Wiring solar to SRNE hybrid HYP4850U100-H in 2+2 split phase parallel OG.

[tialiden]

I'm looking for some wiring advice from you electrician types or skilled Will Prowse types out here.
Backstory:
I am new and interested in going DIY Solar. Sorry for the long back story, but figures it may give some clues. I've built a off-grid 24v (8)272AH pack with 200A BMS and 3000W PSW stand alone with 4 panels. So just got feet a little wet. System works well for the shed and detaches panels for a roller crash cart setup. Recently made Apexium DIY 200A BMS w/16 280AH cells and love it.

Looking for direction:
Now I've got 4 brand new SRNE hybrid HYP4850U100-H all in one inverters which each one has dual MPPT inputs (**reply from Zwy pointed out these units only have one MPPT). My next plan is to begin to plan a solar array that can take my whole house off-grid via the use of a separate load center. I have 200A CH load center today. I want to install about 32 620W bifacial Evo5N panels within 100' from the house on my acreage in Texas. I haven't purchased the panels yet, but leaning into the idea and want to make sure I understand what the wiring is going to look like. Years ago I've rewired a pre-1900's home from 60 fuse panel to 200A service so I did lots of reference to code recommendations at the time. Electricity doesn't scare me, but I do have a health respect for it, and try to lean into safety with proper fusing and wire sizing methodology.

My question stems from lack of experience in the solar field and understanding all the ins and outs of proper wiring techniques as it relates to the whole AC / DC, Solar, latest codes, etc. I'd like to have the solar panels in 8 sets of 4 series strings (edited due to reply and changed to different panel selection) 4 sets of 10 series strings up on tilted above ground mount which I'll fabricate. I'll attach the two key pdfs (solar panel and SRNE hybrid inverter AIO) so you can see the specs. I would like advice on best way to optimize solar output using the 4 inverters paralleled (2 in series producing 10kwh to each separate phase of 120v leg in my new 200A Square D main panel. I'll move over circuits as needed. eventually getting each one off-grid. I'll tie ground wire to house ground main panel, and the pv + and - are of course not tied to ground. Just the SPD has its own separate ground rod Skipping this per more research (1 for all SPDs at solar panels) solely for grounding lightning / sudden surge, as I understand it (*and per Mike Holt

, not having a duplicate shared ground!). Feel free to correct me along the way if any of this sounds off.

Some items I've ordered to this end:
(5 6) SPD DC 1000V 20KA-40KA surge protector, low-voltage arrester device for the 8 4 strings of PV (in metal box at panels)
(5 4) 2P DC MCB 1000V 25A - one for each of the 4PV strings into the MPPTs
(4) 1P+N 230vac Residual current circuit breaker with over and short (RCBO) to feed into the main panel (each going into a Square D main's 2p 1phase 120v 60A breaker (is this even necessary since there is an appropriate breaker at the mains input wiring terminal?) that would be two on right side of the panel for phase 1, and two on left for phase 2.
(4) 100V 60A Din rail Dual display Adj. Over Voltage Current and Under Voltage protective device. between each inverter and the Main panel.
*+ (4) 4P Rotary DC Solar Disconnects (2 strings per) at array and (2 at) inverter
+ (4) Arc Fault Detection Devices

Does this sound about right? Am I being silly on any of this? I know some people use combiner boxes and fewer runs, which with the price of copper cabling may be tempting, but I really want to have some solid redundancy in this setup and try to keep lots of flexibility in future upgrades, and so on.

What wiring tips do you have on this, where do I have this all wrong? What am I overlooking? Absurdities?

 

[Zwy]

I'm looking for some wiring advice from you electrician types or skilled Will Prowse types out here.
Backstory:
I am new and interested in going DIY Solar. Sorry for the long back story, but figures it may give some clues. I've built a off-grid 24v (8)272AH pack with 200A BMS and 3000W PSW stand alone with 4 panels. So just got feet a little wet. System works well for the shed and detaches panels for a roller crash cart setup. Recently made Apexium DIY 200A BMS w/16 280AH cells and love it.

