basement portion of the chimney for mounting, or I will build a unistrut rack for it.

    Thanks for the tip on the pump. I will have to start looking at those as well.
     
  13. Dana

    Dana In the trades

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    SuperStor indirect water heaters are fine, but so are many others. There isn't anything different about setting up a SuperStor to run off the UFT-080w compared to some other indirect. You still have to spec a pumps sufficient to deliver 100% of the boiler's output into the indirect. The pre-plumbed port on the UFT-080W for an indirect simplifies some of the plumbing. The schematics in figures 8-15 in the manual all show how the indirect should be plumbed.

    Don't try to cheap out by skipping the isolating ball valves (you'll need them if the water heater ever needs survice or swapping out) or the drain valve on the heat exchanger return (unless you want to spend the rest of your life purging air from that loop to avoid a vapor-lock/no-flow condition on the heat exchanger.)

    For most indirect water heaters a Taco 007e or similar would be fine with the UFT-080w. That may be enough pump for your radiation too, but have somebody run the numbers. What circulation pump is currently driving your system?
     
    Last edited: Sep 17, 2018 at 1:06 PM
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