perennial proportional cooling water temp control question

archibald tuttle

Looking for a proportional temperature controller for a cold water chiller that feeds fan coil units for air conditioning.

This is twin 7 and 1/2 ton compressors in a single Trane chiller unit, about 15 years old. The supplied controls use an manually adjustable differential to call the second stage. I put in a spdt switch to change the lead lag assignment each year, but there is no 'cool weather shut down'. I'm was going to engineer that with a simple air conditioning control thermostat independently, but it occurs to me that while proportional water temperature control might not be as relevant or money saving in this context -- given that the operating range of water temperatures sawy 35 to 65 F is much more constrained than on the heating side, it still might squeeze a few more energy pennies out of the system if I were to replace the existing controls with some analog of a PC 702 designed for two stage air conditioning rather than two stage heating.

Anyone aware of any control company working in this area. Last time I checked I don't believe there was such a control.

Thanks

Brian

Empire_2

Thoughts

Have you checked out Tekmar Controls? I have used them on the Trane 40 ton chiller, but for the life of me I cannot remember the mod # of the Tekmar that I used. Your Lead/Lag can be controlled in a variety of ways and I think they even offer this option, but I did not use it. Also I don't know how many fans you have , but watch that you are energising them after lead lag changes. That is depending how it's wired.

My .02

Mike T.

mtfallsmikey

How 'bout

Trane itself or Johnson controls? Do you run DDC? If you are in the Metro D.C. area, let me know.