Quite often I find we are installing solar systems on multiple roof faces. For example I am working on a job with both East & West facing arrays. I would like to know more about using EMT as a sleeve to protect the PV wire from damage. Example is running PV wire over a ridge cap in a short EMT sleeve from the west roof to the east roof and then run both east and west array circuits in free air into a wiring transition box at the far end of the east array to switch to THWN-2. Is there a limit to how long a sleeve can be? What is the best way to ground the sleeve? Do I need to run an EGC through the sleeve with the PV wire or can I run my bare copper array EGC outside of the sleeve and use a bonding bushing on the end of the sleeve to bond the sleeve to ground? Technically by code the EMT can act as an EGC. Alternatively, can I run the bare copper racking/array EGC through the sleeve with the PV wire while still using a bonding bushing to bond the EMT to ground? I understand that an EGC must be run inside a raceway with the ungrounded conductors. The way I understand the definition of a sleeve is it doesn't have boxes on either end and one would use a pull bushing that has a piece of plastic to protect the wire from the sharp ends of the EMT. If possible I would like to prevent having to set two boxes with strain reliefs on both ends of the EMT running over the ridge cap. Is this doable or is this a code violation? Is there somewhere in the NEC that provides definitions & requirements for sleeves?
EMT Sleeve for PV Wire
- Thread starter SunFish
- Start date
- Status
- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
EMT can only be used as an EGC when it is part of a raceway system. I would not allow an EMT sleeve to be used as the EGC.
Any particular reason for using EMT rather than PVC as your sleeve?
I don't recall much if anything about sleeves in the NEC other than they are what you have for protection when it does not meet the definition of a raceway.
Ferrous sleeves, like ferrous raceways, must be used properly when containing AC circuits or GECs. Will your DC EGC be only an EGC or will it double as a DC GEC?
(Not a good place to be dyslexic.)
Any particular reason for using EMT rather than PVC as your sleeve?
I don't recall much if anything about sleeves in the NEC other than they are what you have for protection when it does not meet the definition of a raceway.
Ferrous sleeves, like ferrous raceways, must be used properly when containing AC circuits or GECs. Will your DC EGC be only an EGC or will it double as a DC GEC?
(Not a good place to be dyslexic.)
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ggunn
PE (Electrical), NABCEP certified
- Location
- Austin, TX, USA
- Occupation
- Consulting Electrical Engineer - Photovoltaic Systems
You can't run in PVC exposed to sunlight, can you?
- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
Sure you can as long as you use UV resistant PVC. (Electrical gray instead of plumbing white.)
Although painting it would add even more protection.
Although painting it would add even more protection.
MasterTheNEC
CEO and President of Electrical Code Academy, Inc.
- Location
- McKinney, Texas
- Occupation
- CEO
Unless of course the paint you use has something in it that breaks down the PVC conduits chemical compounds...then you might not want to use THAT specific paint again:angel:Sure you can as long as you use UV resistant PVC. (Electrical gray instead of plumbing white.)
Although painting it would add even more protection.
- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
Look for UL listed conduit paint?
jaggedben
Senior Member
- Location
- Northern California
- Occupation
- Solar and Energy Storage Installer
The best way to ground the EMT is with bonding bushings on both ends, preferably with a direct burial rated lug substituted for the one that comes with. It would be nice if someone would invent a simple stainless steel part that would do the job, but I don't think it exists.
Yes, you must run the EGC through conduit.
No, there is no limit on the length.
- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
Can you point to where the EGC is required to be inside the non ferrous sleeve, since we do not have a raceway here?
jaggedben
Senior Member
- Location
- Northern California
- Occupation
- Solar and Energy Storage Installer
690.43(F)
I'm not sure why you are saying we don't have a raceway.
Not sure why you are invoking a section on underground service cable or raceway when we're talking about rooftop installations.
Also, see 690.43(B) about connecting an array to 'other equipment'.
Gee, that's surprising. Answer's can be found in the section of 690 dedicated to equipment grounding.
Also folks, don't forget about 250.97 since most PV DC conductors are over 250V.
