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hvac:solar_ac [2018/03/25 15:19]
frater_secessus created
hvac:solar_ac [2024/02/05 14:25] (current)
princess_fluffypants [12v/24v/48v DC Units]
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-====== I want to run A/C off solar ======+[[lifestyle:words_of_wisdom|Words of Wisdom]]:  "It's not a lost cause..  we just seem to be at that frustrating cusp where it's technically possible with current technology, just not easy or cheap." -- thatswhatsup((http://www.cheaprvliving.com/forums/showthread.php?tid=18184&pid=206165#pid206165))
  
-Understood, we all would like to do that.  We wish it were simple and inexpensive enough to be common.  It'not common Some folks do have A/C but the great majority of them are getting power from a [[electrical:generator|generator]] or [[electrical:shore_power|shore power]].+> Running AC on [an inverter] is rich man'game -- HaldorEE((https://diysolarforum.com/threads/anyone-running-a-ac-unit-from-a-modified-sinewave-inverter.19723/post-229971))
  
-Unfortunately, if you are reading this you probably haven't done the math.  Prepare for some unpleasant news, because at this point you probably aren't familiar with:  
  
-  * how much power it takes to run the A/C unit continuously +====== Running A/C off solar ======
-  * how much power it takes to //start// the A/C unit (usually much more than running it) +
-  * how much [[electrical:solar:output|solar panels are derated]] in actual use.  If it's hot enough to run A/C it's hot enough that you are already losing 25% of your solar panels' rated output due to voltage depression. That is before [[electrical:12v:wiring|wiring]] and [[electrical:solar:charge_controller|charge controller]] losses. +
-  * how much space those panels will require+
  
-And that's just considering running the unit in optimum solar conditions in the daytime Running A/C at night requires a magnitude increase in [[electrical:12v:deep_cycle_battery|battery bank]].  That is either $$$, heavyor both+**TL;DR - It is technically possible, but very expensive and complexBe prepared to spend at //least// $5,000, and probably closer to $10,000.** 
  
-There is a reason people [[camping:snowbirding|snowbird]] (follow good weather) and use [[hvac:roof_vent|roof vents]] to control [[hvac:dehumidifier|humidity]] and temperature+More expensive than the A/C system itself is everything you'll need to power it. A/C takes //huge// amount of electricity; to operate successfully off grid you'll want at least 8-12KwHr of lithium batteries, 800-1200w of solar, and the required massive charge controllers to run it all. If you want to run the A/C //overnight//, be prepared to double that battery bank size.
  
