I have a friend named Tom who is a bit of a
Curious Fellow. He and I had traded thoughts and academic discussion on the power requirements of RV air conditioners and the power supply capabilities of various generators, so when I finally decided on the generator I wanted, Tom was interested in the real-world application of the technology.
I decided to buy an inverter-style generator because they are very quiet, and I know several people who have been quite satisfied with the reliability and performance over the years of both the Honda and Yamaha models. Based on the power requirements of my A/C unit, the
Carrier AirV low-profile 15K BTU w/ heat strips, I felt that a 2000W unit wouldn't provide quite enough power. Yamaha makes a 2400W unit that just barely covered the max-load current draw for the Carrier AirV, so I eliminated that as an option as well. A that point, it seemed that the two most viable options would be a 3KW unit (which were quite heavy and bulky), or to tie two 2K units together in parallel (which would cost more than a single 3K unit). I was worried that my wife wouldn't be able to handle a single 3K unit if I were unavailable to help for any reason, but I wanted to avoid spending the extra $$$ that two 2K units would require, as well as finding the additional storage space while in transit.
But then my buddy Steve (aka ByamCaravanner) pointed out to me that Honda had just come out with a new 3K unit, the Handi3000. It weighs close to half of its big brother, and has convenient wheels and a large folding handle for easy transport. Drawbacks include its smaller fuel tank, and it is also a bit louder than the larger version. Still, the advantages seemed well worth it to me, so that is what I purchased.
Part of our discussion centered on the current and voltage requirements for a standard RV A/C unit, and how well a generator could supply that. Since the AirV requires approximately 14.1A at max capacity (including both compressor and blower current draw), and the Honda genset can supply 21.7A at rated capacity, I felt comfortable that the A/C unit was receiving adequate current during steady state operation.
But the words of caution from various members at the AirForums resonated strongly with me, concerning the potential damage to the compressor if operated in low voltage conditions. Though these units are designed to operate at nominal 110-120VAC, the words of warning from those "in the know" was that anything under about 107VAC could be very severely hazardous to the health of the compressor. I take these warnings seriously, because these A/C units are much too expensive to risk by operating outside acceptable parameters.
So, armed with my trusty Fluke Multimeter, I set out to determine whether or not I might be destroying my compressor and costing myself major bucks.
Voltage at the generator 20A outlet output (the 30A was obviously in use, driving the Airstream power mains). The load for this test was a couple of lights and a TV turned on inside.
Next, inside, with no load at all:
Now, with the A/C blower and heat strips on:
And finally, with the A/C blower and compressor on, and several lights, as I would normally use it:
So I see a voltage drop of only 2.2V from the no-load to max-AC-load state, which makes me feel pretty confident that I am not risking any damage to the compressor.
Next, I'm going to perform the same tests while hooked up to my 15A house breaker through 50' of power cable to see what kind of voltage drops I see in the system. Since the A/C should draw a max of 14.1A, it should be okay to run in steady-state from the house power without installing a dedicated 30A circuit for it, but the initial startup does require considerably more current, so it's likely that the current and voltage will fluctuate quite a bit before the system reaches its steady state.
Hope everyone has a great Thanksgiving!
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