4400w inverter / grid assisted solar charging

[ripple4]

I have a question about auxiliary ground electrodes (GEs) related to ground PV arrays. what have the solar people here done and did it protect from PV equipment failures? looks like grounding is the main concern with any solar array roof mounted or ground mount. much ink is being spilled and there are revisions in NEC that go back and forth on the subject from '04 to current that add to the confusion.

how does this video which Mike Holt discourages auxiliary GEs because it could potentially cause side strikes inside of a building from a nearby lighting strikes' ground voltage gradient align with your understanding of with NEC 690.47 for solar arrays and 250.32 for sub panels? further in NFPA 780 auxiliary GEs are required with no mention of the voltage gradient idea.

https://www.youtube.com/watch?v=Ypo99VRxT44

I had previously grounded my HF-start arc welding table, welder frame and the garages 8 circuit sub panel with an auxiliary GE with 2AWG ground electrode conductor (GEC) and an intersystem bond point. there is also a 6awg GEC from the 8-circuit sub panel to the main panel which, of course, has its own GE, just like 250.32 seems to show. without that extra grounding work any arc welding was knocking out my TV reception and after this it fixed the interference.

could it be because NFPA 780 has the wire outside the protected building that ground voltage gradients are not an concern? would bonding three GEs on the East, West and South side (new array would be on the south side) of the 36"x30" house with new buried GECs fix this potential "side-strike" ground voltage issue?

NFPA780
https://www.ul.com/wp-content/uploads/2 ... tionAG.pdf

discustion on 250.32
https://forums.mikeholt.com/showthread.php?t=147362

pre-2014 NEC690.47
http://solarabcs.org/about/publications ... report.pdf

[Oilpan4]

Grounding and bonding is the most misinterpreted sections of nec.
If the inspector sees anything out of the ordinary they may just fail it.
If it works for you good.

[Marktm]

May have missed it, but what have you found for the "L2H" unit? Several have used the Setec that operates at 220 VAC single phase:
viewtopic.php?t=25164

I've wondered if using a center tapped xformer to produce 110 VAC split phase would have enough voltage to run most US based circuits. Total cost could be quite high for ~3000 watts power.

[ripple4]

May have missed it, but what have you found for the "L2H" unit? Several have used the Setec that operates at 220 VAC single phase:

here is my post on a small L2H. like my graphic shows mine is 1500w, enough for the fridge, furnace and sump pump. i'm not sure why i put so much thought into emergency power contingencies, in the last 7 years i've only lost power twice for more than a few hours.

viewtopic.php?f=37&t=27873

I've wondered if using a center tapped xformer to produce 110 VAC split phase would have enough voltage to run most US based circuits. Total cost could be quite high for ~3000 watts power.

in my system layout you can see my idea to solve that problem, run two load centers, one for 220v loads, then from that 220 load center power a step down transformer for a second load center that is only 120v loads. this will always allow full power, where as a split phase situation will limit the 120v loads to 1/2 the max power if the loads are not balanced. industrial surplus stores have 1 3-7KVA phase 480/240 240/120 Xmers in the $20-$30 range. HGR will ship, but picking up will save on shipping. https://hgrinc.com/

also there is a setec 6KW L2H that is showing up on Alibaba, again 200v (japan?) output only, but its twice the power. i really like how it can charge too, so even as a home level3 it would be useful for us with the 3.3kw charger. only issue is with a 24-30kwh leaf with roughly 16-20 usable KWH, a 6kw or even a 3kw draw will suck the battery flat in hours. at least 1500w draw will last an 8 hour session.

https://www.alibaba.com/product-detail/ ... 3e5fwXD0Cr

I

Yes almost all the MPPT controllers will max out at whatever they are rated for. I would suggest 6000w on that south face if you can get it, there might be an hour or so the MPPT will max out and not use some of the power, but the 2 hours either side of that you will get the additional power from the panels. In winter or hazy days or mornings or evening the extra panels would help out a bunch.

I did verify with the inverter supplier that this one i link to will support more than rated PV input, never more than rated power output, but it will serve to widen the peak power at mid-day. this will have to be stage 2, if and after i can get the 5.3kw peak PV stage 1 working. I ended up ordering 18x of the 295w peak panels instead of 280w.

