Multi-conductor cables in PV
- Thread starter pv_n00b
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shortcircuit2
Senior Member
- Location
- South of Bawstin
I've seen 12-4 MC used for 2 DC Strings rooftop to inverter.
jaggedben
Senior Member
- Location
- Northern California
- Occupation
- Solar and Energy Storage Installer
If you need to run any distance on the roof, and you usually do, then flexible methods don't work too well, especially for avoiding rooftop temperature adders. Most of the time you need to do part of the run to the roof outside, too, and any time I need to splice costs more in time and hassle than material saved. If I'm doing flexible methods anywhere along the way, might as well do FMC and save myself splicing wires.
With that said, we've used NM plenty of times on the AC side.
Finally, yes, I think there's some bias left over from when the code effectively prohibited cables on the DC side.
With that said, we've used NM plenty of times on the AC side.
Finally, yes, I think there's some bias left over from when the code effectively prohibited cables on the DC side.
electrofelon
Senior Member
- Location
- Cherry Valley NY, Seattle, WA
We have used tray cable a lot for inverter output circuits for medium/large roof top systems. For the DC side, if they are 1000V, I cant think of any cables that we could use.
- Location
- Massachusetts
1. Well I think FMC or MC is not allowed on an exterior wall. And 95% of my dc runs are exterior on existing homes.
If you are working on new construction, it could work.
2. Also I am remembering ......15 years ago we wanted to use MC...... and the other issue was that MC has the EGC downsized. Code dictated that the EGC must be the same size as the current carrying conductors. This was the major issue.
3. And then to second Jaggedben....running PV type wire .....then MC cable....then EMT conduit with THHN.....with three splices and types of wire and conduit. more hassle than it's worth. Also introducing that many more potential failure/short/fire points.
- Location
- Massachusetts
Oh you were talking about outside, in that case you can run jacketed MC down the wall but it's pricy so no.
Yeah, that is an issue with most premade cables that dependent on the job specifics can be a problem.
To me this is also job dependent, I am not afraid of asking splices but the cost to do so is a factor.
jaggedben
Senior Member
- Location
- Northern California
- Occupation
- Solar and Energy Storage Installer
For sure, Zee and I are speaking as residential solar guys. Our biggest consideration is avoiding an extra day on the job beyond the one or two that we scheduled for. Material cost difference is negligible compared to another truck roll. So following keep-it-simple-stupid it makes sense to do as much as possible with one wiring method, with maybe a little of one or two more. That way you keep your truck stocked without looking at job specs. Not to mention avoiding discussions with many different inspectors over 'can you do that with PV?'.
The considerations definitely change as the jobs get larger.
The considerations definitely change as the jobs get larger.
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