×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Electrical conduit for PV system in exterior wall

Electrical conduit for PV system in exterior wall

Electrical conduit for PV system in exterior wall

(OP)
Hello,

I'm working on a plan to install 4kW, 1-phase, 240VAC, grid-tied, micro-inverter based, Photo-Voltaic System no a rooftop in a multi-unit residential building. I wanted to inquire if it is an acceptable practice to run the AC cables from the rooftop junction box to the PV AC Disconnect on the buiding's exterior wall, in EMT conduit installed inside the building's exterior wall. Exterior wall cladding work is also planned around the same time, so I wanted to inquire if it is acceptable to run the EMT conduit inside of the exterior wall.

This work is conducted on an existing building, so going through the attic and ceiling space of the building is not an option. Another alternative could be installing the EMT conduit from the rooftop junction box on the surface of the exterior wall. I'd appreciate your comments/suggestions on the best practice to install the EMT conduit from the rooftop junction box to the PV AC disconnect on the exterior wall. Also, is rigid EMT conduit preferable or flexible, galvanized steel conduit?

Thank you.

RE: Electrical conduit for PV system in exterior wall

Yes, according to the National Electrical code. (NFPA....70E?). Local codes however may have something to say about it, though I doubt it. Your concern would be whether the tradesmen doing the cladding work are using long, self-drilling screws, and their location. If you don't mind waiting to pull wire, or come back and pipe the surface if your embedded emt gets damaged.

Regarding "rigid emt", there is no such thing, nor is there flexible emt. Flexible metallic conduit (galvanized or aluminum) is not acceptable in wet locations including where exposed to rain, however flexible liquid tight conduit is. Exposed runs of any distance are best done in a non-flexible raceway such as emt, galvanized rigid, or aluminum rigid conduit.

.


Me wrong? I'm just fine-tuning my sarcasm!

RE: Electrical conduit for PV system in exterior wall

Can I ask how will you manage the cable dangling on its wieght over a high vertical drop in the conduit?

RE: Electrical conduit for PV system in exterior wall

If there are bends in the conduit, the conductors may well be self-supporting. If there is a straight vertical run between two enclosures with open space, cable ties to fasteners may suffice for conductors #3 and smaller. Large conductors and elevations should be hand taped into a short length of "cable" style section, and suspended by compression style cable grip fittings, or "kellems grips" inside of enclosures large enough to contain them.

Bends can and should be used to deal with this type of stuff, as well as the problems of cumulative expansion and contraction of the raceways and conductors.

.


Me wrong? I'm just fine-tuning my sarcasm!

RE: Electrical conduit for PV system in exterior wall

Thanks HCBFlash

Is there a maximum vertical drop length after wich bends should be used, something like a rule of thumb?

RE: Electrical conduit for PV system in exterior wall

Canadian Electrical Code;
Rule 12-120
Appendix B; Notes on 12-120
Table 21
Also;
12-516 Protection for cable in concealed installations (see Appendix G)
Other options are Rigid PVC Conduit, NMD or AC cables with a junction box to transition to a wiring method suitable for exposed locations where the cable exits the wall.
Best to talk to a local residential Electrical contractor. He will know the most cost effective method that is acceptable to the local AHJ.

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Electrical conduit for PV system in exterior wall

In the National Electrical Code (US), it's section 300.19. Up to 1/0AWG copper, you are allowed a 100' vertical run without support.

EMT should be fine in the application you describe. My only concern would be if it is a high traffic area, I would reccomend RMC for the bottom section.

JFPE

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources