Time to add Panels to 2 X 6000XP

[BrianVeg]

I’ve currently implemented a battery backup system using 2 X 6000XP’s and 4 X Ruixu Batteries. See this thread if you’re interested in what I did.

Thread '6000XP’s/Ruixu Batteries in Production for Home UPS System'
https://diysolarforum.com/threads/6000xp’s-ruixu-batteries-in-production-for-home-ups-system.78032/

Now it’s time to add my panels. The 6000XP’s have the following specs/limits that I am using in my planning:

• Max temperature adjusted VoC of 480 Volts
• Optimal operating voltage of 320 Volts
• Optimal current of 17A with a max of 25A
• Max wattage per MPPT is 4,000 watts

I’ve got limited space for a ground mount so I’m looking at 16 panels, possibly up to 24 panels.

I’ve been looking at using the attached BlueSun panels in 2 strings of 8s (one per inverter) or 3 strings of 8s.

Specs for these panels are:

Wattage - 460watts

VOC - 50.8 volts

ISC - 11.5 amps

low temp coefficient -0.26%

Impp -10.86 amps

Vmpp - 42.4 volts

If my calculations are correct. That should give me per string:

• Temperature adjusted max VoC of ~450V
• Operating voltage of ~340V
• Assuming a nominal bifacial gain of 10% the operating current should be ~12amps
• Optimal wattage of ~ 4080 watts

Which will give me across 2 strings ~8000 watts.

If I do 24 panels I was going to just add one more string to one of the 6000XP’s which will give me 12kW.

Does this make sense? Am I missing anything?

Thanx!!!

 

[hwy17]

Sounds right.

 

[BrianVeg]

Trying to decide between these two panels. They end up close with the BlueSun’s able to produce more wattage, but for a higher cost.

Does anyone have experience with either of these panels?

Is it worth the extra $684 to get nominally 1kW extra?

	bluesun bsm460m-72hbd	Boviet BVM6612M-450S-H-HC-BF-DG
number of panels (series)	8	8
Max Voltage	458	447
Voltage at Vmpp	339	326
# Parellel Strings	1	1
Total Current	11.95	11.07
Wattage at Vmpp	4051	3609
2 Strings @ avg high temp
Total Wattage @ Vmpp	8102	7218
Total # of Panels	16	16
Cost per panel	$207	$164.25
Total cost	$3,312	$2,628
cost per watt (my calcs)	$0.41	$0.36

 

[wdwtx2.0]

The one thing you need to realize is that you will almost NEVER get full power from a panel.
Bifacial boost does help some in some conditions, but you will not get 8,102 watts in almost any situation.

 

[AZ Solar Junkie]

The one thing you need to realize is that you will almost NEVER get full power from a panel.
Bifacial boost does help some in some conditions, but you will not get 8,102 watts in almost any situation.

Yeah that's a good thing to be sure you are aware of. For example, I have an array that has a total rated theoretical output of 5730 watts, but in full sun I pretty consistently see 4800 watts when the panels are hot in the sun - or a bit more than 5000 watts when they are colder in the winter. It's actually only on partly cloudy days with the "cloud edge" effect that I see the full theoretical output (sometimes actually a bit more like ~6000 watts) for parts of the day when the sun is breaking through the clouds.

 

[BrianVeg]

Thanx @wdwtx2.0 and @AZ Solar Junkie, appreciate the input.

Let me rephrase my question a bit.

1. Does anyone experience with either panel and does the panel brand really make a difference?
2. Is it worth an $684 to get panels that have the potential to produce more?

Thanx

 

[AZ Solar Junkie]

Thanx @wdwtx2.0 and @AZ Solar Junkie, appreciate the input.

Let me rephrase my question a bit.

1. Does anyone experience with either panel and does the panel brand really make a difference?
2. Is it worth an $684 to get panels that have the potential to produce more?

Thanx

Here are my thoughts/opinions:

Re: #1 - In my opinion, it's really all about the specs more than the brand of a panel. It's worth digging a little deeper than just the watts/volts/amperage numbers and looking at least at the thermal data - like how much the panel voltage goes down with increasing temperatures (at least this is important to me here in Arizona )

Re: #2 - it really depends on your particular situation and if there would really be an ROI in a reasonable time that makes it worth it. If all it's mostly going to mean is that your battery bank gets fully charged up slightly earlier in the day and it isn't going to reduce your electric grid usage, I don't think it would be worth it very much. On the other hand, if you were actually going to be using that extra array energy to offset your grid usage on a daily basis, then if might make more sense. Say on average an extra 6kwh times your electricity rate might add up to saving more than the original cost difference in the long term. If I read your original post correctly, it sounds like you are planning primarily to use your system for grid backup and not using much if any of the solar output to offset your grid usage. If that is the case, then I don't think it would be that valuable to add just 1kw to your array output for additional cost. Or maybe it would be if you consider you would be bringing in an extra ~6kwh or so of energy from your panels during a grid down situation, so you'll have that much more energy on a daily basis to be able to use until the grid comes back. It really comes down to your goals and how you plan to use your system, etc.

