Temp Control for Massive Batch

[osagedr]

Massive for homebrewing, anyway. My brew club (www.rivercitybrewers.ca or @RCMBrewers) is doing a 125 gallon batch of RIS for barrel aging this weekend. Wyeast suggested a fermentation temperature of 68-ish degrees for us. We are fermenting in two 55g food-grade plastic drums (and a few carboys) using Wyeast 1028 London Ale. Wyeast's specs say ferment between 60 and 72.

Our only fermentation temperature control is ambient. It's mightly cold up here and the two barrels are going to be in my garage. So the ambient temp could be anywhere from 0 to 90 degrees F. I have a long probe thermometer to keep an eye on temps. My guess is that we'll pitch just below the recommended range; leave the ambient temp in the garage at 65 or so until we see signs of fermentation, then ramp it down to *whatever* to keep the internal ferm temps from getting too high.

My question is...does anyone have a ballpark on what ambient will have to be to keep actual in the mid-to-high 60s? In a ferm chamber with a carboy we often just ballpark it at ambient being 5 degrees below actual. But for a much larger batch in a bigger vessel, will there be a bigger difference?

Anyone with experience or an informed opinion here?

 

[knuckleheadbrewing]

From what I have heard ambient needs to be ~10* lower then what you actually want to ferment at.

 

[IL1kebeer]

Those big drums filled with wort will have a large thermal mass which will result in ambient temperature swings affecting them a lot less than a 5 gallon carboy. It will take a lot longer for a change in ambient to affect your temps.

I personally wouldn't advise to ferment those by relying on ambient; however, getting precise temp control for fermenters that big is probably not a reality in your situation. My only advice would be to start cool and then let it free rise in a controlled manner so it doesn't get out of hand. Starting warm then expecting to cool that much wort with ambient or an ice bath (is that even possible with drums that big?) during active fermentation could be extremely hard to do

Either way keep us updated. I want to know how this works out.

 

[osagedr]

Thanks. I think we'll chill right to 60, pitch, and try to hold ambient steady in the 50s. I'll keep an eye on the temps.

Wonder if it would be worth the trouble of running a few copper coils through the fermenter & pumping groundwater (45F this time of year) through as needed.

 

[IL1kebeer]

Thanks. I think we'll chill right to 60, pitch, and try to hold ambient steady in the 50s. I'll keep an eye on the temps.

Wonder if it would be worth the trouble of running a few copper coils through the fermenter & pumping groundwater (45F this time of year) through as needed.

I have heard some bad things about exposing fermenting wort or fermented beer to copper. Not exactly sure what the issue is but you might want to research that subject first before you do it.