Grid tie inverter location - by the panels or in the house by the load center?

[oldryder1973]

Ground mount grid tie system design questions.

Panel string (310w. X 11) will max out at approx 525v DC and approx 13 amps. Big box store THHN 14ga. wire rated at 600v. per string would be adequate if I did my numbers right.

Tentative design is 4 strings DC fed approx 90' conduit to inverters located inside close by load center. wire will be noticably cheaper with this approach than locating inverters at the panels and running AC to house. I also like locating the expensive inverters inside.

Inverters have both DC and AC disconnects. Should I expect utility to require additional DC disconnects where DC wiring enters the structure?

looking for feedback on this approach.

 

[snoobler]

525V/13A

Assume your 525V is based on Voc and not Vmp. Assuming Vmp is likely closer to 400V, 400V @ 13A:

Voltage Drop Calculator

This free voltage drop calculator estimates the voltage drop of an electrical circuit based on the wire size, distance, and anticipated load current.

www.calculator.net

1.48% voltage drop.

You can then work the same exercise for 240VAC @ ?A and whatever wire gauge you select.

Concerning additional DC disconnects, you'll have to check with the AHJ and the applicable electric code.

 

[oldryder1973]

thx for reply. I am new to this and unfamilair with "Voc" and "Vmp". The specified 525 volts is the sum of of 11 panels in series outputting their open ckt volts under optimum conditions. Feel free to correct me if I am approaching this wrong.

thx for voltage drop calculator.

mark in MN

 

[schmism]

Voc = Voltage open circuit - nothing attached to the panel.
Vmp = Voltage maximum power - what the Voltage would be under ideal conditions with the maximum output current (good luck measuring this in the real world).

we would expect a 310w panel to have a roughly 36v "normal conditions" operating voltage.

Most grid tie systems I see locate the inverter close to the meter connection as your required to have a disconnect to isolate the solar from the grid. (again refer to your local codes for specifics that are required in your area)