Pimpin' my Fermentation Cupboard

Don't have either space or transport for a proper fridge so I thought I'd try my own interpretation of the frozen water bottles type cooling system. Step one, this post, is using 2 inches of polystyrene sheet to create a cool chamber for the ice to go in. Step 2; If [big if] that works well enough and stays cold for long enough I've got a couple of little PC fans which I'm going to embed into the top of the thing to circulate cold air about the fermentation chamber.

No idea how well this will work, if at all. Lets just say I have time on my hands and 20 quid burning a hole in my pocket. I have a big poster up in my classroom at school with the motto 'Failure is Always an Option'; So long as we learn from our mistakes we're all good. At the very least it will be a warning for others on how not to go about it. Feel free to tell me I'm hopelessly optimistic or even better point out ways I could make it more efficient.

Polysytyrene sheets - £6.50 from eBay
Thin wood/cardboard for the frame - already lying around in the garage
2 x 40mm by 10mmPC fans - bought good ones, £8 for two from eBay
12v PSU - £6 eBay
Roll of packing tape - 50p



Useful cupboard which has mains in it already to power the washing machine. I usually have a bucket, heat belt, and Inkbird in here all year round.



Cut out the polystyrene and use clear packing tape to seal it.



Not worried about the gaps, if it comes anywhere near working properly I'll seal it all up nicely.



A nice tight fit, but I have a couple of inches of headroom spare in the cold chamber, if I make it permanent I'll trim that down. Not going to insulate the upper chamber, have less than half an inch each side of the bucket, but I might put something around the door to make sure that seals well.

Got three 2L bottles of water in the freezer, taking bets on how long that insulation will keep water frozen. How long till all the ice is gone? Hours? Days?

A cool box is basically polystyrene/foam wedged between the plastic inner and outer wal so you might be in with a shout I reckon. Let us know how you get on.

I am only kicking the tyres here as i have never built anything like this, the only thing i can see that may hinder the cooling effect is you have put insulation inside the part the FV is sat on, would it not be more efficient without it.

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Chippy_Tea said:

I am only kicking the tyres here as i have never built anything like this, the only thing i can see that may hinder the cooling effect is you have put insulation inside the part the FV is sat on, would it not be more efficient without it.

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I did think of that, and especially if I were to be trying to brew lager at temps permanently below ambient it would be good to be cooling permanently. But once the weather warms up I'll have no way to chill down to lagering temps so it's unlikely I'll be wanting to do that, I'll just be using it to hopefully maintain 19C ale temps.

So there will be cold days when the the Inkbird will turn the heat belt on. My thinking is that it would be counterproductive to be simultaneously heating the bucket with a belt and cooling it from below. Hopefully more efficient for the fans to be blowing cold air exactly when needed.

I missed the bit about a belt under the first picture so assumed you were trying to make a cooling system, keep us posted.

Chippy_Tea said:

I missed the bit about a belt under the first picture so assumed you were trying to make a cooling system, keep us posted.

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If it does anything at all I'll be amazed :lol:

They're out of the traps and the race has started. How long will the ice last? I'm guessing perhaps a couple of days before the last is used up.

nigelnorris said:

They're out of the traps and the race has started. How long will the ice last? I'm guessing perhaps a couple of days before the last is used up.

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I usually find with my brew bag the ice bottles last about 24 hours but I usually swap them out every 12 hours. 2L of ice drops the ambient temp by 1C.

Yes, I'm guessing once the fans are installed I'll have to recycle the bottles fairly frequently.

Last summer I put my FV in a garden trub with water in and a t shirt over the FV. The t shirt wickes water which then evaporates giving a cooling effect. It stayed at about 20° even on the very hot days. I've got a fridge now though.

Great idea, but just a few points:

1) Cold air falls so putting the ice at the bottom of the space is counter productive.

2) Using a circulating fan will needlessly generate heat from the fan motor.

3) Using water evaporation as a cooling method is only effective if the water is encouraged to evaporate by circulating the air. Without air circulation the constant presence of moisture will promote the formation of fungi and moulds.

In view of these factors I recommend that:

o The ice box is moved to the top of the cooling space.

o Channels are installed to allow any melted ice or condensed moisture to be routed around the FV to the bottom of the space and collected.

o The collected moisture is removed from the space when the contents of the ice box is checked and renewed.

o The internal temperature is monitored so that opening the door of the enclosure is minimised.

Hope this helps. :thumb:

Have you ever seen that Poly Urethane foam at hardware stores, it's often a weird pink or purple colour, it's 32kg/m3 density insulates twice as good as polystyrene, it tolerates all kinds of glues and resins, is strong, easy to cut and generally far superior to polystyrene in all ways except availability and price. I believe it is intended to go under flooring. If you were going to make your chamber permanent, this stuff might be better suited. I re insulated a fridge on my yacht with it and works very well! If I was building a chamber like yours I would purchase one of those cheap electric cool boxes and rip out and use the cooling unit from that instead of ice?

