# What are options for cooling a 5 cubic meter proofing box [closed]

I would like to make a proofing box, a piece of bakery equipment used control the environment of leavened dough while it rises.

The electronics part of my project is almost complete.

It has a temperature and humidity sensor. If the temperature goes below desired temperature it should energize the heater. I used a remote power socket and Arduino to control the heater. I may use an infrared bulb for heating.

Electronic components inside the box are an arduino pro mini 5V, DSTH01 digital temperature and humidity sensor, 433 MHz RF transmitter, 16x12 lcd screen, two leds, two resistors. There is also a power socket rated 240V AC 1200W. I also plan to put a pwm controlled Noctua 12V DC fan which dissipates about 1.2 watts in to the box.

I used Arduino to control remote power sockets as described here.

I haven't made the box yet but lets assume that the volume of proofing box is about 5 cubic meter (176 cubic foot). This is enough to hold a large rack of prepped baked goods.

A dough proofer is a warming chamber used in baking that encourages fermentation of dough by yeast through warm temperatures and controlled humidity. It is also called a proofing box, proofing oven or proofing cabinet.

It is used in bulk fermentation and final fermentation stages of bread making. For example after shaping, for the final fermentation the dough pieces are placed in a temperature and humidity controlled cabinet called a proof box. In this context the word proof means fermentation.Typically the dough will almost double it's volume about an hour and a half at 24 ° C (75 ° F) an a humidity of 75 %. If we want to decrease final fermentation time we might increase the internal temperature about 28 ° C (82 ° F) Thus, the final fermentation time is reduced to 1 hour.

For sourdough this temperature might be 20 ° C (68 ° F) or lower.

As far as I know, these temperatures are usually used. But for box I took a wider temperature range because maybe in future I might use it to ferment yogurt.

Operating temperature, that is inside the box might be between 20 ° C and 40 ° C (68 ° F and 104 ° F) The box will stay inside.

Temperature ranges outside the box might varry between 15 ° C and 40 ° C (59 °F and 104 ° F)

Temperature accuracy of the box should be ±0.5°C. It should respond to outside temperature changes quite fast. Let's say if I open the door of the box in one minute or less, it should be able to reach the old temperature again.

At first glance I planned to use a peltier module. But someone with experience in electronics said that the peltier module couldn't have enough cooling.

Controlling humidity is as important as controlling temperature and large air currents are undesirable.

What might be the options for cooling a 5 cubic meter (176 cubic foot) proofing box.

• You've specified the operating temperature, but not the interior requirements. When the outside is 40 C, what do you want the interior to be? And have you considered insulating the box? That will make your job much simpler. – WhatRoughBeast Feb 2 '19 at 22:49
• Can you edit your question to explain what a "proofing box" is? Many of us will have no idea. – Transistor Feb 2 '19 at 22:56
• If the inside temperature will always be higher than the outside temperature (as I expect for a proofing box), can you just blow in some outside air to cool it down? – The Photon Feb 3 '19 at 0:12
• I edited your question a bit to bring up some of the relevant concerns for a bakery proofer. If it is another type, you should edit your question again to provide the same type of information, but for your application. Peltiers make good heaters in some low power low temperature applications because of their capability to move heat rather than just produce it, giving them >100% electrical efficiency. If you need to move a lot of heat it may become prohibitively expensive or move out of your skill level. The amount of power you need, as Elliot is indicating, depends on how fast heat leaves. – K H Feb 3 '19 at 1:23
• For a hobby project I would just start with a used fridge, it's insulated. You can add a heater internally for maintaining temperatures above ambient. – sstobbe Feb 3 '19 at 2:40

$$\5m^3\$$ is an awkward size in terms of HVAC.

A household heat pump would be too expensive and would be overkill. A window air-conditioner unit might work, but again it's probably too much. Such solutions would also have the problem that they'd be moving around a lot of air.

I suggest piping cold water. A great length of thin copper pipe certainly won't be free; this one might be long enough for the intended effect, or it might not.

Depending on circumstances you may be able to just run tap water through it. That will keep your cost down, but if this is really a piece of industrial equipment then that would be too wasteful.

Assuming that it's always cooler outside the box than inside, and that you don't need to be moving a lot of heat out of the box, then a big loop (or a series of smaller loops) would work. You'll just pump the water in a big circle and it'll spend about as much time outside the box as inside. I suspect this will be enough to keep bread dough from overheating.

If you need more cooling power than that, then just have the cool side of your heat exchanger be inside a vat of water to which you can add ice as needed.

And if you're building a "real machine", you could try something like this.