I was curious if the compressor in a typical home air conditioning unit runs at a consistent pressure? I am trying to get an idea for the efficiency of the unit, and how much more efficient would the system be if I were able to cool the pressurized coolent further. I am considering a heat exchanger with cool water from a river, or well, to suppliment the normal air exchange.

So, on a hot day, use the blower to cool it down to the 90 degree temp outside, and then go through the water cooler to see if you can run it down to below 70. How much more efficient would that make the system? Would my compressor run at a lower pressure? Or just kick on less frequently?

Am I correct to assume that the units with a higher SEER efficiency rating run under a higher pressure? And therefore have a higher temp difference across the system?