Run two air conditioners on 30 amps – Wow!
Yes, this appears to be true. You’ve all seen the ad for SoftStartRV™ at RVtravel.com over the last few weeks, and likely read my first article and watched my intro video on how it works. The more I experiment with the SoftStartRV, the more impressed I am with its ability to reduce air conditioner peak startup currents by at least 50% compared to the manufacturer’s standard hard-start capacitors.
So here’s a little more info on what kind of data I’m gathering for my next full-scale report on this technology. But first, let’s take a brief look at the various loads a rooftop air conditioner imposes on the shore power or generator.
Note on the left side of the graph there’s a brief section of zero power while the air conditioner fan and compressor are off waiting for the thermostat to call for cooling. You’ll then see a 8.3 amp inrush current from the fan starting up by itself, which quickly settles down to 2.8 amp of current once the fan mass is up to speed. A few seconds later the compressor kicks in with 35.7 amps of peak current, which in many cases is too much for a smaller 2 kW inverter generator to deal with. But within half a second or so the run current of the compressor motor settles down to 11.4 amps of current, which a quality 2 kW inverter generator can easily deal with and still have some watts left over for battery charging and such.
It’s the 35 amp peak current that gets us into trouble, and not just for generators. If you’re trying to run two air conditioners from a single 30-amp shore power connection, that peak inrush current from a second air conditioner is often enough to trip the pedestal breaker.
Now here’s a more detailed graph of me comparing the inrush current of a stock Penguin II air conditioner before and after I installed a SoftStartRV in place of the stock capacitor. As you can see from the before and after diagrams, there’s a reduction from 35.7 amps of inrush current with the stock capacitor down to 17.7 amps of inrush current from the SoftStartRV modification.
Yes, this is me measuring and graphing everything myself on my test bench and computer, not a jpg I lifted from some sales literature put out by the manufacturer. This does appear to be the real deal, and in another week or so I can produce an even more detailed comparison that’s sampled 48,000 times a second with an accuracy around 1 ppm (part per million). I’ll then be able to show a split-screen video of the before and after starting current envelopes including a real-time peak current graph.
You can watch my first video discussing how this SoftStartRV technology works HERE.
In the meantime, SoftStartRV has been kind enough to offer a discount page for anyone who wants to order one, two or three units. Yes, if you’ve got a coach with two or three air conditioners you will indeed need two or three of these SoftStartRV units. But in the long run it should be worth it with less circuit breaker and generator trips, allowing you to run more of your other electrical things while staying cool in your RV. You can get your discounted SoftStartRV HERE.
Mike Sokol is an electrical and professional sound expert with 50+ years in the industry. His excellent book RV Electrical Safety is available at Amazon.com. For more info on Mike’s qualifications as an electrical expert, click here.
Email me at mike (at) noshockzone.org with your questions.
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