Running PV wires in an attic/indoors/basement guidelines?

[zanydroid]

Hi Zany. As some of you are aware I had a PoCo run in where they investigated this unit then eventually waved it off as OK. One thing I thought I learned, was UL1741 compliance requires Arc Fault and Ground Fault - IS THAT CORRECT? Asking, not saying I know...

Can we trust China if it says it complies

View attachment 165665

It has the mark and it's sold by a US based company so you have someone onshore to yell at or get Intertek to yell at on your behalf.

 

[pvgirl]

The unit is definitely listed to UL1741 see: https://ramuk.intertekconnect.com/W...a67e94b8814c30c88625883700152c93?OpenDocument

I'm not sure if UL1741 covers arc fault, and ground fault for solar. But if it had listed arc fault it would also be listed for UL1699 which is the standard for pv arc fault, which this unit doesn't seem to be to listed to. Also on page 24 on the manual seems indicate that ground fault protection must be provided, but not that it is not included.

 

[Cptx]

EG4 did provide these PV cable MC4 terminals.
Thus, I suppose I could purchase the 10 AWG brand PV cable compatible with the roof panels, then run the cable in conduit (either pvc or metal) ; DC disconnect shut down switch at the roof ; DC disconnect breaker just prior to going to outside unit ; then that final run, cut off the PV brand terminals compatible with the panels and crimp on these provided MC4 terminals compatible with the unit….thus, the MC4 terminals will be in accord with their instructions at both ends of the run.

 

[Marine359]

Thank you for the feedback; I was unaware regarding the 10awg requirement in solar DC PV cables while running through the house. Easy change to my purchasing list.

The only way I could avoid the attic would be to run the wires off the roof, over the gutters and then pvc conduit all the way around to the north side in 3/4 pvc conduit. I actually like this idea a lot as cosmetics/aesthetics are low on my goal/appreciation list. I know my wife thinks otherwise and I would worry more about squirrels and wiring shenanigans going this route.

Thanks again.

That’s pretty much what I want to do because I don’t want to route through roof and walls. PVC conduit would keep out water and critters. in my case, I think I can tuck the conduit into a gable corner where it’s out of sight as much as possible. I’m thinking of punching through to basement right above the foundation, then down the wall to a breaker. I’m not planning on conduit once inside the basement. Is that a must? Interested in learning more about your plan.

 

[wheelman55]

Marine359. Contact your local AHJ (building inspector) and ask them about the wires inside the house.

That way you’ll get a solid answer, rather than opinions?

Start with a phone call followed by an email confirming what the AHJ said. Keep the email in case you ever need to deal with your insurance company or another inspector.

 

[zanydroid]

DC circuit needs to be in conduit or cable after exiting array. DC circuits also need to be in metal conduit within the building. Solar is allowed to use FMC or MC within building with extra protection or big enough conduit size to be strong enough to not need it.

Need to comply with the solar specific rules in 690 as well as the general rules in 3xx.

Digital Codes

ICC Digital Codes is the largest provider of model codes, custom codes and standards used worldwide to construct safe, sustainable, affordable and resilient structures.

codes.iccsafe.org

 

[wheelman55]

Cptx. If you are concerned with critters, consider using SS sleeving over the PV wires.

I used this on all of the PV wires at our solar array. It’ll deter mice, rats, squirrels, birds, etc. A neighbor had some of his wires destroyed by hungry cows, who ate the insulation?

https://www.amazon.com/Electridct-Stainless-Steel-Braided-Sleeving/dp/B007KA7FZG

 

[Cptx]

I found some flexible 1” aluminum conduit for a good price on Amazon….think I’ll be able to avoid making 90 degree elbows with this.

 

[zanydroid]

I believe with 1” you can avoid extra protection requirements, but it’s in the code sections I pasted above. And I’ve used flex for exactly the reason of getting out of doing complex EMT bends beyond my scrub DIY skill set.

 

[x98myers7]

metal clad cable absolutely IS permitted to be used in attic spaces.

flexible conduit is unlikely to be allowed. I don't know and won't answer for it. just go with MC cable properly sized.

make sure you account for temperature derating in your cabling size

look over the FAQs in my signature for guidance

 

[zanydroid]

metal clad cable absolutely IS permitted to be used in attic spaces.

flexible conduit is unlikely to be allowed. I don't know and won't answer for it. just go with MC cable properly sized.

make sure you account for temperature derating in your cabling size

look over the FAQs in my signature for guidance

FMC is specifically called out in 690.31

690.31(D) Direct-Current Circuits on or in Buildings.

Where inside buildings, PV system dc circuits that exceed 30 volts or 8 amperes shall be contained in metal raceways, in Type MC metal-clad cable that complies with 250.118(10), or in metal enclosures.

www.electricallicenserenewal.com

This section also covers the minimum unprotected MC size

 

[Zwy]

That’s pretty much what I want to do because I don’t want to route through roof and walls. PVC conduit would keep out water and critters. in my case, I think I can tuck the conduit into a gable corner where it’s out of sight as much as possible. I’m thinking of punching through to basement right above the foundation, then down the wall to a breaker. I’m not planning on conduit once inside the basement. Is that a must? Interested in learning more about your plan.

Any PV wires inside the structure need to be in metal conduit. Doesn't matter if an attic space, basement or other location.

Semper Fi brother

 

[WolfbaneAries]

- If any PV wiring inside a structure need to be inside metal conduit, at what point can the wires exit the conduit for the final connections to the solar controller? For example my victron 250/100 simply has two screw terminals for the pv input.

