Setting Up A Fermentor Fridge

[Tilt]

Righto - with all that hilarity of now deleted threads out the way....

The real topic of the evening at my place is "How to modify my newly purchased fermentor fridge (Fisher and Paykel/ Kelvinator c270 circa 2000 total internal height approx 1500mm, no freezer box) so it runs two separate chambers at different temps?".

I'm thinking of setting up a half way shelf with an mdf backboard that shields off the condensor plate at the back of the fridge.
I'll then insulate the top "chamber", place a heat pad inside and stick some insulation to the door at the right height so it effectively isolates the top chamber from the rest of the fridge.
The theory being that cold air form the condensor will fall to a cold conditoning/ lagering section at the bottom of the fridge, and the top shielded section will be warm enough for ale ferments.
I've got a temp controller to run the heating/ cooling circuits and will place the probe in which ever space is most critical at the time.

Has anyone done something similar? Any tips or traps to watch for if so?
Cheers

 

[raven19]

Oh boy, that sounds like a lot of energy would be wasted keeping two comparments at different temps.

Cant you use two fridges? :unsure:

 

[Tilt]

For sure - would love to, but I've got restricted space and am losing valuable small shed elbow room with just the one fridge now.
The future plans are definitely for a larger brewing space (... and bar/kegging set up...and 3 tier purpose built rig etc) but for now I have to work with what I've got.
Over winter I'm keen to do my first lager - but don't want to tie up the space for weeks, and not be able to brew an ale or two to keep stocks up.

 

[Nick JD]

I'd make a "warm" compartment in the fridge with little computer fan on a little intake (at the bottom of the compartment, not the top) that ran on a separate temp controller and came on to draw in warm outside air when it got too cool.

I think you'd be lucky to have more than a 10C differential though without killing you power bill or compressor.

 

[michael_aussie]

I'd make a "warm" compartment in the fridge with little computer fan on a little intake (at the bottom of the compartment, not the top) that ran on a separate temp controller and came on to draw in warm outside air when it got too cool.

I think you'd be lucky to have more than a 10C differential though without killing you power bill or compressor.

+1
If you are going to do this, this is the sort of thing you'd need to do, but I suspect you will also need to have a heater.

I saw a thread on an American site where a guy has done something similar with a freezer.... 1/2 for kegs, 1/2 for fermenting.
Insulation between the two sections, and a heater on the fermenting side.

I appreciate you have a space issue.... but I think there is something wrong putting a heater in a running fridge to try to end up with two different temperature zones... sort of like driving with one foot on the brake and the other on the gas..... just my opinion, no offence intended.

 

[brocky_555]

why don't you just brew two lagers if you have the space for it. Then you wont be tying up the fridge for one batch you will have two batches on the go.

 

[yum beer]

I dont know what the weathers like where you are, but seeming its NZ I asume winter is fairly cool.
I cant see why you cant brew lagers direct in the shed( maybe with a wet towel around fermenter if needed )-Ive managed a 5 degree reduction in temperature this way.
You should be able to do ales with a heat pad???.
Dont worry about the fridge till summer.

 

[Strange Brew]

For your insulation shelf the best way to do it would be by having an air gap which is resonably sealed to stop air moving through it. You could use two layers of mdf not even 10mm apart, even if you have to use thinner mdf with an air gap it would still be heaps better. You could glue a couple of wooden struts between the layers for support if needs be. I think insulation around the doors is an excellent idea. Obviously you are correct in putting the warmer compartment at the top.

Either way I'm sure what you end up with will be an awesome setup. I would just buy a second fridge and temp controller because I'm lazy.

Be very interested to see how you go with photos please!

 

[[email protected]]

This depends on the ambiant temp. If your at a temp where both ales and lagers need cooling then my thoughts would be play around with the cooler section first, and then calibrate the warmer section to maintain a 10c difference, without warming, to avoid the whole fridge fighting with itself. Place two fermenters full of water in there. Run the top half at 10C and then put varying layers of insulation between till you arrive at the happy zone.

But if you're at an ambient temp where your ale only needs heating, why put it in the fridge in the first place? Your better off keeping the fridge at one temp and just using the heater on the ale outside the fridge with a seperate temp controller.

