Zapper77
Renaissance Man
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Depends...is the inverter in an accessory building or a primary residence?
EG4 18kPV Q+A general thread
- Thread starter SignatureSolarJames
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Would you mind sharing the ref no and code where the NEC hand book states not to put 6 ga copper stranded sjo wire inside 1 1/2 elec pvc conduit, please.
NEC 690.31(G)
timselectric
If I can do it, you can do it.
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The conductor type doesn't matter.
Just the fact that it is DC solar circuits.
2020 code does appear to have an exception to this if rapid shutdown is in use: https://www.electricallicenserenewa...ation-Courses/NEC-Content.php?sectionID=965.0
rmacgurn
New Member
I don't use micro inverters but I have noticed on PV3 input which I am not using it often shows random low voltages from 2-7v normally, this spurious reading only happens when The two strings on PV1 and 2 are putting our higher currents at 370-400v. not sure if that helps.
ksmithaz1
Solar / EV Junkie
Wow. So if it goes "inside" it has to be in metal. That just sounds stupid. Really stupid. No really really stupid. Like someone making up the rule sez, you can run simple insulated wire outside in nothing, but it has to be in MC or conduit if it goes inside. wow.Well known it is in NEC Section 690
PV wires in the house - conduit question
I have 6 stings of #10 thhn entering my basement. The amperage is 11 amps/string. My EG4 inverters are about 50 lineal ft away from the basement entrance. I'm thinking I should run the strings in pvc conduit to the inverters ? Am I on the right track ? I'm using 1.5" pvc conduit buried from...diysolarforum.com
The PV circuit doesn't have any fault protection on it, so they want extra protections. A few kW of PV can start a good little fire with an arc fault. I was talking to an installer and he actually puts the whole run in metal conduit (in a coastal environment). It is safer... but like most things with the NFPA now, they are well into the realm of diminishing returns for life and property (but ever increasing returns for the equipment manufacturers).
Well I did read through the nec 690-30 some thing. It go's into explaining there reasoning for this being the amount of strings/size of wire and combinations with safety in mind. This reasoning is discussed in the 2023 NFPA report I read. So NO it don't matter what size wire you use, they made there ruling. I do have fault/overload and shut down protection out side before and after the circuit comes into the building. I did only run 1 string in through the conduit and it is oversized 224 and then 6/3 copper stranded. with a max of 196v or up to 3800w, over kill for the load in a controlled temperature climate. May be I should have just ran all the wires on the wall like a race track like many of the posts here, no body probably say any negative about that. Thanks for the positive like Zappy.
Hey, I’m as opposed as the next fellow to regulations that go too far. And I confess to have sometimes fudged or bent some rules on my own premises. But in this instance we are talking about DC, not AC. And it’s not unusual for PV circuits to be carrying upwards of 400 or 500 volts. It’s no joke.
I just pointed out the code violation for whatever it’s worth. Good luck to everyone out there.
DC PV conductors.
Zwy
Emperor Of Solar
Nothing stupid about it. This is DC voltage, many times in the 400V range. An arc fault with DC is hard to break, it would take melting the wire back far enough to break the arc. This creates molten metal spray which could cause pvc to burn.
DC is difficult to break the arc, breakers need arc chutes and magnetic or spring loaded trip action to help break the arc. One needs to be aware of this if they work on any solar system.
timselectric
If I can do it, you can do it.
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It's carrying a very high Hazzard and requires extra safety. Not burning down your house, is kinda important.
ksmithaz1
Solar / EV Junkie
<rant>
Don't buy it. Sorry. I have a decent understanding of DC, and high voltage, and arc fault, but the breakers on the outside are going to trip before the wire heats up. I suppose you *could* get an ARC fault in the jacket somehow because the copper strands somehow got broken where it runs between the breaker and the inverter, inside the conduit, connected to a device which has arc-fault detection, but this starts to get pretty esoteric. Arc fault is actually an interesting topic, and modern detection circuits are actually pretty amazing about detecting them, and this is a "good thing" (tm), but somehow thinking that a continuous piece of jacketed wire is somehow going to catch fire inside a conduit, not trip any breakers, or trigger a fault. and set your house on fire is getting pretty far out on that safety limb. I mean it would be safer yet if you encased all your wire in metal conduit and wrapped it in concrete, and never actually connected it to anything. 99% of wiring faults are at a junction or tie point, pretty much all the rest are because of an environmental change, it got crushed or cut or ...
Everyone probably be wearing a helmet when you walk around outside because you might hit your head on something and cause brain damage. I'm all for safety, but I think I would have focused on something that will actually have a tangible benefit, like arc-fault detection.
</rant>
So, .... How many fires have been caused by bad wiring between a solar panel array and an inverter?
ksmithaz1
Solar / EV Junkie
At least we listened to Westinghouse and not Edison... Arc welding is a skill I suck at... DC arcs will also melt through steel rather quickly. Then again an MC4 connector is made out of plastic.
Zwy
Emperor Of Solar
No, you don't get it.
First, where are you finding PV DC breakers with arc fault protection? I'd like to see the unicorn.
Second, the load won't change unless there is a short to ground. So that broken wire will just continue to arc and the breaker will not trip until there is a direct short. Metal conduit will help to create a short condition to trip the breaker.
There is something about brain damage to certain individuals that don't understand why things need to be a certain way..... maybe a helmet can help them retain some of the remaining brain cells.
Many.
timselectric
If I can do it, you can do it.
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It's to protect the wires from physical damage. From people or rodents. Your breaker will not stop an arc fault. Because solar power is power limited. The arc current is limited by the arrays output. Which is less than the breakers rating. If the breakers rating was low enough to trip under an arc fault. It would also trip every time you reached full production.
ksmithaz1
Solar / EV Junkie
Most grid-tie inverters have arc-fault built in, which is what I was referring to. You can easily drop one on a din-rail, for example:
There are a couple of outfits that have inlines, and I think the TIGO optimizers also have detection/protection built in. Arc faults are bad, just don't see where putting the feed wire thru 6 feet of steel into the inverter is somehow significantly safer than feeding the wire thru pvc. Not saying that arc faults are not the Achilles Heel of PV, and inline arc fault detection should be required everywhere (and isn't in some places).
Frankly, I'm a little suprised we don't have panels with built in TIGO style devices, prehaps has component costs come down.
Of those many solar panel DC related fires how many occured in the conduit? And how many at some junction point along the way? If you start welding with your dc output from your solar panels, you have a problem that needs to trip a breaker
There are a couple of outfits that have inlines, and I think the TIGO optimizers also have detection/protection built in. Arc faults are bad, just don't see where putting the feed wire thru 6 feet of steel into the inverter is somehow significantly safer than feeding the wire thru pvc. Not saying that arc faults are not the Achilles Heel of PV, and inline arc fault detection should be required everywhere (and isn't in some places).
Frankly, I'm a little suprised we don't have panels with built in TIGO style devices, prehaps has component costs come down.
Of those many solar panel DC related fires how many occured in the conduit? And how many at some junction point along the way? If you start welding with your dc output from your solar panels, you have a problem that needs to trip a breaker
SignatureSolarJames
Try Solar, the Grid will always take you back
the 18kpv has arc fault protection built in
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