(206) 949-5683, Top Rated Plumber, Seattle
Results 1 to 13 of 13

Thread: High Efficiency Boilers

Hybrid View

  1. #1

    Question High Efficiency Boilers

    Background:

    I have a 4000 square ft living space with a 30 year old Boiler in Michigan. The home is a Brick colonial built in 1948, with an addition built in 1978. I don't believe the walls in the older section are insulated, and it is likely to be of a balloon framing.
    My natural gas bills during winter are very high and I would like to slash them by investing in a Very High Efficiency boiler. I have measured and totalled the number of radiators and baseboard heaters.

    I also want to heat my hot water with this boiler, however, I have been told that I should have a storage tank. My understanding was that Buderus and Baxi provide instant hot water and I would not need a tank. These add on storage tanks are very expensive and my father in-law suggests that I keep my current gas water heater, but insert a stripped down, unpowered electric water heater in-line, ahead of my water heater so I could prewarm supply water to the tank to room temp and thereby save money.
    Trouble is, I don't know which boiler/setup is best for my home?

    My father works as an electrician and has been impressed by Viessman and Buderus.

    My local plumber recommends Baxi bc it fully modulates something...

    Another guy seems to only installs Knight/Lochinvar

    I figure someone here truly knows the best device. Key points for me are, if it breaks can I get parts?

    Will the company be around for sometime to come?

    Are standard parts compatible? (I understand Lennox does not have standard parts or fittings)

    Which boiler presents the best value?
    Last edited by clappr; 06-22-2009 at 11:47 AM.

  2. #2
    Plunger/TurdPuncher kingsotall's Avatar
    Join Date
    Aug 2008
    Location
    Flagstaff, AZ Sitting on an upside down 5 gallon bucket next to the GO 68HD
    Posts
    1,260

    Default

    So you're going to choose the plumber by which mod/conboiler you decide to go with┐ A homeowner can go with whichever they choose but we will, 'til we're blue in the face, steer you in the direction of Lochinvars's Knight boilers.
    I would say do the research, call up some reps after you have some knowledge to work with and then hopefully the plumber/mechanic you have designing the hydronic system agrees with a boiler you find appropriate.
    I just post cuz I like to see my avatar.

  3. #3
    DIY Member msgale's Avatar
    Join Date
    Sep 2006
    Location
    Ohio
    Posts
    90

    Default

    Some thoughts:
    you will save more money by insulating than by a high efficiency heating system.

    A tripped down old electric water heater as tempering tank: you will convert the heated air next to the tank into heated water.
    No net gain or loss, since the money you spend to heat the air is now going instead to heat the water.

    Tank less water heaters are not storage tanks, are very expensive, and not cheap to run either, I see little gained there.

  4. #4
    Retired Defense Industry Engineer jadnashua's Avatar
    Join Date
    Sep 2004
    Location
    New England
    Posts
    21,401

    Default

    I have a Buderus at my home. It's been in a couple of seasons now. I have an indirect WH (a priority zone off the boiler) that works well at filling a big 6' tub with other simultaneous uses. It can modulate down to as low as 20% of max to match the heating load. There is almost no volume of water in the boiler so response is quite fast. The US distributor is about 15-miles from my house in NH. I've not needed any service or parts, and as with any system, the quality and knowledge of the installer is very important to getting a system up and running efficiently.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  5. #5
    Web Development | HVAC patsfan78's Avatar
    Join Date
    Jun 2009
    Location
    Maine
    Posts
    33

    Default LAARS Mascot

    There is another boiler out there that also is a high efficiency, fully modulating, wall-mounted boiler. It is called the LAARS Mascot and is available in either heat only or "combi" (heat and domestic hot water).
    It is similar to the Baxi boiler. They run around 96% efficient.

    My opinion would be to insulate the home better first, then install a new boiler/system if need be. That way you can get the most out of your investments. It is all about the return on your investment.

    Do the research and find out which is best for you. Get several opinions.

    Mike
    www.HiTechHeat.com
    Home Heating Solutions

  6. #6
    Homeowner Thatguy's Avatar
    Join Date
    Aug 2008
    Location
    MD
    Posts
    1,460

    Default

    Quote Originally Posted by clappr View Post
    I have a 4000 square ft living space
    My natural gas bills during winter are very high
    While I have your attention could I get sq. ft. of the basement, the therms for last winter and the heating degree days for last winter (or the nearest city in Michigan, so I can look up the HDD)?

