Idea for refrigerator heat
 

Has anyone ever made a system to vent refrigerator heat out the roof, in the summer?

People have thought of this idea, I don't think I've ever seen it done. One of our members ducted the heat out through the wall into the next room over to keep it away from the fridge though (along with a few other things).

Ecomodded Fridge saves $$ (added foam insulation)

Most refrigerators function as a sort of dehumidifier. They cool and dry the air in the box, condensing some moisture in the process. The moisture either drains to the bottom or forms frost in the freezer. This frost is periodically melted during defrost mode, and lands the same place as the drained moisture. Lots of the heat transferred out of the box is put back into the water as it evaporates in the warm air stream, recycling this wasted heat/cold back into the box. Some heat leaks into the box through the insulation, lots leaks in when the door is opened. The net heat gain is the compressor power, usually 100-300 watts while running.

To be honest, I don't know if you could achieve net home cooling from the unit without major mods. Although the heat transferred out of the box is greater than the waste heat, the temperature rise of the condenser isn't drastic like a large heat pump. In the summer, the exhausted air may not be heated enough to reach the outdoor temperature. Passive ducting into a cool basement would be more effective.

However, I could be wrong. Please experiment with this idea and post your findings along with pictures of your tinkering. Others have suggested splitting a fridge, moving the condenser and compressor outside. Others have contemplated water heating/cooling systems, but never with a refrigerator. You could break some new ground here.

I think the potential issue with this approach is that the air which is vented out the roof is going to have to be replaced with new air coming into the house. Now if you happen to have a basement or some other cool location that the incoming air can be pulled from, then you'll see a benefit... but if you're on a slab (like I am) and the replacement air is as warm as (or warmer than) what you're venting out, then you're not gaining anything.

I agree! that incoming air is the issue, if you vent the back of the fridge it'd be wasteful to have it just be an open vent so you'd need an active damper and if the air exiting is the same temp as the outside air then you gain nothing because the make up air is just as warm only it's warming up a different part of the house.

You paid for that heat, best option in my mind would be to use it instead of dumping it.

But if you did have a sealed duct with cool incoming air coming from a crawl space or basement, then sure, do it!

On a slight tangent with heat recovery, I have a customer with a compressor room that is always ridiculously hot. There is another part of the factory that is really cold in winter, so I have been asked to put in a smart extractor system. This will dump heat in the summer and then put the heat into the cold areas in winter, whilst keeping the compressor cooler and raising the efficiency. Efficiency is increased, as the colder the air intake temperature, the more dense it is. I guess the smart move would be to have the compressor intake from straight outside, especially in winter.
The heat dump in summer could be used to preheat the incoming water for handwashing etc.

I like the idea of using the heat for water. It could make the fridge more efficient and the heat wouldn't be wasted.