No ground in PVC conduit?

[ggunn]

A contractor (a master electrician) installing an ungrounded bipolar (AE Solaron) system for us made a few changes for the sake of economics/expediency, and one of them was to omit the ground wire in the DC runs in buried PVC conduit from the arrays to the remote PV tie. He says that since the components at each end of the conduit are grounded, the ground wire in the conduit is unnecessary. Is he correct?

 

[GoldDigger]

A contractor (a master electrician) installing an ungrounded bipolar (AE Solaron) system for us made a few changes for the sake of economics/expediency, and one of them was to omit the ground wire in the DC runs in buried PVC conduit from the arrays to the remote PV tie. He says that since the components at each end of the conduit are grounded, the ground wire in the conduit is unnecessary. Is he correct?

One of the things you see here every week is the statement that for low voltage the earth is not an adequate fault clearing conductor.
Where an EGC is required, an earth ground at both ends does not provide the same function.
Even if for some reason there is no possible fault that would put ground current between the two ends, the equipment still needs an EGC, IMO.
Also, the ground electrodes at both ends, as part of the same system, need to be interconnected.
Any idea how the AHJ feels about this?

 

[iwire]

I would not use this EC again and I would demand he installs the EGC.

250.4(A)(5) Effective Ground-Fault Current Path. Electrical equipment and wiring and other electrically conductive ma-terial likely to become energized shall be installed in a manner that creates a low-impedance circuit facilitating the operation of the overcurrent device or ground detector for high-impedance grounded systems. It shall be capable of safely carrying the maximum ground-fault current likely to be imposed on it from any point on the wiring system where a ground fault may occur to the electrical supply source. The earth shall not be considered as an effective ground-fault current path.

 

[jaggedben]

How is the GFDI going to operate?

I agree with iwire.

 

[ggunn]

One of the things you see here every week is the statement that for low voltage the earth is not an adequate fault clearing conductor.
Where an EGC is required, an earth ground at both ends does not provide the same function.
Even if for some reason there is no possible fault that would put ground current between the two ends, the equipment still needs an EGC, IMO.
Also, the ground electrodes at both ends, as part of the same system, need to be interconnected.
Any idea how the AHJ feels about this?

I got a little more information. There are several DC combiner boxes on the upper and lower arrays, and each combiner feeds the remote PV tie through a buried PVC conduit. One combiner box from the upper array and one from the lower array has a ground wire to the remote PV tie in its conduit, and the rest do not. All the combiner boxes have ground wires back to the inverter ground ring traveling with the positive conductors from the upper array and the negative conductors from the lower array.

The design engineer for the project and I share a knee-jerk (and quite possibly unsupported by code) reluctance to design conduit runs with no ground wire, so he has communicated to the PM for the project that the responsibility for building a code compliant installation is on the contractor's master, and if the installation fails the AHJ inspection due to changes he made to the design, he will be required to bring it up to code at his own expense.

 

[ggunn]

I got a little more information. There are several DC combiner boxes on the upper and lower arrays, and each combiner feeds the remote PV tie through a buried PVC conduit. One combiner box from the upper array and one from the lower array has a ground wire to the remote PV tie in its conduit, and the rest do not. All the combiner boxes have ground wires back to the inverter ground ring traveling with the positive conductors from the upper array and the negative conductors from the lower array.

The design engineer for the project and I share a knee-jerk (and quite possibly unsupported by code) reluctance to design conduit runs with no ground wire, so he has communicated to the PM for the project that the responsibility for building a code compliant installation is on the contractor's master, and if the installation fails the AHJ inspection due to changes he made to the design, he will be required to bring it up to code at his own expense.

I just wanted to add (too late to edit) that our original design called for a ground wire from every combiner box to the remote PV tie.

 

[shortcircuit2]

Could the installation be code compliant under what 690.43(F) says?

"(F) All Conductors Together. Equipment grounding conductors
for the PV array and structure (where installed)
shall be contained within the same raceway or cable or
otherwise run with the PV array circuit conductors when
those circuit conductors leave the vicinity of the PV array."

 

[ggunn]

Could the installation be code compliant under what 690.43(F) says?

"(F) All Conductors Together. Equipment grounding conductors
for the PV array and structure (where installed)
shall be contained within the same raceway or cable or
otherwise run with the PV array circuit conductors when
those circuit conductors leave the vicinity of the PV array."

We definitely looked at that, but the "where installed" modifier makes it look ambiguous on the point of whether or not the EGC is actually necessary for a particular run, which is the central question.

 

[iwire]

Could the installation be code compliant under what 690.43(F) says?

"(F) All Conductors Together. Equipment grounding conductors
for the PV array and structure (where installed)
shall be contained within the same raceway or cable or
otherwise run with the PV array circuit conductors when
those circuit conductors leave the vicinity of the PV array."

That does not eliminate the need of an EGC.

 

[shortcircuit2]

That does not eliminate the need of an EGC.

I agree with that...ggunn said in that all equipment is grounded.

Take a look at 250.134(B) ex#2...it has a similar allowance...


