We have a 100A main feed at the road, I have a 2 - garages within 2000' of it. I need to ppower each garage. I have 8/4 cable at my disposal, and have 100A sub boxes at each garage. Does each sub need its own grounding rod? And do I isolate each sub's neutral?

My answers to your questions and comments are in red.

I have 8/4 cable at my disposal, and have 100A sub boxes at each garage.


Does each sub need its own grounding rod? YES.

And do I isolate each sub's neutral? YES.

I have 8/4 cable at my disposal. #8 is too small to deliver 120 volts 2000 feet.

# 8/4 cable is only good for 40 amps max, and assuming a 40 amp 120 volt load, the max distance would be about 65 feet.

At this distance of 2000 feet, transformers should be used to deliver 480 volts, at least, this distance.

To do accurate voltage drop calculations, the maximum amperage load is needed, along with accurate distances.

You really need to re-think your plan.

I may be overstaing the 2000' - I will get a better measurement, but what plan would you advise to me?

Quote:

---

Originally Posted by bubble_up

I may be overstating the 2000' - I will get a better measurement, but what plan would you advise to me?

---

It may be within 750' to 1000' - I know it's a long way, but the original service only has #6 coming in from the meter...

Call the power company. You need more than just a bunch of cable to do what you want. Have the service brought to the building.

Sorry Missouri Bound- that would be the wise thing to do, but it's not in the budget.

I measured it today at 650' to the 1st garage, and an additional 200' to the second garage. I just want to split the 100 A service between the 2 garages - simple fans & lighting + 1 small air compressor
(15A @ 240V)

Well... to the first building. Assume you use a dbl pole 50A breaker... you would need 2/0 copper for that installation alone. 100amp dble pole would require 500 mmca wire. After you price that, you may reconsider calling the power company.

Quote:

---

Originally Posted by bubble_up

Sorry Missouri Bound- that would be the wise thing to do, but it's not in the budget.

---

Is it in the budget to do it wrong and have to re-do it?
Or do it wrong and burn up equipment because you are only getting 90 volts?
If doing it right is not in the budget don't do it at all.

Quote:

---

Originally Posted by Missouri Bound

Well...to the first building. Assume you use a dbl pole 50A breaker...you would need 2/0 copper for that installation alone. 100amp dble pole would require 500 mmca wire. After you price that, you may reconsider calling the power company.

---

I completely agree.

All we can do is give advice to a particular questions or situation. Our advice does not need to be considered. If someone does not want to follow our advice for whatever reason, that is their decision.

The Ohm's Law will always win.

Thank you all for the input... We hired a local licensed electrician, it wasn't that bad of a deal...

Enlighten us and please elaborate as to what the electrician plans to do for you. I, for one, am interested in the route you take.