Making Your Air Conditioner Generator Friendly

June 7, 2009

Some RV air conditioners have a difficult time starting when using a generator, especially portable generators. There are a number of factors that contribute to hard starting but most often it’s because there is not enough available power to start the compressor quickly. The compressor motor in a typical RV air conditioner system can draw a tremendous amount of current during it’s start-up time. This can be as high as 50 amps for a typical 15,000 BTU A/C on a hot day. All but the largest of RV generators can struggle to provide this kind of power without significant voltage droop. Not having enough voltage and current to start the A/C compressor, the generator goes in to overload and pops it’s circuit breaker. What can be done to help this situation? Modify your RV air conditioner with a hard start boost capacitor.What is a hard start boost capacitor you ask? It’s an electrical device that is added to your A/C system to provide a short term power boost that assists compressor starting. The capacitor stores electricity and provides it all at once when the compressor is starting. Most newer RV air conditioners may already have a booster capacitor, but they tend to be a bit undersized. So even those that do have them, can still benefit from this mod.

A typical RV A/C provides 13,500 BTU of cooling, and generally requires a generator that has a minimum surge rating of 3500 watts. Many of the popular portable generators, such as the Honda EU2000 or the Yamaha 2400i, cannot provide this level of surge power. Many folks have tried starting their A/Cs using these generators, and while a few have been successful, most have not. Those that were successful likely had a boost capacitor installed.

If after installing a boost capacitor you still have start-up problems using a small generator, here are a few tips that can help get your A/C going.

Turn off all AC breakers except for the main power and A/C breakers. This ensures that the battery charger and no other AC accessories are demanding power and thus reducing available start-up power to the A/C.
If your generator has an economy switch, be sure to switch it off economy. This ensures the generator is at it’s highest speed which can provide the required power more quickly.
If tips 1 and 2 don’t work, there are 2 possibilities: your generator is too undersized even with a boost capacitor, or you are at too high of an altitude. Generator power decreases by around 3% for every 1000 feet of altitude. If you are at 5000 feet, then your generator will produce 15% less power. That might be just the missing amount you need to get the A/C compressor going.

I personally use a Kipor KGE3500i inverter generator which has a surge rating of 3500 watts and a run rating of 2800 watts. At high altitudes, I have to switch the economy switch off or my TT’s 13,500 BTU A/C will refuse to start. And I have a boost capacitor installed! Only at sea level will the generator start the A/C on economy.

For more information, tips, pictures of how to install a hard start boost capacitor, and where you can buy one, head on over to ModmyRV.com and have a look at this article:

Happy modding!