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Bartender, Design Temps for everyone!

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knotgrumpy
knotgrumpy Member Posts: 211
in THE MAIN WALL
Looks like most everyone will get to see whether their boilers are over or under sized in the next week.  Looking at -12f here on Monday.



Can I assume that if my WM cast iron boiler is not running mostly non-stop then (and not shutting off because it is hitting high limit), it is oversized?

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  • icesailor
    icesailor Member Posts: 7,265
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    That may be true:

    That may be true. As long as you don't turn your thermostats down at night and then turn them up in the morning, and the boiler is oversized and fired for such, you won't have a problem.

    Dropping the thermostat at night is the same as raising the outside temperature for the night and lowering it outside in the morning. At night, the pumps will be off longer and pipes in the wall might freeze and break.
  • knotgrumpy
    knotgrumpy Member Posts: 211
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    TRV's

    I leave the TRV's alone and everyone is happy.  No setbacks.  My cast iron radiators like the higher water temps that the ODR is ordering up right now.  So does the gas company!



    Very happy with all of the advice I've received from the regulars on here in rebuilding my system this past summer.  Nothing like coming in from the cold and enjoying warmth from something you have put together with your own two hands.
  • Gordy
    Gordy Member Posts: 9,546
    edited January 2014
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    True

    IF -12 is the design temp for your heat loss calculation in sizing.



    How long is it running in a 24 hour period?



    If I recall you have rad convectors right?



    We are going to have some forecast temps that would put me in a design day temp -10 for a 24 hour period or 75 HDD. A rarity for a whole 24 hours. A first since I have lived in this house in the last 13 years. Knowing my boiler is oversized this will give me good feed back on my btu per HDD per sf for a 24 hour design condition.
  • knotgrumpy
    knotgrumpy Member Posts: 211
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    A little of both

    Some radiators and some cast iron convectors.



    I think we are both in Illinois, am I right?  I used -5 for design temp, but it looks like there will be a 48 hour period that that could be an average. Strangely, I am sort of excited to see how it performs even though it will be nasty out.



    110,000 btuh output boiler  - 3200 square foot house.  Boiler size/type hurts me in shoulder seasons.  ModCon or tiny CGi to couple with the large boiler for shoulder seasons and DHW for next year.



     
  • SWEI
    SWEI Member Posts: 7,356
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    Asymmetric multi-boiler

    setups can work very well.  Controls get a bit tricky at times, but pairing a small mod/con with a larger conventional boiler can work out quite nicely.  A multi-boiler job will surprise (well, more like shock) you with the amount of the load a single boiler can meet.  Based on this, I'd have to say that our heat loss calcs are probably high by 25-30% on average, with some more like 40%.



    A heat pump for the shoulder seasons is another possibility -- especially if you have weather that can "flip" on short notice (April in Minneapolis comes to mind.)
  • knotgrumpy
    knotgrumpy Member Posts: 211
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    Control

    Hi SWEI,



    Is there an off the shelf multi-boiler control?



    Mark
  • Gordy
    Gordy Member Posts: 9,546
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    Illinois

    Yes we are. It was -17 at 6 this morning. As of right now 11:45,my behemoth has only ran 3.5 hours. It's 9 above.



    We share the same strangeness sun/ mon looks favorable for the strange.
  • knotgrumpy
    knotgrumpy Member Posts: 211
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    Hour meter

    What kind of hour meter have you hooked up to your boiler?
  • Gordy
    Gordy Member Posts: 9,546
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    Tstat

    Has run time for present day, and previous day, yearly total. It's a lux.
  • SWEI
    SWEI Member Posts: 7,356
    edited January 2014
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    Multi-boiler staging

    If you allow the onboard mod/con controls to run the lower part of the curve, you can install a simple two-stage outboard control as long as you disable rotation (lead boiler is always the mod/con.)  Tekmar 263 or Heat-Timer TSC Elite should work just fine.  Look for a mod/con with a low minimum firing rate to maximize savings.  Lochinvar Cadet CDN040 is priced quite attractively -- we're spec'ing them for several upcoming jobs.
  • Jamie Hall
    Jamie Hall Member Posts: 23,466
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    So far so good...

    I think we are just about at design conditions for this place; I suspect it was done for 0 out/70 in, and we are at plus 5 as I type (going to -10 tonight) (and no, I don't have the original design specs -- that was 80 years ago!).  Cedric seems to be running at about 40% duty cycle -- roughly 40 minutes on, one hour off -- at the moment.



    Another 15 degrees colder outside, though...



