Do I Need 2 Neutral Wires

I have a Schneider SW 4024 inverter/charger. I am not using a generator but instead use Grid power to power the charger of the SW when solar is not available. The SW has an L1/L2/Neutral Input AND an L1/L2Neutral Output. At the Inverter I bring all this together with a Midnite Solar E-Panel. In the E-Panel both the Input and Output Neutral connect to the same bus bar.
I am getting power (Input) for the SW Inverter/charger from my main grid panel using 8/3 NM-B with ground.
My inverter sends power out (Output) to a Reliance Controls 510C ProTran 2 Toggle Transfer Switch Inverter Load Panel also using 8/3 NM-B with ground. This allows the Inverter Output on L1/L2 to be toggled between the Inverter power and the grid power.
BUT all the Neutral wires coming and going ultimately connect at the Main Load Panel Neutral Bus Bar inside the Main Load Panel. And all loads, both Inverter Powered Loads and Grid Powered Loads ALL connect to the same Neutral Bus Bar in the Main Load Panel. This same Neutral Bus Bar is also connect to the Grid Neutral. This is the way Reliance Controls wires the 510C transfer switch according to their manual. The only difference I am doing with the 510c is using an Inverter instead of a generator (which is the 510c's typical usage). And obviously, generators have no need to have Grid Power Input like the SW Inverter/Charger does.
Questions.
1. Do I need the Neutral both coming and going (Input and Output) run from the Midnite Solar E-Panel to the Main Load Panel?
2. Or can I just use a single Neutral (assuming correct size - I am using #8 for L1/L2 and Neutral) for both Input and Output after the Neutral Leaves the E-Panel?
3. Would it cause problems to use both a neutral for the power to the SW and power from the SW like in the case of an Input and output using 8/3 NM-B with ground? (or effectively 2 Neutral wires from/to the same busbar in the Main Grid Load panel and from/to the Midnite Solar E-Panel)
4. Is it best to only use 1 neutral wire, or include both in the run between the E-Panel and the Main Load Panel?
Note that the Neutral that goes to the 510c Transfer switch does not connect to the 510c it merely passes thru the box via a wire nut connection and does not touch or interact with the 510c transfer switch at all.
See Diagram for how I have it connected now.

REC TwinPeak 2 285W 3S-3P 2.6kW-STC / 1.9kW-NMOT Array
/ MN Solar Classic 150 / 2017 Conext SW 4024 Inverter latest firmware
/ OB PSX-240 Autotransfomer for load balancing / Trojan L16H-AC 435Ah bank 4S connected to Inverter with 7' of 4/0 cable / 24 volt system
/ Grid-Assist or Backup Solar Generator System Powering 3200Whs Daily / System went Online Oct 2017 /
System, Pics and Discussion
Comments
Attached pdf shows the wiring using Schneider AC switchgear, which essentially is the same as MNE175SW. , the transfer switch would only be required if a generator were used. Just trying to understand your question.
Second system 1890W 3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.
5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
Second system 1890W 3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.
5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
I have a panel for "critical" loads with multiple source feeds, but it's immediately apparent there are multiple sources because each has a separate breaker and a mechanical lockout preventing both breakers being closed at the same time. Both breakers are at the top of the panel, where someone working on the panel would expect input source breakers to be. Opening both makes the panel safe to work on, even if one is a klutz (which I am).
The box may be code compliant as far as the box itself is concerned, but I'm not sure it's safe in the overall context.
Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
The AC input of the CSW would not require a neutral with a 240V supply, the output is split via a center tap of the transformer to provide the neutral, but there would be no ground bonding internally, that would be done in the main panel.
The absence of the bypass breakers makes the use of the toggle/transfer clearer
Second system 1890W 3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.
5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
The box may be code compliant as far as the box itself is concerned, but I'm not sure it's safe in the overall context.
htps://offgridsolar1.com/
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You could also expand the AC switchgear panel breakers for your critical loads if you have too many.
htps://offgridsolar1.com/
E-mail [email protected]
My understanding is that the Reliance transfer switch is made for connecting a generator to supply specific loads in case of power failure. Many generators bond neutral to ground so the transfer switch also switches or lifts the neutral so that it's not connected to the houses neutral circuit which is bonded in the main panel under normal conditions. In light of the way you're using the transfer switch, I agree, the neutral line in question is redundant since the loads have a neutral connection on the common buss.
Rick
1. Do I need the Neutral both coming and going (Input and Output) run from the Midnite Solar E-Panel to the Main Load Panel?
my concern is if you just use 1, you lower the overall amperage rating , even if it is a common neutral on the inverter