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Thread: Is a TriangleTube Prestige Trimax Excellence PTE 110 the right one of the job?

  1. #1
    DIY Junior Member AlexanderNY's Avatar
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    Default Is a TriangleTube Prestige Trimax Excellence PTE 110 the right one of the job?

    Situation:

    1800Sf, 1920 2 story Colonial house located in Westchester NY,
    insulated attic (R20), new windows.
    3 heating zones, the largest zone uses cast iron radiators,
    the two smaller zones are using the fine tube baseboards.

    Current heating: 25 year old oil burner.

    I am interested to convert over to gas.

    A contractor friend recommended the TiangleTube Prestige Trimax Excellence PTE 110.
    This is a high efficiency combi condensing boiler with a 14 gallons build in water thank for domestic
    hot water.

    So far, we received several estimates but none of the contractors
    performed an actual load analysis.

    At best, an estimate for the output of the radiators was done and it
    came in at 80K BTU's.

    Questions:

    - If we need a heat load analysis, where do we find a good contractor to do
    that? None of the 7 heating companies or plumbers that came out so far
    even mentioned a heat load analysis.

    - Do we need to be concerned about the temperature of the return water
    given that two of the heating zones are using fine tube baseboards.

    - How do we figure out if the TriangleTube Prestige Trimax Excellence PTE 110
    (which has output of 86K BTU's) is properly sized for this application?

    - Given that part of the radiator are the thin fin baseboard type, Is installing a high efficiency
    condensing boiler a waste of money?

    Regards,

    Alexander.

  2. #2
    Retired Defense Industry Engineer jadnashua's Avatar
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    Read some of the other threads. If you have your oil usage figures with the 'K' factor, you'd then download the heating degree day info for your zipcode. This will give you a reasonable upper bound on heating requirements. It's almost certainly much less than the output of the 110K unit.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  3. #3
    In the Trades Tom Sawyer's Avatar
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    At 86,000 out its probably a bit oversized but not grossly so. A heat loss would be a good idea but I don't think you would run into anything serious with that unit.
    [B]No, plumbing ain't rocket science. Unlike rocket science, plumbing requires a license[B]

  4. #4
    In the trades Dana's Avatar
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    Quote Originally Posted by Tom Sawyer View Post
    At 86,000 out its probably a bit oversized but not grossly so. A heat loss would be a good idea but I don't think you would run into anything serious with that unit.
    It may not be grossly oversized for the whole-house load, but it's minimum modulation of 30,000 BTU/hr is likely to be grossly oversized for the low mass fin-tube zones, and that could be an issue.

    If the house has been air sealed & insulated, 30K could even be the whole-house load at 10F or 15F or whatever the 99% outdoor design temp is at the particular zip code. (The 99% design temp for White Plains is +12F, NYC's is +15F.) I too have a 1920s house with 2400' of conditioned space (+ ~1500' of insulated basement), and my heat load is less than 30KBTU/hr @ +15F, and I DON'T have new windows (double-hungs + 1980s vintage clear storms).

    But whether the minimum modulation output of concern can be sorted out using back-of-napkin math. How many feet of fin-tube is there on the smallest/shortest zone?

    There are mod-cons with minimum modulation less than half that of the -110 combi that are probably better suited to the application, and if you had to add some thermal mass to keep the fin-tube zones from short cycling, that's possible too. If the 80K number they cooked up for the radiation presumed 160-180F water and your true heat load is under 30K, that's IDEAL for running a condensing boiler, since it will always run in condensing mode.

    With a K-factor from a mid-winter or late-winter oil bill it's pretty easy to put an upper bound on the whole-house heat load. With that plus the size of the fin-tube zones we can narrow down on what actually makes sense. A true Manual-J or I=B=R type load calc on the fin-tube zones might be useful too, since it's likely that those zones will have the highest water temp requirements.