    The oil company just loves this weather.  At least I got the drive plowed so they can bring me some more of that liquid gold...
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Gordy
    Gordy Member Posts: 9,546
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    I should note

    That there is some inaccuracy using the tstat.  Basically there is the Prepurge, and boiler proving before the burner lights off about 30 seconds for every thermostat call. then if it bounces off high limit (hardly ever) there is that lapse of time before burner relights.



    All in all close enough for me.
  • knotgrumpy
    knotgrumpy Member Posts: 211
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    Cedric

    Have you ever posted a picture of Cedric, or is he camera shy? I'd love to see your boiler setup.
  • Jamie Hall
    Jamie Hall Member Posts: 23,466
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    Cedric is camera shy...

    but if I can figure out how to post a picture, I will!
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Jamie Hall
    Jamie Hall Member Posts: 23,466
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    I hope this works.

    If it does, the building is Cedric's home, on a suitably winter day.



    Cedric has a lovely drop header; the riser piping is 3", and the header is 4".  All welded.  The risers from the header to the original steam drum from the H. B. Smith boiler from 1930 are 2 1/2".  If you look closely at the left hand side, you can see the Hoffman Differential Loop piping.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • knotgrumpy
    knotgrumpy Member Posts: 211
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    Very Cool!

    Or hot, as it were.  Makes my system look tiny.



    Thanks Jamie, that is pretty impressive, and such a little house!
  • SWEI
    SWEI Member Posts: 7,356
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    Is that a dependency?

    or the back of the main house?



    Nice basement...
  • ttekushan_3
    ttekushan_3 Member Posts: 958
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    Temps where Tekmar Cancels Setback.

    A Happy New Year to everyone here!



    We're expecting about -10 F Monday as well. The Tekmar 269's and 279's will be canceling deep night setbacks, no doubt. I've found myself the steward of several sizable steam systems and I'm sure glad the owner of this one finally sprung for the retube of these (pictured) cuties since the photo was taken. That kind of thing can keep me awake on cold nights! My end of the job is the redesign and fine tuning of, well, everything steam. But I have the Big Guns come out to do the heavy lifting! The building's a wonderful rambling combination of radiator, steel fin tube, projection heaters and make-up air coils. EDR about 17,500. Design temp -5 F.



    These temps (and very mild ones, too) tell me if I've done my job right! And as everyone here can imagine, I'll know right away if I've come up short on the control strategy.



    To make yourself feel warmer, I've included a photo taken during our very late summer heat wave. The retube was going on at that time and it was hard to even relate to the kind outdoor temps we're now experiencing. This photo warms me right up!
    terry
  • knotgrumpy
    knotgrumpy Member Posts: 211
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    Wow

    What do those beasts heat? 
  • ttekushan_3
    ttekushan_3 Member Posts: 958
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    This place.

    It looks about the same today (from the outside) except the steam heated water tower is gone. Built in I think 5 stages, the original was a high end coach builder for Cleveland's local auto industry (before Henry Ford changed everything) and then Baker Motors/Baker Electric, and then American Greetings, etc. It's a vibrant arts mecca today. And the steam piping is a labyrinth! "Rust Belt Chic" at it's finest!
    terry
  • Gordy
    Gordy Member Posts: 9,546
    edited January 2014
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    The results

    Yesterday was a mean temperature of -12. Deign temp is -9 for my area, 77 HDD for yesterday.



    Boiler with 172000 doe ran for 8 out of 24 hours for the period.



    HDD per sf called out to 8.93 btus sf HDD, this is with window treatments drawn , fire in masonry fireplace burning for 18 hours. This load actually was down all most 1 HDD per sf from calculations through out season this far which were 9.5 HDD sf. With not particular attention to window treatments.



    SWT to radiant ceiling and floors were 114* with an average wt of 107*. Panel temps were 84*. Ceiling, and 78* floors. After settling in from heat call. System under constant circulation.



    So all in all this works out to a boiler size of 57750 doe would have covered the loss for this actually below design condition period. Putting my present boiler 196% oversized. Calculated loss was 79000. That puts the program , and my inputs 37% padded.
  • knotgrumpy
    knotgrumpy Member Posts: 211
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    Run time

    "That puts the program , and my inputs 37% padded."



    Sort of proven out by your boiler's run time.  8 out of 24 hours.  One third of the day.



    I did not have any means to measure my run times.  Just observed that my boiler was running most every time I listened during the -14 below evenings, yet the house maintained 72f.  I think I am happy with the boiler sizing during this subzero weather.

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