Single point ground or??

zozomike · February 2014

Grounding is a bit confusing sometimes, and seems to have several options as noted in previous posts. I am relocating my existing array then adding a second array and second CC. The equipment however will remain in its present location which is 125' from the array (which will be mounted on the new house now under construction.)
I provided a UFER ground in the footing of the new house. The equipment is currently all grounded to rods very close to its location and the current array location is also grounded to that single point. I have planned to run #6 bare from the equipment to tie into the UFER ground. This would be about 90' of bare in the ditch. My question is should I tie this #6 to the existing ground close to the equipment, or should I abandon the existing ground and use only the UFER at the house. I hope my hasty diagrams below clarify this. To repeat, should I tie the existing ground rods into the new system, or abandon them?

Cariboocoot · February 2014

Re: Single point ground or??

I hate to say it but it will depend mostly on what the inspector, if any, has to say.

As a rule you tie everything to one ground point and one ground point only. But as with all rule there are exceptions. The array that's 125' away from the other equipment could have its own, independent ground rod. Multiple grounding points can also be tied together, providing it's done the right way (which it sounds like you would).

You probably know the easiest way to start an argument amongst electrical engineers is to ask "how do I ground this?"

zozomike · February 2014

Re: Single point ground or??

Cariboocoot wrote: »

I hate to say it but it will depend mostly on what the inspector, if any, has to say.

As a rule you tie everything to one ground point and one ground point only. But as with all rule there are exceptions. The array that's 125' away from the other equipment could have its own, independent ground rod. Multiple grounding points can also be tied together, providing it's done the right way (which it sounds like you would).

You probably know the easiest way to start an argument amongst electrical engineers is to ask "how do I ground this?"

Last thing I want is more arguments!!!!

No inspections BTW, We are far enough out that I am trying to avoid that, I spent 20 years dealing with inspections ( but not without learning from those guys, no criticism intended) Based on what you say, I think I should probably abandon the existing ground, and since the arrays will only be 15' from the UFER ground I will tie everything to that. The equipment ground run to the UFER will be 90' #6 bare buried with the underground cables.
BTW is there an easy volt meter test to check a UFER ground?
Make sense?
Thanks again.

vtmaps · February 2014

Re: Single point ground or??

Cariboocoot wrote: »

The array that's 125' away from the other equipment could have its own, independent ground rod. Multiple grounding points can also be tied together, providing it's done the right way.

I agree, two ground rods, tied together.

zozomike wrote: »

Based on what you say, I think I should probably abandon the existing ground, and since the arrays will only be 15' from the UFER ground I will tie everything to that. The equipment ground run to the UFER will be 90' #6 bare buried with the underground cables.

Abandoning the existing rod is NOT what Cariboocoot said. Use that #6 bare to tie the rods together.

btw, my (limited) understanding of code is that there must be an insulated green ground wire in the conduit with the power wires. Personally, I think it is better to have #6 bare in the trench. I guess the code is paranoid that the #6 bare could be interrupted, but the green wire in conduit is better protected.

It looks to me like you're going to be moving power all over the place... panels to equipment (125 ft, DC current) and equipment to house (125 ft, AC current). Make sure you have lightning arrestors on each end of each run. Also, you should have separate conduits for the AC and DC power. Hopefully you will have monitoring and control capabilities in your house... those wires can usually run with the DC, but should NOT run with the AC.

--vtMaps

ws9876 · February 2014

Re: Single point ground or??

just to be clear...there is nothing wrong with multiple ground rods for different uses,no??the more the merrier.. why would there be if they are down in the ground and not
next to other conductors..??

Cariboocoot · February 2014

Re: Single point ground or??

ws9876 wrote: »

just to be clear...there is nothing wrong with multiple ground rods for different uses,no??the more the merrier.. why would there be if they are down in the ground and not
next to other conductors..??

Ah, "different uses". As far as the NEC is concerned one power system is a single use no matter how many pieces there are to it.

Connecting grounding points underground with bare wire constitutes a single ground point even if wires from the system connect to it many feet apart.

It all has to do with the conductivity to Earth, which is practically impossible to measure objectively as, guess what, that requires a ground point reference.

zozomike · March 2014

Re: Single point ground or??

Cariboocoot wrote: »

Ah, "different uses". As far as the NEC is concerned one power system is a single use no matter how many pieces there are to it.

Connecting grounding points underground with bare wire constitutes a single ground point even if wires from the system connect to it many feet apart.

It all has to do with the conductivity to Earth, which is practically impossible to measure objectively as, guess what, that requires a ground point reference.

sorry, family issues prevented me getting back for a few days..., I laid the two 8/2wg ufb and one 8/3 wg ufb for 120/( future240) cables, covered with sand and ran the monitoring cat 5 cables a few inches above that, about to fill the ditch and start the panel relocation. What with work/family and daily off grid survival everything takes more time and money than anticipated.
Sorry I misunderstood about the reply of the ground tie. BTW My earth has poor conductivity I would reckon it is so as it is high/dry and rocky. So I will tie the #6 bare to existing ground, ( which is actually actually several spaced rods tied together and also the Rebar of the small slab of the Batt house.) that is easy and reasonable. I have Delta arrestors at both the CC and the 120v main panel.
Are you suggesting I need to work in an Arrestor at the sub panel also? that is the only other end unless you mean the arrays?

In addition, if I tie the relocated array 1 and the soon ( I hope array 2) with continuous #6 to the ground which is 120' X4 ea pcs rebar ufer in the footing and located 15' from the arrays + the value of 125' of #6 18" underground + existing 4 each 4' driven rods ( god awful rocks here) I see no reason to add extra rods next to the arrays? Then again lightning does not listen to reason.....
Make sense?

Yes I am running power both ways, but I have enough to do without moving all the equipment to the house, besides then I would still have to run 120 VAC back to the existing structures...
Thanks again guys for all you do!

Cariboocoot · March 2014

Re: Single point ground or??

I wasn't actually talking about lightning arrestors at all. People often think that the purpose of the grounding is for lightning protection. It isn't. It is Electrical Safety Grounding. The only time it is associated with lightning protection is if you do put the arrestors on; they provide a path to ground for any high-frequency high Voltage that is induced into the conductors by nearby lightning strikes.

Single point ground or??

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