Brew Fridge Build

[beer1965]

I'll apologize in advance (it's a Canadian thing I know), but I'm going ask some questions about building a mini-fridge fermentation chamber. I've searched google and the site and there are tons of comments on this issue - but I haven't found what I'm looking for.

I have the fridge for free - turns out university kids don't want them when they graduate. It's likely well inoculated with beer yeast! The coils are exposed on the outside back.

I've also bought an inkbird 308.

#1 searches point to the need for an internal (computer) fan to circulate the air - do you want air from outside coming in or just circulate what's inside the fridge to maintain a more even air temp inside the fridge. ? And have it on 24 hours a day?

#2 If the fridge is kept inside is there really a need for a heating element? I almost feel it's not necessary - but that would lead to more temp variability. I'm thinking of buying a seed heating mat but think something that heats the air is better (especially if I run a computer fan) than having direct contact. I'm thinking of taping the matt to inside fridge wall to create radiant heat.

#3 The fridge coils are on the outside. Someone on a site somewhere talked about the fridge running for 15-20 minutes at times which is not what their built for an the coils would overheat and a fan on them would be needed to get rid of that heat. True/false?

#4 The inkbird temp probe taped to the carboy - not ideal but good enough or buy one of those probes that goes into the carboy?

Thanks again -

 

[Craigerrr]

My thoughts
#1 - I don't have a fan in my ferm fridge (I have a full size fridge)
#2 - I used to have a wrap around heater, huge PITA, I now have a little cube heater, works great. My fridge is in my garage which I keep at 40F in the winter. The heater is good any season, especially when you want to increase temp to encourage complete attenuation
#3 - sorry, no idea, the inkbird does have an automatic delay though to protect the fridge
#4 - I use to use a thermowell for the probe, but have been taping it to the fermenter for some time now, works fine. I just have some insulation so that it is reading the wort temp, not the air temp.
Cheers
Where in Canada are you?
I am in Cambridge Ontario

 

[beer1965]

My thoughts

My fridge is in my garage which I keep at 40F in the winter.

Where in Canada are you? I am in Cambridge Ontario

Thanks - are you using it as a fermentation chamber in the winter too? I wasn't sure if you could operate a fridge in a Canadian winter outdoors. I'm just down the highway in Toronto. Cambridge is a nice place.

 

[Craigerrr]

The fridge in my garage is my fermentation fridge, yes year round. I have a 240V heater and keep the garage at 40F degrees, so it is fine.

 

[Bubba Wade]

#3. I don't think this is a concern. You'll be running the fridge a higher temperatures than it was designed for. Once you get the carboy to temperature, you'll be only offsetting heat loss and any exothermic yeast activity.

To reduce the time the fridge is running per cycle, you can hang the probe in the air and not tape it to the carboy. The air will cool and warm much more quickly than the beer. Yes, this may not be quite as accurate, but the cycle time will be shorter. If you have a large deadband on the controller, the fermenting beer will be a large thermal mass. The default deadband on the inkbird is 2 degrees C. It takes a long time to cool 5 gallons by 2 degrees.

 

[Mark Farrall]

Similar to Craig
1 - wouldn't bother with it
2 - would bother with it. I just bought a pad heater from the home brew store. It works well. Especially useful if you ever intend to kettle sour.
3 - wouldn't worry about it
4 - always wanted to do that, haven't bothered with it

I don't notice the difference in a ferm that moves 1-2 C, so that's as far as my obsession goes for temp control.

 

[Craigerrr]

The fridge won't care if it's run time is long or short, what the fridge won't like is being cycled on to quickly after being cycled off. The inkbird has a delay programmed into it to prevent this. Another reason to try and measure the wort temperature, not the air temperature. The air temperature can change quickly and call for heat, or cool when it isn't actually needed.

 

[E K Brewer]

I agree with Mark. I would add: don't bother drilling holes in the fridge walls. The heater cable can go up the condensation drain hole at the back of the fridge and the Inkbird sensor cable is so thin that it can just be trapped by the door seal when you close it.

 

[BOB357]

1. No need for a fan. if the design if the fridge design requires a fan it already has one built in.

2. If your desired temperature range includes temperatures above room temperature where the fridge is located, you'll need a heating device inside the fridge. Opinions on what works best vary, but I don't like the idea of something in direct contact with the fermenter(s).

3. As long as you follow the guidelines for distance from walls in the owners manual you'll be fine. Again, if a fan was needed, it would be built in.

4. Either using a thermowell or taping the probe on the outside with insulation does a good job of sensing the actual temperature of the beer during active fermentation. Before and after the active stage, when the liquid isn't in motion, I prefer controlling air temperature. Either way, it's what works best for you and your equipment/process.

 

[GFHomebrew]

I have been using a fan in my ferm chamber until it died last ferment.
On taping the probe to outside of fermentor i do this but last ferment I was wondering why my temperarure was swinging rapidly more so than normal (I thought the temp probe was buggered) well that thing was swinging in the breeze down the bottom of the chamber.

So my advise tape it to the side of fermentor if you don't want your temp swinging up and down.

And good on you for going the temp controlled fermentation route it just gives you peace of mind knowing your brew is tucked up ready for fermentation at the right temperarure.
Good luck

 

[sbaclimber]

After trying the swamp cooler idea....with relatively little success, I decided to go the fermentation fridge route quite a few years back. Cheap (20€ for the fridge) and totally jerry-rigged (analog probe + thermostat + toggle switch for heating vs cooling mode + aquarium heating pad), but workes like a charm at keeping ale yeast just below room temperature for fermentation or just above for diacytle rest.
I just attach a layer of insulation over the probe on the outside of the bucket to keep the measured temperature fluctuation to a minimum.
Side note...I recently moved and now have my fridge in a basement with an ambient temperature of around 15°C. I now no longer need to cool at all and am struggling to hit any temps above 20°C for a diacytle rest. No big deal, but I am really thinking of switching to brewing more lagers!

