Walk in cooler and air conditioner losses

[IsaacCarlson]

I built a walk in cooler with an air conditioner and temp controller. I ran it for a week and took measurements to check efficiency. It used roughly 33,000 btu/day. I thought I could improve on that and started taking measurements to target heat gain/loss. I couldn't find anything wrong with the cooler itself or the doors. Everything was airtight and well insulated. I started messing around with the laser thermometer and pointed it inside the blower housing of the air conditioner. WOW! A 20* difference!? What the.....ok, this is getting fixed.

I grabbed my regular thermometer and poked it in the blower housing to measure the air temp rather than the housing temp. The air coming out was at least 2* different from when it went in there. That is definitely a problem. I punched the numbers into a heat exchanger app and it said I was losing at least 10,000 btu/day through the blower housing!

The air conditioner was promptly removed from the wall and the case was removed. The blower housing was just a thin piece of plastic with no insulation at all. I covered it with flexible foam, foiled bubble wrap, and aluminum tape, put it back together, and reinstalled it. I turned it on and started my timer. The run times were WAY lower. They went from 56% to 19%! I was losing 22,000 btu/day through the blower housing before the insulation.

It is now near zero loss. The cooler only uses 11,670 btu/day to maintain temperature and the cost to run is ~34 cents/day or $10/month. I think that's less than we were paying for netflix, lol.

[oil pan 4]

Is that an old air conditioning unit?
All the newer ones I have looked that deeply into used a Styrofoam blower housing.
Is that your meat cooler?

[IsaacCarlson]

Yeah, it's my meat cooler. The blower housing has some styrofoam on the circumference, but it isn't actually insulated. It's weird. Here is a picture of my insulation job. That whole housing was just thin plastic. I cleaned and painted the foam when I had it apart for cleaning and thought "hey it's insulated", but didn't really pay attention. There was no insulation between the inside and outside, but there is now.