Chicago Boiler Replacment Question

Discussion in 'Boiler Forum' started by chsitko, Jul 26, 2010.

  1. chsitko

    chsitko New Member

    Messages:
    7
    Location:
    Wheaton, IL
    Hi Everyone, and thanks in advance for any advice or opinions you can offer, and sorry for the length

    I live in Northern Illinois (Wheaton) in a 1500 sqft ranch with a basement. We have cast iron raditors throughout the house and newer double pane windows. Our currently boiler is a "ACK-O-MATIC" rated at 160,000 BTU input with a 128,000 BTU output. I've tried to attach pictures of the current unit for reference. We just moved into the house a year ago and had it serviced before winter. The technician noticed that the boiler casting was breaking up (leaving a rusty dust pile which is referenced in a picture below). I imagine the unti wont last much longer, but who knows, it looks to have lasted a long time allready.

    I had a installer out to give me a couple of quotes. He quoted 3 products.
    1) A Dunkirk MDL PWXL-5ENG2 140,000 BTU (Base Price)
    2) Burnham Series 2 130,000 BTU ($458 over Dunkirk price)
    3) Triangle Tube Solo 110 ($3253 over Dunkirk)

    When he was here, he took measurments, counted the number of baseboards and number of windows. Based on that information he said he calculated the load based off a Manual J. I know from reading the forum that the Manual J is the best method, but I dont know how to go about doing the calculation. Did the installer look at the appropriate areas to make a good calculation? He said he used a -10 degrees for the chicago metro area.

    Without giving specific of the pricing, the Triangle Tube is more expensive than the Dunkirk by a good margin. However i can use rebates to bring the price off the Triangle Tube to $853 over the Dunkirk. So it makes the Triangle Tube a more interesting option. I've heard that the condensing units dont work as well with Baseboard heating because of the high temps needed, is this true?

    Also, if we went with the Triangle Tube, I might consider adding a zone for our hot water needs. Can this be done at a later time, post install? Do i need to install a larger unit?

    Based on the above information and the below pictures, would the smart choice be to upgrade, or will the below boiler last another 10 years. I dont expect exact numbers, but on average how much savings would i gain by switching to the Triangle Tube. THe wife likes the house kept around 72 in the winter.

    Lastly, is there things i need to consider that i might be overlooking.

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]


    Thanks
    Chris
    Wheaton, IL
    Last edited: Jul 26, 2010
  2. Furd

    Furd Engineer

    Messages:
    446
    Location:
    Wet side of Washington State
    I didn't see any pile of rust, did you mean that slight amount of combustion debris in the picture of the gas burners?

    There is no question that you could improve the efficiency of the system by getting a modern boiler but from what little I can see on the pictures it appears the existing boiler has been well cared for so I think I would get another opinion before going the route of a new boiler based on a little bit of combustion debris that looks entirely normal.

    BTW, the installer did NOT do a Manual J if all he did was measure the lengths of the baseboards and counted the number of windows. Gathering the information for a complete Manual J would normally take about an hour and includes the area of all the external wall, area of the floor over unheated spaces, the area of the ceiling below unheated spaces, area of windows AND the total linear feet of the perimeter of all windows and doors along with several other items. The installed heat emitters (baseboards and radiators) is not used in a Manual J but could be a factor in determining if a modulating/condensing boiler would be appropriate.

    Without being there and making my own inspection I couldn't state if the existing boiler might last ten years or ten months. I will state that even if the boiler is in like-new condition you could save an awful lot of fuel over ten years by going to a modern boiler.

