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View Full Version : 7.5 ton Aqua Products Glycol Chiller alternative



dfalken
07-23-2012, 11:20 PM
I missed it by a few weeks! 7.5 ton Aqua Products Glycol Chiller was the size of chiller I was looking for but I ended up building my own. Using two 60k btu AC compressors and passing the refrigerant through coils inside 250 gallon glycol insulated tank I am having built. We'll see how it ends up working, but I think it should work well, and the dual compressors give me redundancy. If one goes down I could stumble along on 60k BTUs while it got fixed or replaced (at about $1k a pop they are basically throw aways). Anyone every tried this successfully?

Starcat
08-12-2012, 02:49 PM
Your compressors mentioned will be working at refrigeration duty rather than AC duty and as such will be derated from the original design BTU/hr. The range the evaporator coil ends up running in can be used to roughly determine what kind of real capacity to expect from MFG. data. I would ask the compresor OEM what the compressors will do at 20F evaporator which is typical design figure. We have an older type built up system that uses a plate type heat exchanger made by Alfa Laval which ports to a good sized well. The way the condensing units are sized for this setup has proven to be tricky.
I would be interested in hearing how the coils were sized, the control arrangement, and how the system performs.

SC

dfalken
08-12-2012, 07:10 PM
Your compressors mentioned will be working at refrigeration duty rather than AC duty and as such will be derated from the original design BTU/hr. The range the evaporator coil ends up running in can be used to roughly determine what kind of real capacity to expect from MFG. data. I would ask the compresor OEM what the compressors will do at 20F evaporator which is typical design figure. We have an older type built up system that uses a plate type heat exchanger made by Alfa Laval which ports to a good sized well. The way the condensing units are sized for this setup has proven to be tricky.
I would be interested in hearing how the coils were sized, the control arrangement, and how the system performs.

SC

I realize that at the lower cooling temps the compressors will be derated and consequently I am going with 40% more cooling power than my peak need (plus I have a 10HL tank that acts as a buffer during peak demand as well). I haven't actually figured out the exact derating factor but from what I've read, with my 40% overcapacity I should be way more than covered. The good thing is that AC compressors are cheap enough that oversizing substantially is really not an issue. The coil size was determined by my cooling guy (not sure what formula he used) and he will also be taking care of the control arrangement. The glycol tank is being built now and I should have the system complete in about 2 weeks. I would offer to report back in 2 weeks but I have so much stuff on my plate right now that I am sure I will forget, however if you remind me, I will be glad to do so.