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Thread: Newbie with Alpine issues

  1. #16
    In the trades Dana's Avatar
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    The other very-excellent way to get a handle on the whole-house heat load is to use the boiler as a measuring instrument, charting fuel-use against heating degree-day data. Most gas utilities in MA post both a daily fuel use and average outdoor temperature for the billing period. First, calculate the average heating degree days by subtracting the average temp listed on the bill from 65F. eg: If the billing says it averaged 34F, the average HDD is (65F-34F=) 31 HDD

    Then multiply the fuel-use number by the name-plate efficiency or AFUE of the boiler (if you've been running only 150F+ output temps, use 0.87, not the AFUE number). eg: If the billing says it was 6.4 therms per day and the boiler's AFUE is 93, the boiler output was (6.4 x 100,000BTU/therm x .93= ) 595,200 BTU/day.

    Then calculate the BTU per degree-day by dividing your BTUs by the HDD:

    595,200/ 31= 19,200 BTU/HDD

    From there, get BTU per degree-hour by dividing by 24 hours in a day:

    13,200/24= 800 BTU/degree- hour.

    To find your heat load at +10F, first calculate the difference from your base temp of 65F (outdoor base temp, not indoor), to get

    (65F-10F =) 55F

    Then the heat load is your degree-hour number times 55F: 800 x 55F= 44,000 BTU/hr

    Even with overnight setbacks etc, the fuel-use calculated number is going to be an upper bound, since it did not correct for hot water, clothes drying or cooking use. And if the thing was short-cycling or running at a non-condensing temp it'll also be on the high-side of the real heat load. The best thing about this method is that it doesn't matter how the house is built, how leaky it is, or how many gaps are in the insulation, or what types of windows it has, all factors which would add error to a Manual-J. It's not an calculated estimate- it's a MEASUREMENT. Although there are inherent errors in the measurement, it's a smaller error than for Manual-J, if it's done on a mid-winter billing period.

    But unlike Manual-J, it tells you nothing about the room-by-room or zone-by-zone issues, which are still important from a system design point of view.

  2. #17
    DIY Member tom3holer's Avatar
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    Again thanks everyone for the help and advice.

    Two days ago the heating tech from a large heating contractor came over to look things over. He spent over an hour looking over the boiler setup and took measurements of all the rooms in the house. I had asked for him to come over and do a Munual J so as to see exactly where we were. He didn't think a manual J would be much more accurate than the shorter method he wanted to use. He said that in older homes like mine ,1860, that the manual J was kinda a wag as there was so many variables. I agreed and received the heat load estimate yesterday. The home is a 1860 built mansart roof of about 2300 sq/ft. I have 166 feet of baseboard all being regular except the kitchen which is 30 feet of Hicap.All exterior walls have had blown in celious (sp) insulation, with some gaps. Two floors and attic with 3-4 inch of rock wool. Windows are, for the most part, older double hung but all have dead glass interior inserts and others are all thermopane with kitchen being all Anderson. There is 166 feet of baseboard all being regular except the kitchen which is 30 feet of Hicap Three quarter full basement unheated. I think his estimate is on the high side but he came in at 91,460 BTU heat loss at 0 deg. With that heat loss he thought the Alpine 150 was probably slightly oversized but the next one down, the 105 would be too small considering we also have SuporStor SSU45 being heated by the boiler. I think I will do some calculations on a few rooms myself using some simplified manual j type math I have found here to see if we agree. It does seem quite high to me. I did use the 25btu/cu ft quickie. Based on the square footage and cieling heights of 8.5 ft. I came out slightly more than half of what he calculated.

    Dana, I get my gas from "National Grid" and do not see anything on the bill about an average outdoor temp. I will give them a call and see if its available.
    Also
    As always, thanks for the help

    Tom

  3. #18
    Retired Defense Industry Engineer jadnashua's Avatar
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    This has been discussed lots of times...you can get a fairly good idea of your actual heat load by knowing how much gas you've used. Since each 100cuft or whatever measure they use produces a fairly well known amount of heat to burn it, then the efficiency of the boiler used to burn it compared to the degree-day for the period in question. Degree-day info is readily available for free for your zipcode. While that guy may have talked a good line, I think he's likely full of it...
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  4. #19
    DIY Member tom3holer's Avatar
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    I took the numbers from several months and they were quite consistant.
    As the Alpine return temps as it set up now very seldom get into the con mode I used .9 as an efficiency number.

