Electrical – Please help me choose: single phase vs 3 phase HVAC compressor

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My residence is supplied with single phase power. The previous owner installed a single phase to 3 phase converter to run a 12 ton compressor (Phase Perfect PT355). I am getting rid of the 12 ton compressor and replacing it with 3 5-ton compressors. I can buy these in single phase or 3 phase.

Correct me if I'm wrong but if I'm taking single phase power, converting it to 3 phase power, and then running compressor, I'm not gaining any efficiency. Any increased efficiency of 3 phase compressor is going to be offset by the losses in converting from single to 3 phase.

The sticker on the converter reads: Input 240VAC, 50/60Hz, 1 phase 98A; Output 240VAC, 50/60Hz, 3 phase 55A. Also, the single phase compressors have a 10 year warranty, while the 3 phase units have a 5 year warranty.

Best Answer

That's a crazy-large unit for a house. That's why he was stuck with 3-phase.

Stand-by power consumption on that inverter is 240 watts. That will cost you between $240 and $500 per year in electricity simply to have it idle depending on your local electricity prices.

Generally there's no earthly reason to go from single-phase to 3-phase (variable frequency drive for tools notwithstanding).

Single phase motors aren't significantly less efficient; if they were, they'd need enormous cooling fins. Because inefficiency turns into heat.

I think you're better off with 3 units instead of one. Not least, if one fails, it's not such a big deal.