 

[beer1965]

May thanks to all for all the feedback!

@sbaclimber @Trialben - will tape it to the side of the carboy with insulation

@BOB357 - my basement is finished so temps are around 70; i don't know why I'd want higher temps than that but I'm sure I'll learn about higher temp brews at some point. But think I'll get a heating pad and tape it to the wall for radiant rather than direct heat as it's pretty inexpensive to do and I may as well do it now. But your implies then that heat probably isn't necessary for many brews. And so when liquid isn't in motion you disconnect from the side of your bucket/carboy and only measure air temp?

@E K Brewer - good idea to use the drain hole

@Mark Farrall @Craigerrr - thanks!

I'm really looking forward on setting this up and starting up a brew. !

 

[BOB357]

Good use of a heating pad. No need to put it under or around the fermenter.
Same reasoning behind sensing air temperature when more passive control is all you need.

 

[Craigerrr]

I would definitely recommend thar you tape the probe to the carboy. The purpose of the build is to control wort/beer temp, and for the fridge to dissipate the heat produced by fermentation.

 

[Ward Chillington]

I would definitely recommend thar you tape the probe to the carboy. The purpose of the build is to control wort/beer temp, and for the fridge to dissipate the heat produced by fermentation.

Yeah, save your Loonies! Once the chamber air temp and the wort temp stabilize, there is hardly that much of a difference beyond a couple degrees in a 5 or 6 gallon carboy until you start dropping it down for something like cold crashing or fermenting at less than your ambient.

 

[sbaclimber]

Good use of a heating pad. No need to put it under or around the fermenter.

+1
mine just lies at the bottom of the fridge where the crisper drawer would normaly be...

 

[BOB357]

I've got time now to explain why I prefer sensing air temperature before and after active fermentation.
Most of the year our ground water is too warm to get wort down to a reasonable pitching temperature. Rather than spending a bunch of extra time and wasting more water, I cool to the ~85F range, transfer and put the carboy in my fermentation fridge to finish cooling. After several hours and verifying that my controller was displaying the set temperature, I'd aerate and pitch.

Using a thermowell: Once I returned the temperature probe to the thermowell, I discovered that the wort temperature was actually several degrees colder than the reading indicated before it was well mixed by the aeration process. I had been sensing the core temperature and the periphery was where the heat was being drawn from during the cooling. Without agitation the temperatures were considerably different.

Attaching probe to the outside: Without going into detail, attaching the probe to the outside of the fermenter had the opposite affect, so I tried just dangling the probe to measure air temperature. I found that the fridge ran shorter cycles and I wasn't under or ove rshooting the temperature setting.

Once I had aerated and pitched, the wort was at my set temperature throughout, so the probe went into the thermowell. At this point attaching the probe to the outside of the fermenter would work just as well. Very little temperature correction would be needed until active fermentation began to generate heat and cause enough agitation to equalize the temperature throughout.

I reasoned that the more passive temperature control approach of sensing air temperature would prevent over or under shooting temperatures when heating for a diacetyl rest or crash cooling.

 

[Craigerrr]

That makes a lot of sense Bob, thanks for the detailed explanation!

 

[Nosybear]

+1
mine just lies at the bottom of the fridge where the crisper drawer would normaly be...

I have my heating pad taped to the back of the upright freezer I use for a fermentation chamber. I've hit 90 degrees in there with it (saison, long story).

 

[56 Firedome]

About 5 years ago I came across a Mini Fridge & decided to use it in a Fermentation Temp Control Chamber. I removed the Mini Fridges door & attached it to an MDF box I had lined with 1" foam Insulation. I cut a hole in the box at the floor level of the Fridge & installed a 3" computer fan to push air out of the box & into the Fridge. At the top of Fridge is the "Ice Compartment". That's the cooling/evaporator coil. I mounted 2 3" computer fans to push the cold air out of the Fridge into the box. There's a grate in the bottom of the box to lift the carboy 2" above the floor of the box to allow surround air flow.

Since the carboy is in the box, my Temp Sensor goes is into the Temp Well through a hole in the lid of the box. I found when the cooling is on & the Fermentation is rolling, I need to remove condensation from below the Ice Compartment with a drain pan connected to a hose which drains to a pan under the Fridge. I would suggest a drain in the bottom of the box to help with cleanup after a vigorous fermentation blows off in the box.

I also use a heater called a Brewers Plate. It sits under the carboy, on the grate, in direct contact with the bottom. No issues. The Controller is an Inkbird, far superior to the Ranco I was using before. It can control the Temperature, automatically switching between Heat & Cool with no input from me. The Inkbird controls the 120V Heater & a Computer Power Supply to run all the 12V Fans.

As an old hot rodder, I'm always trying to squeeze a little more out of my equipment. I mounted a Computer Fan Rack, 4 3" 12 Volt fans, to the back of the Mini Fridge to push air over the compressor & other hot stuff. I got about 15% improvement in cooling. Next I will probably mount 2 more 3" computer fans to blow air over the outside skin. That would further boost the condenser performance. This is currently not necessary as I'm able to pull a fermenting carboy down to the low 40's & heat it to 80F. I've never noticed any issue with the Mini Fridge cycling off & on or over heating because of long cycles.

I use the Compartment for Fermentation Temp Control, heating to recommended Fermentation Temps, eg: 60 F for 2 days & 45 F for 6 days & to crash my Secondary while Dry Hopping & later to fine the beer before moving it to the Keg. Temp Control Control has improved my beers dramatically over the time I've been using it. I would recommend it as the 1st piece of major equipment you aquire.