[Marktm]

also there is a setec 6KW L2H that is showing up on Alibaba, again 200v (japan?) output only, but its twice the power. i really like how it can charge too, so even as a home level3 it would be useful for us with the 3.3kw charger. only issue is with a 24-30kwh leaf with roughly 16-20 usable KWH, a 6kw or even a 3kw draw will suck the battery flat in hours. at least 1500w draw will last an 8 hour session.

https://www.alibaba.com/product-detail/ ... 3e5fwXD0Cr

This newer unit is much more to my liking! Thanks. Most of my 240 VAC users do not require a neutral - and are the highest power users. This would allow me to use a much smaller xformer for the 120 VAC split phase users. The 6kw unit is also large enough for a small cabin off grid - with a good generator for those extended bad weather days. (Would need to be careful about surge current). I've already installed a solar charging system (arduino controller with the OpenEVSE charge controller ) that uses a small battery buffer system. The issue is convincing Setec to up their voltages to 220-240 VAC - cannot believe that would be an issue! Combine this with the 60 kwh Leaf

So many options - at least for me since I'm retired and can schedule my Leaf travel around the sun!!

[ripple4]

An update on the surge protection on the PV array outputs, I got every book in the library out about solar power and combined with E-research found that 1 MOV per string is a good idea when the negative side of the array is grounded. The negative PV input on my inverter is not connected to ground, so doing this will not make a ground loop. Wired this way a surge on the negative wire will go straight to ground on the GEC and the array GE, and on the positive wire will go thought a MOV to negative conductor and then right to ground. I like this because it’s simple and should be effective. With that plan I bought lots of V250L40B MOVs for $1.15 each. If two MOVs are paralleled it will double the energy, in joules, they can dissipate. And also if a ~.01uF, 300V+ high voltage capacitor is also parallel to the MOV it will increase the already ‘lightning fast’ reaction speed of the MOV to even higher frequencies that might be present in an eletric storm.

https://ibb.co/H2Rb04L


Littlefuse white paper that advises to add capacitors for MOVs in DC circuits pg7.
https://www.littelfuse.com/~/media/elec ... n_note.pdf

On the grounding it I think I’ve decided to add a GE next to the array on the screen porch roof and also run a buried bare 6AWG GEC between all three GEs I’ll then have, it will be a 100’ “U” shape around the house and patio. As best I can tell It is code compliant to 690.47D and allowable in 690.47B. I reason that its best to have the shortest path to earth at distant parts of the house. The buried GEC will locally equalize ground voltage gradient at the distance GEs. In the event of a very strong surge, I would not want so much “antenna” of home wiring, PV frames and welder tables leading inside my load center to get to the only GE. Here is an explanation in one of the books I read.

https://ibb.co/DDWkgph

[ripple4]

The issue is convincing Setec to up their voltages to 220-240 VAC - cannot believe that would be an issue!

i've installed 100v japanese and 380v chinese equipment industrially and used a buck boost transformers if the difference in voltage is more than the tolerance allowed. this type of transformer is like a 1:1 ratio but with lots of taps on the HV and LV side to allow tuning the voltages to exactly what you want. a new one might cost more than $1500 at a 6+KVA size, but if setec doesn't have a 240v option, it may be your only option.

these guys have a 7.5KVA 200/240v one.
https://jeffersonelectric.com/wp-conten ... kBoost.pdf

[ripple4]

The solar panel install is done, it went up very easy with one person for all the work, setting the beams and rafters was tricky but not too hard for one guy. I might make a cut list and bill-of-materials and make it available because I think the screen room alone is worth the cost, its 11'x25.5' inside. Then the solar part of it pays for itself 4 times over. the only site prep would be a concrete patio about that size or a paver patio like i did.

All the people i tell about this project, (that is people who care and don't roll their eyes and go back to their phones) indicate that they would want it to work with the grid power off, so the off-grid functionality i think is critical for marketability. looks like i'll be able to take what i learned testing after-market traction pack batteries and use that info to make a powerwall battery for this. lead acid just does not have the cycle life i think i want. does anyone see any issues or problems in the pictures? what could i do better?

[Oilpan4]

Any reaction to HF welding?

I couldn't even take a picture of my old century HF box with a digital camera while it was running because of the RFI EMI it put off.
I eliminated most of the HF box run time at least when running DC by adding a foot switch.
Then used MOV, bleed resistor and an internal Faraday cage to eliminate most of the leakage.
My setup is arcane aside from the water cooled torch.
What it lacks in sophistication it makes up for in raw power.

[goldbrick]

Sorry if this is a dumb question but is the 'roof' waterproof? Is so, how did you seal the gaps between the panels.

In all, it looks great and I have been considering something similar although the orientation of my house makes it a bit problematic.