Anyone see any issues with using type UF to feed micro inverters? I will have 91 panels on a roof. This is divided into 13 systems, 7 panels each. All 13 circuits will feed into a J box via the UF. The cable will be zip tied to the rails under the modules, protected from physical damage. UF is sunlight resistant, but most will be shaded. Thoughts?
Romex feeding micro inverters
- Thread starter sketchy
- Start date
- Status
single jbox for all 13 branch circuits...or individual j boxes at each branch circuit?
I s the jbox under or adjacent to panels? Or apart?
Isn' t that what the trunk cable is needed for?
Zipties are not a 30 year, or even more than couple year way to attach pv wiring. Even if "sunlight resistant" and black. That just means they won't fail immediately. there are clips for that.
jaggedben
Senior Member
- Location
- Northern California
- Occupation
- Solar and Energy Storage Installer
The standard solution would be to simply run conduit to junction boxes out on the array(s).
That's what I'm trying to avoid, liquidtite & wire, due to material and labor costs. I was leaning toward PVC coated MC but that is expensive as well. I like the UF idea because it is fast and cheap and it will be 99% covered by the solar modules.
jaggedben
Senior Member
- Location
- Northern California
- Occupation
- Solar and Energy Storage Installer
You don't need liquidtight. EMT with rain-tight fittings is fine.
As c_picard pointed out, UF is not well rated for the temperature, so check your ampacities.
I would use stainless clips instead of zipties.
As c_picard pointed out, UF is not well rated for the temperature, so check your ampacities.
I would use stainless clips instead of zipties.
A couple more Q's:
---So, a single 12 x 12 jbox for all 91?
---All 91 panels are in one physical array?
That would be a lot of j-boxes to mount, ground and splice in......i see....
---How do you intend to splice UF to trunk cable ends?
---I assume they are using 7-module-long trunk cable cut sections per each branch circuit?
---They just don't want to extend trunk cable from 7 panel sections all the way back to jbox, right?
Totally understandable. That stuff is $20/module length increment.......
Here is what i would do: Get Enphase's (assuming they are the micros here) "extension cable"...have you seen that? They make it.
Buy an inline, big splice tube from them also, one per circuit. Splice that extension cable to the end of the trunk cable.
It's basically like an appliance cord or romex for a roof(TYPE SE???), flexible and black. You can run that under panels w/o conduit.
Or figure out what that cable is and get equivalent - or better - for cheaper, on your own.......
MasterTheNEC
CEO and President of Electrical Code Academy, Inc.
- Location
- McKinney, Texas
- Occupation
- CEO
Well one issue is your title says "Romex" feeding micro inverters and then in your question you refer to UF Cable. As I am sure you are aware, "Romex" is a tradename of SouthWire Corporation and the proper term would be Nonmetallic Sheathed Cable and UL Cable is neither NM Cable or Romex.
Typically the micro-inverters will come with a cable designed for use with the micro-inverter and since the connections within these cables are also evaluated I would say you have to use the cable specified by the manufacturer and I do not believe UF cable will be one of them. However, I could be incorrect on that so check with the manufacturer of the micro-inverter. I know that Enphase directs you to use their specific cable from their product to the junction point.
Just my thoughts on the subject.
jaggedben
Senior Member
- Location
- Northern California
- Occupation
- Solar and Energy Storage Installer
Enphase recommends a type TC-ER. Don't ask me why. I'd say SOOW could also be appropriate, regardless of the micro brand.
Enphase's splice is more expensive than a j-box, cover, UF connectors, and wire nuts. Maybe a teeny bit saved on labor with it.
I'd not assume the system is Enphase, based on the design numbers. 7x13 panels would make more sense. Also the 7.8 amps doesn't make sense unless that is already multiplied by 1.25%, (but then it should be 7.9).
Enphase's splice is more expensive than a j-box, cover, UF connectors, and wire nuts. Maybe a teeny bit saved on labor with it.
I'd not assume the system is Enphase, based on the design numbers. 7x13 panels would make more sense. Also the 7.8 amps doesn't make sense unless that is already multiplied by 1.25%, (but then it should be 7.9).
fmtjfw
Senior Member
- Location
- Fairmont, WV, USA
Safety?
Safety?
I assume you know that the lifespan of a solar installation could be 40 years. Are you sure it is a good idea to try to cut corners in the cable, since it is likely to be a small percentage of the total cost and a weak link in the system?
I believe I have seen failed UF on rooftop installation less than 40 years old.
Safety?
I assume you know that the lifespan of a solar installation could be 40 years. Are you sure it is a good idea to try to cut corners in the cable, since it is likely to be a small percentage of the total cost and a weak link in the system?
