Burnham MPO-IQ versus Buderus G125BE Oil Boilers

Discussion in 'HVAC Heating & Cooling' started by danboston, Mar 29, 2011.

  1. Dana

    Dana In the trades

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    The buffer (in any plumbing configuration- either in-series or at the point of hydraulic seperation in a primary/secondary) doesn't appreciably affect the average return temp or the overall duty cycle, but HUGELY affects the number of cycles and efficiency losses related to the fixed losses of ignition & flue purges, and the wear & tear on the boiler.

    Cast iron or flat panel radiators add mass (and work linearly at lower temperatures than fin-tube), but you still have to do the math on the total mass & heat-emission at the temperature you're operating to know whether you'd need a buffer. But since you probabably still need a buffer on the other two zones to run at 120F withtout short-cycling, making it a commoned buffer in series with the return manifold and the boiler is probably the right thing to do ( and not a seperate buffer just for the basement zone.) Plumbed on the return manifold is slightly better than on the output side, since then it doesn't slow the response time of the system when under low- partial load- the radiation gets to it's peak temp sooner without having to raise the temp of the buffer first.

    A quick refresher on the simplified math: At your low-load minimum of 120F your existing 40' zone with the 31lbs of water the fin tube would be delivering something on the order of 200BTU/foot x 40' =1600 BTU/hr into the rooms, but the boiler is putting out nearly 10x that at 15000 BTU/hr even at it's min-modulation, for a ~13,400 BTU/hr shortfall. Assuming a 10F hysteresis in the boiler you'd get 31lb x 10F/13,400= 0.023 hour= 1.4 minute (83 seconds) of burns- a seriously short cycle. If you raise the temp to 130F the output of the fin tube would rise to something like 250BTU/foot stretching it out a bit, but not enough to matter.

    To deliver the full 15K in a 40' zone you need 375 BTU/ft, which would take 150F water, with a return temp over the condensing point. You'd need to buffer your existing zones to be able to operate in the condensing region without short-cycling the boiler into both lower efficiency & an early grave.

    To stretch the burns to ~10minutes (.17 hours) with 13.4K of extra takes a system with 10F of hysteresis at the boiler takes 13400 x 0.17/10F= 228lbs of water, which is 228/8.34= 27 gallons. You already have 3.7 gallons in the zone, so a 20-25 gallon buffer will do. But if the hysteresis is closer half that (sometimes is) a 40gallon buffer would be better. (30-50 gallon electric HW tanks are CHEAP compared to a 30 gallon Boiler Buddy or a Ergomax BT26 or BT48 buffer, and won't add much pump head to a low-flow system like this.) It would take ridiculously large diameter & expensive distribution plumbing to achieve that much thermal mass.
     
  2. danboston

    danboston New Member

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    Dana:

    So, when I put heating in the basement, I should absolutely go with cast iron over fin-tube?

    After weighing all my options, I have definitely decided to go with the Burnham Alpine 80. Burnham has a good reputation and the Alpine 80 modulating range looks good (16 to 80 K btu/hr) for my Heat Load (~35 K btu/hr). Also, I have found a couple of local contractors who seem competent and have installed quite a few Burnham boilers.

    To get a better handle on the likely hysteresis of the Alpine, I looked up the Central Heating Setpoint discussion in the Alpine Installation & Operation (I&O) Manual (http://www.usboiler.burnham.com/products/residential-boilers-indirect-water-heaters/alpine)

    According to the I&O Manual (page 94):

    8. Boiler Temperature Regulation
    a. Overview
    Based on the call for heat type, the Sage2.1 controller
    selects a firing rate target temperature setpoint.
    Sensed temperature is compared to this Setpoint
    to both adjust firing rate output and along with the
    corresponding “Diff Above” and “Diff Below”
    settings cycle the boiler.
    b. Central Heat Setpoint
    The Central Heat Setpoint is fixed at the contractor
    selected value unless Outdoor Air Reset is enabled
    or a “Setback” thermostat is connected. The value
    of this setpoint is set up based on the type and
    quantity of radiation installed.

    Also on page 106 of the Alpine I&O manual:

    The range of temperature values that the installer can input for the Central Heating Setpoint "DIFF ABOVE" is 2 F to 10 F (factory setting is 2 F).
    The range of temperature values that the installer can input for the Central Heating Setpoint "DIFF BELOW" is 2 F to 30 F (factory setting is 10 F).

    Does this help in the evaluation of buffer size?

    It is interesting to note on Page 108 of the Alpine I&O Manual that the recommended Central Heating Setpoint temperature for Convection Baseboard Fin Tube Convective Heating elements is 160 F - 190 F.

    Finally, which of the three diagrams that you provided in earlier threads of this post best represents what you describe as "a commoned buffer in series plumbed on the return manifold"?

    Thanks, I appreciate all of your help!
     
    Last edited: Apr 6, 2011
  3. Dana

    Dana In the trades

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    All prior schematic were variations on buffer-as-hydraulic seperator, none were a simple series-return diagram a partial schematic would look like this:




    |boiler return input|<============<[buffer tank]<====<|zone1 return|<|zone 2 return|<|zone 3 return|

    indirect return Tees in here-^

    The returns from the zones all come together and feed into the cold input of your buffer tank or elec. HW heater, and the output of the buffer then feeds the return input to the boiler. If running an indirect HW heater as a seperate zone it needs to Tee in between the buffer tank and the boiler's radiation return.

    Cast iron or high mass radiators aren't essential, but generally provide more comfort than fin-tube, since you can feel the direct radiation on exposed skin, whereas fin-tube is primarily just heating the air. Since you'll need a buffer to deal with your existing zones to run at low-temp, using the same buffer for all zones means you don't have to use some monster-sized radiators in the basement just to raise the thermal mass of that zone.

    The fact that the hysteresis on the Alpine is programmable up to 10F means that you can indeed use a 20-25 gallon buffer rather than a 40-50 gallon buffer without short cycling on your 40' baseboard zone, as per the last paragraph of my prior post. If you run at least 40' of baseboard in your basement it'll be pretty similar to the setup for the other zones as far as buffer sizing. If left at the hysteresis programmed to the 2F default you'd still run into sub-5 minute burns, which would be bad for the boiler maintenance & efficiency. At 5F or less you'd need 40gallons or more to really stretch it out with that type of radiation.

    Whatever you put for radiation in the basement zone, make sure it's output @ 120F water temps is at least that of your other zones, but in the same ballpark. Read the specs carefully. (If you're up for it, radiant ceiling is pretty nice, but that's a whole 'nuther design issue.)
     
  4. danboston

    danboston New Member

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    Dana:

    That helps a lot. However, if you have an example of a simple-series return schematic that would be really great since I am having a hard time picturing that.

    Yes, we plan to add a 50-gallon indirect water heater (Burnham Alliance stone-lined). One of the Burnham contractors said that the water in New England is not good and that a stainless steel IWH would not last as long as a stone-lined one. Do you agree with that?

    On a side note I was able to download the free Slant/Fin Hydronic Explorer Heat Loss program. It is the same program that a previous contractor used to calculate a heat loss of 90 K btu/hr for my house. In addition to using an outdoor design temp of -10 F for my area (about 20 miles north of Boston), there were also some omissions they made for insulation. I plugged in an outdoor design temp of 0 F and added the appropriate insulation factors and came up with about 56 K btu/hr. That is still more than 1.5- times greater than the rate that I calculated using the NORA Fuel Savings calculator (~30- 35 K btu/hr), but I guess as long as it is less than the net I-B-R for the Alpine 80 (which is 63 K btu/hr) it should make the contractor feel good about the sizing. Do you know what the ASHRAE Outdoor Design Bin Temp is for: Boston , MA and Concord, NH ? If not, do you know where I can find those?
     
    Last edited: Apr 7, 2011
  5. Dana

    Dana In the trades

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    The ASHRAE 97.5% design temp for Lawrence MA next door is 0F, the 99% number will be something like -3F or -5F. If the boiler's output is even 15% oversized for the heat load at the 97.5% number it'll keep up at -10F. For a listing of some ASHRAE 97.5% numbers see:

    http://www.crownboiler.com/educate/heatloss.asp

    For some 99% numbers see:


    http://www.chromalox.com/resource-center/design-guide-pages/dg-comfort-heat.aspx


    Note, Boston's numbers are +9 F and +6F, due to the moderating effect of being on the coast. Figure on Lawrence/Andover's 99% number will be about -3F or -4F, not -10F.

    Whenever I've used the Slantfin tool it's come out 35-40% ahead of measured reality. Other Manual-J or IBR type tools tend to hit in the 15-25% overage. If you use fuel use and degree-day data carefully to calculate the K-factor and parameterize the boiler carefully the NORA tool tends to hit within 10%, but can sometimes hit 10% low. The NORA tool tends to use some 99.9% number for design or somethingfor the cities on their pull-down menus. If the Slantfin tool is telling you your 0F load is 56K, measured reality will be no more than 45K. If the NORA tool is telling you 32K, it could be as high as 36K, but it's probably 32K. Unlike heat loss calculators, the NORA tool is using the boiler to MEASURE the heat load.

    I suspect the Slantfin tool assumes an unrealistically high infiltration rate compared to that of tighter homes built in New England generally have, and pads out the result a bit from there. Better tools allow you to play around with air-leakage factors a bit more.

    I have no opinion of stainless vs. stone lined. A generalized characterization of New England water is pretty bogus though- town water differs widely depending on source and treatment, but most towns don't have water hardness issues the way they do in the midwest. Call your town water department or if online, look up the water quality reports and see the average grains of hardness. Worcester uses primarily surface water from reservoirs, and I ran a tankless HW heater (notoriously sensitive for liming) for 15 years without ever having to de-scale the sucker, and retired it fully functional when I replaced it with a reverse-indirect buffering the heating system (necessary due to micro-zoning.)

    To clarify in my previous post, "Whatever you put for radiation in the basement zone, make sure it's output @ 120F water temps is at least that of your other zones, but in the same ballpark." , I really meant to say "...at least that of your other zones relative to the calculated heat load for that zone..." The heat load of the basement will be much lower than the upper floors due to less above-grade exposure and less glazed area.

    A series connection means that it's one pipe in , one pipe out, no Tees. Think of the tank as a fat spot in the pipe between where the heating returns come together and the boiler. All heating returns dump into the tank, not the boiler, only the tank's output feeds the boiler.

    But IIRC from a recent thread on the boiler forum on this site the Alpine's min-flow requirements are such that it REQUIRES a primary/secondary configuration, so using the buffer (rather than closely spaced tees) as the hydraulic seperator is the right way to go, if that's you're boiler. (The Solo 60 could probably be done in series though.) See TK03's comments about P/S requirements for the Alpines here:

    https://terrylove.com/forums/showthread.php?39849-Modcon-with-IHW-Tweaking/page4

    You may want to read that entire thread- it's essentially the same design and setup issues that you'll have to address.

    The LAST thing you'd want to do is up-size it to the Alpine 105, since it's min-mod output is probably going to be over half of your design-day heat load. The 73K DOE heating output of the -80 is well over even the Slantfin calc. The IBR number shouldn't be used here, since that's essentially a ~15% allowance for pipe & boiler losses when the boiler & distribution piping are outside of conditioned space, such as an unconditioned attics or crawl spaces, etc. Even if the boiler is installed in your basement, it's a conditioned basement inside the insulation, not a ventilated/uninsulated crawlspace. You very likely have 80-100% more burner than you need on the high-end even using the -80, but the fuel efficiency is dependent on how low you can go on the minimum. If your true 0F heat load is 35K, the -80 would nearly continuously (mostly in condensing mode) whenever the the outdoor temps drop below 40-45F once you have the flows & reset curves tweaked in. If you upsized the boiler to a higher min-mod, you'll experience more cycling losses when it's 30F or above (unless you added even more buffer), which is MOST of the heating season.
     
    Last edited: Apr 7, 2011
  6. danboston

    danboston New Member

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    The hardness of Town water has been consistent for years at 2 grains per gallon or 34 milligrams per liter. Is this enough to cause scaling problems?

    As provided in the Chromalox web-site, the 99.9% ODT values for the following cities are: Boston [6 F], Worcester [0 F], Concord, NH [-8 F].
    I re-ran the Slant/Fin Hydronic Explorer Heat Loss using -4 F for Lawrence as the ODT (average of the 99.9% ODT for Worcester [0 F] and Concord, NH [-8 F]) and that gives me 63.5 btu/hr. As I mentioned, based on oil consumption, the NORA calculator gives me about 35 K btu/hr.

    After reading TKO3's thread, do variable speed pumps help with reducing short cycling by increasing the delta T?

