Dave Solberg is a leading expert in the RV industry and author of the “RV Handbook” as well as the Managing Editor of the RV Repair Club. Today he discusses an RV’s roof air conditioner.
We have a 28-foot Zinger made by Thor. Even though the owner’s manual says you can run the AC on a 110 outlet, I’ve heard that this will shorten the life of the unit, as opposed to running on a 30 amp. I also heard that you should never run the AC on low because it’ll freeze up. Is this true or false? Thanks, Dave. —Ron
The typical roof air conditioner operates on 120-volt power supplied by the distribution center of an RV. This is often referred to as “110 volt.” However, it should be somewhere close to 120 volts. This 120-volt source can be sized for 15/20-amp, 30-amp, or even 50-amp power.
The typical roof air conditioner will run at approximately 14 amps at full draw, with older units (pre-1990) pulling as much as 18 amps. So, when your question refers to “110 volt” listed in the owner’s manual, I believe you are referring to a residential-type outlet such as a garage versus a 30 amp referring to a campground source like the one pictured, right?
Most of your residential outlets such as this are connected to a 20-amp circuit breaker, which would typically be enough power to run your roof AC. However, these are usually connected to other outlets in the garage that have refrigerators, air compressors and other energy-drawing items. Plus, when you plug in your shoreline power of the RV and turn on the roof air conditioner, it is typically not the only thing drawing power, as you probably have the refrigerator or water heater on too. These all draw power as well as draw 12-volt power from the house batteries, which means the converter/charger will turn on occasionally.
Use a surge protector
What can harm your compressor and fan motor in a roof air conditioner is running on low voltage. The ideal voltage is 120 volts and nothing lower than 113 volts as the unit will still run, but so will labor and increase in amp draw and eventually go bad. Using a surge protector such as this Surge Guard model will monitor the voltage, show the amp draw, and shut down if the voltage drops below a safe level.
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