A Question For Fridge Mechanics

[paul]

Was talking in the pub the other day about beer fridges. Im using a chest freezer as a keg fridge. To make it work at the temps that I needed I removed the thermostat and replaced it with one from a fridge.

A fridgie there told me that a freezer isnt designed to work as a fridge and it'll make it shit itself. Its been working like this now for a few years and hasnt had problems.

Is this correct or is it bull? And, what are the differences between a fridge and a freezer?

 

[timmy]

Absolute crap.

There is a theory that running at higher temperatures than design specs will push the superheat up too high and cause the compressor to run hot.

The fact the compressor only runs part of the time prevents it getting as hot.

If you really want to be anal about it drop in 20g extra refrigerant. Just don't ask me to do it.

My old keg fridge has a gas leak and all I had to replace the charge was R22. Any fridgey would shudder but it still runs, although a bit hot. I only wanted it to get through summer.

Does this fridgey actually have a ticket?

 

[blue]

Is this correct or is it bull? And, what are the differences between a fridge and a freezer?


Yes you could shorten the life of the compressor. The defference is a freezer is a low back(LT) pressure compressor and a fridge has a medium(MT) back pressure compressor.
To aid in the compressor cooling the system is designed to have a sub cooling effect, this is supplied by the refrigerant coming back to the compressor.
So running the compressor at a higer temp would not allow for the lower temp needed for the sub cooling. Although saying that some compressors are rated for both LT and MT.

As well you could seize the compressors do to poor oil return to the compressor.

My old keg fridge has a gas leak and all I had to replace the charge was R22. Any fridgey would shudder but it still runs, although a bit hot. I only wanted it to get through summer.

Does this fridgey actually have a ticket?

I do have a ticket and have worked in the industry for some 11 years. Putting R22 into a low back pressure compressor is some thing not recommended. R22 normaly runs on Air/Con but is used in some refrig applecations desiged for its use.

Hey with the amount of people on this site that have converted a chest freezer to a keg set up seems to prove all the above wrong.

Happy brewing
Blue

 

[timmy]

Only 9 years in the industry here.

Blue what your saying is true but like i said, addinng an extra bit of refrigerant will drop the superheat and increase the subcooling at the expense of a higher coil temp (not an issue in a converted freezer). A

Any well built electric motor will run for years above its max rated current provided it's kept cool, a compressor is no exception.

Also the duty cycle of the freezer will be a lot less running as a fridge so less time running hot.

BTW I never said i recommended the use of r22 in a fridge just that i was surprised it still goes after 12 months You can hear it working harder as the bottles never used to rattle in the door.