Hi,
First of all, how many amps Can the inverter make? I would also guess that the battery fuse is a limiting factor too. So in my case I installed a Trace M1512 inverter in my motorhome with a 300 amp fuse and very large wire. The inverter can not continue to put out more than 30 amps without tripping the 300 amp fuse.
The circuit breaker feeding my RV is on a 20 amp branch, so that is the limiting factor while connected to shore power. If the inverter/charger is fed from a 20 amp shore power circuit breaker, no other protection is needed to protect the output wiring from exceeding 20 amps. However this can be limiting when you are trying to run the charger at full capacity as well as run some load fed by the charger circuit beaker, such as a microwave and also a heater at the same time.
Some RV's have a 30 amp circuit breaker in the shore power panel feeding the inverter/charger. Then the internal transfer switch feeds two circuits protected by inverter mounted 15 and 20 amp circuit breakers or sometimes 2 each 20 amp internal circuit breakers. This is the case with my friend's Country Coach and it's Trace inverter/charger.
Without looking at the pictured inverter/charger or it's installation in a RV, I can not determine how the wiring is protected. But it is safe to say that the inverter output will not exceed 50 amps for very long before the main circuit breaker feeding the RV trips. So the wiring is protected to some extent, but might not be protected properly from a prolonged overload that is just above the wiring's limits.
Lets take one look. If the RV has a 30 amp circuit breaker feeding the inverter and has two each #12 wires leaving the inverter output, then each goes to a separate area in the RV, the RV user might plug in 2 each 1,500 watt 12.5 amp heaters in the RV. This will not trip the 30 amp main breaker, but might overload one of the #12 wires. Probably not to the melting point, yet the wires might get warm or hot to the touch.
So if the inverter/charger does not have limiting circuit breakers or fuses on it's output, you might consider installing something. You can do this by limiting the input 12 volts with a fuse to only about 3,000 watts with a 300 amp fuse. You can protect the shore power size with a 20 amp or 30 amp breaker, depending on the load size wiring.
You can also buy "Edison" fuse holders. They are basically the size and shape of a standard light bulb holder, and will have two wires coming out of them. They fit into standard 1/2" knockouts. They hold a round Edison fuse, you can purchase those in 10, 15, 20, 25 and maximum 30 amp sizes, among others below 30 amps. Home Depot has a wide selection of Edison fuses.
Fred.
