Ladies and Gentlemen,

Here is the situation: I have a basic climate chamber room approximately 11' X 23' X 8' that is insulated with 2" high density foam insulation panels. For testing purposes in the past we have needed to keep the room at a set temperature of 60 +/- 2 degrees Fahrenheit. We were able to do this using a basic in-window air conditioning unit that we modified to run a little cooler than normal. We mounted it in one of the chamber walls. The climate room in located inside a warehouse where the ambient temperature ranges from around 55 degrees Fahrenheit in the winter to 80+ degrees in the summer.
Some new tests may require us to maintain ambient temperatures inside the chamber of 44 degrees Fahrenheit and 14 degrees Fahrenheit. I am looking for a cheap and reliable way to make this happen. By cheap I mean less than $3K so we're talking about a very small budget. Unfortunately I don't get to make budget calls so before any of you tell me I'm being cheap, please realize I have little to no say in the matter. If it can't be done for that price, so be it, but I'm interested to hear from anyone who has constructive thoughts or advice.
One idea we considered was using a reefer unit like those used on cooled semi-trailers. I know there are a few electric reefer options, but most of them cost $10K and used ones are difficult to come by, although I've seen one or two for around $3.5K. We also wondered if it would be possible to modify a gas/diesel powered reefer unit to run on electricity without too much modification or rebuilding. We have 3-phase and potentially 1-phase input to work with. Any thoughts or input on this idea would be appreciated.
I'm sure alot of you have concerns about the way the room is insulated. While I will be the first one to admit that the test chamber is far from perfect, for now let's just assume that it will be sufficiently insulted and enclosed.

Thank you all for your time and consideration!

-Joel