Looking for direction:
Now I've got 4 brand new SRNE hybrid HYP4850U100-H all in one inverters which each one has dual MPPT inputs.

According to this sheet, the unit has one MPPT. https://www.srnesolar.com/wp-conten...ybrid-solar-charge-inverter_datasheet_1.1.pdf

My next plan is to begin to plan a solar array that can take my whole house off-grid via the use of a separate load center. I have 200A CH load center today. I want to install about 32 620W bifacial Evo5N panels

Electrical Parameters (STC*)

Maximum Power (Pmax/W)	605	610	615	620	625
Maximum Power Voltage (Vmp/V)	45.63	45.76	45.90	46.03	46.16
Maximum Power Current (Imp/A)	13.26	13.33	13.40	13.47	13.54
Open Circuit Voltage (Voc/V)	55.30	55.41	55.53	55.64	55.75
Short Circuit Current (Isc/A)	13.97	14.04	14.11	14.18	14.25
Module Efficiency (%)	21.64	21.82	22.00	22.18	22.36
Power Output Tolerance (W)	0/+5W
Temperature Coefficient of Isc	+0.045%/°C
Temperature Coefficient of Voc	-0.250%/°C
Temperature Coefficient of Pmax	-0.290%/°C

Bifacial Output-Rearsid Power Gain

5%	Maximum Power (Pmax/W)	635	641	646	651	656
Module Efficiency STC(%)	22.73	22.91	23.10	23.29	23.48
15%	Maximum Power (Pmax/W)	696	702	707	713	719
Module Efficiency STC(%)	24.89	25.10	25.30	25.51	25.71
25%	Maximum Power (Pmax/W)	756	763	769	775	781
Module Efficiency STC(%)	27.05	27.28	27.50	27.73	27.95

55.64 VOC times 8=445 VOC

Operating range is 450VOC for your inverter. Over the operating range the unit will probably shut off PV. If over 500VOC in colder weather, it will fry the MPPT.

I went here and inputted the above data for 620W panel. At 10F, 486 VOC. I guess it is up to you.

within 100' from the house on my acreage in Texas. I haven't purchased the panels yet, but leaning into the idea and want to make sure I understand what the wiring is going to look like. Years ago I've rewired a pre-1900's home from 60 fuse panel to 200A service so I did lots of reference to code recommendations at the time. Electricity doesn't scare me, but I do have a health respect for it, and try to lean into safety with proper fusing and wire sizing methodology.

My question stems from lack of experience in the solar field and understanding all the ins and outs of proper wiring techniques as it relates to the whole AC / DC, Solar, latest codes, etc. I'd like to have the solar panels in 8 sets of 4 series strings up on tilted above ground mount which I'll fabricate. I'll attach the two key pdfs (solar panel and SRNE hybrid inverter AIO) so you can see the specs. I would like advice on best way to optimize solar output using the 4 inverters paralleled (2 in series producing 10kwh to each separate phase of 120v leg in my new 200A Square D main panel. I'll move over circuits as needed. eventually getting each one off-grid. I'll tie ground wire to house ground main panel, and the pv + and - are of course not tied to ground. Just the SPD has its own separate ground rod (1 for all SPDs at solar panels) solely for grounding lightning / sudden surge, as I understand it (*and per Mike Holt

, not having a duplicate shared ground!). Feel free to correct me along the way if any of this sounds off.

Some items I've ordered to this end:
(8) SPD DC 1000V 20KA-40KA surge protector, low-voltage arrester device for the 8 strings of PV (in metal box at panels)
(4) 2P DC MCB 1000V 25A - one for each of the 8pv strings into the MPPTs
(4) 1P+N 230vac Residual current circuit breaker with over and short (RCBO) to feed into the main panel (each going into a Square D main's 2p 1phase 120v 60A breaker. that would be two on right for phase 1, and two on left for phase 2.
(4) 100V 60A Din rail Dual display Adj. Over Voltage Current and Under Voltage protective device. between each inverter and the Main panel.
Does this sound about right? Am I being silly on any of this? I know some people use combiner boxes and fewer runs, which with the price of copper cabling may be tempting, but I really want to have some solid redundancy in this setup and try to keep lots of flexibility in future upgrades, and so on.