    Average is ~6 BTU/sq. ft./HDD

    Here's what I have so far.
    SW Ontario, Canada
    398.7 cubic meters = 140 therms of NG in 28 days = 5 therms/day
    2900 sq. ft. including basement gives 5/2900 = 170 BTU/day/sq. ft.
    664 HDD/28 = 24 HDD in one day
    170/24 = 7.1 BTU/sq. ft./HDD
    Effic. factor 0.8
    final 5.7

    D.C.
    838 therms of NG in 90 days = 9.3 therms/day
    3100 sq. ft. including basement gives 9.3/3100 = 300 BTU/sq.ft.
    2658 HDD/90 = 30 HDD in one day
    300/30 = 10 BTU/day/sq.ft./HDD
    Effic. factor 0.8
    final 8.0

    SF, CA
    2.3 therm/day
    2700 sq. ft. gives 85 BTU/day/sq.ft.
    540/30 = 18 HDD in one day
    85/18 = 4.7 BTU/sq. ft./HDD
    Effic. factor 0.8
    final 3.8

    San Diego, CA
    29,000 BTU/hr = 21 therms/30 days = 0.7 therm/day
    1560 sq ft including basement gives 0.7/1560 = 45 BTU/day/sq.ft.
    270 HDD/30 = 9 HDD in one day
    45/9 = 5.0 BTU/sq.ft./HDD
    Effic. factor 0.8
    final 4.0

    victoria, BC
    So 750 gals of oil giving 1100 therms for 4900 HDD for 180 days for 2000 sq. ft.
    6.1 therms/day
    2000 sq. ft gives 6.1/2000 = 305 BTU/day/sq.ft.
    4900/180 = 27 HDD in one day
    305/27 = 11 BTU/sq. ft./HDD
    Effic. factor 0.8
    final 8.8

    Cincinnati, OH
    600 gals/yr, 680 therms for 5096 HDD for 365 days for 1250 sq. ft.
    1.86 therms/day
    1250 sq. ft. gives 149 BTU/day/sq. ft.
    5096/365 = 14.0 HDD in one day
    149/14.0 = 10.6 BTU/sq. ft./HDD
    Effic. factor already in there
    final 11

    Wisconsin Energy Study gives
    4.4
    1.7

    Ranked
    1.7 least heat loss
    3.8
    4.0
    4.4
    5.7
    8.0
    8.8
    11 most heat loss

    Range 1.7 to 11
    Median 5.0
    Average 5.9

    Histogram
    0 to <3|*
    3 to <6|****
    6 to <9|**
    9to<12|*

    Thanks.
    Last edited by Thatguy; 06-22-2009 at 01:24 PM.

  7. #7
    In the trades Dana's Avatar
    Join Date
    Jan 2009
    Location
    01609
    Posts
    2,720

    Default

    Don't let ANYBODY install a boiler in your house without first doing an actual ACCA Manual-J type heat loss analysis (and/or reviewing your fuel billing against degree-day data.) And oversized modulating boiler only does marginally better than an oversized cast-iron beast.

    But a PROPERLY sized unit will beat the socks off a properly sized cast iron beast. And a properly-sized unit will be smaller, and cost less up front. t's common to see them 3-4x oversized, which makes a 78% AFUE boiler run at a true 60-65%, or a 90% condensing boiler at a mere, 80%, etc. If anything, undersize it a bit relative to the Manual-J calculation (20% smaller is usually safe enough.) If you actually get cold after having done that it's usually because there are some easy/cheap to fix heat leaks (insulation gaps, air-infiltration paths that can be sealed, etc.)

    If you're radiation (radiators/baseboards/radiant floors, etc) was designed to run at 180F on design-day (coldest hours of the year) and you actually RUN them there, you won't get the condensing benefit of the modulating-condensing boilers, but you'll get some if you utilize "outdoor reset" controls.

    An indirect-fired tank will...

    A: ...be more efficient than running the mod-con boiler as a tankless, since the boiler won't see as many cycling losses, and...

    B:...will keep the boiler's ignition & control systems from a premature death, since it won't cycling on/off as often and...

    C.... will even outlast the boiler itself- it'll be the last hot water heater you'll ever buy.

    The Baxi Luna has a bad rep, but I don't have any direct experience with them (maybe they've fixed their problems... or maybe not?.)

    There are many good mod-cons out there. The Triangle Tube Solo series has a good rep and getting better. Peerless Pinnacles too.

    First time installation costs on a mod-con are substantially greater than for a cast-iron or steel replacement, as is the boiler itself. If you don't have sufficient radiation to get the heat out at low temp you may get better (and permanent) payback by insulating the place, if it's the typical brick-veneer/cavity/un-insulated studwall that was prevalent in the 1940s. Most insulation installers can pound cellulose or loose fiberglass into the cavity wall without creating other problems, but get references before going that route.