  5. #5
    In the Trades Tom Sawyer's Avatar
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    Yep, it probably is but I have no idea what the split between base and radiators is nor how the system is piped and zoned. If I had too I'd bet that the contractors bidding it are figuring around 35 thousand of that output for domestic hot water. A mistake to be sure but a common one.
    [B]No, plumbing ain't rocket science. Unlike rocket science, plumbing requires a license[B]

  6. #6
    DIY Junior Member AlexanderNY's Avatar
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    Thanks for the answers so far.

    The home is located pretty close to White Plains, NY, so the suggested outdoor design temperature
    will be close to the one suggested by Dana.

    Regarding the 3 different heating zones, this is what we have:

    zone 1: 34 feet fine tube baseboard.
    zone 2: 30 feet fine tube baseboard.
    zone 3 20 feet cast iron radiators.

    Given the amount of fine tube baseboard, should we be concerned about the water return temperature?
    In other words, will a condensing boiler be condesing and be worth the investment?

    Regards,

    AlexanderNY

  7. #7
    In the Trades Tom Sawyer's Avatar
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    Typical 3/4" copper fin tube baseboard is rated at 580 btu/ft @ 180 degree input temperature so those two zones are capable of 37,120 btu/hr. the cast iron radiators depend on the size and number of tubes. There are charts that come pretty close so I'm gonna assume by your post that you have the equivalent of another 60' of baseboard and that rounds up to another 34,800 btu/hr and a grand total of 71,920 btu/hr possible @ 180 degree input water temperature. The heat loss of the envelope is unknown at this time but even if we go a little high, it's probably not more than 50k btu/hr. this isn't too bad because since you have more radiation than you need, return temperatures and inlet temperatures can be reduced although single zone operation may create a issue, however there are ways around that problem too. Anyhoo, if it were me I'd drop down to the prestige solo trimax 60.
    [B]No, plumbing ain't rocket science. Unlike rocket science, plumbing requires a license[B]

  8. #8
    DIY Junior Member AlexanderNY's Avatar
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    Two more pieces of information that might be relevant:

    1. One big reason that I am attracted to the TriangleTube Prestige Trimax Excellence PTE 110 is the fact that this
    is a combi unit, supplying both heat and domestic hot water.
    The direct venting option on the boiler means that we no longer need the chimney (nor have to put in an expensive
    chimney liner).

    2. Hot water to the heating units (both radiators and baseboard units) is distributed by rather inefficient uninsulated 2.2 inch diameter network of cast iron pipes.

    Alexander

  9. #9
    DIY Junior Member AlexanderNY's Avatar
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    O Yeah, getting the TriangleTube Prestige Trimax Excellence PTE 110 installed around here costs about 10.5K.

    Alexander

  10. #10
    Retired Defense Industry Engineer jadnashua's Avatar
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    FWIW, you may find that using an indirect WH is more efficient in the long run, connect it as a priority zone, and if sized properly, you should never run out of hot water, or let the house cool off. It doesn't make sense to me to have the boiler running to keep the water hot 24/7 when a good indirect may only call for heat once a day after a big use and the boiler can idle at essentially off for 23-hours in the summer.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  11. #11
    In the trades Dana's Avatar
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    It only makes sense to buy a modulating condensing boiler if it can run in condensing mode with out short cycling itself into low-efficiency & early failur, and actually modulate much of the time. The size/mass of the fin-tube zones will prevent that with a boiler as big as the -110 unless you add more radiation or add more thermal mass, but the -60 can modulate low enough at minimum fire to get you there, with some adjustments to the zoning.

    With only 30' of fin tube on the smallest zone the -110 will short-cycle like crazy running it at condensing temperatures. While it's output @ 180F AWT is on the order of 18,000 BTU/hr, when you drop the AWT to 135F (where it has to be to get any condensing efficiency) the output is half that, and the -110 boiler would be dumping 3x the amount of heat into the fin tube than the fin tube can deliver to the room at those water temps. If you tied the two fin-tube zones together (presuming the room-to-room temps would still be reasonably balanced, which isn't a given, though that could be tweaked slightly with ball-valves) it would limit the short cycling a bit, but it would still be doing 10 cycles/hour or more, and adding some thermal mass (or better yet, more radiation) might be necessary to really tame the beast.

