Brew Shed Exhaust Fan – Need More Power!Sunday, May 6th, 2012
Choose your brew shed exhaust fan and ducting design carefully. My shed is exactly what I was after with one exception: the exhaust system. On wet days the condensation from the boil off can become a bit of a problem. Note that there are zero problems on warm days, but doing a 90 minute boil on a rainy day leads to this situation:
I did a lot of research on fans in terms of price, noise level, and cubic feet per minute (CFM). The more CFM you want the more expensive they get and the more noise they put out. The ideal solution is a reasonably priced fan that can keep the room dry but not drive me nuts with racket. Going in I knew a kitchen hood fan like the ones that normally go over a stove would not be powerful enough.
Where to find a powerful exhaust fan? It turns out exhaust fans are a big deal for ‘growers’ too. Their supply stores have several models to choose from. It felt a little strange ordering from one of these places. Thankfully, the shed has a sky light so big brother can already see what is going on in there.
After trying to find a balance between noise level, cost and CFM, I went with this:
Can MAX Fan 6″ – 334 cfm w/ Speed Contrl
The max fan is $150 before shipping. The noise level is tolerable and I thought 334 CFM would be plenty. It works fine for a 60 minute boil in dry weather. However, it is too weak to keep up with a 90 minute boil if the relative humidity is over 75%. What I ended up having to do a couple times earlier this winter was wrap a towel around the unit since there was so much dripping coming out of it. That works pretty well and has gotten me by until I have time to make a more permanent solution.
- Get something with a higher CFM, and then build an insulated box around it to block out some of the noise.
- Redesign the duct work. What I accidentally created is a reflux chamber – doh! When the hot gas goes up through the fan, some of it cools and condenses on the walls of the ducting and then drips back down (all the way). My fault for designing it that way, but it was the shortest distance. What I probably need to do is orient the fan sideways and rig a dip tube that goes outside.
Other considerations when it comes to condensation in the brewery:
Selecting a hood is another issue. The loft makes for a built in hood, but it is not the same thing as a professional stainless steel hood. Those things are insanely expensive, coming in upwards of $1,000 for a cheap one. I had a left over dust collection vent from my wood shop so I mounted that. I don’t think the problem is the hood, I think the main problem is the reflux.
Looking forward to anything our readers can share on this issue! Don’t build a re-flux chamber like I did!