    As far as the size of the buffer, I just double-checked the pipe diameter associated with the smallest (40-ft) zone and it actually is only 3/4-inch copper pipe (the other zone is conveyed with 1.5-inch pipe). Apparently this smaller zone was added as part of an addition that was put on before we bought the house and they used smaller pipe for that zone. Therefore, we have a little less than 1 gallon in that zone. So, is a 20-25 gallon buffer still appropriate? Also, looking at the room-by-room Heat Loss numbers that I calculated using Hydronic Explorer, I added up the Heat Loss for the smallest zone on the ground floor and it is roughly equal (slightly less) than the predicted heat loss for the entire basement (insulated).

    So you think the Alpine 80 with a 25-30-gallon insulated buffer and 50-gallon IDW heater is appropriate? The low end of the Alpine 80 is 16K btu/hr and the high end (DOE value) is 73 K btu/hr? Do you think that is still too much boiler and maybe a smaller combi-unit might be the better way to go? Do combi units provide a lower output (< 16 K btu/hr) than the Alpine 80?
     
    Last edited: Apr 9, 2011
  7. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    Combi units (those with a built-in HW coil) aren't the best idea when considering efficiency - the output is limited, and you have to maintain the boiler hot 24/7. An indirect, especially on a mod-con, means on a warm summer day, it may only fire once to bring the WH up to temp after the morning rush.

    On a boiler plumbed with p/s, except for a few situations (heating the indirect may be one), the heated output goes in one loop back to the input. On that loop, there are some T's where there is a takeoff for your heating zones. It inserts the cooler return water on another T. So that there is actually flow in the secondary loop, the placement of the T's in the primary loop is somewhat critical. There would be one circulator pump for the primary and other(s) for the secondary loop(s). On mine, it pulls off the primary loop for the indirect, but that is not always done that way.
     
  8. danboston

    danboston New Member

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    The water piping diagram for the Alpine is shown here (see attachment):

    View attachment Alp WP 100Res.pdf

    Where would the buffer go?

    I looked at the HTP VERSA, which has a modulating burner that appears to range from 100 K btu/hr to a low of ___? Not sure what the low end is although they say it has a 5 to1 turndown ratio on the main combustion unit and a 10 to 1 turn down ratio for space heating - does that mean it will go as low as 10 btu/hr? It does appear to have built-in coil. So this does not act like a Indirect hot water heater and the storage temp of the combi must be maintained hot 24/7? Is'nt that how an indirect water tank works - it must be kept hot all the time?

    See http://www.htproducts.com/versa-hydro.html

    I am also considering having a solar hot water panel installed in my backyard. Massachusetts is offering a significant ($3,500) rebate program in addition to some Federal tax credits. I assume that would save the boiler from generating any hot water at least 9 months of the year. Of course I would need a larger IDWH (80 gall) and it would need to have two coils (one bottom coil for the solar heated fluid and the top one for the boiler). The other issue with the panel is location - it would be about about 80 feet from the house and another 50 feet to the tank in a conditioned space. The vendor stated that the piping would be installed in a trench 1.5' below grade and would be well-insulated. Not sure what the heat loss would be over that distance but have a feeling it would be pretty bad in the winter-time?
     
    Last edited: Apr 11, 2011
  9. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    That's a hybrid, similar (I think) to an older designed Trianco HeatMaker (Which I owned, but eventually threw out). Not in a position to evaluate it at the moment.
     
  10. Dana

    Dana In the trades

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    Maybe I was too wordy in my response on that thread but simply put:

    No, variable speed pumps do not and cannot reduce short cycling. It doesn't change the minimum modulated output of the boiler, or the rate at which the baseboards emit the heat into the room.

    The lower the water temp, the lower the heating rate of the baseboard. When the boiler's output is many times that of the heat emitted the water temp rises rapidly and the burner kicks off.

    To eliminate short cycling at condensing temps you either need more baseboard, or add mass to the heating zone, or increase the hysteresis of the boiler temp to use the thermal mass of the water in that loop.

    From a practical point of view with 50 ' of baseboard at 120F you're looking at 1000BTU/hour, or about 7% of the boiler's ~15K output. Putting in 750' of baseboard won't cut it.

    Raising the hysteresis of the boiler for 10minute min-burns on a sub-5 gallon loop takes it well out of the condensing zone for most of the burn.

