A few months from now I will be installing a 220 volt recirculating infusion mash system (RIMS) in my new brewroom, I've already said goodbye to my old natural gas powered system. My previous brewroom was awesome I brewed over 100 batches in there, it was located indoors in a well ventilated basement and was powered by two natural gas burners. For me at the time this was a really beautiful setup, after some initial trial and error in the layout, it became a very efficient brewroom that was a lot of fun to use. The brewroom was big, it included enough space for a yeast lab, storage area, beer conditioning and an awesome brewing setup. I brewed on that all grain setup for three years and produced some of the greatest tasting beers ever. I looked forward to my time brewing there and inviting fellow brewers over to share recipes, beers, new ideas and to lend a hand from time to time.
|High Gravity Electric Brew In A Bag|
Being only months away from moving into the new place I decided that building my next brewroom around an electric brewing system would be the best way go. I'll admit at first I had no idea exactly what the pros and cons of using electric were versus gas powered brewing systems. I soon found myself doing a ton of research to learn everything I could about the electric option and it's benefits over gas. Understanding the power line size was pretty straightforward, there's a lot of useful information on the manufacturer websites to help with that and other concepts.
A dedicated 220 volt 30 amp GFIC is used to power a 4 wire 30 amp receptacle located near the brewing area and as with any indoor brewroom setup adequate ventilation is an absolute necessity. With electric brewing though we only need to exhaust boil vapors and brewing aromas to maintain a safe and comfortable working environment. Unlike gas powered systems electric brewing systems don't consume oxygen and they don't produce poisonous carbon monoxide so there's no need to worry about exhausting poisonous fumes too. There are other things to consider when comparing electric verses gas like the lower installation cost of a 30 amp 220 volt electric line compared to installing a gas line to power the brewing system.
Indoor brewrooms powered by gas burners have to be well ventilated to quickly remove poisonous combustion gases and replace them with fresh makeup air. As the volume of air required to maintain a safe and healthy brewroom environment gets higher the more cubic feet per minute (CFM) of fresh air the exhaust system will need to remove and replace. In my gas powered brewroom I used two 7,000 btu gas burners to heat the mash and boil the wort for a combined rating of 14,000 btus.
I tried using the same gas BTU to CFM theory published by John Blichmann in BYO Magazine's November 2012 issue. The article was written to show the CFM differences when used with electric heating elements as opposed to gas burners. It seems that John chose to use a simple shorthand formula that converted BTUs to Kiliwatt hours, so the formula could be used for both gas and electric calculations. As to why John chose to use the number 30 in his formula for gas and 17.6 for electric is still a mystery to me though. Using John's formula the 14,000 BTUs created by my gas burners divided by 30 would require a 466 CFM fan. While a 4,500 watt electric heating element in my brew kettle divided by 17.6 would only require a 255 CFM fan.
As far as heating efficiency goes a gas burner loses about 50% of it's BTU rating because the heat produced by the flame rapidly radiates outward and away from the wort in the brew kettle. Electric powered kettles are 100% efficient because the heating elements are in contact with the wort at all times. Due to these major differences in heating efficiencies an electric heating element rated at 5,000 watts is capable of heating wort at the same rate as an 18,000 BTU gas burner. The standard calculation used to convert watts to BTUs per hour is to take the wattage of an electric heating element and times it by 3.412, the answer represents the number of BTUs. (Example: A 220 volt 5,000 watt heating element times 3.412 converts to 18,766 btus per hour.)
John's formula still leaves a few questions unanswered since there is no mention of room size or the number of times the air in the room needs to be changed to provide a comfortable brewing environment. My electric powered brewroom will measure 20 feet wide by 20 feet long by 10 feet high and contain 4,000 cubic feet of space. Using the formula (20 * 20 * 10) / 8.75 = 457 CFM, so a fan rated at 450 CFM will change the air in the entire brew room completely in about 9 minutes. But wait there is still something missing, an exhaust fan hood over the brew kettle.
It only makes sense that the use of an exhaust hood located directly above the boil kettle will guarantee that all the the boil vapors and aromas will be removed as efficiently as possible. The industry standard calculation to vent a kitchen stove recommends dividing the total BTU output of the stove, or in my case the brew kettle heating element, and divide it by 100 to determine the exhaust hood's minimum CFM rating. In order to do this I had to convert my 4,500 watt 220 volt heating element to BTUs by multiplying 4,500 by 3.412 where 4,500 * 3.412 = 15,354 BTUs. Then finally dividing 15,354 by 100 to get the exhaust hood rating where 15,354 / 100 = 153 CFM.
So now I'm left with two seemingly conflicting pieces of information where 450 CFM will change the brewroom air once every 9 minutes and the exhaust fan located above my kettle has to be rated at 153 CFM. A possible explanation for the differences is in another industry standard formula for sizing range hoods, where each foot of stove width requires 100 CFM of air. If this formula is used then that 450 CFM fan needed to change the brewroom air every 9 minutes would also need a 4.5 foot wide exhaust hood to balance everything out.