    I came up with an average of 71,822 at 0deg OAT and 60,756 for 10deg OAT

    I used 90% as the efficiency number and the National Grid published average OAT for the months calculated.

    As the output temps usually are above 150deg then the numbers would even be lower.
    We do heat DHW with a Superstor connected to the boiler and stovetop and drier are gas. Just the two of us now so drier and cookong is not excessive.

    As a note, I had a large contractor sent their senior tech over to do a Manual J calc on the home.
    He spent time looking at the boiler setup and said he would get the Tech rep from Burnham over with him in a week or so to go over tweaking the setup.
    He did not seem to want to do a full Manual J and said instead he would do a heatloss calc that should work as accurately as the manual J is not as accurate on an older home. I agreed as he was spending a lot of time just answering my questions. He emailed me the results and I thought they were way off and after doing the "Fuel Used " method I am sure they are off. He said the heatloss was 91,470 at an OAT of 0deg.

    He will be comming over next week with the Factory Rep and I will show him the results I came up with.
    I read here, I thought, that a factory rep has the ability to derate the boiler system. If so does that mean they can lower the min fire rate? That would be nice but thought that the min fire rate was as low as it could go and still burn properly.

    Thanks again for any suggestions,

    Tom

  5. #20
    Retired Defense Industry Engineer jadnashua's Avatar
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    When you use the fuel for multiple items, it's best to subtract a summer month when heating the house is not happening, from a winter month. Otherwise, you're calculations are going to be off, maybe way off. It is a rare day when your boiler would need to be running constantly at full output. As a result, making it bigger to account for the water heating is a big waste. So, if you averaged say 50 therms in the summer per month and 450 in a winter month, your actual heating load would be 400, not 450; the rest being water heating, cooking, drying clothes, or whatever.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  6. #21
    Master Hot Water Mpls,MN BadgerBoilerMN's Avatar
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    Quote Originally Posted by tom3holer View Post
    Again thanks everyone for the help and advice.

    Two days ago the heating tech from a large heating contractor came over to look things over. He spent over an hour looking over the boiler setup and took measurements of all the rooms in the house. I had asked for him to come over and do a Munual J so as to see exactly where we were. He didn't think a manual J would be much more accurate than the shorter method he wanted to use. He said that in older homes like mine ,1860, that the manual J was kinda a wag as there was so many variables. I agreed and received the heat load estimate yesterday. The home is a 1860 built mansart roof of about 2300 sq/ft. I have 166 feet of baseboard all being regular except the kitchen which is 30 feet of Hicap.All exterior walls have had blown in celious (sp) insulation, with some gaps. Two floors and attic with 3-4 inch of rock wool. Windows are, for the most part, older double hung but all have dead glass interior inserts and others are all thermopane with kitchen being all Anderson. There is 166 feet of baseboard all being regular except the kitchen which is 30 feet of Hicap Three quarter full basement unheated. I think his estimate is on the high side but he came in at 91,460 BTU heat loss at 0 deg. With that heat loss he thought the Alpine 150 was probably slightly oversized but the next one down, the 105 would be too small considering we also have SuporStor SSU45 being heated by the boiler. I think I will do some calculations on a few rooms myself using some simplified manual j type math I have found here to see if we agree. It does seem quite high to me. I did use the 25btu/cu ft quickie. Based on the square footage and cieling heights of 8.5 ft. I came out slightly more than half of what he calculated.