    Adding thermal mass to buffer the heat is the only real solution.

    An Alpine 80 + indirect + buffer tank could be an appropriate solution. In that scenario, place the buffer at the point of hydraulic seperation to the heating zones, but not the indirect (I think you can eliminate P3 if you plumb it tight & right):


    [​IMG]

    The HTP Versa is also an appropriate solution, and will run as efficiently as the Alpine 80 if usng fin-tube as the heat emitters. With radiant floors and/or panel radiatorsit's possible for a good designer to squeak 3-4% more efficiency out of an Alpine 80, since you could then run the heating zones at temps much lower than domestic hot water for high combustion efficiency. The Versa is inherently self-buffered, and making the system design & implementation comparatively simpler- you'd have to work at it to really screw it up (but I'm sure there are installers up to the task. :) ) Unlike Trianco or Bradford-White combis, the Versa is fully modulating & condensing, with a 5/1 turndown ratio to (same as the Alpine 80's high/low ratio)- they're not really in the same class. Even though the smaller-burner Versa only cranks down to ~25K of outuput compared to ~15K for the Alpine 80, the 55 gallons of water in the smallest Versa is more than 2x the minimum buffer we were talking for the Alpine-80 solution with 10F of hysteresis, for less than 2x the min-mod burner output. There's literally no way to short-cycle it, and it'll average better than 90% efficiency at your anticipated fuel-use derived heat load using your given lengths of baseboard, since you won't need to it up above typical DHW storage temps- it'll ALWAYS be firing in condensing mode.

    The heat loss out of a trenched-in solar loop isn't as bad as you might think. Heat loss is all about the total surface area, delta-T and R values. The surface area of the pipe is around 1/3 of a square foot per running foot, so at 80 feet out, 80 feet back you're looking at about 50 square feet. Assuming an average water temp of 90F and an wintertime soil temp average of 40F at that depth, and R10 of insulation (2" of closed cell foam) that's 50F x 50sq-ft/R10=250BTU/hr. That's the order of magnitude, and likely overstated by 34x, since the temps are only significantly elevated during mid-day sunny hours, which are less than 1/4 of all winter-hours, so the average delta-T may in fact be far less than 60F. Any losses to the conditioned space portion comes directly off the heating load, and can be ignored. Insulating underground flat-panel solar plumbing to a reasonably high-R can be done by sheathing the pipe in an R4 high-temp pipe insulation then strapping it to a strip of 2" of XPS and spraying 1.5-2" of closed cell polyurethane foam over that. If using evacuated tubes you may run into higher temps than XPS or SPF are rated for- let the solar designer spec the insulation.

    The heat loss in summer would actually be higher, since the soil temps wouldn't be more than 20F higher, but the average water temps would be substantially higher due to lower panel losses and a greater fraction of sunny hours.
     
    Last edited: Apr 11, 2011
  11. danboston

    danboston New Member

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    Dana:

    Great. I really appreciate your help.

    So, if I decide to add solar hot water, I should stick with the Alpine 80 and a 30-gallon buffer tank. Under the solar scenario, for the IDHW tank I would need an 80-gall IDHW heater with two coils.

    If I decide NOT to go with solar hot water, then the 55-gal HTP Versa sounds like a better option than the Alpine 80 with a 30-gall buffer. It would essentially be one unit, versus three; easier installation; roughly equivalent efficiencies, etc.

    For the Versa-Hydro, would not a 10:1 turn-down ration on the space heating module result in an output of 13.5 to 135 K btus/hr? The Main Combustion System has a turn-down ratio of 5:1.

    However, if I did want to go with Solar Hot Water, I do see on the HTP web-site that they offer an 80-gallon Phoenix Solar Hot Water tank (with 2 coils) that apparently can be used in conjunction with the Versa-Hydro.
     
    Last edited: Apr 11, 2011
  12. Dana

    Dana In the trades

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    If going solar price out a Versa Hydro Solar solution before commiting to an Alpine 80 + solar solution. The Versa Solar is a fully integrated single tank system, with very little difference between the 80 gallon Versa and an 80 gallon Versa Solar, beyond the extra coil for the solar loop and some extra controls. With 80 gallons of buffe it would guarantees even longer minimum burns in space-heating mode.