  8. #8
    Master Plumber nhmaster's Avatar
    Join Date
    Jul 2008
    Location
    S. Maine
    Posts
    2,039

    Default

    Here, I'll get my 2 cents in. If you have old cast iron radiators and a high volume delivery system, installing a low volume, mod-con boiler, without using a properly sized buffer tank will give you nothing but problems. The boiler (without a tank) will constantly short cycle leading to lower efficiency and constant service problems. If it was me I would go with a Buderus GA series boiler. It has the capacity to deliver the btu's you need and it has enough water capacity to keep from cycling. In an older home there is more to consider than raw efficiency. The cost\payback ratio for very high efficiency boilers is not very good even with optimal delivery systems such as radiant or baseboard. In my own home (1800's colonial with CI radiators) I have a Buderus G125 oil fired boiler with the Logamatic control and a 40 gallon indirect for domestic hot water. The system operates flawlessly and has reduced my oil consumption by 22%. We convert about a dozen homes a year and have found out through trial and error that low mass boiler with high mass delivery are nothing but problems.

  9. #9
    In the trades Dana's Avatar
    Join Date
    Jan 2009
    Location
    01609
    Posts
    2,720

    Default

    Quote Originally Posted by nhmaster View Post
    Here, I'll get my 2 cents in. If you have old cast iron radiators and a high volume delivery system, installing a low volume, mod-con boiler, without using a properly sized buffer tank will give you nothing but problems. The boiler (without a tank) will constantly short cycle leading to lower efficiency and constant service problems. If it was me I would go with a Buderus GA series boiler. It has the capacity to deliver the btu's you need and it has enough water capacity to keep from cycling. In an older home there is more to consider than raw efficiency. The cost\payback ratio for very high efficiency boilers is not very good even with optimal delivery systems such as radiant or baseboard. In my own home (1800's colonial with CI radiators) I have a Buderus G125 oil fired boiler with the Logamatic control and a 40 gallon indirect for domestic hot water. The system operates flawlessly and has reduced my oil consumption by 22%. We convert about a dozen homes a year and have found out through trial and error that low mass boiler with high mass delivery are nothing but problems.
    Can you elaborate? Adding the buffer adds mass, but you're saying mass is the problem?

    Low mass boilers in ANY mass system can work well using a reverse-indirect as the buffer (TurboMax, ErgoMax, Everhot EA, etc.), making the system buffer-centric, slaving the boiler only to the buffer. All heat flows to/from the buffer while the boiler remains agnostic of zone calls. In a foggy-goggle view this sort of like the Energy Kinetics System 2000 approach with simpler controls. But the boiler can be almost arbitrarily low mass- lower than the Sys-2K steel boiler, so the cycle losses can still be quite small. In a system like this the boiler loop can be low-flow high delta-T, and the radiation flows can be whatever they need to be.

    You lose some of the condensing efficiency with this approach since you won't let the buffer get much below 130F, thus the return water doesn't drop much below 120F except during extended DHW draws. But it'll never short-cycle on micro-zones, and the minimum burn cycle can be preset by tank hysteresis & boiler loop flow & output temp. But some efficiency can be gained with outdoor reset on the tank temp if the highest temp zone has a design-day temp requirement of 160F+. In high delta-T radiation/low-temp systems the return water can still be in the condensing zone though- there may be some plumbing optimizations to keep the boiler return water closer to the radiation return temps, isolating it somewhat from the mixing turbulence in the reverse-indirect when the boiler is firing. (Details will depend on they system, but it's that always the case?)

    I'm familiar with a number of unbuffered high mass hydronic systems that continue to work just fine retrofitted with low mass mod-cons (sans-buffer) so I'm very curious to know more about the "...nothing but problems" issues. (Forewarned is forearmed.)

  10. #10
    Master Plumber nhmaster's Avatar
    Join Date
    Jul 2008
    Location
    S. Maine
    Posts
    2,039

    Default

    The best way is to separate the high mass delivery (piping & radiators) from the boiler loop by using an indirect tank with a coil in it. One of the dirty little secrets out there is that all of the low mass mod con boiler manufacturers are having tons of warranty problems directly related to component failure due to short cycling. System 2000 has been trying to address the problem for 20 years now by installing aquastats and controls that increase cycle time on the post purge. It does help to some degree but the problems persist. In the early days System 2000's would regularly rot out the bottom of the flue collector due to unwanted condensation.

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •