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DC air conditioning units


Micky852
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My entire 12kw array is comprised of secondhand panels (more or less).  No issues so far.  First panels (SolarWorld SW245) were from a retired solar farm...they performed above expectations.  Remaining panels were from a solar farm that encountered severe damage during installation (unexpected windstorm), so they're technically pretty new.  No issues there, if you discount bent frames 😉.

As long as you get a significant discount on secondhand "used" panels, I would say "go for it."  Over time, the solar panels' output wattage will slowly decrease, but this will be characterized in the specification sheet for the panels, so we can run DC window AC on solar too?

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Split to separate topic.

I personally had a lot of interest in some Chinese mini-split units that ran on 48vDC.  I really like the concept, as there's theoretically a lot less "power handling", and it should be a lot more efficient, right...?  At least in my case, it turned out that the Chinese units' power rating was given at an arbitrary "room is cooled down" state, and NOT at the full-blast rated output.  After I did the math, it turned out that it was both significantly cheaper and considerably more power efficient to simply buy an off-the-shelf Pioneer regular 120vAC mini-split unit.

It is worth noting that the Chinese units I was looking at seemed to use the same 3-phase variable speed compressors that are used on the regular AC units--meaning that they had to generate a 300vDC supply from 48v anyhow.  (They weren't using native 48v compressors.)  Not to mention I get a U.S. backed warranty with Pioneer, instead of some Chinese company saying, "good luck."

While I really like the concept of a direct DC-powered A/C unit, it has to show some significant efficiency improvement over a regular AC-powered A/C to be viable.

For example, my Pioneer 12,000btu (1 ton) A/C is rated at 21.5 SEER, and I've seen it max out at around 8 amps in A/C mode--that's 960W.

The native DC A/C you linked is rated 750w.  But the problem is that they don't indicate what heat load this is at.

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I   plan to use  my 14000btu  portable AC  to directly cool   your  12000 watt  GS inverter in patio outside   and use the GS  inverter to run the  4 ton house AC  240 vac directly  .    The  temperature in the patio now is 102 degree  and the  PS  inverter   will  only run 1 hour  and  shut  down  .     No  way to  cool the PS inverter  but wait  2 hours  for  the   ASL 9   transformer to cool down  .   

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Back in the good old days( pre Amtrak HEP ) railroad cars used 32, 64, or 110 VDC to run the cars A/C. When Head End Power became available and the cables mandated for any cars used on Amtrak trains, most owners converted to 230 VAC 3 phase units. From 1951 to about 1960, the crew car for the communications crew of the Communication Car, Presidential had ice bunker  A/C cooling with just 32VDC fans and pumps ( same as would be found in the Presidential Pullman ) but had 32VDC freezers and refrigerator. The Communications car itself had 32VDC A/C. It needed it as just the lights in the Comm room would generate a lot of heat. And then you had the two transmitters and the receivers in the car. Those transmitters generated a lot of heat as they were tube type units. Those same units however were still in use into the 90s as they were the only things that could be guarantied to work under many conditions. So while the RRs switched to AC A/C units, many are learning of the benefits of having DC units. Thing is, I don't know of any that are sealed units. All were motor and compressor units which sooner or later will leak Freon at the seal of the shaft.

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Always interesting to see how things were done in another country.  Long haul passenger trains in my state, QLD Australia, weren't air-conditioned at all until 1953 when a new set of diesel hauled trains replaced the old steam hauled wooden carriage trains that only had fans.  The new train had a dedicated generator car that provided 240/415 50Hz AC.  That set ran until 2014 when they were replaced by a tilt train (diesel and electric versions depending on where in the state it runs) that is permitted to run up to 160km/h on QLD's narrow gauge track.

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Posted (edited)
7 hours ago, TheButcher said:

Always interesting to see how things were done in another country.  Long haul passenger trains in my state, QLD Australia, weren't air-conditioned at all until 1953 when a new set of diesel hauled trains replaced the old steam hauled wooden carriage trains that only had fans.  The new train had a dedicated generator car that provided 240/415 50Hz AC.  That set ran until 2014 when they were replaced by a tilt train (diesel and electric versions depending on where in the state it runs) that is permitted to run up to 160km/h on QLD's narrow gauge track.

In between the ice bunker designs and the DC units was a third type that use pumps and fans. It was steam ejector A/C. Where the steam drew a vacuum on a water tank and the evaporation/boiling of the water gave up the heat. The chilled water then, like in the ice bunker style was pumped up to the radiator unit in the ceiling where the fan blew air into the rest of the car.  Ice Bunker A/C was very good at cooling a car down quick as by the time the water had made two passes in the system it had cooled down to 34°. It could take a car in 90° temps inside and out and cool it to 70° in about 15 minutes. It also was very good at pulling the humidity out of the air such that the unit needed two 3/4" drains to dump it. Excess water to the needs of the system was dumped automatically when it was was coming back from the coil before being pumped over the ice again. The units were rated at 2 tons per day and the bunkers held 1400 pounds at a time each. The steam vacuum systems required add in water all the time to make up for the use. So it came out of the cars water tanks. Almost all of the cars built in the 40s had Ice bunker A/C while late in the 40s they started the switch to mechanical A/C. In some cases, simply sliding units into the bunkers to replace the ice and still using the rest of the systems already in use. All of the units used Freon 12. Cars that ran in the SW of the US had started using DC A/C in the middle 1930s. The car my friend had was built in 1936 for the Santa Fe Railroad and had DC A/C. It got AC A/C when it was rebuilt to meet Amtrak requirements in 1994-96. It is the oldest Stainless Steel car that meets those specs and one of the earliest Stainless cars that were interchange capable instead of units like the tilt trains are.

Edited by Waterman
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And by the way, while the car was rated by Amtrak for speeds not to exceed 110MPH, on one stretch of the NEC, near Philly, we clocked in on the GPS at 115MPH and was also clocked the old fashion way, by RR approved watch.

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