Planning on using a phoenix inverter. The charger is separate so we can use EU shore power.
Thanks.

Rich,

Unless there is a frequency synchronization function (which the inverter may have but the generator almost certainly will not) if you do not isolate one power source before connecting another there likely will be a big ‘bang’ and substantial damage!! I once saw the crankshaft on a large diesel engine snapped in half by improper synchronization.

So yes, you absolutely need some kind of a switch (typically a rotary switch) which disconnects one AC power source from the boat’s circuits before connecting another power source. The one exception being many modern marine inverters (notably the Victron Multiplus and Quattro inverters) which have the capability of synchronizing their AC output with the frequency of a shorepower or generator AC input source, in which case they can operate in parallel with these sources.

Nigel

Is it necessary to separate AC sources using a rotary selector switch? We have a Genset, and shore power, and an inverter. The tolerance on the genset frequency is much higher than for the inverter.

Thank you very much. Installation constraints require that the main DC bus bar that parallels the batteries, and the battery switches, need to be 10 ft away from the batteries. I have 0AWG parallel cables from the batteries to the switch, with 110A Class T fuses, and 1AWG cable from the switches to the bus bar. The cable difference is due to engine compartment. The battery switch is rated at 350A.

Rich,

The key thing is to have the same conductor lengths, etc, on the individual sides (pos; neg) but they can be different between the two sides (pos; neg).

Nigel

Understand. That clears it up. Thanks.
Can I ask about paralleling LFPs?
Two 460Ah, 12.8V, and off the pos of ea, I have a Class T, going to a batt sw, then to the busbar that parallels them. On the neg side, cables to another busbar. How identical does the resistance need to be between pos and neg busbars?

Rich,

The fuse rating is based on the conductor ampacity regardless of slow blow, fast blow, etc. However, the fact it takes so many more amps to blow the fuse than its nominal rating reinforces the point we make repeatedly that it is better to be conservative than it is to push the technical limits of the ABYC and ISO standards.

Nigel

Question about selectiing OCP. 4/0 cable has ampacity of 445A. A 400A Class T fuse does not trip until the current exceeds 150% of rated, well above the ampacity. Does this get taken into account? Would a 300A fuse be required to protect the cable?

Rich,

That’s an excellent way to go. Separate the shorepower/dockside charging side from the onboard inverter-based AC side. That way, so long as you have a suitable charger you can plug into shorepower anywhere.

Nigel

Thank you. I’m leaning toward a Victron IP43 charger, a separate Phoenix inverter to run AC loads on the boat. Not all of the loads on our boat can tolerate 50Hz.