What wiring tips do you have on this, where do I have this all wrong? What am I overlooking? Absurdities?

 

[tialiden]

Thank you for the quick and very helpful response. I appreciate that you pointed out the calc tools and numbers you used. Wow, I overlooked that it has 1 MPPT per unit, since I saw 2 PV inputs and have been looking at dozens of models, so great catch!
So in that case, your point was that I could drop from 8 runs (4s), and go to as few as 4 runs of 8s, at risk of overvoltage, which is a real concern, so now I'm seeing I need to drop to 5 runs: 4 being 7s, and with one inverter just getting PV input from 4s.
Based on that MSinc calc and adjusting for our temp extremes, that would give me:

7string series array:

PV Array
Rated PV Array Power:	4340	Watts
Anticipated Array Power @ 46C:	4112	Watts
Rated PV Array Current:	13.47	Amps
Battery Charging Current @ 57.6 V:	75.3	Amps
VMP (Maximum Power Point Voltage) :	322.21	Volts
VOC (Open Circuit Voltage):	389.48	Volts
VMP @ -23 C°:	361.2	Volts
VOC @ -23 C°:	451.5	Volts

...and the odd set of 4s:

PV Array
Rated PV Array Power:	2480	Watts
Anticipated Array Power @ 46C:	2350	Watts
Rated PV Array Current:	13.47	Amps
Battery Charging Current @ 57.6 V:	43.1	Amps
VMP (Maximum Power Point Voltage) :	184.12	Volts
VOC (Open Circuit Voltage):	222.56	Volts
VMP @ -23 C°:	206.4	Volts
VOC @ -23 C°:	258	Volts

That sounds good right?

Now back to how my connections and intended use of the DIN rail devices to get me from panels to the house in my OP, does the items I mentioned sound ok? One thing I catch if it were to really matter at all, is the manual mentions AC output / input going to 63A circuit breaker, which seems overkill to me. Max. output current (A) is showing 41.7A. So it seems logical for me to use a 60A instead of their mention of a 63A (which doesn't make sense to me, since 125% of 41.7A max, is way less than 60A). Open to ya'lls thoughts.
It's specified here:
Refer to the table below for recommended AC input wire diameter and switch:

Models	Recommended AC input wiring diameter	Maximum bypass input current	Recommended circuit breaker type
HYP4850U100-H	10mm2/7AWG	63A	2P—63A

Note: There is already an appropriate circuit breaker at the Mains input wiring terminal, so it is not
necessary to add one more.

 

[42OhmsPA]

The reason you'd use the 60a breaker is because of the current that can be passed through from the grid.
I don't see any issues using the other items you mentioned but I'd skip "(4) 100V 60A Din rail Dual display Adj. Over Voltage Current".
I've been running the SRNE ASF 10kw for almost 3 months with no issues. I used a 60a breaker on the output and 6awg.
Zwy knows a whole heck of a lot more than I do, you can trust his advice to be safe and accurate.
You could also consider running parallel strings to the mppts since the inverters can handle it (5500w each) , this could allow you to keep an mppt free for future expansion.

I'll be following this, I've been interested in the parallel version for awhile.

 

[zanydroid]

You are also supposed to size the breaker at 125% of continuous inverter output.

I don’t know if there is an exception for off grid in NEC if the breaker is guaranteed to be used only for AC charging / behave like a generator. There is a somewhat heavy bias in NEC to grid tie, which is very likely to hit continuous operation during the summer. Hybrid set up for local consumption is much less likely to be continuous in the AC side.

 

[tialiden]

You are also supposed to size the breaker at 125% of continuous inverter output.

I don’t know if there is an exception for off grid in NEC if the breaker is guaranteed to be used only for AC charging / behave like a generator. There is a somewhat heavy bias in NEC to grid tie, which is very likely to hit continuous operation during the summer. Hybrid set up for local consumption is much less likely to be continuous in the AC side.

