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Old 05-29-2010, 04:35 AM   #1
bsdx's Avatar
Apr 2010
Perry, Michigan
Posts: 328
Liked 20 Times on 8 Posts

I did some more in-depth reading of some of the aquarium heater threads today and took down some notes before heading to some local stores to build a prototype.

Question: do I still set the water bath temp to 5 degrees below optimal
fermentation temp for the yeast, or will this water bath conduct the fermentation heat away?

First pics, then info.
Some product labels:

Safety first! Water + Electricity = GFCI:

Submerged heater:

Height comparison, plus visual reminders for insulation and bleach:

I figured with two pails I should have the heater in the middle:

Sufficient room for water to surround pails:

The lid fits flat even with an airlock installed on the pail and the electric heater cord coming out from under the lid.


- higher heater cost in prototype, wasn't pinching pennies
- unfinished temp control

incomplete goals / testing:
- temp control. This unit only goes as low as 67, but there are ways you
can trick it but it sounds like they need fine tuning. Alternatively an
external temp control sounds desirable to simplify/improve temp accuracy
and reliability. I did not decide to commit to buying another ranco yet,
I may depending on the price and hassle of other methods. There may be
cheaper thermocontrols I could use.
- really wanted to design this scaled for only one bucket/carboy so if/when
I make several I can just have each wort at the ideal temp. I ended up
with this larger dualie for a prototype because I'm hoping to brew this
weekend and I wanted to try this with more than just one pail, but did not
want to buy two prototypes. When I've made multiple batches in the past
I was lucky to end up with yeast with agreeable temperature ranges without
thinking ahead. Given that we've had up to 5 pails in my air chamber before,
I figured I could handle up to 2 in this build. I can either plan ahead or
use it for a single. I was also thinking that the faster I get my yeast
to take off using healthy methods means the faster I am past the point where
temperature mistakes will matter, reducing my risk.
- I was considering some kind of pump to circulate the water, but didn't
find one cheap enough yet. Probably will wait to see water tempts in

- temp range: wanted enough wattage to take the wort and the water bath
from 55 ambient to 70ish at least.
- shatterproof heater (glass ones could overheat if taken out of water
and shatter when put back in. There are also "shatter resistant"
ones, at least one design had pyrex glass.)
- auto shut off if the heater runs dry, auto heat re-enable when re-submerged
- fully submersible (stealth) so I don't have to worry about attachment
- avoided cheap ones according to 'get what you pay for' rule

- wheels for moving tub might be helpful
- lid will keep thirsty dogs away from bleachy water, retain more heat,
and reduce light
- tub was high enough to accomodate airlocks without even pushing the lid
- heater cord easily fits under the side of the lid

- Items purchased:
45gal Sterilite tub with wheels and lid from Home Depot: $16.98
Marineland aquarium heater at local family owned pet store: $40.99

- Items I already had:
1" styrofoam board recycled from basement project
gfci outlet already installed (I would have bought an inline one if needed)

- If I get a reasonably fast ferment to near the FG, I think I could move
fermenters to an existing heated air chamber with temp control set to 70.
When we don't have pails in the air chamber, we put bottles in.
I might not need as many water baths as I thought if I can move them out
to dia. rest within a week. Room for new brews!
- Unless I want my tub water around the high 50s for some time after I add
pails or carboys, its obvious that I'll need to preheat this thing with
plenty of time before I brew.
- My basement will probably stay around 58-60 for much of the year because
the a/c keeps it down. Thus it seems to me like a nearly perfect starting
temperature for fermenting at ideal temps. The temp is not stable in the
rest of the house and I have it cool in the winter.

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Old 05-29-2010, 11:21 AM   #2
Sep 2008
WarehamI?, Massachusetts
Posts: 702
Liked 39 Times on 29 Posts

You probably want a heat shield on the heater. Those suckers get very hot and will melt plastic, even at the low temperatures of fermentation (depends mostly on the room temperature and how hard it has to work to keep the temperature). You have to make sure the heater stays submerged or it will crack or burst.

A couple marks on the inside of the container to show what water level to fill to before the buckets go in is nice so you can start the temperature control a few days in advance (especially if it is in a cold place).

If you aren't pinching pennies, something to circulate the water would prevent hot spots. An aquarium air pump, power head, or other.

Keep your eye open for a free chest freezer on Craiglist or elsewhere, the combination of the two help me in my non-insulated basement.
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Old 05-29-2010, 09:52 PM   #3
bsdx's Avatar
Apr 2010
Perry, Michigan
Posts: 328
Liked 20 Times on 8 Posts

Thanks for the tips, I marked the fill line this morning. I'll probably use it often enough that I won't bother emptying it much, I don't have a faucet in the basement.

I think I solved my temperature control problem for now by moving my ranco controller to it, since 70 degrees is within the adjustable range on the air heater in my conditioning cabinet and temperature stability will be less of a problem there. The aquarium heater itself brought the whole bath up to 67 on its own last night (its lowest setting) and now I have a day or so to let it drop to desired fermentation temp.

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