Long run from ground mout array to house

[jimmychacha]

Hello all, I'm thinking of installing a ground mount on my property about 100 feet from my house. What are the pros and cons of inverting at the array and running AC to the house, or running high voltage DC (small conductor) and invert to AC once inside?

[russ]

Hi Jimmy - Welcome to Solar Panel Talk!

1) For DC from the panels in you will use a substantially larger cable size

2) Voltage loss even with the larger cables.

Much better choice to make the run in AC.

RUss

[jimmychacha]

Thanks Russ. I am under the impression that wiring panels in series and building as high DC voltage as possible is the most efficient method, because total power delivered to the inverter is voltage * current, thus a high voltage means low current, thus smaller wire. ?

[russ]

Hi Jimmy - Right but that is not what you asked I don't believe.

In the panel to inverter section you are building voltage.

I understood you to ask whether to put your inverter by the panels and run AC to the house or if it was better to make the 100' run DC.

Better to make the 100' run AC.

Russ

[Sunking]

I am under the impression that wiring panels in series and building as high DC voltage as possible is the most efficient method, because total power delivered to the inverter is voltage * current, thus a high voltage means low current, thus smaller wire. ?

That is correct, but you are aware it is 3-wires right?

[russ]

Hi Sunking - for the 100' run from the panels to the house which would you choose - say 500 volt DC or 240 AC?

Russ

[Sunking]

Pretty simple Russ. 500 is greater than 240. The other thing you might be over looking is the differences between AC and DC. No not the band from down under or the Bee-Gees.

With DC you only have pure resistance that factors losses. With AC you have resistance plus reactive resistance called reactance. So for a given voltage, current, and wire size AC will always have more losses because of the added reactance on top of the resistance.

[russ]

Just learned that I have misunderstood something important - thanks!

[Sunking]

Russ how is your Trigonometry? Do you understand how 1 + 1 = 1.41, and 3 + 4 = 5?

1 ohm of resistance + 1 ohm of reactance = 1.41 ohms of impedance.

[jimmychacha]

Sunking, when you say 3 wires you are referring to the equipment ground as the third?

[Sunking]

Sunking, when you say 3 wires you are referring to the equipment ground as the third?

Yes Sir.

[So solar]

I must be dumb. But, I thought DC doesn't transmit as far. Or so Edison said.(I think). I always shorten the DC run as much as possible......

[Sunking]

I must be dumb. But, I thought DC doesn't transmit as far. Or so Edison said.(I think). I always shorten the DC run as much as possible......

It can go as far as AC. In fact it can go even further because it does no have an impedance factor as AC does. In fact electric utilities use DC for long haul transport from point to point. It is called HVDC

[So solar]

With all things being equal. Same wire, same voltage, same amps. ( Even though AC fluctuates between positive and negative). Who would win in the long distance race with more strength?

[Sunking]

With all things being equal. Same wire, same voltage, same amps. ( Even though AC fluctuates between positive and negative). Who would win in the long distance race with more strength?

DC every time.

As I eluded too earlier with a DC circuit all you have is pure resistance in the wire. In an AC circuit you also have the pure resistance of the wire, plus the reactive resistance called impedance. Th ehigher the frequency the higher the reactive resistance. So for a given voltage, size of wire, and length Ac will always have more resistance to impede current flow, thus more loss of power.