Max. output current (A) is showing 41.7A x 1.25=52.125A... Still way less than the 63 mentioned in manual, and why I said I don't see any reason not to use a 60A breaker instead.

 

[zanydroid]

Max. output current (A) is showing 41.7A x 1.25=52.125A... Still way less than the 63 mentioned in manual, and why I said I don't see any reason not to use a 60A breaker instead.

Got it.

The 63A is also weird in that probably 1% of customers in the US will bother to set up a box that can hold a UL489 63A MCB just to meet the recommended circuit breaker type, instead of making it easier and using a 60A or 65A in a regular split phase panelboard (both sizes code compliant). Looks like SRNE still hasn't had somebody from the US go and "fix" this common quirk in their manuals.

 

[tialiden]

While each string will have its own 25A MCB, would code typically require Rotating Handle Isolator Rotary Switch Disconnect device for solar panels? Wasn't sure if there was something about that. Also, what's a bargain price per watt of new panels like the ones I've listed, these days? I'm starting with a pallet.

 

[zanydroid]

While each string will have its own 25A MCB, would code typically require Rotating Handle Isolator Rotary Switch Disconnect device for solar panels? Wasn't sure if there was something about that.

I think code just requires a disconnect. You can use anything listed to disconnect, probably even a UL1077 MCB if it's not needed for OCPD (see below), in this case it's just a switch. You would need 2P per string, i don't know if common trip or handle tied (I would guess handle tied since this is just a service disconnect not OCPD)

You don't need any breakers or fuses if you stay 2P or lower on the strings. Solar is inherently self-limiting on current and 2P cannot exceed 1P per branch in a fault. If you are in a situation where the panels can output more than the wire can handle after paralleling, then adding OCPD to protect the wire can potentially cause the OCPD to trip.

I think there is some debate on polarized vs non-polarized MCB for solar only strings (some failure modes will have backwards polarity). So I think the reason to go with rotary is fewer moving parts, smaller esp if you get something like 4 pole disconnect for 2 strings, and no need to worry about whether the MCBs you picked make sense.

 

[Zwy]

While each string will have its own 25A MCB, would code typically require Rotating Handle Isolator Rotary Switch Disconnect device for solar panels? Wasn't sure if there was something about that.

Big question is if the MCB is rated for high DC voltage and switching under load. For a disconnect, I use the IMO units.

Also, what's a bargain price per watt of new panels like the ones I've listed, these days? I'm starting with a pallet.

I look for any panel that is new, (I'm not fond of used), and fits the SCC's well but has a low price per watt. As for bifacial, you have to size wire according to max panel output even if the bifacial only adds a few percent gain or none at all. I once thought bifacial would work better with snow on the ground but if you have a tilting mount and move panels to over 60 degrees, then you can get reflection off the snow ahead of the array.

In other words, I just look for panels based upon how it fits with the SCC followed by price per watt, not limiting myself to one particular panel.

Your panel choice fits well with your SCC limits for single strings without clipping. With 4 MPPT's you have room for 28 panels with an odd set of 4S that need to go somewhere. I'm assuming you plan on adding a standalone MPPT for those 4?

Max. output current (A) is showing 41.7A x 1.25=52.125A... Still way less than the 63 mentioned in manual, and why I said I don't see any reason not to use a 60A breaker instead.

The reason for the 63A breaker is the SRNE is rated at 63A bypass power according to the spec sheet. I'd use wire and breaker for 60A. I would assume the unit will shut down if 5000W is exceeded under inverter power.

 

[tialiden]

I just ran across this somewhere, happy to hear thoughts on this as well, but does seem like added expense but with advantage of added safety and flexibility, and firemen and contractors would probably really appreciate this approach. I am wondering if this is a guideline or a requirement in the U.S.

"In most solar PV installations, two DC isolator switches are connected to a single string. Normally, one switch is placed close to the PV array and the other close to the DC end of the inverter. This is to ensure that disconnection can be achieved at ground and roof level. DC isolators can come in polarized or non-polarized configurations. For DC isolator switches that are polarized, they come in two, three and four pole configurations."​

Also, I would like feedback on whether the isolator handle can be inside a closed metal box, or does it have to be through the door/wall of the box instead. Sorry to get so granular but it seems that often the relevant term coming to mind: the devil is in the details. Thanks so much for your patience with my ignorance and exploration.

