Brewing With Total Confidence
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Discussion in 'Feature Requests' started by LarryBrewer, Aug 8, 2013.
From a user who contacted us by email:
Anybody have a source for equations on this?
This link has some info:
http://homebrew.stackexchange.com/quest ... ou/592#592
Besides the formula in perfect conditions, its also relative to the conditions, different pots, different insulation, different weather, pressure temps, elevation ?? Whether you're using pid pulse or on full power also??, with the lid on or off too
read down at Fun With Heat Elements and Math
he has done some work on the subject with electric only
The basic forums looks like this:
target temp - start temp = temp rise needed
temp rise needed / temp rise per hour provided by element * 60 minutes = minutes needed to reach target temp from start temp with element
(18766 BTU/h) / 83.4 = 225F / hour
50F rise needed : 50F / 225F rise per hour * 60 min = 13 minutes to strike
(18766 BTU/h) / 62.55 = 300F / hour
57F rise needed : 57F / 300F * 60 = 11.4 minutes to boil
(4691.5 BTU/h) / 83.4 = 56.25F / hour
50F / 56.25F * 60min = 53 mins to strike
(4691.5 BTU/h) / 62.55 = 75F / hour
57F / 75F * 60min = 45.6 mins to boil
(2 * 4691.5 BTU/h) / 83.4 = 112.5F / hour
50F / 112.5F * 60min = 26.5 mins to strike
(2 * 4691.5 BTU/h) / 62.55 = 150F / hour
57F / 150F * 60min = 22.8 mins to boil
See this: http://www.phpdoc.info/brew/boilcalc.html
and also cross-referenced to my request today: http://www.brewersfriend.com/forum/viewtopic.php?f=7&t=1085
One issue in the source code of that equation is that when both "Start Temp" and "End Temp" are in units of Farhenheit and "End Temp" exceeds 99F, it always throws an error message of "Start temp cannot be greater than End Temp" even when "Start Temp" is less than "End Temp". It only does it when "End Temp" is in triple digits >=100F and my guess is that it still error checking based on a maximum boiling point of 100C and doesn't recognize hot, but not boiling water temps of 100-212F.
All of that mattters, yes, but the main point is to give electric brewers a ballpark idea of how to size their element or what to expect when mashing, boiling, etc... Real world conditions aside, they'll only affect the difference between boiling with an aluminum pot and a PID heater and boiling with a keggle and a PWM heater by about 5-10%, which equates to only a handful of minutes either way.
The more important aspects are insulation and elevation, but even those won't affect the heating times by more than an additional 10-15%. Still well within a ballpark limit of 20% to either side for heating with electric.
posted this on the other post too take it its simple