    Even if you never install the solar end it's efficiency would be as-good. It's a matter of the up-front costs of an 80 gallon Versa Hydro Solar with an as-yet unimplemented solar loop relative to the proposed non-solar solutions up front. An 80 gallon solar tank by itself is a pricey piece of hardware, and adding that to an Alpine-80 + buffer solution would mak for a more expensive total package.

    Not to mention, with either a solar or standard version of the Versa most of the system-integration is pre-engineered, whereas with the Alpine 80 you're at the mercy of the system desginers/installers, and the quality of the design & commissioning a full-custom system will vary. It's pretty hard to screw up with a pre-packaged pre-engineered system.
     
  13. danboston

    danboston New Member

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    Dana:

    I called HTP and they gave me more information about the Versa-Hydro. They offer three different-sized Hot Water Storage units (50-, 80-, 119-gal), but they all have the same burner. The Main Combustion Unit modulates from 26 - 130 K btus/hr, whereas, the Space Heating component modulates from 13 - 130 K btus/hr. Apparently they use a variable speed pump to convey hot water from the hot water storage tank to the heating elements and that is how they achieve the wide modulating range for the space heating. But to compare apples to apples, the Alpine has a lower modulating range (16 - 73 btu/s/hr) than the Versa-Hydro (26 - 130 K btus/hr) for the main burner. The smallest Versa-Hydro Solar unit comes with a minimum 80-gal dual-coil tank. As you said, an 80-gallon tank will provide plenty of mass and it will never short cycle. It is all one unit - no need for a separate buffer tank or separate IDHW tank. We also have the option of connecting solar hot water now or at a later date.

    It does not appear that the Versa-Hydro tank or heat exchanger is made of stainless steel. Apparently, the heat exchanger is a 90/10 cupronickel alloy. Not sure if a cupronickel alloy heat exchanger is reliable?? The lack of a stainless steel tank and cupronickel heat exchanger makes me hesitate....

    The Warranty on the Versa-Hydro is as follows:

    Residential Use Warranty (1 year – Parts, 12 years – Tank)
    COVERAGE
    A. HTP warrants that it will repair or replace, at its option, any defective Versa-Hydro™ Combined Hydronic Appliance or malfunctioning component thereof that is found to have failed due to manufacturer’s defect during the first year after installation.
    B. 1. Residential Use - During the second through seventh year after the date of installation, HTP will repair or replace, at its option, any defective Versa-Hydro™ found to have failed due to leaking heat exchanger, tank, or brazed plate exchanger.
    C. Residential Use ONLY - During the eighth through twelfth year after the date of installation, HTP will repair or replace, at its option, any defective Versa-Hydro™ found to have failed due to leaking heat exchanger, tank, or brazed plate exchanger, at a cost to the purchaser equal to the following percentages of the manufacturer’s list price in effect at the date of replacement.
    Year of Claim:
    8 & 9 (25% to be paid by purchaser)
    10 & 11 (50% to be paid by purchaser)
    12 (75% to be paid by purchaser)

    Here is the Warranty information on the Burnham Alpine:

    ONE YEAR LIMITED WARRANTY ON RESIDENTIAL GRADE BOILERS
    AND PARTS / ACCESSORIES SUPPLIED BY U.S. BOILER COMPANY, INC.
    U.S. Boiler Company, Inc. warrants to the original owner that its residential grade
    water and steam boilers and parts/accessories comply at the time of manufacture with
    recognized hydronic industry standards and requirements then in effect and will be
    free of defects in material and workmanship under normal usage for a period of one
    year from the date of original installation. If any part of a residential grade boiler or
    any part or accessory provided by U.S. Boiler Company, Inc. is found to be defective
    in material or workmanship during this one year period, U.S. Boiler Company, Inc.
    will, at its option, repair or replace the defective part.
    HEAT EXCHANGER WARRANTIES
    U.S. Boiler Company, Inc. warrants to the original owner that the heat exchanger of its
    residential grade boilers will remain free from defects in material and workmanship
    under normal usage for time period specified in the chart below of the original owner at
    the original place of installation. If a claim is made under this warranty during the “No
    Charge” period from the date of original installation, U.S. Boiler Company, Inc. will, at its
    option, repair or replace the heat exchanger. If a claim is made under this warranty after
    the expiration of the “No Charge” period from the date of original installation, U.S. Boiler
    Company, Inc. will, at its option and upon payment of the pro-rated service charge set
    forth below, repair or replace the heat exchanger. The service charge applicable to a
    heat exchanger warranty claim is based upon the number of years the heat exchanger
    has been in service and will be determined as a percentage of the retail price of the heat
    exchanger model involved at the time the warranty claim is made as follows:

    Year 8 (30% to be paid by purchaser)
    Year 9 (40% to be paid by purchaser)
    Year 10 (50% to be paid by purchaser)
    Year 11 (60% to be paid by purchaser)
    Year 12 (70% to be paid by purchaser)

    Both of these warranties look pretty similiar.

