My gosh, I have to ask this. I am hoping to intrigue Poodle Head or some of the older techs here that have seen it all.
I have a farmer friend of the family that sells produce. He is trying to rig up walk in cooler, and when i say trying, I mean he has already done it. He has an 8 x 10 utility building with R13 insulation and drywall nicely finished. The door is sealed up pretty decent. He has a concrete floor, couple shelves.
Now here is the kicker. He is using a 5,000 btu window air conditioner to cool this contraption. Of course the a/c unit only goes down to 60, but it is maintaining 60 except the other day when it got up to 95 outdoor ambient he said it got up to 70.
So he is asking me if I can make the unit cool lower than 60, preferably around 45, but 50 would be ok, but really he wants 45. I said I would have to have a medium temp stat and cycle the compressor with it. Of course I will have to have a coil temp of about 25 to get 45 if I recall, and my biggest worry is that if I can get it down to 45 with this A/C unit is how low will it take the humidity down, because you don't want low humidity with produce. Oh and I told him when it got to 95 he would probably need to have a fine mist of water spraying on the condensor coil.
For the time being I moved the temp sensor of the a/c away from the coil, so maybe it will drop a couple more degrees. I know this is kind of funny, but you got to give the guy props for trying, and he is a farmer so I am wanting to help him out some if I can. Now I haven't done a load calc on a cooler in about 3 years, so I am wondering what btu removal is required to cool a structure like this down to 45 degrees. Again it is 8 x 10, probably 8 foot celing, R13 insulation with drywall, something like wood sheathing sideing. I don't know if we can use the U values from manual N on a refrigeration calc, but don't see why not.
He just asked me right now if the 5000 btu is enough. maybe I could plug the numbers in on my load calc program with a 55 degree TD. Wow, that sounds like it would take a lot of btu's. Kind of interesting, but mostly entertaining this is. I am really hoping that he had this building already constructed for another purpose and just decided to try this out. I am pretty sure he is willing to buy a bigger A/C unit to get it to work though.