I've installed an HRV system (heat recovery ventilation) in an effort to remove co2 from the cider house. But, even though the unit is rated to remove far more than ought to be necessary, Co2 is still noticeable and very unpleasant in the fermenting area. For now, we're flummoxed. My research included a very useful thread from this group, where I was able to verify facts about co2 production during fermentation. Here's the relevant information as it applies to our space:
Right now we're fermenting 12 x 1000L tanks, and the co2 levels are totally out of control.
We designed the system to easily handle 40 x 1000 L tanks, fermenting all at once, by appeal to the following sort of reasoning:
Assuming a maximum of 150g of sugar per liter, 40 tanks ought to produce a maximum of 6,000,000g of sugar, which ought to convert to no more than 3,000,000g of Co2.
Since 44g of Co2 = 24.47 L, this means 3,000,000g/44g*24.47L = 1,668,409L of Co2, or 58,394 cubic feet.
If we pretend all tanks were to ferment to dryness in a single day (which of course they won't), they would produce 58,394/1440, or 40.55 cubic feet per minute.
Yet the HRV unit we've installed is rated to remove and replace 179 cubic feet per minute!! The unit seems to be working, but the co2 build up is so bad I have to open all the doors in order to work! (The vents are located a couple inches above the floor, and there are two of them in a space sized L60x24Wx15H, and a third in an adjacent bottling area (no door), sized 20x40x10).
Could it be that even though our unit removes way more volume than necessary, the velocity is not sufficient? So, maybe reduce the diameter of the vents? Or, maybe there should be more vents in the space? But why?
Any thoughts about this would be truly appreciated!!
Thanks!
Mike
Perfect ventilation, ferment outside.
Tim in Dorset
-----Original Message-----
From: cider-w...@googlegroups.com [mailto:cider-w...@googlegroups.com] On Behalf Of Wes Cherry
Sent: 20 October 2017 21:23
To: cider-w...@googlegroups.com
Subject: Re: [Cider Workshop] Co2 in the cider house
Can confirm. We have to wait a bit when opening the ciderhouse with active ferments.
Co2 makes carbonic acid in mucous membranes. At higher concentrations, definitely something you immediately *feel* before any cerebral effects.
Ventilation is a design parameter in our new ciderhouse design. Our mechanical engineer had specific recommended ratios of flow to volume for wineries. Can't find the #s on my phone though.
-'//es Cherry
Dragon's Head Cider
Vashon Island, Wa US