Tom Klein

I have read articles stating that scroll compressors are more efficient than piston models and that if you want to save electricity, a scroll model is the way to go. Then in the next article I read where scroll compressors have at least a 5% less heat output than a same size piston model. If this is the case, I see the scroll running longer for the same amount of temperature rise in my pool, which I would think equates to a higher electric bill.......is this the real story??? Also hear that the piston is way more efficient as the outside ambient air temperature gets higher. True or false and at what air temperature does that become a reality?? I like the scroll for a number of reasons, less parts, better compression, etc., etc., but I also want the most heat, in the least amount of time, for the least amount of electricity.   

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Marcus Miller
Dear Mr. Klein:
Thank you for writing to me. I hope that you and your family are well. You ask great questions. I am afraid that depending on who you talk to you will get a different argument. I can only tell you what I have seen in the field which might be right or just my experiences. The way I understand it is that piston compressors give a little more heat due to the friction of all the moving parts and higher compression. You will pay for that buy losing a little efficiency. Sometimes it is worth it if you have a big pool. There is no difference in reliability. That I know for sure. I serviced both for years. A compressor failure is such a rare event anyway. Some people say a piston compressor makes more noise. I usually can't tell. They can vibrate a bit more because they have more moving parts and sometimes if anything is lose on the machine it might sound louder. I had one under my bedroom window for 5 years and it didn't bother me. It didn't run at night though. Usually scroll compressors get a little more efficiency out of their heaters. Rome and Heat Siphon have got some great BTU and COP numbers out of piston compressor though. Heat Siphon uses both kinds. Rome only uses Trane compressors. Same as Pentair. Trane (American Standard) piston compressors have been around forever. I think over 60 years. They have an incredible reputation in the air conditioning world. If has been explained to me by one of the heat pump engineers at one of the larger pool heating companies that if you have a piston and a scroll compressor and the piston is 10,000 BTU's higher than the scroll at 80 degrees F then when the outside temperature drops to 60 F they will have equal BTU's. Everything that I just said will get you into an argument with an engineer someplace. At the end of the day the heater the higher COP should give you a lower electric bill regardless of the BTU's. The main thing for me is to get a heater from a major manufacturer, with their name on the heater that had a reputation for customer service, a long warranty and you should be fine; and I know who they are and who is doing everything right.
Sincerely,
Marcus Miller
360 568 3718
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