Electrical Run - ground wire question

[sodamo]

In the process of taking my cottage off is standalone solar PV electric and hooking in to my main system at the house. You can see the trench work here: http://www.tractorbynet.com/forums/kioti-owning-operating/245828-kb-2375-trench.html

I am running approx 375 ft of #2 copper from my main distribution panel to a sub panel at the cottage. 70AMP breakers, 240 volt. Loss will be just over 3%.

My question is regarding ground wire. Do I need to run 2 separate grounds panel to panel or is a single sufficient. I can buy 3 conductor w/ ground to run in my 2inch conduit. If I need the 2nd ground I suspect I'll have to run 3 separate conductors plus the 2 grounds. Naturally, the 3w/grd would be easier for me to handle. This is not a grd rod issue as there are double rod.

A friend is bringing over a copy of the NEC, but thought I'd tap into the BN brain trust.

David

 

[hr3]

I don't have the book at home but I'm thinking #8 copper for the ground,, and you only need one.. Saying that you will have 3 # 2 copper and 1 #8 copper ground,,
PS don't forget the ground rod and the building,,

Here is a neet chart for you..

electrician2.com Wire Size calculator

 

[trumpeter]

HR3 is right as what he said. The big thing to remember is to seperate the grounds and nuetrals at the cottage and the nuetrals don't get bonded to the panel. They realy do have to be seperate.

 

[sodamo]

Thanks guys, appreciate it.
There are 2 ground rods at cottage from the current solar that will be uninstalled.
So if I understand, my new ground will tie into this ground at the panel. My neutrals will be separate and not bonded to panel.

Another 20 ft of digging and can emplacement the last 50ft of conduit and get a final measure for the cable. At $8/ft, don't want to be short, but don't want too much excess either.

David

 

[John47]

HR3 is right as what he said. The big thing to remember is to seperate the grounds and nuetrals at the cottage and the nuetrals don't get bonded to the panel. They realy do have to be seperate.

Some utilities require the neutral to be grounded at the house service!!
Check your untility to find their requirement!
NEC goes either way.. It's correct to ground the neutral or leave it ungrounded at the house, again, if the utility requires it so will your home insurance company..

 

[sodamo]

Some utilities require the neutral to be grounded at the house service!!
Check your untility to find their requirement!
NEC goes either way.. It's correct to ground the neutral or leave it ungrounded at the house, again, if the utility requires it so will your home insurance company..

Totally, off grid, standalone solar systems - no utility company.

 

[tlbuser]

Totally, off grid, standalone solar systems - no utility company.

Must be one heck of a system. How large of a collector system?

 

[John47]

Totally, off grid, standalone solar systems - no utility company.

Looked like you were saying you were going back on grid from a stand alone solar plant.

My guess then would leave the neutral "floating".

 

[John47]

I'm also putting the parts together to get off grid, I am starting with four 240watt/24 volt panels, one 4Kw Magnum 120/240V stackable Inverter, and four Trojan L16RE-A batteries with a backup wind generator.
All to be upgraded before winter to another 4 solar modules, a second inverter to give us 8Kw and batteries up to three banks of four to give us nearly 1000Ahr capacity.

DON'T forget to ground the negative side of the solar modules and if they don't come with them, add blocking diodes to each module!

 

[sodamo]

Must be one heck of a system. How large of a collector system?

Current house system is 4.5kw, 36x125 panels. 24kw diesel backup gen. This is an exiting system, been online since 2007. Rolls Surrette 1350 amh battery bank, 4 Outback 3048 inverters.

Once I Get the new line hooked up, I'll move the 8 cottage panels (992 watts) to the main and add another 4 panels (560 watts) effectively increasing the system by a third.