I believe I have seen failed UF on rooftop installation less than 40 years old.
texie
Senior Member
- Location
- Fort Collins, Colorado
- Occupation
- Electrician, Contractor, Inspector
At the risk of sounding overly harsh, this screams "hack" job to me.
jaggedben
Senior Member
- Location
- Northern California
- Occupation
- Solar and Energy Storage Installer
Sierrasparky
Senior Member
- Location
- USA
- Occupation
- Electrician ,contractor
Add me three.
Thanks for all the responses, it's nice to get different perspectives. Let me try to address some things. First, I know romex is a trademark and that UF is not the same. The title should have said UF.
Next, I tried to talk the powers that be into making the trunk cable long enough to get to the 12x12 box, but they tell me the cost is too much. Same for the "extension cable".
My plan is to terminate the trunk cables in a bell box with the UF, then run the UF to the 12x12. The micro inverters are Enphase 215's which equals 7.8A continuous. The temperature correction factor for this area will be .91, well within range of #12 UF.
I pride myself in being a craftsman, if something looks bad I'm the first to point it out. The last thing I want is to be called a hack, never have, never will. That being said, as long as the UF is secured properly, how is that worse than trunk cable or liquidtite or SO cable or MC? UF is sunlight resistant, rated for wet locations and like I said before, will be 99% shielded from the sun. I agree that zip ties are not the best way to go, but again, they won't be exposed to the sun.
I appreciate all the help and input.
Next, I tried to talk the powers that be into making the trunk cable long enough to get to the 12x12 box, but they tell me the cost is too much. Same for the "extension cable".
My plan is to terminate the trunk cables in a bell box with the UF, then run the UF to the 12x12. The micro inverters are Enphase 215's which equals 7.8A continuous. The temperature correction factor for this area will be .91, well within range of #12 UF.
I pride myself in being a craftsman, if something looks bad I'm the first to point it out. The last thing I want is to be called a hack, never have, never will. That being said, as long as the UF is secured properly, how is that worse than trunk cable or liquidtite or SO cable or MC? UF is sunlight resistant, rated for wet locations and like I said before, will be 99% shielded from the sun. I agree that zip ties are not the best way to go, but again, they won't be exposed to the sun.
I appreciate all the help and input.
mwm1752
Senior Member
- Location
- Aspen, Colo
I did not know 12 ga UF carried a USE-2 marking as service entrance cable -- I don't have a piece infront of me but a quick confirm from one of you would be nice
No problem.
I certainly agree with you that finding a cable solution would be ideal to run from trunk cable, under array, to j box.
Especially when the alternative is running trunk cable with its bulky connector receptacles...that are unused...... for 10 or more module lengths.....:slaphead: At 20 bucks a single module increment....adds up quick!
As long as you use an equivalent weather rated - or better - cable than the enphase extension cable, I would rest easy. After all the standard install is to run a cable under the array.
Either the splice from Enphase or bell boxes are fine...6 or half dozen. I have regularly used Bell boxes and appropriate strain relief connectors (not "rx conn.s" as you surely know, but the circular "cord grips"..... also, there are nice, metal ones with rubber insides ).
Back in the day we ran the nonmetallic flexible (gray colored) conduit underneath arrays. Called, I forget which is which..... liquidtite or sealtite......to 48V battery systems. Maybe that + pulling in THWN-2 is affordable vs cables mentioned???
TC-ER or SOOW, i dunno others seem to know more about conduit and UV rating which is definitely what will matter!
jaggedben
Senior Member
- Location
- Northern California
- Occupation
- Solar and Energy Storage Installer
Is this in a really cool area? Like, the Arctic?
hmy: I'd be surprised if that's really an appropriate correction factor given that roof temps are typically higher than surrounding ambient temps. Technically you are exempt from 310.15(B)(3)(c), but it still strikes me as appropriate to have an adder for the roof.Also, if you are using #12, you should take a serious look at Enphase's voltage drop application notes. Granted this concern is mitigated by your small number of inverters per circuit.
Personally I wouldn't trust any jacketed cable that wasn't 90C rated and black in color. 'Sunlight resistant' really doesn't mean that much. If it doesn't have concentration of carbon black it won't last as long. There's going to be spots between panels where the sun get's through. That 1% is all it takes for a failure.
If this is a big tilt up system that can be serviced from underneath without removing panels, then the stakes are lower. If it's a flush mounted system that would be really difficult to service if all this UF started to break down in the sun, then I think you are taking a risk that's not justified by the small amount of money saved as a percentage of the overall project. Just my opinion...
- Status