    Dana, I get my gas from "National Grid" and do not see anything on the bill about an average outdoor temp. I will give them a call and see if its available.
    Also
    As always, thanks for the help

    Tom
    This is crazy. First, a proper room-by-room Manual 'J' 8 is, by no stretch of the imagination, WAG. To suggest otherwise is insulting. If the a "heating tech" suggests otherwise, he is too ignorant, or lazy, to do his job. If he is "just" a heating tech, his supervisor should be providing him with the tools, be it software, or office staff, to do a professional job. We have replaced dozens of old cast iron, low-efficiency boilers, with new condensing boilers, in very old homes. We start with a proper heat load and do not inflate the calculated heat load for domestic hot water (bad practice), "big" pipes, cubic feet or any other such nonsense. If we happen to under-size a boiler (none yet) when design conditions were exceeded (temperatures dropped below 25 year averages), yes, the thermostat may drop off a couple of degrees for a matter of hours, and no, no one will die. However, for the next 25 years our customer will spend less on fuel and be more comfortable. It is very likely that the boiler will last longer and require fewer repair parts.

    With all due respect. I am still not convinced past fuel usage is an accurate reflection of future building loads (the past winter here in Minnesota vs the previous year a prime example) and the industry as a whole rejects this as well. ASHRAE preferring a 25 year cycle to develop their design conditions data.

    http://minnesota.publicradio.org/col..._metro_s.shtml

    http://www.thefreelibrary.com/Updati...s.-a0250825197

    ASHRAE outdoor design conditions represent long term average temperatures (not the mean extreme) that will not be exceeded more than a few hours per season. Over-sizing a boiler, or the pipe and pumps connected thereto, is detrimental to energy use, comfort, and equipment durability. Short-cycling and elevated operating temperatures are symptomatic of poor hydronic design, which often starts with and over-sized boiler. An over-sized HVAC system will have both a higher initial cost and a higher cost of operation. The frequent starting and stopping of short cycling can also lead to premature failure of the equipment. The ASHRAE tabulated temperature data is adequate for calculating peak heating and cooling loads, and should not be increased as an additional safety factor.

    We use Wrightsoft to calculate heating/cooling loads and design radiant heating, warm air heaiting/cooling and ventilation packages. When designing system each room, and wall, may be modeled. Infiltration can also be modeled per detailed method. But with a properly administered blower door test, even this educated guess work is turned in to more-than-reasonable loads calculation accuracy.

    By the way, no one can do this for free, at least not for long. Even the subsidized power companies usually charge a token sum for home energy audits, which may include a blower door, thermal imaging, insulation measurement or a combination thereof.

    I spent 12 hours last Friday (referred by Lochinvar) on a Knight condensing boiler installed in 2008. After a dozen technicians looked over the troubled boiler (years of various error codes) my diagnosis was; poor installation. I have not done the heat load yet, but having done a few on these old four-square homes, I am guessing the boiler is over-sized. What I know for sure is that the boiler suffered over 25,000 ignition cycles in less than 7 heating season (no DHW loads). I found the supply sensor hanging in free-air, having been pulled out of the dry-well provided, and found a primary loop without the benefit of a pump. Oh, yes, the 200sf finished basement micro-zone (I will estimate the load <2000Btuh) was calling the 105mBtuh boiler, which was of course bumping off the bottom of its 20,160Btuh minimum-fire output. So much for modulating output, eh?

    The only way to make the boiler run at all, was to leave the supply sensor in free-air to fool the boiler into firing when there was no "apparent" load/demand. Lochinvar was taking a beating for the ill-informed contractor that installed the boiler and the various technician; one of which worked for a company who's name started with "Air", please people; this should be your first clue.

  7. #22
    DIY Member tom3holer's Avatar
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    Last night I used the "SlantFin" heatloss calc program and ran the heat load on my home to compare it to the Fuel used method thanke to Dana's excellent explaination, thank you again Dana. I came in slightly lower than what I calculated using the Fuel Used method. If I correct for the average use during the summer so as to get a true heat use I imagine it will be almost the same. That puts the Alpine 150 that was installed more than 2X the size I needed. It looks like I am stuck with it and need to make the best of it. I thought I read somewhere that a Factory Rep could derate the boiler. If so would that make the min fire rate lower? That is where the problem is right now. If I lower the temp to 140deg even with two zones on it overtemps (limit set at max of 10deg overshoot now) and starts to short cycle. It seems that it is going to be very difficult to get it to run in the condensing mode.