    You need several more evaluations and estimates for replacement before making a decision.
  3. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,005
    Location:
    New England
    A mod-con boiler can be the more efficient item. By its nature, the boiler will adjust the output to match the heat load on the house. this means that the temperature of the output changes, based on need. It also means that the radiators don't cycle on/off as much - you're typically more comfortable with a constant output that matches the need, rather than an on/off you get with a conventional boiler system. A mod-con boiler is most efficient with lower return temps, but still may be more efficient than what you have at full output. By virture of the modulating feature, on a mild day, the water temps will be lower than on a design-day where it may need the max temp, and output. I have a Buderus in my townhouse with an oversized indirect (I wanted to be able to fill the 6' tub, washing machine, etc. and follow-on showers without fail - probably overkill, but the tank cost isn't that great). Typically, an indirect doesn't need to be as large as the stand-alone unit it replaces. It is usually connected as a priority zone. This means that when it calls for heat, it shuts off heating to the other zones. This also means that you don't need to add capacity to the boiler to handle an indirect. A small mod-con has typically got a larger burner than a stand-alone gas heater, so the recovery is fast, and you'll never notice it stopped supplying heat to the house for the short time it takes to reheat the water in the indirect.

    An indirect WH tank is normally much more efficient on a mod-con verses a stand-alone gas-fired tank because there is no flue up the middle, and the boiler efficiency is generally a third or more more efficient than the internal burner. Plus, they generally have more insulation in them. Some have a lifetime warranty. A good one can be rated at 1/4-degree per hour drop, so once hot, may not need to run until the next day's run of showers. this time of year, the internal temp of my boiler is often room-temperature, since it hadn't run for a long time. A typical stand-alone tank often would need to run a few times to maintain the set temperature during a 24-hour period.

    It wouldn't surprise me if all of the units you looked at are oversized. A proper manual-J is required. that isn't as big a deal with a mod-con, since it can adjust to the needs, but bigger still costs more and if it isn't needed, why?
  4. chsitko

    chsitko New Member

    Messages:
    7
    Location:
    Wheaton, IL
    Thanks to both for the replies.

    I asked the rep how he determined the boiler size and below is his response, he spent maybe 20 minutes looking over the house
    "I used Manual J calculations for heat loss to determine the boiler capacity needed. This includes the total heat loss from window square footage, roof area, linear wall footage, basement wall above & below
    grade, basement floor, pipe loss, etc. For the metro Chicago area we use -10 degrees as the starting point per Manual J."

    I plan on getting additional opinions as well.

    Furd, so the material in the 3rd picture is common? I think you referred to it as combustion debris?
  5. Dana

    Dana In the trades

    Messages:
    2,840
    Location:
    01609
    Manual-J typically oversizes by ~25% from the true heat load (sort of a built-in safety margin.) Insulation type (as opposed to rated R value) can make as much as a 15% difference in the true peak heat load as well, and Manual-J is a generous estimate. Going more than 10% over what Manual-J comes up with is almost certain to be oversized and somewhat less efficient in operation.

    Fin-tube baseboard works fine with a modululating condensing (mod-con) like the Triangle Tube, but the outdoor reset curve isn't going to be a great match at water temps below ~120F or so. But that's still in the condensing zone- you'll get ~90%+ true seasonal efficiency out of it if you tweak it in properly, but you won't have temps low enough to break 95%. But in selecting a mod-con look at the minimum modulation, not just the peak output, since it's the minimum modulation that will determine the duty-cycle. Turning on/off a lot kills the efficiency of any boiler, so what you want is something that can still run long slow burns at 1/4 of your peak load or less, since 0-25% of full-load accounts for over half the fuel burned in a heating season. Most mod-cons are deliver their highest combustion efficiency at their minimum modulation as well.

    If your current HW heater is an atmospheric-drafted gas burner going into the same flue as the old boiler and you're going to either a forced-draft boiler or a mod-con you'll be money ahead by decommissioning it now, and doing an indirect. It can't share a flue with an active-draft boiler, and if you side-vented the boiler, the flue it had previously shared with the boiler will be grossly oversized, leading to flue-condensation/deterioration and a high potential for backdrafting issues. At that point, you can seal up the old flues and get rid of a significant air-infiltration driver for the building. Closing it off helps retain the heated/air-conditioned air better, reducing both heating and air-conditioning loads.

