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Modulating boiler efficiency

Mark_46
Mark_46 Member Posts: 312
in THE MAIN WALL
Mark,

May I ask what software allows you to do that? And, could it be adapted to a Munchkin?

Comments

  • Joe_20
    Joe_20 Member Posts: 25
    Boiler efficiencies....

    Someone asked me if a 93% or 97% efficiency on a modualting boiler was constant over the modualtion range....thought that was a good question, but didn't know the answer....Also, along the same line, if heatloss calculations show you right at the peak of a boiler rating or alittle over, is it best to jump up to the next size boiler, or run the "snot" out of one slightly undersized?.....75,000btu/hr heat loss....would an 80 or 105 boiler be best?
  • [Deleted User]
    [Deleted User] Posts: 1,160
    My experience...

    These little wonders are more thermally efficient with the lower input values. The higher the input and the higher the operating tempratrure, the lower the thermal performance.

    Also, these amazing pieces of mechancial wonders LOVE working uphill, against traffic under extreme stress. That is when they shine. I have seen my litle one at 99% efficiency coming out of set back, running at 140 degrees F.

    I wouldn't suggest that you over size them. Size them for the load, and if it appears that you may be slightly short, ignore it. It will work just fine. There are WAYY too many factors working in your favor that weren't taken into consideration in the first place. FLy wheel mass effect, solar gains, internal gains, less real time infiltraion and so on. All of these things will end up causing the heat source to be over sized, but these amazing devices can modulate around the real time loads, thereby fine tuning themselves to the real time needs of the dwellings.

    I do not understand why they are not the minimum required standard...

    I think that in the near future, they will be. Get ready.

    ME
  • Mike T., Swampeast MO
    Mike T., Swampeast MO Member Posts: 6,928


    All other conditions being equal a modulating boiler will have a touch less efficiency operating at 100% as compared to 50%.

    NEVER forget however that the entire premise of boiler modulation is that 100% output is VERY rarely needed! So, you only have to "run the snot out of the boiler" in the coldest weather--likely below your design conditions! The vast majority of the time, the boiler will be purring along at significantly less than full output.

    If you OVERSIZE on the idea that "I'll get better efficiency because the output percentage won't be so high", you get another problem--cycle losses increase. Modulating boilers currently can't fire down to nearly nothing--no matter how sophisticated your control system the boiler will still cycle when loss is less than minimum modulation. Larger boiler means higher minimum output. This means that the oversized boiler will spend more time cycling--the very thing at modulation tries to eliminate!

    Modulation is not an excuse to oversize!!!
  • hr
    hr Member Posts: 6,106
    I'd error smaller

    also. Keeping in mind all load calcs have some slop or error room. And I'd bet there are a few places you could tighten up the building insulation or weather striping.

    hot rod

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  • Mark_46
    Mark_46 Member Posts: 312
    Ah ha

    Joe,

    I too think this is an excellent question and one I am faced with to make a decision on. My house has a BTU loss of about 51,000. My installer came up with 48,000 and I came up with 55,000. I will be using a Heat Transfer Munchkin. But the 80M goes from 27 to 80, the T80 from 19 to 80 and the T50 from 18 to 50.

    So you can see my house puts me at a point of indecision. Should I go with a T50? Also, anybody now what the 'T' satnds for?
  • Mike T., Swampeast MO
    Mike T., Swampeast MO Member Posts: 6,928


    I have no idea what the "T" stands for but I'd choose the T-50. As long as you use little or no setback in extremely cold weather you shouldn't have any problem and you have the potential to SAVE BOOCOO BTUs in most conditions!

    Of course your emitters MUST be able to deliver the heat! Bare tube floor heat has a problem in this regard...
  • Pat_12
    Pat_12 Member Posts: 27
    modulating boiler

    My limited experience is this. I replaced my 40 year old Pennco boiler rated at 125,000 BTU's with a Peerless PI-80 boiler (same boiler as the Munchkin). I also got rid of my old water heater rated at 50,000 BTU's and added a nice indirect water heater. My heat loss calculation was approximately 75,000 BTU's and my new boiler is rated at 74,000 btus. I have outdoor reset and priority zoning for the indirect water heater. I can tell you that it is very rare that this boiler runs on high. This boiler just purrs and does a wonderful job of heating my home. I also have a hot water capacity of 165 gallons an hour. I have never run out of hot water yet. Wife and 4 kids. I often find myself going to my basement to just watch this little wonder. My wife believes that I have lost my mind, but I know you wallies will understand what I am talking about. I truly love this appliance. I would reccomend undersizing boiler and look into indirect hot water tank. Sorry about my rambling and good luck with your project.
  • [Deleted User]
    [Deleted User] Posts: 1,160
    We understand Pat...

    Of course, our wives don't understand us either. That's why we're part of an extreme organization known as Wallies. We live, sleep, eat, teach and breath hydronics.

    I've moved up in life though... I no longer have to hang out in my laundry room to watch my boiler. I hooked it up to my home PC and can check in on it any time I want:-)

    Now she KNOWS i'm crazy...

    ME
  • Mark_46
    Mark_46 Member Posts: 312
    Thanks

    > I have no idea what the "T" stands for but I'd

    > choose the T-50. As long as you use little or no

    > setback in extremely cold weather you shouldn't

    > have any problem and you have the potential to

    > SAVE BOOCOO BTUs in most conditions!

    >

    > Of course

    > your emitters MUST be able to deliver the heat!

    > Bare tube floor heat has a problem in this

    > regard...



  • Mark_46
    Mark_46 Member Posts: 312
    A little research

    Mike thanks for the feedback. I called Heat Transfer to get an explanation of the 'T' abbreviation. It stands for 'top flue' which are the wall hung units. They do not make a floor standing 50,000 BTU model, bad for me. But your suggestion to go with a 50,000 BTU is in line with my instinct. But I'm on the fence to be honest. What further complicates this is heat loss calc results vary as all of you already know. The software is limiting or vauge sometimes and doesnt always fit exactly to your situation. But if I average my result with my installers, I get 51,500. I will go with that. But that number is over the rating of the T50. You still think I should choose the T50?
  • Mike T., Swampeast MO
    Mike T., Swampeast MO Member Posts: 6,928


    What type of emitters and what supply temp do you estimate is required to maintain indoor conditions at outside design temp?
  • [Deleted User]
    [Deleted User] Posts: 1,160
    HTP 925 service software...

    Given to authorized Vision 1 dealers for servicing and diagnostics in the field. I just loaded it onto my home PC and ran an extension back to the boiler controller.

    This is not something that a typical homeowner would have access to, just to be clear.

    ME
  • Mark_46
    Mark_46 Member Posts: 312
    Data

    Mike,

    When you say emitters, I presume you mean the 'delivery' method of the heat (radiant, baseboard radiator, etc) ? If so, I will go with hydro air using a Unico Miniduct system and a Munchkin.

    For my heat loss calc I used:
    70 degree indoor temp
    9 degree outdoor design temp
    176 degree system design water temp

    Supply temp I do not know nor am I sure how that's measured. Can you fill me in?
  • Mike T., Swampeast MO
    Mike T., Swampeast MO Member Posts: 6,928


    Oh, hydro-air. I respectfully bow out of the discussion as I'd be truly guessing. IMHO temps too high and control system too crude to take good advantage of the abilities of condensing/modulating boilers. A conventional, simple, very long-lasting high-temp boiler may well prove more cost-effective and nearly as efficient in such an application.

    That super-long thread regarding Viessmann & Unico is based on just using the Unico as an OCCASIONAL air temp boost with most of the heat provided by radiators and radiant floors.
  • Unknown
    Unknown
    very cool!

    but i was under the impression that the new Tekmar tN4 system with the gateway addition allowed you to similarly keep remote tabs on your system through a net connection.
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