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okpiddler · 03-04-11, 09:40 PM

I may be able to get some prices on some good tube in tube heat exchangers. The exchangers in my Climatemaster have the refrigerant running on the outside and water running in the middle. Or you could make one. I do not rememer exactly how long mine was but it was close to 8' and I know it was between 7 and 9 for a 9k btu comp. I just slid the copper inside flexible pvc leaving the copper at least 6 inches longer on ea. end. 3/8" copper in 3/4" pvc. Roll it up nice and tight, secure with zip tyes. Then slide on a PVC T at ea. end, point your water inlet and outlet in the proper directon and glue the tubing to the t's. Then put a reducer bushing, 3/4" slip by 1/2" FNPT over ea. end and glue them to the T's. Easy so far, here comes the hard part to keep it from leaking. This is what I did and it worked but there was not much pressure on it. I know it would have leaked it I had like 15 or more PSI. You may have a better Idea or maybe use all copper and run the water in the middle. Anyways next I slide on copper reducers 1/2" MNPT by whatever slides over the copper. I think 1/4" in the plumbing dimensions. Then put on some teflon tape and rector seal thread sealant. Thread on and tighten after applying flux to copper. Keep the threads cool with a small stream of water and sweat it together. You could make an extension on that copper reducer so you could do the brazing 2 or 3 inches away. I have done the same thing with all copper straight tubing. I can go out in measure it before it goes to scrap. I only used it for testing with barrels of water.
Right now my evaporator is flooded or close to it. An accumulator will catch excess so liquid will not go to the compressor. This makes for good heat exhchange. On the other hand my condenser is like 95% super heated vapor. I do not have to open my TXV much before I see vapor bubbles in my sight glass. This keeps my high side pressure low enough not to trip my safety lockout switch that I have set at 350 PSI. My plate HX's are only rated for 435 psi.
My exchangers are rated for 17k btu and I am only using 9K. My hot side brass circulator pump is too small. I should have done a pressure drop test across it before ordering the pump. I guessed. I am still very happy with the unit though. Bills are low.
Hopefully you have time and don't get in a hurry. Do it right because it is going to be around for a long time.

03-04-11, 09:40 PM	#628
okpiddler Lurking Renovator Join Date: Feb 2011 Location: NE Oklahoma Posts: 15 Thanks: 0 Thanked 0 Times in 0 Posts	I may be able to get some prices on some good tube in tube heat exchangers. The exchangers in my Climatemaster have the refrigerant running on the outside and water running in the middle. Or you could make one. I do not rememer exactly how long mine was but it was close to 8' and I know it was between 7 and 9 for a 9k btu comp. I just slid the copper inside flexible pvc leaving the copper at least 6 inches longer on ea. end. 3/8" copper in 3/4" pvc. Roll it up nice and tight, secure with zip tyes. Then slide on a PVC T at ea. end, point your water inlet and outlet in the proper directon and glue the tubing to the t's. Then put a reducer bushing, 3/4" slip by 1/2" FNPT over ea. end and glue them to the T's. Easy so far, here comes the hard part to keep it from leaking. This is what I did and it worked but there was not much pressure on it. I know it would have leaked it I had like 15 or more PSI. You may have a better Idea or maybe use all copper and run the water in the middle. Anyways next I slide on copper reducers 1/2" MNPT by whatever slides over the copper. I think 1/4" in the plumbing dimensions. Then put on some teflon tape and rector seal thread sealant. Thread on and tighten after applying flux to copper. Keep the threads cool with a small stream of water and sweat it together. You could make an extension on that copper reducer so you could do the brazing 2 or 3 inches away. I have done the same thing with all copper straight tubing. I can go out in measure it before it goes to scrap. I only used it for testing with barrels of water. Right now my evaporator is flooded or close to it. An accumulator will catch excess so liquid will not go to the compressor. This makes for good heat exhchange. On the other hand my condenser is like 95% super heated vapor. I do not have to open my TXV much before I see vapor bubbles in my sight glass. This keeps my high side pressure low enough not to trip my safety lockout switch that I have set at 350 PSI. My plate HX's are only rated for 435 psi. My exchangers are rated for 17k btu and I am only using 9K. My hot side brass circulator pump is too small. I should have done a pressure drop test across it before ordering the pump. I guessed. I am still very happy with the unit though. Bills are low. Hopefully you have time and don't get in a hurry. Do it right because it is going to be around for a long time.