    Although it apparently does not appear in the Warranty description above, I saw in the Alpine brochure that US Boiler offers a free 5-year warranty on all parts and labor for the first 5 years from the date of installation. What are the chances that something will go wrong in the first 5 years with the Alpine?

    Thoughts?
     
    Last edited: Apr 12, 2011
  14. Dana

    Dana In the trades

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    Boilers & HW heaters are all pretty reliable for the first 5 years- even the crummy ones, and these aren't crummy ones. Both HTP and Burnham make quality goods that hold up when installed correctly, but a bad install can kill any piece of equipment. HTP also sells some low-end mod-cons (MC series) that DIYers seemed to manage to screw up the installations on, but work pretty well when done right. People have done combis based on their Phoenix condensing hot water heaters for something like a decade(?) without running into reliability issues.

    On the heat-exchanger front, as long as you don't have leaks in the heating system or gross materials incompatiblity with sub components, the water side of the heat exchangers will last pretty much forever. Aluminum heat exchangers on boilers-past have had issues on both the fire side & water side, but SFAIK there aren't any generic or widespread issues with cupronickel alloys.

    For the sub-flooring, even pressure-treated ply is overkill in a basement that NEVER floods. The XPS is an excellent capillary break against wicking up ground moisture, and at 1.5" it's only semi-permeable to water vapor. The only time you'd need anything other than a standard ply or OSB subfloor over an XPS-on-slab situation, is for flooding events. Structurally it's fully supported by the XPS & slab- it doesn't even need to be as thick as in a joist-mount but IIRC you need at least 1/2" of wood between the room and the foam as an ignition barrier. As long you don't have wood in direct contact with the concrete (pay attention at the edges) and don't put down a vapor-barrier type of flooring such as asphalt tile or vinyl-linoleum it'll have the same moisture content of any other piece of wood in the room. (Hardwood, bamboo, or carpet are all fine.)
     
  15. Dana

    Dana In the trades

    Joined:
    Jan 14, 2009
    Location:
    01609
    Ultimately, the quality of the system depends more on the quality of the system-design and how well it's implemented. Going with something that both installer & manufacturer back up with local support is more important than any warranty clauses. What this thread has given you is the basic education by which you can disuss the pros/cons of different approaches with the contractor better than the average homeowner/buyer would, and also gives you a handle on their competence or lack thereof. At the very least you're more likely to end up paying too much for something 4-5x oversized guaranteed to short-cycle itself into an early grave, expiring 10 minutes after the warranty does. Most residential boiler installations in MA are oversized relative even for the heat-load calculation software numbers, which are as a rule oversized to begin with. Modulating burners can mask some oversizing issues, but getting it right-sized (or adequately buffered) for the loads is always a better way to go.
     
  16. danboston

    danboston New Member

    Joined:
    Mar 19, 2011
    Occupation:
    Geologist
    Location:
    Lawrence, Massachusetts
    Dana:

    Great. Your knowledge of boiler systems and the ability to convey that information is unbelievable and you have been of immense help. I really do appreciate it!

    I will price out the HTP Versa-Hydro Solar. Looks like a great system and hopefully dummy-proof installation.

    P.S., What about the 2x4 plates that need to be installed near the base of the interior foundation wall for the new framed wall? Those really cannot be "floated"? I plan to use pressure-treated 2x4s for the foundation wall plates that would be nailed into the concrete using a concrete nail gun. I should put a moisture barrier down between the concrete and the PT-2x4 plate? Are there any other options or steps I missed?

    For the partition walls in the basement, I was planning to use 2x3's and float them on top of the 1/2"-plywood (which overlies the 1.5" XPS foam boards). They would be glued and nailed to the plywood - however, am not sure that would be sturdy enough. Should I nail them to floor like the 2x4's (I would have to rip PT-2x4s down to 2x3s but that is easy enough).