Oh, and yes, installing PVC on rooftops is a very bad idea, it will not last. If you need a code reason, it probably violates the temperature rating of the conduit even if the stuff is UV rated. See 352.12(D). So, it needs to at least be UV rated and rated for over 122degF in most cases, or you need to set it well above the roof (which probably eliminates it from residential installs that need to look nice).
Forgot about the indirect citation: 250.110(5)
I have to assume the exception applies to non-service scenarios because I can't deduce any other reason for the re-direct.
shortcircuit2
Senior Member
- Location
- South of Bawstin
If you are running PV wire, I'll assume that you are running PV DC source circuit conductors.
Section 300.3(B)(2) will provide guidance for the equipment grounding conductors and equipment bonding conductors.
Section 250.134(B) exception #2 allows the EGC to be run separate of the circuit conductors with DC circuits.
jaggedben
Senior Member
- Location
- Northern California
- Occupation
- Solar and Energy Storage Installer
But again, 690.43(F) overrides this.
shortcircuit2
Senior Member
- Location
- South of Bawstin
I interpret 690.43(F) to apply to PV conductors and equipment grounding conductors (where installed) that have left the vicinity of the array.
jaggedben
Senior Member
- Location
- Northern California
- Occupation
- Solar and Energy Storage Installer
...which, at least with respect to the original post, is what we are talking about.
Carultch
Senior Member
- Location
- Massachusetts
Interesting. Although it is easy to miss, it does say "cable assemblies".
I'm not sure if individual field-installed wires bundled together would count as a cable assembly. To me, a cable assembly would mean a factory assembled multiconductor cable.
JMO, I think it is a bad idea to use short sections of ungrounded metal raceway for sleeving. The requirement is that all non-current carrying conductors shall be grounded. That means any piece of metal that doesn't intentionally carry current, needs to be bonded to the EGC system.
A bonding bushing with a swapped out lug for direct burial, is the way to do it. Or a split bonding bushing, if you need to do it after you forgot. I've seen installations with grounding ring terminals attached to the mounting straps. Theoretically that works, but it isn't a listed connection.
Yes, it does say cable assemblies... which I stretch to encompass any wire conductors permitted to be used in a non-raceway wiring method.
Agree with Jaggedben, PVC is absolutely to be avoided on rooftops.
1. PVC changes in sunlight to become less flexible and more brittle and can shatter from minor impact....within a year or two.
2. The claimed "UV resistance" for PVC is seriously under-whelming: it was meant to test PVC to ensure it can be stacked in a yard before sale.....don't quote me on this one, but it amounts to about a year of rooftop exposure. (A PV system will last 30.)
3. Personal experience has shown me PVC on a rooftop PV install that, within 3 years, shrank and ripped out of glued fittings in multiple locations , exposing the conductors.....
4. PVC expands and contracts at a rate triple that of steel and aluminum conduit (!).
Given that the thermal cycle is most extreme on a roof, this means it can damage the roof....and loosen very qucikly.
....And "sag" between all straps. Can look cheap.
4. From a safety and environmental standpoint PVC (Poly Vinyl Chloride) is seriously toxic, especially when burned. (Dioxin)
1. PVC changes in sunlight to become less flexible and more brittle and can shatter from minor impact....within a year or two.
2. The claimed "UV resistance" for PVC is seriously under-whelming: it was meant to test PVC to ensure it can be stacked in a yard before sale.....don't quote me on this one, but it amounts to about a year of rooftop exposure. (A PV system will last 30.)
3. Personal experience has shown me PVC on a rooftop PV install that, within 3 years, shrank and ripped out of glued fittings in multiple locations , exposing the conductors.....
4. PVC expands and contracts at a rate triple that of steel and aluminum conduit (!).
Given that the thermal cycle is most extreme on a roof, this means it can damage the roof....and loosen very qucikly.
....And "sag" between all straps. Can look cheap.
4. From a safety and environmental standpoint PVC (Poly Vinyl Chloride) is seriously toxic, especially when burned. (Dioxin)
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Carultch
Senior Member
- Location
- Massachusetts
- Status