 

[zanydroid]

Are you getting a full pallet? If not then biasing towards what is stocked locally can be a good idea

16 is a partial pallet. Full is in the mid 20s. I believe 16 is enough to be shipped somewhat safely edge stacked on a pallet.

 

[wdwtx2.0]

Let me rephrase my question a bit.

1. Does anyone experience with either panel and does the panel brand really make a difference?
2. Is it worth an $684 to get panels that have the potential to produce more?

Thanx

I have 2ea. 16 panel arrays of the Blue Sun 460W bifacials, and a 4 panel array for my PV direct mini split..
I got them because they were around the size I want, and they were in stock.
I have no complaints with them, they are working as expected.

 

[BrianVeg]

if you were actually going to be using that extra array energy to offset your grid usage on a daily basis, then if might make more sense

@AZ Solar Junkie Actually that is what I’m going to do. Battery backup was Phase 1, adding solar to reduce reliance on grid is Phase 2.

it's really all about the specs

Thanx for this.

I got them because they were around the size I want, and they were in stock.

@wdwtx2.0 That’s kind of what I’m looking at, specifically size = voltage.

 

[zanydroid]

That’s kind of what I’m looking at, specifically size = voltage.

Not sure what this was referring to, but size != voltage. Voltage comes from how many cells are in series and cell sizes vary across different panels and generations of panels.

Size (area) = power though.

 

[BrianVeg]

size != voltage

Get it. For me getting voltage where i wanted it was what was driving my decision. I was looking at Vmp specs to figure out which panels to get.

 

[zanydroid]

Get it. For me getting voltage where i wanted it was what was driving my decision. I was looking at Vmp specs to figure out which panels to get.

In that case look for the cell count and understand the different increments of cell counts / how to spider sense half cut vs full cut without looking at the spec sheet

 

[BrianVeg]

I ended up ordering Qty 16 of the BlueSun panels earlier in this thread. I am purchasing a Ready Rack System from APA Solar.

Pretty excited to get this going.

The diagram below provides a picture of my current working design.

I have a couple of questions on the PV circuit.

• Do I need the Circuit Breakers at the rack - they are the only OCPD in the circuit. My string are 8S
• After my PV enters the house - can I run the PV wire in same wireways as the rest of my inverter circuitry including AC-IN and Out and Battery connections? The PV Wire will be THWN

 

[AZ Solar Junkie]

I ended up ordering Qty 16 of the BlueSun panels earlier in this thread. I am purchasing a Ready Rack System from APA Solar.

Pretty excited to get this going.

The diagram below provides a picture of my current working design.

I have a couple of questions on the PV circuit.

• Do I need the Circuit Breakers at the rack - they are the only OCPD in the circuit. My string are 8S
• After my PV enters the house - can I run the PV wire in same wireways as the rest of my inverter circuitry including AC-IN and Out and Battery connections? The PV Wire will be THWN

View attachment 212605

As far as I understand, the breakers for the array can be near the inverter, rather than needing to be by the array.

Re: running the AC and DC wires in the same wireways, I don't know about NEC rules around that, but personally I would avoid the potential for the AC lines to induce AC frequencies on your DC lines. I'm sure someone who knows more like @timselectric can clarify if that's a real concern or not.

 

[zanydroid]

There are some exceptions for solar DC sharing conduits. But it is pretty complicated and my personal decision is to separate completely.

I believe physical barriers in wireway might loophole you out too.

Or switch philosophy to ignore code.

 

[zanydroid]

The diagram below provides a picture of my current working design.

BTW your +/- colors are not necessarily code compliant (or helpful to installation) in the sense that you need to have some means of keeping the two circuits distinct. Having two sets of colors (legal for ungrounded DC) achieves that

 

[BrianVeg]

I believe physical barriers in wireway might loophole you out too.

That's what I read in the code which drove me to ask the question. To achieve this will take some rework of my existing install.

The inspector for my battery backup verified that I could run DC and AC in the same wireway, but solar DC seemed different.

Or switch philosophy to ignore code.

Passed inspection on my inverters and batteries for battery backup - really want to do the same for the panels

Having two sets of colors (legal for ungrounded DC) achieves that

Ah - that actually makes sense - I was going to do two black wires and two red wires - Thanx for that

 

[BrianVeg]

@zanydroid I just talked to my AHJ and he's good with two reds and two blacks as long as they are zip tied whenever they are in a box or otherwise "exposed". Different interpretations in different states I guess.

He also validated that solar DC circuits need to be separated from everything else.

