Any trick to sizing a coaxial condensor?

jeff5may · 07-02-17, 12:35 PM

For your setup, water loop or well and coaxial HX outside and DX window unit HX indoors, you could use the existing cap tube in the window unit if it's not plumbed with a reversing valve. The cap tube will be matched to your indoor coil, and the water side of the cycle will do a superb job at dissipating your waste heat. The thing to do in this case is to watch your high side pressure and the water entering and leaving temperature. The water flow should be sufficient to heat the discharge into the range of body temperature or higher to keep the indoor coil from frosting up. This will get you good dehumidifying action and sensible cooling. Too little water flow and your head pressure goes through the roof, killing efficiency.

When and if a reversing valve goes in, you can run the thing with the original cap tube for simplicity. If your water temperature doesn't drop too much in winter, the cap tube may not try to freeze the coaxial HX. Again, watching the pressure and water temps will let you know what's going on with the refrigerant cycle. Measuring the suction line temperature leaving the coaxial HX will allow you to calculate the superheat. Some superheat is good, but too much is not good. Window unit design targets the superheat to never fall below about 15 degF. Sometimes it rises into the 30's. With a txv you can do better, but with extra performance comes extra plumbing.

07-02-17, 12:35 PM	#12
jeff5may Supreme EcoRenovator Join Date: Jan 2010 Location: elizabethtown, ky, USA Posts: 2,428 Thanks: 431 Thanked 619 Times in 517 Posts	For your setup, water loop or well and coaxial HX outside and DX window unit HX indoors, you could use the existing cap tube in the window unit if it's not plumbed with a reversing valve. The cap tube will be matched to your indoor coil, and the water side of the cycle will do a superb job at dissipating your waste heat. The thing to do in this case is to watch your high side pressure and the water entering and leaving temperature. The water flow should be sufficient to heat the discharge into the range of body temperature or higher to keep the indoor coil from frosting up. This will get you good dehumidifying action and sensible cooling. Too little water flow and your head pressure goes through the roof, killing efficiency. When and if a reversing valve goes in, you can run the thing with the original cap tube for simplicity. If your water temperature doesn't drop too much in winter, the cap tube may not try to freeze the coaxial HX. Again, watching the pressure and water temps will let you know what's going on with the refrigerant cycle. Measuring the suction line temperature leaving the coaxial HX will allow you to calculate the superheat. Some superheat is good, but too much is not good. Window unit design targets the superheat to never fall below about 15 degF. Sometimes it rises into the 30's. With a txv you can do better, but with extra performance comes extra plumbing.