    Efficiency-wise, heating hot water with a mod-con & indirect is a huge step beyond heating it with a standalone atmospheric-drafted HW heater as well, and is comparable to best-case scenarios with tankless on-demand HW heaters, but without any of the quirks & headaches that can come with the latter. Absolute combustion efficiency in HW heating mode will be in the mid-80s, and the standby losses will be low. Heating an indirect with a mid-mass boiler like a Burnham series 2 will improve the AFUE during the heating season, but will be pretty lousy during the off season (about as crummy as with a standalone tank, but sometimes worse.) That can be helped quite a bit if heat-purge controls are added to the system so that the boiler purges heat into the indirect at the end of every burn cycle, but you'll still never hit anywhere near it's heating-mode AFUE during water-heating-only months.

    FWIW: What did he give you for the real Manual-J peak load? 95KBTU/H 100KBTU/H? At the temps the baseboards will likely need to be to keep up at peak load the most you'll get out out of the Solo 110 is ~ 95KBTU/H, but that feels about 2x oversized to me (!). My house is somewhat larger in size than yours, and at 0F my heat load isn't quite 30KBTU/h (measured), with known gaps in the insulation. The simple math says at your design temp of -10F I'd be looking at ~ 35K. I've tightened up the place a lot, and I've sealed the band-joist & sills with foam, and insulated the basement walls with rigid-foam board, so if I ripped that all back out I might be looking at 40-45KBTU/hr, not more...

    ... which is still less than half the rated output of a Solo 110 when running with ~150F water returning to the boiler from the baseboards. It's lowest modulated input is 30KBTU/h, which would be about enough to run my place on design-day. It's li'l brother, the Solo 60 modulates down to 16K-in, which will be measurably more efficient as-operated, but you'd need to be sure that at -10F it doesn't need more than the ~50KBTU/h it would deliver with your radiation.

    As much as I like the Triangle Tube design, you might ask the folks who handle Burnham to quote you on the Burnham Alpine 80 or Alpine 105, which will modulate down to 16KBTU & 21KBTU, respectively. The max output on the -80 will be ~68KBTU/h, the -105 puts out 90KBTU/h. IIRC the Peerless Pinnacle PI-xx series and PureFire PF-xx series have similarly low lowest-mod outputs.

    If the incentives & rebates can knock the out of pocket difference down to a grand or less it's something of a no-brainer to go mod-con at your seasonal heat load. Your annual heating bill with a right-sized mod-con will be something like ~70% of what you've been paying with an aging 4x oversized beast, which was probably running something like 60-70% AFUE, provided it was reasonably well maintained, tuned up every half-decade or so etc., It doesn't appear to even have a flue damper on it in the picture, which might have brought it up to 75% as-used efficiency. Going by it's nameplate specs it's steady state thermal efficiency is only ~80% which is typical, and not bad, really, if it weren't 3-4x oversized for the load. If you were paying $1500/year heating with the old boiler you might be paying ~$1300 with a newer-smaller cast iron boiler, but more in the range of ~$1100 with a mod-con. At any reasonable discount rate the $1000 upfront price delta it turns net-present-value positive on the delta in fuel savings in well-under a decade (but it's paid in full in the first season, in terms of comfort, since the modulation runs the radiation at a more constant temp.)
  6. chsitko

    chsitko New Member

    Messages:
    7
    Location:
    Wheaton, IL
    Does anyone have any recommendations on how to locate a local Triangle Tube installer. The site doesn't list installers and I'm struggling to find others to give me a quote?
  7. Dana

    Dana In the trades

    Messages:
    2,840
    Location:
    01609
    If you can find the local distributor, they'll typically know which installers working in your aream who are competent to install the goods. (They also will know some who aren't, but may not tell you that straight out- better to ask for a list of 2-3 contractors, and they'll likely pick the ones who don't call back wtih complaints or require a lot of support, which tends to be the ones who have read & understood the manual BEFORE hanging it on the wall.)

    There are many distributors listed in IL, don't know which are closest to Wheaton: http://www.triangletube.com/TriangleTubeDistributors.aspx?link=dist
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