heat of fermentation
fermentation generates 252 BTUs of heat for every lb of extract lost. For Ales, in our brewery, I look at a peak rate of fermentation of 0.4 °P/hour (That's generous but better to aim high). Using the formula:
(P+259)*P*B/100= lbs extract/hour
Where P is the peak °P/hr and B is the volume of fermenting beer (in Bbls)
gives 14.5 lbs/hr for a peak rate if 0.4 °P and a volume of 14 Bbls.
Take that times 252 and you get a cooling load of about 3,660 BTU/hr
FYI, I usually use 0.15 °P/hr for calculating lager loads.
Free State Brewing Co.