the 802 is only 5kw (6kw in reality), the 50 amp plug is good for 12kw. If you do the 30 amp plug you are good for 7200 watts, which is more than enough for this size generator.
The only reason to go 50 amp instead of 30 would be to allow for future upgrade of the generator to a 10-12KW unit.
Checking the home depot website, they don't have the 50 amp version in stock in store, but I've bought the 30 amp version before and it's always on the shelf when I check.
As for the long wire run, it shouldn't matter. Any decent electrician knows how to size wires for the circuit length and calculate voltage drop and all that stuff, even if they don't there are charts everywhere and he can look it up.
Side note: I don't know the size or layout of your garage, but these things weren't really designed for interior installation, and I'd recommend against it. If your garage is attached to the house then just flat out don't do it, as the risks of carbon monoxide poisoning are not worth it. It's physically possible to do it, and it may run for a long time without issues, but if it does have any type of exhaust leak or anything, carbon monoxide is odorless and colorless, and will kill you and your family dead without you even realizing it.
Much better to install it outside under an overhang and surround it with chain link fencing or something similar that provides unrestricted airflow.
That being said, make sure you have carbon monoxide detectors and stuff like that, and probably also an exhaust fan with a temp sensor to automatically vent the garage if it starts warming up too much, as these things need cool air to operate. Just opening the garage door isn't always enough ventilation, as they require a LOT of air movement and fresh air to stay cool. All the ones that are designed for interior installation require at least one and sometimes 2 vents in the walls, the intake somewhere in the room, and the exhaust usually sealed to the outside wall to prevent air from recirculating.
Thanks for the info. I did the calculation and you are correct that I can use a 30a receptacle with my 43' run. Calculator said 10a copper wire. I'll probably use 6ga SOOW and mount one of those boxes on the genset that has the a 50a, 30a and 20a receptacles. On the off chance that I need more generator down the road I'm set.
My genset is installed and exhausted so no looking back now. I completely understand the risks. Our place is an off grid monitor style 2x6 barn with 1,600' of garage space and 800' of living space. Genset place next to an exterior wall and is exhausted through a thimble. Total exhaust run is less than 5' and was done properly with the 5" thimble, 2" exhaust pipe, flexible exhaust piece and flapper on the outside. It's the proper distance from the windows.
Under no circumstances would this genset ever be running when we are sleeping. Yes our living quarters is attached to the garage. Living quarters has spray foam and the attics are not connected. I have a plug in CO detector right by the genset with battery backup. Another CO detector in the garage right by the living quarters door. An two more plug in CO detectors with battery backup in the living quarters.
Genset only gets used to charge our 48v solar battery bank. During the summer it is rare for us to need it.
Garage has a 14' garage door and an 8' garage door. Four awning windows. I don't see ventilation being an issue.
I was sick and tired our pulling the generator/trailer out and hooking up the wire. So the convenience of the garage install made the decision.
The CO detector that is right by the genset has never read anything other than 0 ppm CO even when I was testing with both doors and all windows closed.
The doors to the living quarters will always be shut when the genset is running (noise and CO both factor in here).
At our remote place there are no codes or inspectors so you figure it out yourself or hire a professional.
I did all the solar, electrical and plumbing myself but for this I decided I needed a professional.
I will check all exhaust bolts and connections on a regular basis and make sure all CO detectors are working properly.
Actually I have more concern about the genset catching fire than I do about a CO problem.
Since our place is remote and a vacation place for now I wasn't comfortable having it permanently sitting outside.