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How to calculate BTU output?

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  • 24-07-2013 12:46am
    #1
    tea and coffee
    Registered Users Posts: 1,826 ✭✭✭


    I have worked out how to convert 50 delta to 60 delta so I can get the radiators on a level playing field. but now how to calculate the BTU... I ahve looked at 3 different online caluculators and they all come up with a different measurement for the same room

    e.g. 4 x 4 x 2.5 m3 room. One calcultors says 3338, another 4500, another 5200. Approx)

    What is the most accurate way?

    Thanks


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    #2
    shane0007
    Closed Accounts Posts: 4,677 ✭✭✭shane0007


    The 50 delta & 60 delta refers to the delta T & the 50 or 60 refers to the return temperature depending on the delta T.
    50 delta is referring to condensing boilers which require a delta T of 20 so if 70 being the flow temperature, you would end up with a return of 50. You will notice rad size being larger on the 50 than the 60 to give the 20 DT. On the 60 delta it is working of circa 10C DT so return of 60 from a flow temperature of 70. This would be for standard efficiency boilers.


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    #3
    LIFFY FISHING
    Registered Users Posts: 1,791 ✭✭✭LIFFY FISHING


    For years the rule was ; lenght x breath x height x 6 = your btu requirements & its as accurate as will ever be required and then crossreferance your figures against the rad charts.


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    #4
    tea and coffee
    Registered Users Posts: 1,826 ✭✭✭tea and coffee


    Thanks Shane. Yes the European rads are in 50 delta and the sizes I need are bigger anyway as they arent as efficient a radiator.
    My issue now is trying to work out which actual radiator i need for which room. Every online calculator is giving me a different figure of btu needed to heat my room so I dont know which one to trust.
    They are all wildly different numbers.


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    #5
    tea and coffee
    Registered Users Posts: 1,826 ✭✭✭tea and coffee


    Thanks LF. Some calculators were asking about dbl glazing, north facing walls, french doors and how warm do I like my house?!?!?!?!
    I will see what figures i get now using your method. Cheers


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    #6
    Outkast_IRE
    Registered Users Posts: 7,515 ✭✭✭Outkast_IRE


    tea and coffee wrote: »
    Thanks LF. Some calculators were asking about dbl glazing, north facing walls, french doors and how warm do I like my house?!?!?!?!
    I will see what figures i get now using your method. Cheers
    That's because a radiator is sized to cover the heat losses from that room, the amount of glazing, insulation etc etc makes a massive difference in the size of rad needed.


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