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Searching for a simple whole-house heat loss calculator.

Mike_Y
Mike_Y Member Posts: 9
Good morning,

In prep for replacing a 40yo 145k BTU output oil boiler that is grossly oversized for our 1300 sq foot ranch, I'm looking for a simple to use heat loss calculator. I used to use the Slantfin Hydronic explorer when I was still in the trades (first on CD on my old PC, later online through Slant Fin.com) but when I search for that now all I get is an internet run-around that takes me to a British trade site selling rads and other materials. Does anyone here have a link that will get me to the Hydronic-explorer calc or a recommendation for a simple, easy to use whole house calculator?


Thank you,
Mike

Comments

  • Hot_water_fan
    Hot_water_fan Member Posts: 1,792
    For an existing house, this method works well. 

    https://www.greenbuildingadvisor.com/article/replacing-a-furnace-or-boiler. It’s essentially watching your boiler fire all winter and timing it. Since you live there, you’ll already know if certain rooms have more heat loss than radiation.
  • jesmed1
    jesmed1 Member Posts: 553
    edited September 2023

    For an existing house, this method works well. 


    https://www.greenbuildingadvisor.com/article/replacing-a-furnace-or-boiler. It’s essentially watching your boiler fire all winter and timing it. Since you live there, you’ll already know if certain rooms have more heat loss than radiation.
    Just to clarify, that method doesn't require timing the boiler. You only need to know roughly one month's worth of oil consumption, preferably during the coldest month, which you can find by checking a mid-winter oil bill, noting the delivery amount, and the date of the delivery. Then find the date of the previous delivery, and you know roughly how many gallons were consumed between those dates.

    From there, you download the number of heating degree days for your area during that same period, from a website given in the link. Then it's a straightforward calculation.
    Hot_water_fan
  • Hot_water_fan
    Hot_water_fan Member Posts: 1,792
    Exactly, you let the meter do the work. 
    jesmed1
  • jesmed1
    jesmed1 Member Posts: 553

    Exactly, you let the meter do the work. 

    Yes. I've done the heat load calcs for our condo building four different ways, and I trust this method most since it uses actual fuel consumption data. But I was surprised that all four methods got within about 10% of each other, so you can get fairly accurate results even if you don't have fuel consumption records.
  • STEVEusaPA
    STEVEusaPA Member Posts: 6,506
    Tell me your zip code and how much oil you used in the last calendar year, and if you use oil for domestic hot water.
    steve
  • hot_rod
    hot_rod Member Posts: 21,844
    A room by room load is nice to see and correct high load areas. I think you can download a manual J form at ACCA if you want old school.
    https://www.acca.org/standards/technical-manuals/manual-j

    You might try the free demo at HydronicPros.com
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Robert_25
    Robert_25 Member Posts: 527
    Mike_Y said:

    Good morning,

    In prep for replacing a 40yo 145k BTU output oil boiler that is grossly oversized for our 1300 sq foot ranch, I'm looking for a simple to use heat loss calculator. I used to use the Slantfin Hydronic explorer when I was still in the trades (first on CD on my old PC, later online through Slant Fin.com) but when I search for that now all I get is an internet run-around that takes me to a British trade site selling rads and other materials. Does anyone here have a link that will get me to the Hydronic-explorer calc or a recommendation for a simple, easy to use whole house calculator?


    Thank you,
    Mike

    If you just want to size the boiler itself, use Steve's method based on fuel consumption. You will likely find out that the smallest oil boilers made are plenty for you house.

    If you want to do a room by room heatloss, I have a copy of the original Slantfin Hydronic Explorer software. If you want to figure out a means of getting it send me a PM.
  • Mike_Y
    Mike_Y Member Posts: 9
    HotRod, the free version at Hydronics pro confirmed the info I needed and that the current amount and sizes of the radiation per room was sufficient, as well as confirming the capacity of the new boiler I'll need. Now on to design. Thank you all.
  • CFH
    CFH Member Posts: 71
    https://slantfin.com/slantfin-heat-loss-calculator/
    Slant Fin Hydronic Explorer has an app for your phone. If you can find a older version it goes on the computer.
  • OldawgBryant
    OldawgBryant Member Posts: 69
    I just used the slant fin app & it worked great. Go room by room. I also recommend the system syzer app or computer program from xlem. They are easy to use.