Dutto said:

Great idea, but just a few points:

1) Cold air falls so putting the ice at the bottom of the space is counter productive.

2) Using a circulating fan will needlessly generate heat from the fan motor.

3) Using water evaporation as a cooling method is only effective if the water is encouraged to evaporate by circulating the air. Without air circulation the constant presence of moisture will promote the formation of fungi and moulds.

In view of these factors I recommend that:

o The ice box is moved to the top of the cooling space.

o Channels are installed to allow any melted ice or condensed moisture to be routed around the FV to the bottom of the space and collected.

o The collected moisture is removed from the space when the contents of the ice box is checked and renewed.

o The internal temperature is monitored so that opening the door of the enclosure is minimised.

Hope this helps. :thumb:

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All good points, thanks. I'm already seeing that condensation will be an issue, so yes if it looks like being useful I'll have to seal it properly and treat the inside. Not too worried about the fan heat, they're tiny little 4cm 12v things, milliwatts being used.

I think placement of the cool chamber is going to be swings and roundabouts. I agree with everything you said, but as I see it the counterargument is that if it's at the top then the cool air is likely to simply fall down out of the fan ports. Plus as you say the upper part of the chamber will be the warmest so will be likely to warm the cool chamber quicker from underneath and make the thing less efficient. I was thinking possibly duct the fan inlet and outlet from the chamber at the bottom and have the air collected and released at the top. A couple of feet of inch plastic tubing would do the job. Something to experiment with.

Brett74 said:

Have you ever seen that Poly Urethane foam at hardware stores...

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No I haven't, but I'll certainly give it a look-see.

Brett74 said:

If I was building a chamber like yours I would purchase one of those cheap electric cool boxes and rip out and use the cooling unit from that instead of ice?

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Another good idea, I'll investigate.

Thanks!

24 hours came and went and the bottles are still something like 75% ice, so the insulation is working quite well. Temperature inside the coolbox was down to 2C when the bottles had been in for an hour or two, first thing this morning was at 5C and is still at that now.

I've just had a great idea that is way too Heath Robinson to take seriously. Instead of fans take some copper tubing and use that for heat transfer. Bend it into a flat pad that the bottles would lie on top of, feed it up into the top chamber and have it bent into another pad fixed to the roof, then put a down tube from that back into the ice box. Then fill the tube with water [maybe even just air would do] and put a little pump to circulate cold water through the spirals top and bottom. Cool it under the bottles then send it up to exchange the heat at the top. Seal it up nicely so no fan holes for air to leak out of the bottom chamber, much more efficient.

nigelnorris said:

I've just had a great idea that is way too Heath Robinson to take seriously. Instead of fans take some copper tubing and use that for heat transfer. Bend it into a flat pad that the bottles would lie on top of, feed it up into the top chamber and have it bent into another pad fixed to the roof, then put a down tube from that back into the ice box. Then fill the tube with water [maybe even just air would do] and put a little pump to circulate cold water through the spirals top and bottom. Cool it under the bottles then send it up to exchange the heat at the top. Seal it up nicely so no fan holes for air to leak out of the bottom chamber, much more efficient.

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I was going to recommend this, similar idea to a water cooled PC.

r-evans said:

I was going to recommend this, similar idea to a water cooled PC.

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Nice bit of lateral thinking, be perfect to use a couple of radiators one each end. Mind you PC gear is eye wateringly expensive.

Meanwhile two days gone by and still no sign of the big defrost, the cool box has been at a steady 5C for two days now and there's 3/4 of the ice left. So hopefully come the weekend I can start embedding the fans in and not have to worry about changing the bottles every 2 hours once they're powered up.

Thinking of sticking 18 inches of 2 inch plastic pipe above each fan to move the airflow to the top of the upper chamber, might offset Dutto's concerns about too much cold down at the bottom.

Still a little bit of ice in there. 5 straight days at 5C [-ish, it's drifted up towards 6 now but that's with barely any ice and the central heating on] in the cooler so test one is a success, the insulation works better than I expected.

Tomorrow I'll fit the fans and see what temperature the upper chamber can be brought down and then held to.

Interesting idea Nigel but the reason it's keeping the ice frozen at the moment is there's no heat load on the small insulated space. You will need to insulate the whole cupboard where the FV sits including the door for it stand a chance, otherwise the environment outside the cupboard, especially from your washing machine machine will transfer heat into the comparatively large fermenter space and your ice will be water in no time compared to your experiment. I'd buy a fridge personally, mine was £20 on gumtree.

You don't teach physics do you?