    The -60 would do fine with the fin-tube zones combined into one even at 120F AWT, temps where efficiency would hit the mid to high 90s, but would still do a bit of cycling with the fin tube zones were left separated. There is some figurin' & plumbin' to do here.

    The radiator zone will do fine no matter what, because it undoubtedly has enough thermal mass to inhibit short cycling.

    A 50-60K mod-con plus an indirect is probably the right solution. If the heat loads of the fin-tube zones are under 10KBTU/hr each (which they might be), you may do just fine using a condensing hot water heater with a heat exchanger isolating the potable from the heating loop. Doing a careful Manual-J or even a simple I=B=R using a spreadsheet would tell you if that's a possiblity.

    No matter what you do, it's worth insulating as much of that 2" pipe as you can get to easily, since that represents a rather significant parasitic radiator. The crappy half-inch wall fiberglass R1.5-R2 stuff sold at box stores is nearly worthless, but the 1" wall thickness stuff sold for steam distribution piping is OK at about R3.5-R4.

    The only way your heat load would be anywhere near as high as 50K would be if the place leaks air like a sieve at both the attic-floor plane and at the foundation, and the foundation has no insulation. The air leakage is fixable on the cheap, but the foundation insulation costs will vary depending on how you go about it (but still worth it as a DIY.) If your basement isn't insulated, that's likely to be at least 10-15,000BTU/hr @ +15F, and a combination of air-sealing & insulating the band joist and insulating at least down to 2' below grade with R10-R15 would be a big uptick in first-floor comfort as well as an efficiency gain. With a big oil boiler and bare 2" pipes it's likely that the basement is the warmest place in the house when it's +15F outside, even uninsulated, but when you go to a more efficient boiler running minimal temps the basement (and first floor floor temp) will run much cooler during cold weather. But if you air seal & insulate, the basement will run in the mid to high 60s, (even with insulated pipes), but without the high heat loss out of the foundation. There are many ways to screw up foundation insulation- don't just slap up a studwall and stuff batts into it or you'll have re-invented the mold-farm. If/when you're going there research it a bit- Building Science Corp has quite a bit of info online on how to do it without creating more problems. (If pressed I can explain how & why some methods fail, others succeed, and how to do it on the cheap too.)

  12. #12
    Master Hot Water Mpls,MN BadgerBoilerMN's Avatar
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    I can heat your home with half the output of an Triangle Tube Excellence combi. We have had one operation in St.Paul, MN for about 5 seasons now without a problem, but the retrofit application was unique.

    We install high efficiency condensing boilers here in Minneapolis on 9 of 10 renovations and 100% of new homes and addions. (OK we install an occasional condensing water heater for low-load combi systems). It is nearly impossible to find the right fit for a combi water heater or combi boiler for the reasons Dana so astutely asserts.

    Every proper hydronic system, new and replacement must start with an ACCA Manual 'J' heat load and system load evaluation. We would never size a space heating boiler base on DHW loads. That is what and indirect-fired water heater is for. A combi-unit is a 'do-all' compromise seldom warranted, that most can ill afford.

  13. #13
    DIY Junior Member AlexanderNY's Avatar
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    Thanks a lot for all the replies and suggestions. I've gotten much better advice here on this forum then from 95% of the
    contractors that have put in an estimate for a new system. Just yesterday we had a plumber over would claimed that
    we should install a 150K BTU gas boiler simply because that's is what the old oil burner delivers.

    At this point, I am seriously looking at the suggested prestige solo trimax 60 plus an indirect.