    Finally, I wanted to use OSB sheets to float over the insulation since they come with a tongue and groove system - that way, I would not have the edges potentially buckling up/down where they butt up against each other. Home Depot has some T&G OSB product made by Home Advantage. The Advantech OSB boards are nice but are about 40% more expensive than "Home Advantage" boards.
     
    Last edited: Apr 13, 2011
  17. Dana

    Dana In the trades

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    Jan 14, 2009
    Location:
    01609
    The studwalls aren't load-bearing, so putting the bottom plate above the XPS tapconned into the slab or just nailed/screwed to the subfloor is just fine.

    T & G OSB is fine. It just has to meet a minimum fire rating (typically a 15 minute barrier per ASTM E 119 test ) to be used as the ignition barrier for the foam, unless you're putting down a wood, ceramic, or other substantial flooring that would add to the fire-rating of the floor assembly. IIRC most 7/16" & 1/2" goods and all 5/8" or thicker OSB out there meets spec on their own. The Home Advantage t &g subfloor goods are nearly 3/4" thick (and probably overkill, since it doesn't have to span between joists, and is 100% supported by the XPS + slab), so the fire-rating would be a non-issue.
     
  18. danboston

    danboston New Member

    Joined:
    Mar 19, 2011
    Occupation:
    Geologist
    Location:
    Lawrence, Massachusetts
    Dana:

    When you say the Versa-Hydro will ALWAYS be firing in condensing mode, does that ssume that the return water needs to be 110 F or lower? Or is it the Delta-T needs to be at a certain threshold value? I had a contractor tell me that it is the delta-T, not the actual return water temperature that determines whether the boiler will enter into and stay in condensing mode. Also, as an FYI, the highest output T that the Versa-Hydro Solar unit (PHE130-80S) can generate is 160 F.
     
    Last edited: Apr 14, 2011
  19. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Joined:
    Sep 2, 2004
    Occupation:
    Retired Systems engineer for defense industry.
    Location:
    New England
    A burner condenses when it's exhaust gasses are cool enough. To get that, the return water must be cool enough to drop those temperatures down. This is a function of the design of the heat exchanger, the exhaust path, the burn rate, and the return water temp...the return water temp must be low enough. Once it gets too hot, it can't condense. Now, if your supply temp was 130, the return would be low enough, but it is still a function of the return water temp.
     
  20. Dana

    Dana In the trades

    Joined:
    Jan 14, 2009
    Location:
    01609
    Depending on the exact mix of combusion air & fuel the dew point of natural gas exhaust in a mod-con is between 120-125F. The heat exchangers are thin & refractory for the lowest possible delta-T from the fire side to the water side, but in practical terms it won't be condensing much at all with return water temps much above 120F. If the contractor believes otherwise, he's saying the laws of physics are violable, and his statements on all matters technical need to be treated with great skepticicm.

    The 160F high-temp limit on the Versa isn't a problem- with 145' of fin tube that would deliver ~60KBTU/hr for a sub-40K load. At 140F you'd be looking at ~45KBTU/hr out of the same fin tube, and with flows low enough for a 20-25F delta-T you'd be in the 88-90% range. At 130F the 145' of fin tube would deliver ~30-35K, bringing the return water temps down to ~110F, at which point your efficiency would hit the 92-93% range. Getting better than 92-93% is unlikely with any fin-tube system (of any length) because the abilty to get heat into the room with boiler water under 120F/return under 100F gets very limited and hard to model or design for, but with panel radiator or radiant floor/ceiling it's possible by carefully tweaking outdoor-reset control schemes. The Versa uses an outdoor reset curve for the heating system (which has to be programmed- the setup instructions are on page 60.), but since you'd probably never want the heating system output to go under ~120F (the fin-tube emittance modeling issue- it's not linear like the curve is) and your design-day heat load would likely never need more than 135F even at -5F outdoors, yours will be a very flat curve. But it's tweakable- and you SHOULD tweak it to as low a temp that still allows all zones to keep up as the outdoor temps fall. (It'll probably do OK at the default settings, but you can probably get another 2-3% percent out of it with some adjustments that costs you nothing but your tweaking & observation time.)
     
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