Fridge And A Fan To Help

[Gout]

Hi brewers, i have a very large fridge i bought just to brew (100Lt brews or less in). Its rather new and seems to work well in a normal state, however with such a large thermal mass it seems to leave the compressor on for longer than i think is kind.

also the rear of the fridge is sealed/covered not like an old fridge with the pipes etc open to air flow ( more like a freezer)

the cold plate inside freezes over then keeps running so i was thinking a fan to blow on it to move the temps around the inside the help cool the wort down and remove it from the chiller plate might be a good idea?

secondly a fan and a thin space over the rear of the fridge might help remove heat outside the fridge???

i think the fridge may have cut out due to over heating a few times - running so long to get to temp

any ideas?

 

[seravitae]

When you say cool the wort down, do you mean after you've finished boiling it in the kettle, you are transferring the hot wort into the fridge to chill it to ferment temps? If so, I highly suggest you do not do this!

A fan inside a fridge will help temperatures be more uniform and in extreme cases with a large mass that needs to be cooled, it can help bring the temperatures down a bit, as the air in the fridge itself acts as an insulator, natural convection of air in a fridge is pretty darn slow and as such your rate of energy transfer is quite low. Regardless of what you're doing, a fan isnt a half bad idea.

Also as for the sealed nature of the condensor outside the fridge, again not a half bad idea putting a fan on this. The covering may be a blessing in disguise - it is easier and more efficient to actively cool a condensor if it is boxed up.

What are the temps like in the fridge? If the compressor is running long time *and* the fridge is warm, you are probably overloading it. But if the cold plate is iced over, the fridge air is cold and the compressor is running a lot, something is wrong with the fridge perhaps.

 

[Gout]

no sorry i mean say 24deg or 20deg wort but as yeast takes off - then when i want to drop the temps to keg


eg its ok at keeping a fridge temp in a normal condition but moving such a mass seems a struggle and i see in new high quality fridges they use fans so thought it might be an option...

the rear looks nice in a fancy house but as a brew fridge i thought it might help take away some heat

i plan to only run the fans when the comp. is turned on.

i also want to hook up the power meter to measure it against the inside fridge to really see if its good or bad.

 

[seravitae]

If the back covering comes off easily, then try it and see how it affects the system.

Yeast does make quite a bit of heat, i'm not sure how much though so I couldnt do much calculations.

But lets say you have 100 liters of fermented goodness at 20C and you want to bring it down to 8C for keg temp (i hav eno idea what a good keg temp is, pulling random number out my arse)

100L of "water" dropping 12C requires removal of 5 megajoules of energy and with a 450W compressor @ COP 3 that would be roughly 61 minutes to drop the thermal mass to this temperature. However, this is only if the evaporator coil is like, inside your fermentor. Since air is a pretty good insulator i'd almost bump running time up by about 5-10 times, and you can see your compressor is going to run for a loooooong time.

It seems that since you talk about changing temperatures that you have a Tempmate or some other digital temp controller on the fridge. May I suggest that instead of just lowering the temperature from 20C to 8C (or whatever keg temp) instantaneously, that you be 'gentle' and reduce the temp a few degrees and give it an hour or so, to see if that stops stressing the compressor as much?

 

[Gout]

sorry sera again i have not explained myself well - its either the fresh air or maybe the brew

I place the beer in at 24deg lets say - i try wait 5hrs for it to settle to temp of 20 then add the yeast and then it kicks off say 5 hrs later - i have a large starter) over the week its on its limit i think - it was hot in melbourne ( for melb temps 35 odd down the side of the house) and i found it 3 times not running due to what i think was a thermal cut out.

I am running a mech. temp controller but looking to get a electronic system asap. also to set it up i only used 50Lt of wort

the inside was frozen and the back was hot - seems like it just could not get the temps away on the outside

i thought ( i know nothing about fridges mind) that it couldnt get the hot temps away and the cold temps into the wort

seems like i should
a) try as is with the power meter
B) try fans ( i have them and it wont use much power and might make it more effective
c) stick to ales

 

[seravitae]

sorry mate just ducked out to see some mates.

The back of a fridge should be quite hot, but if you believe that the back is 'too hot' then yes, it could be because the radiator is not able to remove heat to the environment at a fast enough rate. Most fridges are designed to have a low thermal flux (the amount of energy passing through the insulation) and the food inside does not actually generate any heat, whereas fermentation does, so the fridge will be put under more stress to remove that heat.

I think a good step to try might be to actually stick a thermometer somehow to the radiator and monitor the actual radiator temperature. A fridge mechanic or even maybe calling the fridge manufacturer and asking to speak to one of their techies might land you some information about what is the maximum temperature the system will operate correctly at.

The radiator itself should be able to handle a large heat load, however, the compressor itself uses some of the cool refrigerant to keep the compressor temperature down - if the fridge is running constantly then the compressor can heat up a lot which may be causing your thermal cutouts. I would definately try to measure the temperature of the radiator and find out if you're pushing the refrigeration system outside it's healthy range. If so, you could mod the radiator (void warantee) by having it degassed and either replace it with a better one, or weave copper wire between the lines to give the radiator more surface area. These though would require a lot of effort, possibly more than it is worth.

