I have just started an HVAC business in Columbia, and while I have only been a tech for 4 years, I have someone working with me who has been in the business for 25+ years. He has worked on a little bit of everything over those 25 years. We encountered a problem with a commercial building downtown. There is 3 phase power run to the building. All 3 legs of this 3 phase are run to the disconnects for the air handlers and the condensers, and yet the units themselves are single phase. My associate who has been in the field for 25 years says he has never seen anything wired this way. It is 3 phase wye, with one leg simply capped off at the disconnect. The owner says he has had nothing but problems with the units for years, and that he has replaced more compressors in this one building than in all of the rest that he owns combined. Again these are single phase, 208v, 60hz, compressor motors. I have been working for him for about one year and have found problem after problem that the last guy left behind. These compressors are popping like crazy, just after their 18 month warranty is up, and I don't have any good explanation for why they are doing this. We found fuses laying everywhere on the roof with the disconnects, and I guess they got tired of replacing fuses so non-fused disconnects were installed.
Again, it has always been my practice to never marry the two. And I also know that there is a difference between single phase motors, and three phase motors. But is this an acceptable practice, or are these compressors dying because of the way they are wired?