 

[Zwy]

I have an IMO at the array. Myers hub to the metal box.



Inside the metal box, breakers and SPD's, not recent I finally installed the ground wire from panels to system grounding.





And another IMO to the left of inverters. Originally installed 2 IMO's so I had an extra for future expansion but removed the second one when I installed the SCC's on the left. The IMO's have a lockout feature. My array is 420 feet away and not able to be seen so it is a good idea to have a lockout on both ends. If you have exposed terminals like the DIN breakers, the box containing them needs a locking mechanism so someone couldn't just open the door and get shocked or a cover allowing access to turn off the breakers without access to the terminals. The purpose of the IMO at the array is to allow shutting down power at the array in any emergency, plus it allows isolating power so breakers aren't tripped under load. The IMO is designed to be switched with DC, breakers are not, in my opinion, the breakers are a breaker, not a switch.

 

[42OhmsPA]

Your work is an inspiration @Zwy . Makes me want to get much better with my next upgrades. Thank you.

 

[zanydroid]

I just ran across this somewhere, happy to hear thoughts on this as well, but does seem like added expense but with advantage of added safety and flexibility, and firemen and contractors would probably really appreciate this approach. I am wondering if this is a guideline or a requirement in the U.S.

I think you only need one disconnect but I don't have a code reference.

IMOs are pretty cheap, so I don't think it's a huge major expense compared to all the other Balance of System crap.

I guess you could say an extra $80 here and there adds up.

With regards to metal chassis, I haven't seen people put them in metal boxes. The only time I remember that coming up is if the IMO (plastic body) is within the building envelope, since that would (strictly speaking) violate the rule that all solar DC circuits need to be in metallic conduits/raceways. Putting a IMO in a metal box addresses that.

 

[tialiden]

I have an IMO at the array. Myers hub to the metal box.

View attachment 180098

Inside the metal box, breakers and SPD's, not recent I finally installed the ground wire from panels to system grounding.

View attachment 180099

View attachment 180102

And another IMO to the left of inverters. Originally installed 2 IMO's so I had an extra for future expansion but removed the second one when I installed the SCC's on the left. The IMO's have a lockout feature. My array is 420 feet away and not able to be seen so it is a good idea to have a lockout on both ends. If you have exposed terminals like the DIN breakers, the box containing them needs a locking mechanism so someone couldn't just open the door and get shocked or a cover allowing access to turn off the breakers without access to the terminals. The purpose of the IMO at the array is to allow shutting down power at the array in any emergency, plus it allows isolating power so breakers aren't tripped under load. The IMO is designed to be switched with DC, breakers are not, in my opinion, the breakers are a breaker, not a switch.

This is awesome. Thank you for sharing your fantastic work and details with me. I love how your panels are up high and I want to mount in a similar fashion to be able to have shaded wildflowers and mowing and trimming easily around it. I'd love to see details on the way you constructed your support system and a list of materials if that's OK.

I do spot something that I'm planning on doing differently in the wiring for the SPD. My understanding is I should come out of the SPD and go directly to the independent ground rod very near to the panel itself. In this way the lightning or surge has a path to ground in a direct fashion to dump the sudden spike, but as to not interfere or carry surge current to my main panel's ground. I'm referring to Mike Holt's video 7 on grounding that I linked in post above. Hopefully I'm not missing something here. Obviously I'd run a ground from the SPD/MCB/Solar Disconnect box back to my main panel ground, so those are appropriately tied together.

Edited: relevant info:

&

 

[zanydroid]

I don't understand why the close lightning hit would want to direct most energy into the local ground rod vs also sending significant amount to the one at the other end of the EGC. The EGC is much more conductive than the earth. Feels like it could even be 50/50 between both rods. I guess you could argue that 50/50 is better than 100% on one side, but that's also betting that 50% of the surge can be handled but 100% cannot. Perhaps you could achieve something similar by stacking 2x the SPD clamping capacity.

