Fermentation chamber build verification

Building a fermentation chamber in the upcoming weeks, just want to double check my plans.

Dimensions are roughly 4x3x2. I'm using a 5000 btu air conditioner to cool it.

I'm planning on a dual chamber, one for lagering, the other for ales. The lager chamber will closest to the air conditioner. The ale chamber will be cooled via 120mm fan installed on the insulated wall between the chambers.

The chamber will be in my garage, which is not climate controlled. Max temp is around 100 in the summer, lowest is below freezing in the winter. Heating o both chambers will be accomplished via light bulb. EBay aquarium temp controllers will be used, 1 for each zone.

Crunching the numbers, I get a need of approximately 840 btu's using r-5 insulation, and 1400 btu's using r-3. Since i don't need too much, I'll probably go with the r-5.

Additionally, since it will e sitting on the garage slab, my delta t will probably be less than 70, which I used to approximate worst case scenario: 100 degrees lagering at 30.

Does everything seem in order? Any changes necessary before I start purchasing materials?

Since you don't need too much insulation, you could always use some polyiso with an r-rating of 9.5. More efficient at keeping things cool and warm, reducing your electricity need, hence saving you $$.

$26 for a 1.5", 4'x8' sheet. It is what I used on my ferm chamber:

keep in mind that calculation is in BTU/hr. Meaning that you need 840 BTU/hr. It is not exact, but you can estimate that the total output of the air conditioner can be divided to estimate how long it will run:

840 BTU/HR / 5000 BTU = 0.168 hr = 10 minutes per hour.

Assuming the air conditioner is 500 W:

0.168 hr * 500 w * 24 hr/day = 2 kWh per day

and electricity prices at $0.15/kWh:

2 kwh/day * $0.15/kWh * 30 days/bill = roughly 9 dollars extra per bill.

If thats not enough to make a noticiable difference, than go for it. But I would be looking to get more insulation on that puppy (R5 is low). Regular 2x4 wall insulation can get you to R-13.

Also, how are planning on bypassing the stock thermostat on the air conditioner to get down to lagering temps? Even then, you may run into issues with the coils freezing over.

kpr121 said:

keep in mind that calculation is in BTU/hr. Meaning that you need 840 BTU/hr. It is not exact, but you can estimate that the total output of the air conditioner can be divided to estimate how long it will run:

840 BTU/HR / 5000 BTU = 0.168 hr = 10 minutes per hour.

Assuming the air conditioner is 500 W:

0.168 hr * 500 w * 24 hr/day = 2 kWh per day

and electricity prices at $0.15/kWh:

2 kwh/day * $0.15/kWh * 30 days/bill = roughly 9 dollars extra per bill.

If thats not enough to make a noticiable difference, than go for it. But I would be looking to get more insulation on that puppy (R5 is low). Regular 2x4 wall insulation can get you to R-13.

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Good to know, I'm trying to balance efficiency and cost. I can get r-10 foam sheathing, but it's more than twice as expensive. Perhaps doubling the insulation on the bottom and top would be a more cost effective option.

Ot: nice avatar, I'm in between classes at Penn state Harrisburg at the moment.

kpr121 said:

Also, how are planning on bypassing the stock thermostat on the air conditioner to get down to lagering temps? Even then, you may run into issues with the coils freezing over.

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By moving the ac thermistor to the exterior of the chamber. Ac will only see ambient temps, so it won't shut off. The controller will cycle the ac. Additionally, if I limit the amount of time the ac runs, coil freeze should not be an issue.

o4_srt said:

Good to know, I'm trying to balance efficiency and cost. I can get r-10 foam sheathing, but it's more than twice as expensive. Perhaps doubling the insulation on the bottom and top would be a more cost effective option.

Ot: nice avatar, I'm in between classes at Penn state Harrisburg at the moment.

Click to expand...

How are you framing the box in? if you use 2x4's you can just get the wall roll insulation and be at R-13. I would say that was enough.

Remember too that that the ambiant temp is not going to be over 90 even very much, so you don't want to go overboard.

Sweet about PSU! Are you going to the Blue-White game. I am (hoping the rain holds off)

kpr121 said:

How are you framing the box in? if you use 2x4's you can just get the wall roll insulation and be at R-13. I would say that was enough.

Remember too that that the ambiant temp is not going to be over 90 even very much, so you don't want to go overboard.

Sweet about PSU! Are you going to the Blue-White game. I am (hoping the rain holds off)

Click to expand...

2x4 frame. I'll have to do the math to see which is more cost effective: sheathing or fiberglass. With sheathing, I wasn't planning on facing the interior of the chamber. With fiberglass, I probably would.

I don't know about the b&w game, but im going to try to make it up there for a game this season, wife has never been to one, she is missing out.

o4_srt said:

2x4 frame. I'll have to do the math to see which is more cost effective: sheathing or fiberglass. With sheathing, I wasn't planning on facing the interior of the chamber. With fiberglass, I probably would.

I don't know about the b&w game, but im going to try to make it up there for a game this season, wife has never been to one, she is missing out.

Click to expand...

Thats true, I didnt think about having to have to face the interior. Foam board is better than fiberglass in wet situations as well.

o4_srt said:

By moving the ac thermistor to the exterior of the chamber. Ac will only see ambient temps, so it won't shut off. The controller will cycle the ac. Additionally, if I limit the amount of time the ac runs, coil freeze should not be an issue.