- My understanding from the victron manual is that you must use wire with a high strand count for proper connection:

"• Use flexible multi-stranded copper cable for the battery and PV connections.
• The diameter of the individual strand of the cable used should not exceed 0.4mm (0.016 inch) or have a
surface area exceeding 0.125mm² (AWG26).
• The maximum operating temperature is 90°C (194°F).
• For MC4 models only: The maximum current rating of a MC4 connector is 30A.
• A 25mm² cable, for example, should have at least 196 strands (class 5 or higher stranding according to
VDE 0295, IEC 60228 and BS6360). An AWG2 gauge cable should have at least 259/26 stranding (259
strands of AWG26). Example of suitable cable: class 5 “Tri-rated” cable (it has three approvals: American
(UL), Canadian (CSA) and British (BS)).
• In case of thicker strands the contact area will be too small and the resulting high contact resistance will
cause severe overheating, eventually resulting in fire."

Thus a household 10/2 MC cable would not be acceptable for the connection to the solar controller, is that correct?

 

[zanydroid]

- If any PV wiring inside a structure need to be inside metal conduit, at what point can the wires exit the conduit for the final connections to the solar controller? For example my victron 250/100 simply has two screw terminals for the pv input.

Victron has a high chance of not integrating nicely with US wiring since they don’t focus on that market.

With a proper UL listed equipment the conduit terminates in a knockout integral to the device.

I believe in Europe individual MC4 are allowed to go straight into inverter or MPPT while in US it needs to be conduit or cable.

A photo of the wiring area would help give some ideas.

Thus a household 10/2 MC cable would not be acceptable, is that correct?

Hard to say, does 19 strand comply? You don’t provide enough text for us to answer… also another example of victron being foreign… because US and Canadian code have a simpler to understand (for our materials) spec in it for how many strands PV should have for connection to PV equipment in some cases.

Victron may be protecting their own terminals so if in doubt buy the highest strand you can find as a jumper, and then splice together with terminal blocks or polaris. If there’s a fire it will burn the terminal block or polaris and not MPPT.

 

[x98myers7]

- any PV wiring inside a structure need to be inside metal conduit

I'm not aware of this requirement, nor do I think it's valid. is there an NEC guideline you can point to?

Listed equipment will have provisions for connectors for EMT or MC cable. that victron SCC is not UL listed for residential install.

 

[zanydroid]

If I was installing with this SCC I would find a photo of how it’s installed cleanly in a European country with sane standards and then try to marry that with NEC as closely as possible. Probably exit a gland and strap the gland to the wall as close as possible to the MPPT. Maybe put a protective plate over it to protect it and cover up the shame /s

That victron MPPT will also be missing AFCI FWIW.

 

[x98myers7]

nice ideas... but none of that will meet USA NEC 690 residential requirements because we've started with unlisted equipment.

 

[WolfbaneAries]

If I was installing with this SCC I would find a photo of how it’s installed cleanly in a European country with sane standards and then try to marry that with NEC as closely as possible. Probably exit a gland and strap the gland to the wall as close as possible to the MPPT. Maybe put a protective plate over it to protect it and cover up the shame /s

That victron MPPT will also be missing AFCI FWIW.

Well I don't want to blow up the OP's thread, but here are a couple examples I found online:

https://community.victronenergy.com...34-1865093586977962-8984529522506317620-n.jpg

https://lzd-img-global.slatic.net/g/p/668eac0cc391e26a588cc4048fc8bb9e.jpg_2200x2200q80.jpg_.webp

 

[zanydroid]

The first one looks very similar to what i said.

Notice that those thick rubber conduit things are strapped to a strain relief (clamps on “unistrut”) before reducing down to individual conductors to go in MPPT.

 

[Zwy]

- If any PV wiring inside a structure need to be inside metal conduit, at what point can the wires exit the conduit for the final connections to the solar controller? For example my victron 250/100 simply has two screw terminals for the pv input.

- My understanding from the victron manual is that you must use wire with a high strand count for proper connection:

"• Use flexible multi-stranded copper cable for the battery and PV connections.
• The diameter of the individual strand of the cable used should not exceed 0.4mm (0.016 inch) or have a
surface area exceeding 0.125mm² (AWG26).
• The maximum operating temperature is 90°C (194°F).
• For MC4 models only: The maximum current rating of a MC4 connector is 30A.
• A 25mm² cable, for example, should have at least 196 strands (class 5 or higher stranding according to
VDE 0295, IEC 60228 and BS6360). An AWG2 gauge cable should have at least 259/26 stranding (259
strands of AWG26). Example of suitable cable: class 5 “Tri-rated” cable (it has three approvals: American
(UL), Canadian (CSA) and British (BS)).
• In case of thicker strands the contact area will be too small and the resulting high contact resistance will
cause severe overheating, eventually resulting in fire."

Thus a household 10/2 MC cable would not be acceptable for the connection to the solar controller, is that correct?

In a recent video I posted on Youtube, I need to make a transition from conduit to my Victron Lynx busbar. It was for battery cables not PV but the same could apply to PV wires. I simply butted a box to the Lynx, drilled 2 holes that lined up with each busbar in the Lynx and passed the cables thru the box to the busbar. This made a nice clean transition. Probably have to use a metal box for PV.

However, the NEC code states metal conduit to disconnect, I don't recall if it needs to be in metal conduit after the disconnect.