"Exception No. 2: For dc circuits, the equipment grounding
conductor shall be permitted to be run separately from the
circuit conductors."

 

[ggunn]

That does not eliminate the need of an EGC.

And there is an EGC, just not between every combiner box and the remote PV tie. Every combiner box has an ECG run back to the inverter ground ring, and the remote PV tie has an ECG to one each of the upper and lower array combiner boxes.

 

[iwire]

And there is an EGC, just not between every combiner box and the remote PV tie. Every combiner box has an ECG run back to the inverter ground ring, and the remote PV tie has an ECG to one each of the upper and lower array combiner boxes.

I may not understand the design entirely but it seems to run afoul of 250.102(E)(2) via 300.3(B)(2)

300.3 Conductors.

(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).


(2) Grounding and Bonding Conductors. Equipment
grounding conductors shall be permitted to be installed
outside a raceway or cable assembly where in accordance
with the provisions of 250.130(C) for certain existing
installations or in accordance with 250.134(B),
Exception No. 2, for dc circuits. Equipment bonding
conductors shall be permitted to be installed on the outside
of raceways in accordance with 250.102(E).

250.102(E) Installation. Bonding jumpers or conductors and equipment
bonding jumpers shall be permitted to be installed inside
or outside of a raceway or an enclosure.

(1) Inside a Raceway or an Enclosure. If installed inside
a raceway, equipment bonding jumpers and bonding jumpers
or conductors shall comply with the requirements of
250.119 and 250.148.

(2) Outside a Raceway or an Enclosure. If installed on
the outside, the length of the bonding jumper or conductor
or equipment bonding jumper shall not exceed 1.8 m (6 ft)
and shall be routed with the raceway or enclosure.

Exception: An equipment bonding jumper or supply-side
bonding jumper longer than 1.8 m (6 ft) shall be permitted
at outside pole locations for the purpose of bonding or
grounding isolated sections of metal raceways or elbows
installed in exposed risers of metal conduit or other metal
raceway, and for bonding grounding electrodes, and shall
not be required to be routed with a raceway or enclosure.

 

[shortcircuit2]

Iwire...

250.102 pertains to bonding conductors and jumpers not equipment grounding conductors.

300.3(B)(2) repeats what 250.134(B) ex#2 allows

"or in accordance with 250.134(B),
Exception No. 2, for dc circuits."

Can someone explain why equipment grounding conductors are allowed to run separate in a DC circuit?

 

[GoldDigger]

Iwire...

250.102 pertains to bonding conductors and jumpers not equipment grounding conductors.

300.3(B)(2) repeats what 250.134(B) ex#2 allows

"or in accordance with 250.134(B),
Exception No. 2, for dc circuits."

Can someone explain why equipment grounding conductors are allowed to run separate in a DC circuit?

No excess inductive reactance to fault current, unlike the case for AC when the two current paths are separated.

 

[iwire]

Iwire...

250.102 pertains to bonding conductors and jumpers not equipment grounding conductors.

If you wish to read it that way than there is absolutely no way to run the EGC separate from the conductors.

But 300.3(B)(2) tells us to apply 250.102(E) to EGCs.

 

[jaggedben]

I got a little more information. There are several DC combiner boxes on the upper and lower arrays, and each combiner feeds the remote PV tie through a buried PVC conduit. One combiner box from the upper array and one from the lower array has a ground wire to the remote PV tie in its conduit, and the rest do not. All the combiner boxes have ground wires back to the inverter ground ring traveling with the positive conductors from the upper array and the negative conductors from the lower array.

...

I'm a bit confused. For each array, is the EGC run to all the different combiner boxes on the array, and then run with one of the output circuits to the remote PV tie? If that is the case, and assuming the EGC in one way or another bonds all equipment and racking, then I don't know what code section has been violated.

(Also what is the 'remote PV tie'? The inverter location? A junction box where all the raceways for the output circuits meet?)

 

[shortcircuit2]

If you wish to read it that way than there is absolutely no way to run the EGC separate from the conductors.

But 300.3(B)(2) tells us to apply 250.102(E) to EGCs.

300.3(B)(2) tells us to apply 250.102(E) to equipment bonding conductors.

 

[Sierrasparky]

Ya need a EGC

 

[ActionDave]

If you wish to read it that way than there is absolutely no way to run the EGC separate from the conductors.

But 300.3(B)(2) tells us to apply 250.102(E) to EGCs.

300.3(B)(2) tells us to apply 250.102(E) to equipment bonding conductors.

Further evidence to support my position that tossing in the term equipment bonding conductor into art. 250 does nothing to clear up misunderstandings about a grounded conductor vs. an equipment grounding conductor vs. what needs to be done to clear a fault vs. a connection to the earth.

 

[shortcircuit2]

Further evidence to support my position that tossing in the term equipment bonding conductor into art. 250 does nothing to clear up misunderstandings about a grounded conductor vs. an equipment grounding conductor vs. what needs to be done to clear a fault vs. a connection to the earth.

The NEC makes a distinction between bonding and grounding.