Click to expand...

I have tried this on my fermenting/cellaring closet (see link in sig) and I am not having good luck. The unit gets down to 50ish then the compressor shuts off and only the fan runs. I may have to end up opening it up and bypassing the thermostat electronically, there may be some sort of internal safety shut off, I dunno.

Just something to think about.

kpr121 said:

I have tried this on my fermenting/cellaring closet (see link in sig) and I am not having good luck. The unit gets down to 50ish then the compressor shuts off and only the fan runs. I may have to end up opening it up and bypassing the thermostat electronically, there may be some sort of internal safety shut off, I dunno.

Just something to think about.

Click to expand...

If it's a newer unit, there is a good chance there is another temp sensor internally. If you could find a schematic for your ac, you'd know for sure. I've seen threads where others has gotten their ac powered chambers down in the 30's, just requires some electrical knowledge.

I'm using an older mechanical model, so I don't think it will be an issue. I have not yet looked at the schematic though. The previous homeowners left it when we moved into our house, so i didn't pay a cent for it. I think there I also a 10000 btu in the attic as well.

o4_srt said:

If it's a newer unit, there is a good chance there is another temp sensor internally. If you could find a schematic for your ac, you'd know for sure.

I'm using an older mechanical model, so I don't think it will be an issue. I have not yet looked at the schematic though. The previous homeowners left it when we moved into our house, so i didn't pay a cent for it. I think there I also a 10000 btu in the attic as well.

Click to expand...

Yea, thats what I was thinking. Instead of messing with the internals, I may just swap it for another older one we have (no whole house air = 6-7 window units).

Sorry back on topic: Yes your wife needs to get up to a PSU game!

Perhaps I'll use the 10000 btu. I'd be cutting the cost of operation in half. Plus, I don't foresee keeping it in the 30's year round, so that would further reduce cost.

That would also decrease the chance of freezing it up.

Schnitzengiggle said:

Since you don't need too much insulation, you could always use some polyiso with an r-rating of 9.5. More efficient at keeping things cool and warm, reducing your electricity need, hence saving you $$.

$26 for a 1.5", 4'x8' sheet. It is what I used on my ferm chamber:

<img src="https://www.homebrewtalk.com/attachment.php?attachmentid=23827"/>

Click to expand...

Don't mean to thread jack but how do you cool that thing?

HItransplant said:

Don't mean to thread jack but how do you cool that thing?

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There is an archaic 4cu sanyo mini fridge cooling the unit.

Here is a pic:

Schnitzengiggle said:

There is an archaic 4cu sanyo mini fridge cooling the unit.

Here is a pic:

View attachment 23837

View attachment 23838

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nice..thanks.

sorry for the thread jack.

I have basically the same setup - using a fridge as the cooling source. I built the box out of 3" thick foil back insulation foam with the internal foam dividing wall to define the warm and cold sides of the chamber. it works very well. I also have a fan mounted in the dividing wall to pull cold air through when needed. I can ferment an ale in the warm side and lager in the cold side all year round.
I bought 2" and 1" foam sheets and laminated it. The lid is the same 3" laminate. I sealed it with soft rubber weatherstripping. Its very insulated and very stable. Once the fridge gets the chamber temps where it needs to be it hardly runs at all. I probably could have used less foam but I figured it would pay to get the stability.
I went with a warming blanket for the heat source rather than a lightbulb as I didn't want light in there with the beer.

-Andy

Kpr, I noticed my ac is doing the same thing as yours, found a solution:

http://www.franklinbrew.org/members/sj/walkin.html

About halfway down the page, there are details on how to make the compressor run constantly, which is what we want, since temp control is accomplished by an external thermostat.

o4_srt said:

Kpr, I noticed my ac is doing the same thing as yours, found a solution:

http://www.franklinbrew.org/members/sj/walkin.html

About halfway down the page, there are details on how to make the compressor run constantly, which is what we want, since temp control is accomplished by an external thermostat.

Click to expand...

Hmmm so there should be some sort of adjustment screw in the guts of this thing? And all you gotta do is crank that down and let the external temp controller do its own thing. I hope it is that easy!

kpr121 said:

Hmmm so there should be some sort of adjustment screw in the guts of this thing? And all you gotta do is crank that down and let the external temp controller do its own thing. I hope it is that easy!

Click to expand...

Apparently, and if not , you just need to wire the compressor straight to the ac power line, bypassing the switch and t-stat. I should have thought of that sooner.

Sweet, I'm def gonna try this. Maybe tonight, well see. I'll let you know if I do and try to take pics.

kpr121 said:

Sweet, I'm def gonna try this. Maybe tonight, well see. I'll let you know if I do and try to take pics.

Click to expand...

I can confirm that tying the compressor and the fan to the hot ac line results in both the compressor and fan running when power is applied to the ac.

I got the temp down in the 20's in my test fixture.

Once you do this, you can remove the thermostat and operation switches. You will also have 2 extra leads to the fan motor. Clip these and insulate with electrical tape.

Sorry for resurrecting an old thread... but how do you get an A/C to go down into the 20's without the coils freezing over?