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Culture War Roundup for the week of January 9, 2023

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Oh, they definitely get worse. Even the Mitsubishi has lost 1/3 of its capacity by 12ishF. But the good ones are way overbuilt for their ratings now, and the vapor injection where pre-expanded gas subcools liquid going into the evaporator does a nice job of boosting capacity at lower temps.

(If you can explain how those work, I'd be eternally grateful. Been trying to wrap my head around it for ages--I get how a regenerator heat exchanger works on a steam turbine, but this is way more confusing somehow)

What do you mean by doesn't feel hot? The outlet air from mine is pretty low by furnace standards: 125F on autofan, down to 95 if I turn the fan up to get more airflow over the condenser.

and the vapor injection where pre-expanded gas subcools liquid going into the evaporator does a nice job of boosting capacity at lower temps.

Subcools liquid going into the evaporator? Subcooling in HVAC and refrigeration usually refers to how much sensible heat(that is, over and above that required for condensation) was released in the system in the condenser coil. Unless of course they're(whoever "they" is) referring to the condenser for the heat pump as an evaporator because that's what it is when working as an air conditioner, in which case gas refrigerant used to cool the system from the heat of operation(mostly the compressor motor) is routed directly into the condenser to add heat when the reversing valve(part that switches between an air conditioner and a heat pump) is in use. That would be mildly unconventional terminology but not any worse than usual marketing lies from HVAC manufacturers.

What do you mean by doesn't feel hot? The outlet air from mine is pretty low by furnace standards: 125F on autofan, down to 95 if I turn the fan up to get more airflow over the condenser.

Honestly a lot higher than I remember air coming out of a heatpump.

Nah, this is a weird new thing they do where some of the liquid coming out of the condenser is split off to a separate expansion valve, then through a heat exchanger where it subcools the main liquid line like a mechanical subcooler, then gets injected back into the middle of the compressor at medium temp and pressure without going through the evaporator.

https://youtube.com/watch?v=74o3bPemVUU

Good video on it. I understand how extra subcooling increases capacity and that the injected vapor cools(?) the compressor and reduces outlet temps by shifting to a lower isentrope curve(??), but the rest of it is beyond me. Apparently it works out thermodynamically similar to having a two-stage cycle with two separate compressors coupled with a heat exchanger, like they use for the big cold temp industrial stuff.