This is the outlet right next to the transfer switch

Westinghouse vs Duromax Generator Dual fuel technology: the ability to run on either propane or gasoline provides fuel choice freedom and flexibility. Protects your investment by automatically turning off the generator when the oil level is low. With 12,000 starting watts and 9,500 running watts, this unit is capable of handling heavy loads ranging from lights and a refrigerator to a home air conditioner and high amperage power tools. Plug-and-Play: Comes with a Propane Regulator, Remote Start Key Fob, 12V Battery Charger, Oil, an Oil Funnel, a Tool Kit, Heat Resistant Plastic Wheels with Never-Flat Polyurethane Tires, and a User's Manual (Minimal Assembly Required) The answer is: I'm confident that everyone who believes Toddd made the wrong decision by hiring a certified electrician is mistaken. What exactly is a "manual transfer switch," in your opinion? It's simply a breaker or switch that must be manually activated. It's not a problem as long as the electrician built it properly. In response to your question, I believe the description says the outlet is a 50A RV outlet. This is the outlet right next to the transfer switch. The transfer switch is a twist lock, but the RV outlet isn't; if you look at the photo, it's the one with four holes. It also runs on 120/240 volts. Just so you know.. If you want to do something to the unit that isn't explicitly stated in the manual, such as "convert to run from LP Gas to Natural Gas," you should contact the manufacturer directly. Asking the general public for answers on something that is ONLY designed and indicated to work with gasoline/propane is not a safe way to get your answers. Not to be rude, but that is a VERY good way to get hurt or ruin the unit, so I would get your information directly from the manufacturer if it involves attempting to change the way the unit is designed to work. Only gas; a separate propane tank gauge is required. However, I would not recommend this machine because it does not start in the cold - it is a piece of junk in the cold, and service and support are non-existent - avoid! Having used a number of propane heaters, generators, and torches (large ones), I can confidently state that lowering the pressure in the tank is the most effective way to prevent frost. Getting a larger tank is the simplest and safest way to accomplish this. If a 20lb tank is frosting badly, you are drawing it too quickly. Instead, try a 40lb or even a 100lb tank. Your frosting problem will be resolved.