In part 1 of this series I covered some of the general considerations in planning an electric brewery including size of the system, availability of water and in particular the electrical needs of the system and electrical safety considerations. This week I take a look at the other major physical constraint which is ventilation.
Why Proper Venting is Needed for Brewing Beer
While the ventilation requirements for an electric brewing system are far below what is needed for a gas/propane heated system, proper venting is still important. All we need to do is take a look at the amount of water boiled off during an average brewing session to see that the steam needs somewhere to go. A typical 10 gal (38 l) system will boil 2 gal (8 l) or more of water off from the kettle. A 5 gal (19 l) system puts out about half that. Even in a fairly sizable enclosed room that 2 gal (8 l) of water is enough to raise the relative humidity in the room by 50% or more – all within the space of about 90 minutes!
So what does that mean? In a closed space you will get heavy condensation on the ceiling, walls, windows, floors and even between walls. Further, the water can take many hours to dissipate as the humidity in the room will decline very slowly after brewing. This can lead to mold, permanent damage to the drywall, and other nasty issues.
Obviously the effect is highly dependent on the size of the system, size of the room, availability of outside airflow, and boil off rate. For example a 5 gal (19 l) electric system in a well ventilated kitchen which already has a stove vent and good airflow from nearby windows may be no problem at all. However a 10+ gal (38+) liter system in an enclosed room down in a humid basement may be a real problem.
Venting Requirements for Electric Systems
The requirements for venting steam from your boil pot vary widely depending on the size and efficiency of your hood and size of your system. At the low end is a completely enclosed boiler – of the type you would see in a craft brewery. In these systems the entire boil pot is enclosed in a seamless hood and chimney pipe, which captures 100% of the steam. In this case you only need to enough ventilation for the steam expansion factor – which is about 1600 times the volume of water. So for example a 2 gal/hour (4 l/hour) boil off would produce 1600 times that volume in steam or 3,400 gallons (13,600 liters) of steam. Since that water is boiled off over an hour it works out to a very modest 7.57 cubic feet/minute (206 l/min) flow rate which can be handled easily by even a small blower or fan in the vent. I will note that some commercial systems lack the blower, which can create condensation in the vent pipe that can drop back into the boil creating DMS.
Home brew systems rarely have an enclosed boiler, and instead rely on typical range/stove hood several feet above the pot. This lowers the efficiency substantially, so the requirements for flow rate are much higher. In addition you need to consider venting some of the heat coming from the pot to avoid raising the temperature excessively in the room, again creating a condensation risk. How much higher? Well according to a recent BYO article by John Blichmann the rule of thumb is to have a minumum of 34 cubic feet/min per kilowatt (952 l/min per kw) of heater required. For example a typical 5,500 watt heating coil for a 10 gal (38 l) system would require 5.5 * 34 = 187 cubic feet/min (5295 l/min) of airflow.
However the venting of the heat and steam is not the whole story, as you also need to consider the size and efficiency of your hood. The hood needs to be large enough to capture the steam and also you need sufficient airflow to move the steam collected out of the hood before it spills out of the hood. Most ventilation hoods are set at about 6.5 ft (2 m) above the floor, or roughly 1 yard (1 m) above the kettle. Blichmann recommends you have a minimum hood area that is 6″ (15.25 cm) wider on each side than your kettle, but also that it have 50 cubic ft/min (1450 liters/min) per square foot of hood space. So a small size 2 ft x 2 ft hood would need at least 200 cubic ft/min throughput, and a larger 4 ft x 2 ft hood would need double that or 400 cubic ft/min. So the requirement for proper airflow through the hood is actually larger than the airflow dictated by the heating coil alone.
Other Electric Brewery Considerations
That covers the basics of ventilation. As I mentioned in part 1 you may also want to look at your water requirements, particularly for chilling your wort, as that can be a third driver of where and how to size your electric brewery. In most cases a sink and faucet with a good cold water source is sufficient to drive an immersion chiller or plate chiller, but there are cases where the throughput of water or water temperature may not be low enough to drive your chiller.
I hope you enjoyed this brief two part series on setting up an electric brewery. Thanks for joining me on the BeerSmith Home Brewing Blog. Be sure to sign up for my newsletter or my podcast (also on itunes…and youtube…and streaming radio station) for more great tips on homebrewing. Also check out the How to Brew Video series I shot with John Palmer if you want to learn more about all grain brewing.
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