From what I've seen on the forum, most people seem to interpret Mike Holt as recommending against ground rod at the array. I think it gives more opportunities for a voltage gradient in the earth, induced by close-by strike, to send current through the EGC. The close-by strike could be in various locations. If there is no ground rod then there is no low resistance path for an earth gradient to induce voltage across the EGC (even if the voltage is high under the array there is likely no way for it to hop into the grounding system. Well, it could go up through the footings but I guess this is unavoidable and a higher resistance than a ground rod).

 

[Zwy]

This is awesome. Thank you for sharing your fantastic work and details with me. I love how your panels are up high and I want to mount in a similar fashion to be able to have shaded wildflowers and mowing and trimming easily around it. I'd love to see details on the way you constructed your support system and a list of materials if that's OK.

Review of MT Solar mount. I'll fab my own next time with some changes to the MT design. 7" oil well pipe is way cheaper than SCH 80 6 inch for example. I'd move the screw to farther out and possibly even a 2 stage screw if needed. Buy I beam as on continuous length needed for array length.

I tilt back to 30 degrees in summer, I can drive the Toro Groundmaster with roll bar under it easily. It is close at 45 degrees but still get under it. If you don't get much snow, probably wouldn't need it as high.

The reason for purchasing the mount was time related. I DIY my battery bank, plus all the install and had to revamp my basement in the process so there just wasn't enough hours in a day to get it all done so I could use it.

I do spot something that I'm planning on doing differently in the wiring for the SPD. My understanding is I should come out of the SPD and go directly to the independent ground rod very near to the panel itself.

If you study Mike Holt's work, then you will know he does not recommend a ground rod at the array. I subscribe to that theory.

In this way the lightning or surge has a path to ground in a direct fashion to dump the sudden spike, but as to not interfere or carry surge current to my main panel's ground.

The array still has to be bonded back to your main panel's ground regardless if you install a ground rod at the array. All the auxiliary ground rod does is create a possible transient surge if lightning was to strike close by. Watch Mike's PV grounding video here.

I'm referring to Mike Holt's video 7 on grounding that I linked in post above.

I think you should watch #7 again. You maybe are misunderstanding what he is referring to. First, he mentions the auxillary ground rod would not help prevent the shocks. This is correct as the earth is not a low impedence path. Second, and this plays into #1, the ground path needs to go back to source with low impedence. The ground wire provides this path. The low impedence path will flow power at high current, thus tripping the circuit breaker.

Hopefully I'm not missing something here. Obviously I'd run a ground from the SPD/MCB/Solar Disconnect box back to my main panel ground, so those are appropriately tied together.

Forget the ground rod at the array. It is allowed but not required. If your array suffers a direct hit from lightning, it won't save anything. Any direct hit and you will suffer damage. If you construct the array using metal poles in the ground encased in concrete, it does not provide the needed fault current back to the main panel N-G bond. All panels need to be bonded to the N-G bond located at the service.

As long as you follow this, you will be fine.

 

[tialiden]

Review of MT Solar mount. I'll fab my own next time with some changes to the MT design. 7" oil well pipe is way cheaper than SCH 80 6 inch for example. I'd move the screw to farther out and possibly even a 2 stage screw if needed. Buy I beam as on continuous length needed for array length.

I tilt back to 30 degrees in summer, I can drive the Toro Groundmaster with roll bar under it easily. It is close at 45 degrees but still get under it. If you don't get much snow, probably wouldn't need it as high.

The reason for purchasing the mount was time related. I DIY my battery bank, plus all the install and had to revamp my basement in the process so there just wasn't enough hours in a day to get it all done so I could use it.



If you study Mike Holt's work, then you will know he does not recommend a ground rod at the array. I subscribe to that theory.




The array still has to be bonded back to your main panel's ground regardless if you install a ground rod at the array. All the auxiliary ground rod does is create a possible transient surge if lightning was to strike close by. Watch Mike's PV grounding video here.

I think you should watch #7 again. You maybe are misunderstanding what he is referring to. First, he mentions the auxillary ground rod would not help prevent the shocks. This is correct as the earth is not a low impedence path. Second, and this plays into #1, the ground path needs to go back to source with low impedence. The ground wire provides this path. The low impedence path will flow power at high current, thus tripping the circuit breaker.


Forget the ground rod at the array. It is allowed but not required. If your array suffers a direct hit from lightning, it won't save anything. Any direct hit and you will suffer damage. If you construct the array using metal poles in the ground encased in concrete, it does not provide the needed fault current back to the main panel N-G bond. All panels need to be bonded to the N-G bond located at the service.

As long as you follow this, you will be fine.

 

[tialiden]

Wow, Zwy, I think you are right about the ground rod at the panel. Sorry about my confusion and I truly appreciate your feedback and experience. I thought it was Mike Holt's video that mentioned a short blip about the only solar device that would make sense to use a ground rod too, was the DC SPD. I can't seem to find where I got that idea from, and if I do maybe I'll share, but I went back and watched a number of his videos and can't find anything of that nature. In fact In his video about AC SPDs they have nothing to do with ground. They shunt the excess voltage to the neutral but essentially there is overvoltage is still spread among the other circuits, leading to the mindset that more SPD's downstream in a circuit is actually mutually beneficial at dissipating the overage, much like each SPD is a layer on an onion. I definitely picked up on Mike's point about using multiple ground rods is worse, and the need of bonding the ground from the electrical box at the array and taking that back to my home's electrical panel ground (and hence to the single ground rod already in place for the home).

I knew I had lots to learn, I may slowly get a little smarter.

You also made a point earlier that I overlooked. If I have 1 of the 4 inverters getting a 7s array and a 4s array, I think you mentioned I might consider a MPPT in that 4s leg? Is that right? Can we talk about what would happen if I did not have a separate MPPT? I was thinking that the single MPPT of the SRNE would take the 2 inputs and sort it out as a collective.

I took your advice on the DC Rotary switch isolator disconnects and have ordered those to include in my design.

 

[Zwy]

Wow, Zwy, I think you are right about the ground rod at the panel. Sorry about my confusion and I truly appreciate your feedback and experience. I thought it was Mike Holt's video that mentioned a short blip about the only solar device that would make sense to use a ground rod too, was the DC SPD. I can't seem to find where I got that idea from, and if I do maybe I'll share, but I went back and watched a number of his videos and can't find anything of that nature. In fact In his video about AC SPDs they have nothing to do with ground. They shunt the excess voltage to the neutral but essentially there is overvoltage is still spread among the other circuits, leading to the mindset that more SPD's downstream in a circuit is actually mutually beneficial at dissipating the overage, much like each SPD is a layer on an onion. I definitely picked up on Mike's point about using multiple ground rods is worse, and the need of bonding the ground from the electrical box at the array and taking that back to my home's electrical panel ground (and hence to the single ground rod already in place for the home).

You can't go wrong with Mike's videos, great resource.

I knew I had lots to learn, I may slowly get a little smarter.

We all started out knowing nothing about solar. Once you are hooked, well, it is an addiction.

You also made a point earlier that I overlooked. If I have 1 of the 4 inverters getting a 7s array and a 4s array, I think you mentioned I might consider a MPPT in that 4s leg? Is that right? Can we talk about what would happen if I did not have a separate MPPT? I was thinking that the single MPPT of the SRNE would take the 2 inputs and sort it out as a collective.

You can't connect a 7S string with higher voltage to a 4S string with lower voltage.

I think the 4S string can be handled with a 250VOC rated SCC like the Victron 250V units or the EG4 100A-MPPT which is 500VOC rated. The Victron is of course higher priced. The EG4 unit would allow up to 7S for your panels.

I took your advice on the DC Rotary switch isolator disconnects and have ordered those to include in my design.

The IMO switches can not be beat. One can mount the switch in a metal box if the AHJ requires it for inside a residence (some debate here in the forums about this). The IMO was designed for use with PV, not adapted as some switches are.