Grounted conductor/neutral to GTI

[electrofelon]

Does anyone have any insight or knowledge on what the purpose of running a neutral or grounded conductor to the AC side of a GTI is? Some dont require, others do, some manufacturers' inverters can operate without but they seem to strongly prefer that you run one. Whats the deal? I am working on a 1 MW system now and it was designed with full size neutral on the inverter output circuits (3 Ph 480) and a two sized reduced on the feeder to the panelboards. Some of these runs are long so a few are parallel 250 ungrounded conductors for VD. Could some wire have been saved here? These are SMA tripower 24000.

Thanks!

 

[jaggedben]

Some inverters can be or must be connected single phase with the neutral as a current carrying conductor. But with Sunny Tripower I believe the only purpose of the neutral is to sense voltage and phase angle in order to meet UL 1741.

As far as saving wire see 705.95 (B). Not sure that section can be construed to apply a panelboard feeder so the situation you describe seems a little backwards. Also not sure if voltage drop affects the neutral, I'd have to think about that.

 

[ggunn]

Does anyone have any insight or knowledge on what the purpose of running a neutral or grounded conductor to the AC side of a GTI is? Some dont require, others do, some manufacturers' inverters can operate without but they seem to strongly prefer that you run one. Whats the deal? I am working on a 1 MW system now and it was designed with full size neutral on the inverter output circuits (3 Ph 480) and a two sized reduced on the feeder to the panelboards. Some of these runs are long so a few are parallel 250 ungrounded conductors for VD. Could some wire have been saved here? These are SMA tripower 24000.

Thanks!

You must run a neutral to that inverter for it to operate, but it's just for voltage sensing. It can be sized to match the size of the EGC but no smaller.

 

[Zee]

Right, to sense voltage on each individual hot wire to neutral. For example: you may have 240 Vac across the two hot wires...but that could mean the individual conductor voltages are balanced at 120 v and 120 v each
OR
way unbalanced, e.g., 105 V and 135 V each.
So the neutral allows each conductors V to be sensed.
At least, that is what I had been told for years by others :dunce: