Two EG4 6500 EX-48 to two A510C Pro/Tran 2 Transfer Switches

[nodoze]

Our current home has two 200 Amp main panels fed from grid.

I am considering doing an "off-grid" setup based on Will's 'Complete DIY 48V Offgrid Solar Power System' design here:

48V Offgrid Solar Power System

If you wish to build the ultimate offgrid solar power system, look no further: All-in-one units make setup a breeze. Each unit has it's own Inverter, MPPT, Transfer Switch and Battery Charger. Budget...

www.mobile-solarpower.com

Some deviations I plan:

• -Want grid AC fed into both EG4 6500's to be able to power more than solar &/or batteries would otherwise be able to (when grid is available);
• -Plan to feed Load Center Panel into two 50 Amp A510C Pro/Tran 2 Transfer Switches that transfer desired circuits from my two 200 Amp main panels (mix of double-pole & single pole circuits); More info about this Transfer Switch is at this URL:

Top-Quality Transfer Switch Kit | Reliance Controls

We provide top-quality generator transfer and safety switch, generator transfer panel, power transfer switch for generator, and house generator transfer switch.

reliancecontrols.com

If possible my plan would be to have the first EG4 6500 120V output to go to the single pole breakers in the first Transfer Switch & the second EG4 6500 120V output to go to the single pole breakers in the second Transfer Switch & both outputs combined to provide the 240v to the double pole 240V breakers in both Transfer Switches.

I believe my primary south facing roof has room for approximately 18 of these 410 panels if placed in 3 rows of 6 with each panel rated at 410W & 37.12V Volts Open Circuit (VOC):

Solarever 410W Half-Cell Mono PERC Solar Panel (Black)

Signature Solar provides solar panels, off-grid solar systems, grid-tie, and hybrid systems. Quality solar inverters, bifacial solar panels, complete solar kits, solar batteries. Featuring brands such as EG4 Electronics with their solar battery, LifePower4 and EG4 LLifePower4 and EG4 LL

signaturesolar.com

Overall I think the 18 panels gives an estimated total array of 7380 Watts & array of 684 VOC assuming each panel's W & VOC is summed additively. If I broke up the 18 panels into 2 strings of 9 panels then each of the 2 strings would be 3690 Watts & 342 VOC with the same additive assumption.

Each EG4 6500 is spec'ed to handle 8000 Watts with a Max PV Array Open Circuit of 500VDC & have 2 MPPT each able to handle 18A per MPPT.

Question 1: Would it be safe/advisable to feed one string of 9 panels into a single MPPT on each EG4 6500 or should I break them into smaller strings (4 strings)?

Question 2: If the above is OK, would it be safe/advisable to feed both strings of 9 panels into both MPPTs on a single EG4 6500?

My 2nd question stems from the single EG4 6500 max 8000 Watts specification exceeding my planned 7380 Watts but I am concerned that IF VOCs of each panel are summed additively the 684 VOC may be too much for a single EG4 6500's 500VDC max PV Array Open Circuit... My hope is that each string's 342 VOC does not count additively toward the 500VDC max or that I am calculating total VOC wrong...

In part the reason I ask the 2nd question is because in a true grid down situation my only critical 240V needs can be manually turned on/off during the day (my small septic pump & my small pool pump & maybe a water heater as a dump load) & I was thinking that I could maybe put my most critical 120V loads on just one EG4 6500 and shut down the other EG4 6500 (after manually switching off all 240V breakers in both transfer switches & all 120V breakers in the 2nd transfer switch). My hope would be being able to cut the steady state &/or idle draw in half yet still be able to pull/manage my full 7380W of solar & manage batteries from just one EG4 6500 (& only start the 2nd EG4 6500 when I have excess solar/battery and then do 240V loads).

Note that I do realize that this would limit the amount of 240V load I could run as one leg from the primary would be carrying the most critical 120V loads but I think I can manage that in an emergency... If I find that just isn't doable then I could maybe look into adding a split phase transformer to handle the imbalance of phase loads...

Edit: If the above array VOC is too much for a single EG4 6500 & I really want to be able to do most of what I need on just 1 EG4 6500 I could look to drop the total array to 12 panels which would be 4920 Watts & 456 VOC total or if separated into two 6 panel strings would be 2460 Watts & 228 VOC per string.

 

[Samsonite801]

Question 1: Would it be safe/advisable to feed one string of 9 panels into a single MPPT on each EG4 6500 or should I break them into smaller strings (4 strings)?

Before you decide, look at this link, read the article, and use the calculator to adjust Voc for lowest cold temperature coefficient:

Solar panel maximum voltage calculator - How to work out the max voltage

To get the maximum solar panel voltage you should expect from your solar panel, use our solar panel maximum voltage calculator.

gold-coast-solar-power-solutions.com.au

Question 2: If the above is OK, would it be safe/advisable to feed both strings of 9 panels into both MPPTs on a single EG4 6500?

What is the combined Isc value (sum of both strings Isc)? If it will exceed the max operating amperage figure in the specs sheet, that is called overpaneling, which is not always bad to do, except that I would ping the support people at SS/EG4 to confirm if there is a hard maximum on circuit Isc number, because it is not clear in documentation, about how far one can safely overpanel the 6500EX on amps, beyond the normal operating amperage maximum shown in the specs sheet.

 

[Sundown]

50 Amp A510C Pro/Tran 2 Transfer Switches

How is this working?

 

[nodoze]

How is this working?

Edit: I ordered and have here in my office one of the '50 Amp A510C Pro/Tran 2 Transfer Switches' just so I could study it and make sure it would work as I was hoping. I am very pleased with it and plan to get another if we pull the trigger with a full solar implementation on our new roof.

We got busy with other things and haven't moved forward. At this point the earliest I think I can circle back to revisit this may be April. When/if we do I will try to remember to report back.

Part of the reason we delayed was due to the release of the 'EG4 8kW Hybrid Inverter' with 12K PV input per inverter. I need to research what my utility fully allows & any monthly costs for that. If allowed & not too great a cost I like the idea of going with a Hybrid inverter over an off grid inverter as long as the Hybrid still works when the utility goes down as my main goal is emergency power for our critical loads for my family...

With the above in mind I held back in part as I wanted to study my loads better to see if my critical loads can be easily run from a single 8K inverter. I am thinking I am OK with the 12K PV limit from the single Hybrid inverter (I do have a second roof area that I may later also fill). If I do go with a single Hybrid Inverter I do still plan to feed it into two "50 Amp A510C Pro/Tran 2 Transfer Switches"...

 

[Sundown]

study it and make sure it would work

The recent firmware update has changed wiring and seems to have improved the inverters operation.

This could help, click the orange download for the PDF. Page 13 has the inverter with reliance MTS.

Grounding and bonding for EG4 6500 EX inverters.

In February 2023, EG4 announced a significant change to how their inverters do grounding and bonding. Overall, these changes allow for much greater flexibility in installing the inverter in ways that are both supported and meet the NEC...

diysolarforum.com

This is how GFCI breakers with reliance MTS

Installing GFCI/AFCI breakers in a Reliance Protran Xfer Switch

The multi-circuit Protran Transfer switch has special wiring instructions for using AFCI or GFCI breakers. This brief document explains the wiring and gives an example of using it with an EG46500 EX.

diysolarforum.com

Newer models of EG4 6500ex are built without the bonding screw

One of each model would take up entirely too much space. lol I think I have a pretty good handle on high-frequency inverters. Just one of the Low-Frequency Split-Phase with Neutral in (Like the EG4 6K) and one of the LF Split-Phase without Neutral in (Like the Growatt) would be nice. Does...

diysolarforum.com

 

[SolarDV]

If I do go with a single Hybrid Inverter I do still plan to feed it into two "50 Amp A510C Pro/Tran 2 Transfer Switches"...

Did you ever do this? How would you feed the inverter into TWO A510Cs?
Do you run TWO pairs of 6 gauge wires from the inverter, one pair into each A510C ?
Or do you just run a single pair of 6 gauge wires into one of the A510Cs
and then connect that A510C to the second A510C with another pair of 6 gauge wires?
If the latter, how/where would you connect the two A510Cs to each other?

 

[ChrisG]

I bet you can feed the AC Outs on the inverter into a small loads panel. From there into multiple transfer switches. A double pole breaker for each TS.

 

[SolarDV]

I bet you can feed the AC Outs on the inverter into a small loads panel. From there into multiple transfer switches. A double pole breaker for each TS.

