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Posted by jim on July 20, 2011 at 12:16:31:

In Reply to: Re: mmbtu rating posted by Boiler Guy on July 20, 2011 at 12:11:35:

: : : : : : : I need some help in calculating the mmbtu rating of a steam boiler. Is there a formula for this? what knowns are used for the calculation

: : : : : : First thing are you looking for an input or output? The output is easy, it takes ballpark 1,000 btu to turn 1 pound of water at 212 deg F into 1 pound of saturated steam. So if your steam output is 1,000 lbs/hr that is roughly 1 mmbtu output.

: : : : : : Input is different because that is a function of the efficiency of the boiler. That will require more detail on your boiler

: : : : : Looking for output. The boiler plate list 60,000 lbs/hr with a 250 mawp. The manufactur list the boiler as a 72.84mmbtu. My question is how did they come up with the 72.84mmbtu rating?

: : : : Correction. the manufacturer list the design input at 72.84mmbtu. Question is still the same.

: : : A 60,000 pph boiler is roughly 60 mmbtu output so at 72.84 input is a fuel-to-steam efficiency of 82.3%, right about average. What specifically are you leading towards?

: :

: : I do thank you for your help with this. The rating according to the data plate is 60k. 60k divide by 34.5hp is 1739hp. 1739hp x 33478btu = 58.2mmbtu. So, what am I doing wrong here. Spec sheet says 72.8mmbtu but data plate says boiler is a 60k/hr. What am I missing or doing wrong? if I use a 75k rating in my calculations I come up with the 72.8mmbtu.

: You seem to be confusing input and output. Boiler HP is a measure of output for which the 58.2 sounds about right. 72.8 is an input. The difference is boiler efficiency.

Got it! Thanks for your help.