pv system connected to sub-panel

[SunEagle]

no one wants to commit to an answer on this?

A string inverter usually costs less then micro's as well as reducing the failure point to one instead of one for each panel.

[Jest Waitn]

so then, bar making a long dc power run, there is no real advantage in using the string inverter?

no one wants to commit to an answer on this?

[Jest Waitn]

If you mount the string inverter near your main panel, you can run the 500 Vdc the long distance with less loss and just have a short AC run.

since virtual net metering is not supported by the POCO, an alternate possibility is to relocate the main power to the 'jump pole' about 75' closer to the transformer. the sub-panel can also be relocated and wire the PV array to it with about a 125' hop to the transformer from the PV array. but this would be a lot of work and possibly a greater hassle by having to bring the 'old stuff' up to most recent code. and i'd want to keep the old primary panel on the pole as a sub-panel for the well & house and to run the supply line overhead from pole to pole. don't know if this is allowed & it might cost a bunch of $.

[Jest Waitn]

on this note, then how likely is it that the grid voltage here might hit 261vac and cause disruption to the inverters?

[SunEagle]

some areas are more stable than others but here is a typical example from one of our inverters in PA a little west of Philadelphia.
so just from the 25th to the 26th you have an average day time swing from 248V to 243V Chart.jpg

When I worked at an industrial facility we would see the 4160v main power voltage creep up on Friday afternoon as the weekend started and then suddenly drop as grid line capacitors were switched off. The opposite would happen on Monday morning when you would start to see a drop in voltage as the grid got loaded up and then a sudden jump in voltage again as capacitors were switched back on.

[ButchDeal]

I would also add in the fact that the grid voltage tends to go up at the end of the day or on weekends when commercial & manufacturing loads are turned off.

some areas are more stable than others but here is a typical example from one of our inverters in PA a little west of Philadelphia.
so just from the 25th to the 26th you have an average day time swing from 248V to 243V Chart.jpg

[SunEagle]

The grid voltage is not constant so you will need to measure them at the same time or at least a few times close to the same time.

I would also add in the fact that the grid voltage tends to go up at the end of the day or on weekends when commercial & manufacturing loads are turned off.

[Jest Waitn]

If you mount the string inverter near your main panel, you can run the 500 Vdc the long distance with less loss and just have a short AC run.

so then, bar making a long dc power run, there is no real advantage in using the string inverter?

[Jest Waitn]

The grid voltage is not constant so you will need to measure them at the same time or at least a few times close to the same time.

of course. and neither is the temperature constant.

[Jest Waitn]

If you mount the string inverter near your main panel, you can run the 500 Vdc the long distance with less loss and just have a short AC run.

i don't want to do this. don't want long dcv runs.

[sensij]

i looked tonight at some string inverter specs. it seems that the 'ceiling' for 240vac is 264vac. the range is given 211v-264v. how is this different from the micro-inverter?

If you mount the string inverter near your main panel, you can run the 500 Vdc the long distance with less loss and just have a short AC run.

[Jest Waitn]

Yes. Microinverters operate at line voltage (240 Vac), while string inverters can operate up to 500 Vdc, depending on panel selection and array design. The same power at higher voltage means less current. Less current means less loss.

i looked tonight at some string inverter specs. it seems that the 'ceiling' for 240vac is 264vac. the range is given 211v-264v. how is this different from the micro-inverter?

[ButchDeal]

i measured the plug voltage in house @ 125.3 tonight. tomorrow i'll measure @ the sub-panel. this is rural and the 'end of the line' on this service leg.

The grid voltage is not constant so you will need to measure them at the same time or at least a few times close to the same time.

[Jest Waitn]

Hopefully you won't see any issues and those micro's work for you. Keep us informed.

i measured the plug voltage in house @ 125.3 tonight. tomorrow i'll measure @ the sub-panel. this is rural and the 'end of the line' on this service leg.

i measured the sub-panel voltage this a.m. @ 249vac even.

[SunEagle]

service cable is used up to the sub-panel. the array feeds the sub-panel with 12/3, due to the short distance.

i have already bought the micro-inverters and the cabling.

Hopefully you won't see any issues and those micro's work for you. Keep us informed.