    Tom

  8. #23
    In the trades Dana's Avatar
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    Using feet of existing baseboard is an INSANE way to estimate heat load.

    When using a fuel-use/HDD calc, estimating 0.9 as the efficiency of the mod con that rarely runs in condensing mode is a bit optimistic, may be adding as much as 3-5% to the real number.

    Using a monthly average temp introduces a significant error too. Use either a utility's binned hourly mean temp between meter readings (which is in some cases would take into account even the time of day the meter was read) or sum the base 65F HDD for the exact days between meter readings by downloading a spreadsheet for a nearby weather station on degreedays.net. There's maybe 3-5% of statistical noise using daily HDD methods, but not 10%. Using 2-3 winter-month billing periods rather than a single period reduces the inherent error.

    Using 0F as an outdoor design temp for any Cape Cod location is even worse. There is no location on Cape Cod with a 99% design temp below +10F. Boston's 99% design temp is +12F, Weymouth's is +11F, but out on the Cape being surrounded by Cape Cod Bay & the Atlantic & Buzzards Bay the moderating effects of the thermal mass of the water raise the design temps from there. In P-town or Martha's Vineyard even +15F would not be unreasonable design temps to use.

    Yes, it does get colder than +10F on the Cape, just it gets colder than +12F in Boston. The coldest day this winter was 24 January, where it got down to +4F in Boston, but that very day the coolest temp in Falmouth was +5F, but Brewster only got down to +8F, Wellfleet was +10F, and out on the Vineyard Edgartown hit +8F, according to Weatherspark.com datasets.

    If you sized it EXACTLY for the 99% design temp loads you'd still never wake up to a cold house, since even in a low-mass timber framed house the thermal mass of the house carries it through the 99%+ conditions without losing much ground. Designing for 0F on the Cape would be like designing for a 99.98% condition visited only once or twice over the service life of the boiler, and would be oversizing by at least 15%,

    If you used 0.87 for the efficiency and stick with +10F as the design temp, and you'd probably still be overshooting reality by a bit. Whenever I've used the SlantFin Hydronic Explorer tool it has overshot by about 15-25% of well-executed calculations using more sophisticated tools (like Wrightsoft), and even 30% over fairly carefully monitored fuel-use calc methods on mid-winter billing periods. YMMV.

    If it's been short cycling a lot, even 0.87 would be optimistic. Based on your calculatin', reckonin' & figgerin' so far I'd expect that the real +10F load is probably in the neighborhood of 50-55K, and you maybe should be using something like +13-14F rather than +10F, which may even put you under 50K.

    I've had at least two local heating pros tell me with straight face that the design temp for Worcester is -5F, which is fully ten degrees below the published ASHRAE/ACCA number. At the water temps I'm running I'm radiation-limited to about 20-25% over the fuel-use calculated heat load, and it didn't lose ground when the outside temps hit -8F last year, but according to the SlantFin tool's output I would have had me uncomfortably cool by then. I suspect with the Alpine 150 you're good to better than -100F on boiler output, but you may be limited before then by the max temp output of the boiler and the 166' of fin-tube. So let's hope it doesn't hit below -80F any time soon, eh? :-)

  9. #24
    DIY Member tom3holer's Avatar
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    Just an update to whats been going on.

    I have spent a good deal of time reading and researching hydronic heating. With help from here and others and my copy of "Modern Hydronic Heating" I am getting up to speed. With much thanks to everyone I assembled numbers and had my "Plumber" come over back over. I showed him by both Slant/Fin and "Fuel Used" that because he did not do his homework I wound up with a boiler that is over twice the size it should have been and I will never be able to get the effieiency it can deliver. He is comming back next week to install a new Alpine 80. After he is done I am going to install a Bumblebee pump on the upstairs zone. None of the zone D/t's are above 5-7* except the upstais that comes in , depending on supply temp, at 10*. If it works out I may replace the other 2 zone pumps with the BB. I know that I will never see the payback but this is my interest now and I would like to make as an efficient system as I can. I still have many questions and am hashing ideas around in my head. Having just retired I have found a new interest and am having a ball.

    Tom

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