Okay, good. As I said, I've never encountered this practice.And who said anything about splices? A transition box when it's used this way has terminal blocks for everything.
Normally I would take 'multiple inputs' to mean separate MPPT tracking inputs. (Obviously in such a case you don't want to combine conductors on either side of the circuit that don't go to the same input. I don't see this as something you would do on a conventional inverter any more than a transformerless one.)The question posed was what the differences are between transformerless and conventional inverters. Here's one: If you are running separate DC+ connectors all the way back to multiple inputs on a transformerless inverter, then your DC- connectors must remain separated as well because of the way that transformerless inverters detect ground faults. Such is not the case with a conventional inverter.
But you seem to be using 'multiple inputs' to simply mean multiple available connection points at the inverter (with or without included overcurrent protection as appropriate). In that case I would maintain that it makes no (electrical) difference whether you combine your DC - at the inverter or elsewhere, as long as you use overcurrent protection appropriate to the system. If you wanted, you could still combine your DC - conductors remotely from the inverter and run your DC + conductors to the inverter and combine them there, so long as you included proper fusing at both combining locations.
I don't understand why the inverter's method of ground fault detection makes any difference to this question. Transformerless inverters are not incapable of accepting combined circuits. The only way I can make sense of what your saying here is that the requirement for fuses on both + and - will mean different or additional equipment that will probably discourage the practice you have mentioned.
I didn't say it was a code violation or would cause a problem with system function. Still, I like to have my + and - conductors for any given source circuit combined at the same location, wherever that is. It makes diagnosing ground faults easier, and it makes the system easier to figure out for someone who did not install it.Whether or not you would choose to wire a system with combined DC- andr discrete DC+ into multiple inputs on a conventional inverter is of course your call, but I work in the industry and I know that it is commonly done, and inspectors in the jurisdictions I work in have no problem with it.