    Unfortunately, The two heating zones with the fin tube baseboard are installed on tow different floors. The original house
    was extended with a two story addition. Each story received it's own baseboard heating zone.
    Given the two different floors, I am not sure if it makes sense to combine the two zones. It would
    means that at night, I have to heat the unused downstairs addition because I am heating the upstrairs addition.

    Going with the 60, I assume we can set the outgoing water temperature low enough such that the boiler runs in
    condensing mode?

    Regarding the suggestion for an indirect water thank for domestic hot water, would the indirect basically be an additional zone
    on the new boiler?

    Regards,

    AlexanderNY

  14. #14
    Retired Defense Industry Engineer jadnashua's Avatar
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    If your boiler (many do) comes with or can have an outdoor reset control, it will, if properly adjusted, adjust the supply temperature based on the outside temp and the returning water temps - IOW, it will try to have the boiler output just be enough to operate at peak efficiency and comfort. Most of the time, this should be a condensing mode (again, if it is setup properly!).

    Usually, an indirect is setup as a priority zone. When it calls for reheating the tank, it requests the boiler go to high fire, and then only supply that zone until it is satisfied. This normally doesn't take all that long, and it's rare to notice the other zones are not getting any heat (they don't immediately turn into icecubes and still supply some residual heat in the interim).
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    In the trades Dana's Avatar
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    At an average water temp of 130F (140F out, 120F back) you'd be getting pretty good condensing efficiency. At 130F AWT most fin tube is delivering ~250 BTU/foot, so your 30' zone is good for only ~7500 BTU/hr, which only about half the output of the -60 boiler at minimum modulation, which means it will cycle on/off/on/off fairly often during a call for heat from only that zone. At 110F AWT (120F out, 100F back, about the lowest you'd ever run fin-tube) you're only getting ~150BTU/ft out of it, with a 10,000BTU/hr difference between the boiler output and the fin-tube output.

    There are a few ways do deal with this. The best way would be to add sufficient radiation to those zones to make it balance with the ~15K min output of the boiler when it's in condensing mode. Panel radiators would be the most comfortable, but aren't super-cheap. If there's more wall perimeter that could be used for more baseboard that would be the cheapest.

    Another method is to at thermal mass to the system in the form of an insulated storage tank referred to as a "buffer". But to know whether the distribution plumbing already has enough thermal mass to save you take's a bit of napking math:

    With 2" distribution plumbing you may already have enough buffering thermal mass to make a difference.The fin-tube has about 0.2lbs of water per foot, or 2lbs for ever 10'. The 2" iron is good for about 1.5lbs water-equivalent per foot, or 15lbs for every 10' (when you include the thermal mass oft the iron.) A typical mod-con will run a 7-10F ramp around the outdoor reset's setpoint. If you have say, 30' of 2" pipe in the loop between the boiler and the 30' of fin tube, and say 10' of copper too, that's about 40' of 3/4" copper for 8lbs of water, 30' of 2" iron for 45lbs, you're at 50lbs of thermal mass. The 2.5 gallons inside the boiler is good for another 20lbs, call it 70lbs total.

    With an excess of 7500 BTU/hr (/60 = 125 BTU/minute) going into that water, the temp of the loop rises at a rate of 125BTU/70lb= 1.8F per minute, so with a 7F minimum hysteresis on the boiler's output setpoint you'd have a minimum burn time 7F/1.8= 3.8 minutes.

    That's long enough to get you under 10 burns/hour, and not exactly terrible. If you have even more 2" iron between the boiler & fin-tube zones, so much the better, if it's less, measure it up and do the math. (Both supply & return plumbing counts.)

    But if it's all 3/4" copper or PEX, the thermal mass is dramatically lower, and it'll short cycle. A cheap electric HW heater (not wired up) can often be impressed in to service as a buffer tank, or as a buffering hydraulic separator, but you really need to design the system (or pay somebody to design it, even if somebody else installes it), not just throw hardware at it and hope.

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