If the inside chill plate is icing up and the back is hot then it sounds like the fridge is working 'fine', but may be unable to deal with the heat load. It is interesting though, because one would expect that if the heat load was quite large that the condensor/chill plate temperature would be quite high (no icing). Honestly i've exhausted my very limited knowledge on the topic. There are some fridge techies on this forum so hopefully you will be lucky and one of them might pick up on something I missed or described incorrectly.. good luck mate.. if i think of anything else i'll post

 

[glaab]

no sorry i mean say 24deg or 20deg wort but as yeast takes off - then when i want to drop the temps to keg

? is this a fermentation fridge or a keg fridge ?

 

[FNQ Bunyip]

Gout , YES to both ... a fan on the back will help with the removel of hot air ....

and a small computer fan on the inside will help heaps with keeping the cold air moving around and such be at a more stable temp...

I've got computer fans in everything except the food fridge ... 3 beer fridges ,fermenting fridge , deep freezers, and even put a small one in my 80lt ENGEL....

Anything that makes life ezyer for a fridge is good up this way....

cheers

 

[Supra-Jim]

Gout, does your fridge have a defrost timer/cycle? I had problems with a fermenting fridge (defrost cycle) and on hot days it would cut out. Found out it was the timer for the defrost cycle 'sticking' in de-frost mode.

On my fridge this was a small unit with a little rotating dial on it. As the the fridge ran, this would rotate slowly, and at a certain point, break the cicruit to the motor (hence stopping the fridge and allowing it to defrost). My problem was that it wasn't restarting.

Simple cure, i removed the module and simply replaced it with a short length of wire to the permanently connect the motor circuit. The fridge was controlled by a fridgemate.

Cheers SJ

 

[Gout]

Thanks for the reply to you all, a lot of points to consider and some i didnt even know about. I am using an old mech. thermo that I used 4 years ago - I think maybe that drives the fridge to hard maybe. I will upgrade to the fridge-mate and see if that improves.

I will also try a fan inside to help move the temps about.

Where should the temp probe be placed? on the chill plate or next to it? or in the air to give an average reading?

Fan wise - should it blow onto the chiller or draw air off it? ( also i assume there is the issue of it cavitation if its just a fan without and shroud)

Bellow is some rough pics

Edit: its a frost free and it gathers liquid outside in its tray - i assume that means it has a defrost... the fridge will come back on later so maybe its doing the defrost and i thought it was over heated.... in defrost the compressor wont run correct?

 

[Supra-Jim]

Yep, during de-frost, the circuit power the compressor is broken (i pretty sure this is how it works). Hence i removed my defrost control module and bridged the compressor circuit.

I suspect that maybe, the fridgemate was switching off the fridge during defrost cycle and then when it restored power to fridge, it was still stuck in de-frost mode.

Cheers SJ

 

[Gout]

this sounds like you may have hit the nail on the head - i will have to work out how the defrost works and see if i can fix it.

as i can defrost when the brew is finished each time

thanks

 

[KGB]

I'd be putting a fan inside straight away, even if it doesn't fix the problem it will make your fridge more efficient.

As for the probe, many people put it in a tube filled with oil or water, some people wrap it in foam. The idea is to keep it protected from short term swings in temp, such as when you open the fridge door. Don't put it on the chill plate.

 

[komodo]

I've got computer fans in everything except the food fridge ... 3 beer fridges ,fermenting fridge , deep freezers, and even put a small one in my 80lt ENGEL....

OT : I thought the 80L engels had a fan in them? or is that just the fridge/freezer? how do you find the 80L engel? I've an 80L waeco and I'm concidering selling the damn thing and buying two smaller units as it takes up too much space for as weekend away.

 

[FNQ Bunyip]

Sorry for the Hijack Gout :

Komodo: PM sent ..


Yes put the probe into a jar of water / metho ..

as for the fan don't get over tecnical with shrouds ect I just wedge it between the shelving so its a cross flow ..past the cold plate ...
I leave mine running all the time but others have them just coming on with the fridge ,, If you have an old PC get busy or head down to the computer repairs joint , my local blokes let me pull 5 fans out of old machines out the back for 2 bottles of brew...

Cheers

 

[Gout]

i have a few fans kicking about that i need to use or throw out for room so i will install and see how things go i guess.

To help with the load on the fridge i set my temps to say 20 ( the wort may have been 22-25 depending) let that cool over night then pitch yeast and lower it to say 17 etc and 15 odd after 24 hours, seems to work ok abart from being a pain having to keep changing the settings - but i am often looking to see if the yeast has kicked off at these times so not such an issue.

it was getting the 40Lt down to cold cond. stage that gave me the problems.

I will try the fans (as i have them) and report back any change when i can brew next .... waiting on yeast starter

 

[komodo]

What size fan are you guys using inside your fridges??
80mm? 100mm? 150mm?

As for the fan outside the fridge. My parents had a fridge a while back which was the "enclosed" back type and it had a small barrel type fan at the top to draw air out. They have a liebherr fridge now and that has a fan in every compartment (its a 3 door fridge/freezer). Not sure if this one has a fan on the back and its not real easy to check. Though I'll have a snoop

 

[FNQ Bunyip]

100mm here in 5 fridges and 1 deep frezer..

OT: 40mm in the Engel .. lol..

cheers