Quote:
Originally Posted by stevehull
Jeff, would a change in the cap tube make this setup (air to air changed to water to air) markedly more efficient?
Steve
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That there is the 64 thousand dollar question. The answer is:
Yes, if you know what you are doing.
Most capillary tube metered systems are matched to the evaporator under certain (ASHRAE) design conditions. Air-source window aircon units are not meant to be operated below, say 60 degF ambient, and the evaporator will freeze up solid if forced to run. Contrary to common understanding, a colder evaporator is not always a better evaporator.More mass flow is better, as long as the compressor doesn't see any liquid.
For a water-source heating arrangement, a change in the cap tube will properly feed the evaporator with the proper mass of liquid to improve efficiency. Since water absorbs much more heat than air to force the same temperature change, a shorter cap tube will move more mass and heat. However, lots of trials must be run at various conditions to determine the length that is appropriate for the new arrangement. Unless you are dead broke or have an insatiable love for tweaking, swapping in a TXV is a cheap way to improve efficiency that takes a whole lot less time.