A typical 13500 RV roof unit draws around 13.5 running amps with approximately 70 'locked rotor amps' in the first second. This is what prevents their ability to run on a small 2000 watt generator. Restarting within five minutes after the unit shuts off is also a problem since the pressure in the system needs to equalize before restarting.The new inverter technology is readibly available in residential units. With the innverter system there is no 'locked rotor amp' surge since the compressor gradually ramps up to speed. The running amps are signifcantly reduced, for example the Super Air 12000 btu unit starts up at 1 amp and gradually ramps to a peak of 6.9! As the temp comes down to the set point the compressor gradually reduces its speed (and amp draw) rather than shutting off. This not only gives more stable control but eliminates the restart problem, but then thats already been eliminated by the soft starting feature.Why are we stuck with ancient technology in our rv roof units when we could easily be cooling them with a small 2000 watt generator with power to spare. The company to produce this will surely take over the RV market overnightSo my question - does anyone know of a company planning to offer a rooftop inverter air conditioner?

Not sure why we are so behind? My relatives in Japan all have residential Mitsubishi AC using this technology for as long as I can remember. Though more expensive as they are designed for individual room(s) use, and not whole house per se. Cost must play some kind of factor whether the market is willing to pay a premium?

Moved from Forum Technical Support

Spanishstroll wrote:So my question - does anyone know of a company planning to offer a rooftop inverter air conditioner?Although this doesn't answer your question there are currently A/C units available the manufacturer claims will successfully start and run on a 2K genset, the Atwood Air Command being an example. The Coleman branded A/C series also includes a PS (Power Saving) model that draws much less power than a standard 13.5K BTU model and should also be capable of running on a 2K genset.Obviously any advancement in technology would be welcome but that said most folks don't care how this may be achieved, just that it is. ;)

Also used in Australia for many years, mutch cheaper than ducted and usaly only 1 or to units used as the cooled air travels fairly easy in open designed homes. Both ouer sons used this, one had one unit the other 2. Many use them for ther trailers now, Daikin makes a outside unit for 2 inside most small units les than $1000.Frank.

is this 'inverter' technology or is this 'variable speed' compressoror does the variable speed compressor run off some voltage changing electronics ?

Air conditioning on a small generator | Good Sam Community

15 Replies

Slownsy
Explorer
Jul 29, 2016
I don't know wher you get that it works fine and at a chipper prise than Inverter airconditinor, in Australia they are less than $1000 and use way less pover.
Frank.
AirSupport
Explorer
Jul 28, 2016
I upgraded from a 13.5K to 15K BTU A/C when I ordered my trailer years back. The salesman thought I was wasting the extra $150. I use two paralleled EU2000i's and I also installed a hard start capacitor to the A/C, even though the Honda's ran the a/c "as-is" from the factory with no problems. But with the hard start capacitor, I did notice that the generators didn't choke down for a millisecond like they used to upon starting the A/C. It's just easier on the generators.

With the twin Honda's, I can run my a/c and my coffee pot simultaneously without a problem. I don't want to pay for an inverter a/c, when the current technology works just fine and at a cheaper price.
SoundGuy
Explorer
Jul 23, 2016
wa8yxm wrote:
But when HONDA says 2,000, they mean something like 1,760.. That is the big issue.

Bad example as the Honda EU2000i will easily sustain a surge draw of 2000 watts for 1/2 hr, continuous 1600 watts. Yamaha's EF2000iS has a 20% smaller engine and although also sporting the same ratings is expected to sustain a full surge draw of 2000 watts for a mere 20" ... BIG difference. I've owned 2 EU2000i gensets and it will meet the specs Honda claims.
MrWizard
Moderator
Jul 23, 2016
PWM.. Pulse width modulated motor controllers have been used in machine tools for 30 years or more
I have worked on many CNC mills that use that technology
Installing, maintaining , repairing, CNC machines was my career for many years

We never called them inverters
Three phase 480vac in , three phase variable voltage and frequency out to the motor
Frequency controls the speed

When I think inverter, I don't think of PWM motor controllers
Motor controllers are a lot more complicated than the basic DC to AC inverter

And yes I guess you could say motor controllers evolved from inverter technology
wa8yxm
Explorer III
Jul 23, 2016
I know this.. With "Traditional" technology when one of my 13.5 amp 13,500 BTU A/C's died I replaced just the upper (Rooftop) part with a different make, this one is also 13.5 amps.... but 15,000 btu. More cool, same power.

It does take a bit more to kickstart it though (A hard start kit might fix that).

Thus technology is improving even with the traidtional stuff.

The big problem is the generator makers.. Now I used to have a GENRAC-1000.. And when Genrac (Well Briggs & Stratton) made this traditional but fully enclosed power supplier they did something strange. It said "1,000" and it means "1,000" (and then a bit) I had no problems drawing enough current to trip the 10 amp breaker (1,200 watts) when my electric chain saw jamed.. It ran a Window A/C in my house and more.

But when HONDA says 2,000, they mean something like 1,760.. That is the big issue.

Moral. Bring your magnifying glass to the sales room and READ THE FINE PRINT.
rbtglove
Explorer
Jul 23, 2016
We have a Honda 2000 and have run two different 13500 units with it. Struggles at high altitude but otherwise no problem.
prichardson
Explorer
Jul 23, 2016
The big factor is cost. Another consideration when applied to RV applications is that those types of systems are more are more sensitive to electrical service problems.
steveh27
Explorer
Jul 23, 2016
I bought the 13500 Dometic High Efficiency AC when my original 11k unit died. It draws under 11 amps & runs well with my Honda 2000. Everyone who may boondock should have this one.
Kayteg1
Explorer II
Jul 23, 2016
I have been on the fence for buying RV variable speed water pump for about 15 years.
Having roots in Europe, I know that what is consider "New" technology - is catching much faster in Europe than in US.
You can interpret in several ways :
European own less, while the energy is more expensive - so they spend more time doing the homework on energy efficiency and convenience.
Americans don't worry much if the toilet takes 1.6 gallons or 1.5, but having 3 or more bathrooms in the house - they want them to work for years with no maintenance.
Coming to inverter technology - last year I discover that my +- 10 year old refrigerator has inverter compressor.
When on one side that made me happy as new technology works better - on other side when inverter failed, I spend about 5 hr researching the net and youtube how to troubleshoot the darn thing.
Bottom line -nobody had clear help and I order $150 inverter not knowing if that is the part I need.
I am Hi-tech guy so I could deal with it, but think why original owners sold me $6000 refrigerator for $200?
DrewE
Explorer II
Jul 23, 2016
Generally these systems use a three-phasse induction motor controlled by a variable frequency drive. The variable frequency drive is a form of an inverter; both the output voltage and frequency are modulated together. Thus, it's a variable speed compressor driven by an inverter circuit.

These sorts of drives are used in many industrial applications and some other consumer appliances, like front-loading washing machines and variable speed equipment cooling fans.