I saw a lot of cool stuff at the Hershey RV show last month, and the manufacturers are sending me demo gear to try out. Pretty cool, as I love setting up experiments, gathering empirical data and coming to meaningful engineering conclusions. I don’t do guesses – I do science.
Here’s a topic that I’ve pondered for years but never had a good reason to look at more deeply than a howdy-do: hard (or soft) start capacitors for air conditioners. Briefly, rooftop air conditioners on RVs draw a LOT of peak current when the compressor kicks in. This starting current can be many times the average draw compared to when the compressor is actually running. That’s generally not a problem when you’re plugged into pedestal power because the PoCo (Power Company) can supply enough peak current to literally melt all your wiring in a flash. (And yes, I’m using the word “literally” properly in this context.) But generators are a different story entirely.
Now, the real problem is when you’re using a small generator like a Honda EU2000i to run your RV’s rooftop air conditioner. While 2,000 watts (actually, 1,800 watt continuous) is plenty of power while the compressor is running, the surge current supplied by the starting capacitor generally causes the generator to trip due to the peak current. There have been a number of possible solutions offered as hard-start, soft-start, and whatever-start capacitors. However, the engineers at Micro-Air have designed something called the EasyStart™ which has definite possibilities. A discussion with their engineering group divulged how it works internally.
Basically the EasyStart has a smart chopper circuit which “learns” the peak current your compressor needs to operate and then adjusts the start current based on what your generator can supply. It learns over the first few starting cycles which tunes EasyStart to your particular air conditioner. This is how it determines how to control the amount of peak current it can supply to the compressor without tripping the generator. And voila, even a Honda EU2000i should be able to start a 15,000 BTU air conditioner at sea-level reliably without the need for a second companion or larger generator.
This technology could also useful in campgrounds with only 30-amps of pedestal power that might have trouble starting your air conditioner. And it’s potentially a great addition to solar inverter/battery technology being used to run a smaller air conditioner. For air conditioners with less than 9,000 BTU capacity, there’s another smaller model EasyStart.
Cost is affordable at $299. Installation seems simple enough with just a four wires to connect, and the design looks like it should work. However, I can’t qualify this just yet until I do a few experiments, gather empirical data, etc.
So Micro-Air has already sent me a demo EasyStart unit, Dometic says they can send me a 15,000 BTU air conditioner, and Honda will loan me an EU2000i. (I already have an EX1000 and an EU3000iS in my shop, but no EU2000i.) See the graph from Micro-Air with a comparison of peak starting current of a 15K BTU air-conditioner with (red line) and without (blue line) the EasyStart technology.
As I said, the technology looks very promising. So once I get all the demo gear in place I’ll run some starting experiments with a digital storage oscilloscope so we can see exactly what it’s doing and how well it works.
Yes, I do have too much fun. Stay tuned for a followup article on compressor soft-starting technology. It will likely be a few months before everything arrives and I can set up the test, so please be patient. Good science isn’t quick – it’s thorough.
Let’s play safe out there….
Mike Sokol is an electrical and professional sound expert with 40 years in the industry. Visit NoShockZone.org for more electrical safety tips. His excellent book RV Electrical Safety is available at Amazon.com. For more info on Mike’s qualifications as an electrical expert, click here.