ground always necessary in conduit?

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bekahhren

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I'm running 6 awg hot/neutral 120 v AC in pvc through a trench with a 6 awg copper ground wire in the trench, not in the conduit, with ground rods on both ends of trench. Do I need 10 awg ground in the conduit or is it not necessary?
 
Before I start looking anything up in the NEC, may I ask if this is a service or a feeder? Also, why are there ground rods at both ends of the trench?
 
it is actually a run from a 120 v pv array inverter (in a shed under the pv modules in a field) to a backfed breaker at a main panel (at a house), with a ground rod at the array and the house.
 
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I am still not sure I understand the question. I don?t think you are asking whether the #10 can go outside the conduit (in the trench), or whether it must go inside the conduit. Instead, I think that what you are asking is whether you need to run an EGC at all. Is that right?

It seems to me that you are talking about a service. The power source is photovoltaic (is that what ?pv? means?), and this underground cable run will bring pv energy to some service panel (perhaps the ?inverter? you mentioned) inside the building. You don?t run an EGC from the power source (outside) to the service panel (inside). EGCs run from the service panel to downstream panels and loads.

So my answer is ?no, you don?t need to run the #10.?

But I recommend you wait for other members to chime in.
 
ground always necessary in conduit?

It seems that you are using the inverter as backup system. If so you would have to determine if the inverter is being used as a separately derived system. If you determine it is a separately derived system you would have to ground it per 250.30 and if not then you would use 250.32
 
If the circuit requires an EGC, then it must be in the raceway with the other conductors. A quick look at Part V of Article 690 appears to require the use of EGCs.
Don
 
I agree with Don here....If you are running this # 6 AWG for the EGC for that circuit you will need to run it within the same conduit the circuit runs in. FYI- I also posted for you over on my board......to save you the trip...:)
 
I agree you must run an EG with the circuit. The # 6 and ground rods are the GES for the DC source but dont negate the EG for the circuit
 
definitely running egc, but in or out of conduit?

definitely running egc, but in or out of conduit?

Thanks for the responses -
Don said the egc must be in the raceway with the other conductors - I've been told this is true, I've just never actually seen the section of code that supports it! That is what I'm looking for.
 
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'I am still not sure I understand the question. I don’t think you are asking whether the #10 can go outside the conduit (in the trench), or whether it must go inside the conduit. Instead, I think that what you are asking is whether you need to run an EGC at all. Is that right?"

No, I am definitely planning on running an EGC - the 6 awg bare in the trench (in the dirt itself I mean), but i just don't know whether code requires me to run another grounding conductor within the conduit itself...
Thanks!
 
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bekahhren said:
No, I am definitely planning on running an EGC - the 6 awg bare in the trench (in the dirt itself I mean), but i just don't know whether code requires me to run another grounding conductor within the conduit itself...
Thanks!
Click to expand...
I don't understand what would compel you to run the EGC outside the conduit. Can you explain why?
 
ground ?

ground ?

bekahhren said:
.......... to a backfed breaker at a main panel (at a house), with a ground rod at the array and the house.
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This part of the post stuck in my mind so strongly I can't even think about the grounding.....alternative power supply controlled by a back-fed breaker ??? do I understand that correctly ?
 
300.3(B) Conductors of the Same Circuit All conductors of the same circuit and, where used, the grounded conductor and all equipment grounding conductors and bonding conductors shall be contained within the same raceway, auxiliary gutter, cable tray, cablebus assembly, trench, cable, or cord, unless otherwise permitted in accordance with 300.3(B)(1) through (B)(4).
 
This part of the post stuck in my mind so strongly I can't even think about the grounding.....alternative power supply controlled by a back-fed breaker ??? do I understand that correctly ?
Click to expand...

Good point. Perhaps this is an offgrid system and the inverter is the only source of power? If not is there an interlock on the back fed breaker? is there a battery bank at the pv panels? If not I dont see the inverter functioning very well. Perhaps a more detailed overview of the system would help us answer the question more effectively.
 
don_resqcapt19 said:
300.3(B) Conductors of the Same Circuit All conductors of the same circuit and, where used, the grounded conductor and all equipment grounding conductors and bonding conductors shall be contained within the same raceway, auxiliary gutter, cable tray, cablebus assembly, trench, cable, or cord, unless otherwise permitted in accordance with 300.3(B)(1) through (B)(4).
Click to expand...


Yes! Thanks! That's what I was looking for! But there is the bit in there about the trench...
The circuit conductors are in conduit in the trench, but the egc is just in the trench (not in the conduit). Sounds like a question for the AHJ to me!

In answer to the other questions - I would run the 6 awg bare through the trench to further lower resistance (since it is contact with earth for the whole run), a little extra lightening protection maybe.


About the backfed breaker - this is a totally normal, 690 compliant pv installation, not off-grid. DC disconnect and AC disconnect on either side of inverter, utility accesible disconnect, placards, etc etc. The inverter just happens to be about 150 ft from the panel/meter base, on the other side of a field.
 
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