 

[zanydroid]

@zanydroid I just talked to my AHJ and he's good with two reds and two blacks as long as they are zip tied whenever they are in a box or otherwise "exposed". Different interpretations in different states I guess.

He also validated that solar DC circuits need to be separated from everything else.

Yeah, that is fine for code, you will need to sort it out though for yourself by toning the pairs or something (or connecting the end together and testing for continuity). If you taped them together for a pull you might interfere with the pull or lose the indicator.

Or just buy 4 colors. You don’t have the problem some people here had, where there were so many circuits they ran out of colors.

 

[BrianVeg]

just buy 4 colors.

Yeh - Except he said it has to be red and black. So I guess its testing for continuity. Ugh!

My bigger problem is redoing my wireway and connections to the inverters. When I built the original system I thought it made sense to add the PV conduit into the wireway at the same time. Duh!

Got to figure out a way to run them through the wireway and come out the bottom or elbow inside the wireway and out the end cap. Dunno yet!

 

[zanydroid]

Yeh - Except he said it has to be red and black. So I guess its testing for continuity. Ugh!

Wot?

Well you could propose striped variant of red/black

 

[itech20]

(Note: The comments below are based on my non-electrician research and, AIUI, are relevant only if you are in a jurisdiction that has adopted NEC 2023 as their code basis. And even if they have, it's possible there are local overrides. YMMV

If you want to check my work by doing your own reading, the 2023 NEC is available for free, in a somewhat clunky page by page way, if you click on the "View Free Access" button near the bottom of the following page:

NFPA 70 (NEC) Code Development

Stay informed and participate in the standards development process for NFPA 70

www.nfpa.org

You need to sign up for a free account. There are lots of paths on the web site that give the impression you need to subscribe. You do not. And AIUI, the NFPA has been taken to task for trying to always charge for access to these things, even though they are woven into very public regulations.)

I'm in the planning stages for a very similar setup right now. The project is in Michigan which recently adopted NEC 2023.

TL;DR; - The 2023 version of the code has language that very explicitly allows PV DC to co-locate with AC and battery DC subject to marking requirements and that all conductors (including data cables) have a voltage rating at or above the highest expected voltage in the raceway, which is typically going to be the PV DC voltage. Details below.

I have spent quite a bit of time trying to wade through the text of the standard as well as the various interpretations here and on some other forums. On this particular point, AIUI, the 2023 version was updated to address the fact that we now have quite a lot of highly integrated units like the 6000XP, that make it quite difficult to physically separate the PV DC wiring from the AC runs and battery DC runs and in fact seem to encourage the kind of neatly integrated conduit/raceway setup shown in the photos up-thread.

The specific section that I understand to have been revised is 690.31 - Wiring Methods. (Section 690 is the one that covers Solar PV Systems generally)

Sub-section (B)(1) contains the following language covering exceptions to the requirement to separate PV DC circuits.

"Exception: Where all conductors or cables have an insulation rating equal to at least the maximum circuit voltage applied to any conductor within the same wiring method, the following shall be permitted

(1) Multiconductor jacketed cables for remote control signaling, or power-limited circuits shall be permitted within the same wiring enclosure, cable, or raceway as PV system dc circuits where all circuits serve the PV system

(2) Inverter output circuits shall be permitted to occupy the same junction box, pull box or wireway with PV system dc cuircuts that are identified and grouped as required by 690.31(B)(2) and (B)(3)"

I won't go on to transcribe the rest, but I'll say that the marking requirements mentioned in (2) above are pretty basic and even contain an exception where the difference between the PV DC and other wiring is obvious due to physical spacing, which I'd argue it clearly is in most of these highly integrated inverter setups.

 

[BrianVeg]

@itech20 thanks for that. I passed an inspection on my battery backup system un February under the 2017 code. My inspector told me the code change was coming, so I pulled my permit before March12th (when the 2023 code) went into effect. So I’m tied to the 2017 code for my PV system. I’ve got a workaround that is not much rework that i was planning on deploying. But i will ask my inspector if he’d be okay with mixing.

 

[itech20]

@itech20 thanks for that. I passed an inspection on my battery backup system un February under the 2017 code. My inspector told me the code change was coming, so I pulled my permit before March12th (when the 2023 code) went into effect. So I’m tied to the 2017 code for my PV system. I’ve got a workaround that is not much rework that i was planning on deploying. But i will ask my inspector if he’d be okay with mixing.

Roger that. If you have a moment, given that I'm operating in the same jurisdiction with an almost identical setup, I'm curious about two cable questions, one technical and one code related.

1) Were you able to completely enclose your battery cable runs and is it your sense that is what the inspector was looking for? (I purchased an unenclosed SOK racking system and am starting to think I need to build or acquire something to keep the cables enclosed.)

2) Did you make an effort to have the battery-to-inverter runs be of equal length? I'm aware of that as a requirement for some inverter types but it's not explicitly mentioned in the 6000XP documentation.