 

[QldKev]

I would get another fridge, as I think it would be easier. But if space limitations don't allow it I think you could make it work.

I would put in a mdf/ply shelf at the height you want. You will need to ensure there are no gaps around it, including when the door fridge closes. I would use the top chamber where the cooling is as the cold one. Then cut two round holes as vents between the chambers. On one put a pc fan that is connected to a fridge controller that blows cool air from the top chamber into the bottom one once it gets too warm. The only thing at this level the cold air would drop through the vents even when the fan is not running causing the warm chamber to cool too much; to prevent this you will need to use lengths of pvc pipe to force the pickup higher into the cold chamber. I think the pipes would need to go at least 2/3 of the height into the top chamber. If you do need to heat the bottom chamber if the outside temp is too cold, then a basic form of heating could be also controlled by the stc1000, and the fan from the cold section would not need to come on.


A pic is worth a thousand words






QldKev

 

[Tilt]

Fantastic ideas fellas - cheers for the input and encouragement.

I'm gonna give this a go - and experiment to see if I can get this thing to hold a useful temp differential without the compressor shitting itself.
I like the 12V temp controlled fan circulator and double skin insulation suggestions.
Mate - and Qld Kev even did me a schematic, bloody fantastic!
I'll post pics and updates as I go to keep you informed on progress.

 

[Tilt]

but I think there is something wrong putting a heater in a running fridge to try to end up with two different temperature zones... sort of like driving with one foot on the brake and the other on the gas..... just my opinion, no offence intended.

None taken MA - I guess the idea came from observations that the warm chamber in the cold fridge is sort or what a butter conditioner is....and if they can design one to do this intentioanlly then why shouldn't I try to stretch it a bit (with some decent insulation to give it a fighting chance)
Cheers :beer:

 

[Nick JD]

A pic is worth a thousand words

Gtreat pic. Problems though, I have.

Hmmmm, what's to stop warm air rising up the right pipe?

When the fan comes on it'll cool the bottom compartment - and warm the top one through convection?

You need to block the right pipe to avoid balancing the system.

 

[QldKev]

Gtreat pic. Problems though, I have.

Hmmmm, what's to stop warm air rising up the right pipe?

When the fan comes on it'll cool the bottom compartment - and warm the top one through convection?

You need to block the right pipe to avoid balancing the system.

Yep the idea is the flow will warm the top compartment from the bottom, and the fridge will take care of cooling the top area. If the cooling pipes are long enough it should recirc air only to the warmer region of the cool compartment.

Would it be possible to help slow the natural convection current a basic one way value with just a piece of paper (or cardboard) over the return line? ie the valve will only open when the fan forces a positive pressure in the circuit.




The only other thing I can think of is some 240v fans have vents that close when they are turn off. This would stop any natural convention currents.

QldKev

 

[Tilt]

Good point NickJD.
I've pondered this a bit more.
Without the pictorial skills to back this up I'll have a shot at explaining my plans verbally.
Must admit I was planning on having the warm chamber at the top to use any natural convection flows to my advantage.
I'll try an insulated shelf (2 sheets of mdf separated by a polystyrene sheet) that seals against the sides and door when it closes but not at the back.
At the back I'll have another insulated mdf sheet that slides in a couple of grooves and at its max height extends up to at least 2/3rds the height of the fridge condensor panel at the rear.
This will serve to direct cold air via convection to the cold section at the bottom and shield the top section from cool air.

If I get caught with the top compartment not being warm enough I'll add a heater pad to the chamber and insulate it more (trial calibrating as I go as Paxxy suggests) to prevent the bottom from getting too warm.
If the top gets too warm I'll calibrate by lowering the rear sliding shield panel to let some cool air into the top chamber.

This is all an experiment - but hey, thats why I like this beer making lark - plenty of chances to muck about in the shed while pretending to do useful stuff!!

 

[michael_aussie]

...... but hey, thats why I like this beer making lark - plenty of chances to muck about in the shed while pretending to do useful stuff!!

+1 lol AND at the end of the day you get BEER.

 

[[email protected]]

Another idea would be to insulate it to all bugery so no cold gets In the warm compartment. Then install an adjustable vent between the compartments. The calibration won't work with varying ambient temps, so being able to easily adjust the insulation with a vent will be much easier.