Electrical conduit for PV system in exterior wall

[katwalatapan]

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.

 

[HCBFlash]

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.

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

 

[AusLee]

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

 

[HCBFlash]

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!

 

[AusLee]

Thanks HCBFlash

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

 

[waross]

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

 

[jfpe]

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