No small loads panel needed. Each A510C has a 50 Amp breaker for the incoming electricity from a generator, but in this case we're dumping the output of the inverter instead of a generator. (With a Sol-Ark, you could still add the generator by hooking it to the Sol-Ark generator input.)
The A510C can toggle each load breaker individually between the inverter (solar, battery, generator) OR the grid. So you could have everything in the house running on solar during peak hours and then flip the AC to the grid in late afternoon to save your batteries. When there's an outage, flip everything off the grid and choose which breakers you want to power with the inverter.
My question is does each A510C get a direct connect to the inverter, or just one gets the direct connect and the other is paralleled?

 

[ChrisG]

No small loads panel needed. Each A510C has a 50 Amp breaker for the incoming electricity from a generator, but in this case we're dumping the output of the inverter instead of a generator. (With a Sol-Ark, you could still add the generator by hooking it to the Sol-Ark generator input.)
The A510C can toggle each load breaker individually between the inverter (solar, battery, generator) OR the grid. So you could have everything in the house running on solar during peak hours and then flip the AC to the grid in late afternoon to save your batteries. When there's an outage, flip everything off the grid and choose which breakers you want to power with the inverter.
My question is does each A510C get a direct connect to the inverter, or just one gets the direct connect and the other is paralleled?

I know what a A510C is. If you want to split one inverter output to two A510C safely, you would have inverter->load panel (breakers for input and output)->2x outputs to both A510C.

 

[SolarDV]

No disrespect meant, I didn't want to assume you knew what a A510C was.
According to Reliance Controls support, no load panel needed, you just need to "bridge the two transfer switches’ incoming power." They said "your electrician will know how to do that." I just wanted to understand how that would work.
I can see using a load panel would work as well. Thanks

 

[ChrisG]

No disrespect meant, I didn't want to assume you knew what a A510C was.
According to Reliance Controls support, no load panel needed, you just need to "bridge the two transfer switches’ incoming power." They said "your electrician will know how to do that." I just wanted to understand how that would work.
I can see using a load panel would work as well.

You can’t just bridge two reliance TS safely. The bridge is the small load center that allows you to power the dual 510ac in parallel from single inverter/generator/other source.

 

[SolarDV]

You can’t just bridge two reliance TS safely. The bridge is the small load center that allows you to power the dual 510ac in parallel from single inverter/generator/other source.

I actually asked about using a small loads panel and they insisted the A510Cs could be bridged directly.
What is the safety issue if you could educate me?
I guess I'll need to push their support to tell me why they think a direct bridge is safe.
Obviously I want to do it the safe/right way.

 

[ChrisG]

Here is what I was thinking. This will allow you to have a breaker going to each 510C so you an isolate issues/loads/etc. Two of these will allow you to draw almost 20kw, lot of power. Your output breaker would be limited to your passthrough or inverting power in the small load center. The breakers going to each 510a will allow you to have a breaker one what you think the max draw per 510c is.

 

[SolarDV]

Thanks, exactly as you described it.
But why is it safer than 2 pairs of 6 gauge wires coming from the inverter, one pair to each TS?
Without the small loads panel, each pair of 6 gauge wires would go into a different TS's 50 Amp breaker...how is that much different?

 

[ChrisG]

Thanks, exactly as you described it.
But why is it safer than 2 pairs of 6 gauge wires coming from the inverter, one pair to each TS?

It’s unsafe and will not pass any inspection to have two conductors in one lug, especially at that size. Also doubt two will fit per lug/connecter in the inverter.

 

[SolarDV]

It’s unsafe and will not pass any inspection to have two conductors in one lug, especially at that size. Also doubt two will fit per lug/connecter in the inverter.

True, thanks

 

[Sundown]

This will allow you to have a breaker going to each 510C so you an isolate issues/loads/etc.

That is how my 2nd load panel set up in the house. I also have another 310TS from the first load panel in the garage at the inverter. 1st load panel powers 2nd load panel....

 

[RockOn]

Since this isn't that old, I'd like to piggy back on this thread as what I am looking at doing is similar but with 2 hybrid inverters and 2 of the Reliance 30amp switches. Please see attached for page 1 system design and page 2 for more detailed Ground and Neutral wiring...

Note: G/N wiring diagram is what I found for a L1/L2 split phase Inverter.
But if I assume that there are 2 MPPT and 2 TS then the red and black AC in/out still makes sense to me just going to 2 separate MPPT/TS.

Appreciate the feedback.