-===== one exception ===== +If you are reading this you probably haven't done [[electrical:12v:dailypowerrequirements|the math]].  Prepare for some unpleasant news, because at this point you may not be familiar with:  
-The one exception to this dilemma is available if you live in the desert; [[hvac:swamp cooler|swamp coolers]] do a good job of cooling in areas of low humidity+ 
 +  * How much power it takes to run the A/C unit continuously 
 +    * Even the most efficient 12v A/C units draw upwards of 60 amps at full blast; that's over 700w, //continuous//. That will drain even the biggest battery banks //extremely// quickly. 
 +    * Using a 120v system through an inverter will increase that power draw even more. 
 +  * How much power it takes to //start// the A/C unit (Usually a lot more) 
 +    * Some units have a "soft start" function, using a bunch of capacitors to help the compressor start while smoothing out the massive spike in current draw 
 +  * How much [[electrical:solar:output|solar panels are derated]] in actual use.   
 +    * If it's hot enough to run A/C it's hot enough that you are already losing 25% of your solar panels' rated output due to voltage depression. That is before [[electrical:12v:wiring|wiring]] and [[electrical:solar:charge_controller|charge controller]] losses. 
 +    * In order to generate 700w of power to run an average system, you'll need at least 1200w worth of panels. And that's //just to run the A/C unit itself//. That's not giving you any overhead to charge your batteries or do anything else. 
 +  * How much space those panels will require 
 +  * How much money those panels will cost 
 +  * How much money big [[electrical:solar:charge_controller|solar charge controllers]] cost 
 +  * How much money you will spend on the massive runs of finger-thick copper cabling to connect it all together 
 + 
 +And that's just considering running the unit in optimum solar conditions in the daytime.  Running A/C at night requires a magnitude increase in [[electrical:12v:deep_cycle_battery|battery bank]], and then even more panels that are capable of both recharging the batteries //while// running the A/C during the hotter parts of the day. See [[https://www.fordtransitusaforum.com/threads/7-2kw-altrntr-42seer-minisplit-1-11kw-solar-20-5kwh-lfp-120-240-3-8kw-inv-chg-cfx375dz-25g-fw-tank-awd-2-lift-265-75-16-spare.81387/|this build thread]] of someone who does. 
 + 
 +And it's still not going to give great results; it might be okay for taking the edge off on a very hot day (bringing the inside of the van down to 80f while the exterior temperatures are over 95f), but you're not going to be able to keep the van at 68 degrees on a hot day just off of solar. 
 + 
 +Especially because (rather paradoxically) running A/C off of solar requires that you park your van in the sun; which means the inside of the van will get //MUCH// hotter than it would if you simply parked in the shade. This puts you in a weird catch-22 where you can't run the A/C without parking in the sun, but parking in the sun means you have to run the A/C much harder than your solar can sometimes keep up with. 
 + 
 +---- 
 + 
 + 
 +===== Running A/C off of shore power ===== 
 + 
 +This is very practical, and it's how RVs have been doing it for many years. The A/C systems run natively on 120v AC(Alternating Current) and are getting power from a [[electrical:generator|generator]] or [[electrical:shore_power|shore power]].  
 + 
 +120v AC units are vastly more common, and much cheaper than the 12v or 24v DC units. These are usually roof-mounted, smaller ones can be had for as little as $500 and are very common in the rest of the R/V world. If you have a a big enough inverter, it's possible to run them off of a house battery bank as well (although you'll suffer some efficiency losses). 
 + 
 +See [[https://www.thervgeeks.com/rv-air-conditioner/|this article]] for a good overview on what may be needed. 
 + 
 +---- 
 + 
 +===== But I saw someone on TikTok doing it! ===== 
 + 
 +The things you see on [[lifestyle:faq_instagram|social media]] are either: 
 + 
 +  - Rich people with extremely expensive vans that they paid professionals to build 
 +  - "Influencers" who spend a weekend or two in the van every month and only post pictures or stories from the most ideal situations 
 +  - Completely faked and just being shared around to generate views 
 +  - All of the above.  
 + 
 +There is an extremely small subset of people who have successfully installed A/C in their own van, and been able to use it off-grid for extended periods of time. They are people with an in-depth understanding of the issues and the money and space to make it happen. It does not stand to reason that the average person with average resources and commitment will make the trip from idea to implementation.  
 + 
 +There is a reason that most people [[camping:snowbirding|snowbird]] (follow good weather) and use [[hvac:roof_vent|roof vents]] to control [[hvac:dehumidifier|humidity]] and temperature.  
 + 
 +---- 
 +===== I am rich, foolheardy, or both, and still want to run A/C off of solar ===== 
 + 
 +Don't say we didn't warn you, but here's some links to people who have done it successfully. Start with [[http://www.cheaprvliving.com/forums/showthread.php?tid=29867&pid=373299#pid373299|this post by trebor]] then check out posts by people who have done it: 
 + 
 +  * [[https://www.fordtransitusaforum.com/threads/42seer-minisplit-1110w-solar-20-5kwh-lfp-120-240-3-8kw-inv-chg-dometic-cfx375dz-25g-fw-tank-awd-2-lift-265-75-16-full-spare.81387/|20kw of Battery, 1,100w of solar - Van Gogh]] 
 +  * [[https://www.fordtransitusaforum.com/threads/undermountac-com-install-on-2021-transit-ext.91886/|Undermount AC install on a Transit]] 
 +  * [[https://www.reddit.com/r/vandwellers/comments/13zau8r/solar_panel_question/jmr5x5i/|Pleasedontmindme247]] 
 +  * [[https://www.youtube.com/watch?v=ijk2Z-ebevw&t=314s|WorkingOnExploring]] -- exceptional walk-through of the power and equipment needed to run A/C in a highly-insulated truck camper.  
 +  * [[https://www.youtube.com/watch?v=EaVCNQ_59lM|jimindenver]] (youtube) 
 +  * [[https://www.cheaprvliving.com/forums/showthread.php?tid=30489&pid=381116#pid381116|iTripper]] 
 +  * [[https://encrypted.google.com/search?hl=en&q=site%3Ahttp%3A%2F%2Fwww.cheaprvliving.com%2Fforums%2F+TucsonAZ+a%2Fc|TucsonAZ]] 
 +  * [[https://www.cheaprvliving.com/forums/showthread.php?tid=25403&pid=315206#pid315206|IGBT]] 
 +  * [[https://www.cheaprvliving.com/forums/showthread.php?tid=25482&pid=316619#pid316619|BradKW]] 
 +  * [[https://diysolarforum.com/threads/mppt-question.24235/post-286138|SolarInTheCity]] 
 +   
 +Also see  
 + 
 +  * [[https://diysolarforum.com/threads/dc-air-conditioner-minisplit-rooftop-anything.23184/|this thread]] on DC A/C options and  
 +  * [[https://www.reddit.com/r/vandwellers/comments/p1ejqw/hey_party_animals_anyone_know_of_a_place_that/h8d7zbm/|daficco's advice on installing a mini-split]]. 
 + 
 +---- 
 + 
 +==== 12v/24v/48v DC Units ====  
 + 
 +AC Units that can operate directly on DC current off of your house batteries give some efficiency gains as you don't need to run them through an inverter, but they are very expensive. Higher voltage systems allow you to use much thinner cables for power, which can be a significant cost savings over longer runs. 
 + 
 +**All-in-one roof units** offer a much simpler installation and are usually around $2,500; Dometic has their [[https://www.dometic.com/en-us/outdoor/rv-and-van/rv-air-conditioners/dometic-rtx-2000-262673|RTX 2000]] unit as a good start for most vans. The relative ease of install comes at the expense of taking up quite a bit of roof space (and consequently reducing your available space for solar panels). They're heavy as well, and generally you'll need to reinforce the roof to hold the weight. 
 + 
 +**Split units** separate the evaporator/condenser/compressor into separate parts which have to be plumbed together. This can offer a lot more flexibility in terms of where to mount stuff, but also makes the installation much more complex. [[https://www.cruisencomfortusa.com/|Cruis-n-comfort]] and [[https://undermountac.com/|UnderMountAC]] are the two most common split options, and will generally run $4,000 for the units themselves. 
 + 
 +Beginning in about 2023, cheap Chinese 12v mini-split systems have started to come down to almost acceptable prices ($1k in the USA, or less if you can wait the 1-2 months for shipping from China). Reports on them have been mixed; similar to the Chinese knock-off [[hvac:heating|diesel heaters]] they come with almost no instructions and often missing a few minor parts (most users report some fittings or couplings being missing, or needing to crimp their own lines). Warranty and installation support is non-existent, but if you can fiddle your way through the psudo-DIY installation some people have reported positive results.
hvac/solar_ac.1522005554.txt.gz · Last modified: 2020/10/11 19:48 (external edit)