Replace a positive ground, Sunpower SPR-7000 to a transformer-less inverter

[oregon_phil]

So if I ...

-tighten all connections
-test each panel
-find one or more with little or no amperage
-replace those panel(s)

Then there is a chance my Sunpower inverter might work normally?

Joseph,

You never answered whether or not you are using the SMA DC disconnect switch. Is this the combiner you are referring to? I'm trying figure out what you changed. Now I'm thinking you did not change the SMA DC disconnect switch.

Since you installed your latest inverter, I have to assume you have installer privileges. On the installer webpage for your inverter, don't you have a DC Measurements page or something similar? If yes, the next time the power fluctuations happen, open up that webpage and take a video of the DC voltage and currents.

Your SMA 7000 US has one MPPT input. You have 4 strings of 10 panels connected in parallel. All strings should read exactly the same voltage since they are all connected together in parallel.

When you pulled out the fuse in the combiner box, is that the only thing you did? Did you look at the fuse terminals to see if there was any corrosion on it?

[Joseph.Unden]

Sorry Phil, I didn't make myself real clear.

Yes, I used the original SMA DC disconnect switch (my "Certified used SMA" did not come with a DC disconnect). Since the inverters just sit above the switch, we just lifted the Sunpower from the top of the disconnect and placed the new "Certified used SMA" back on top of the disconnect.

I am not sure what you mean by installer privileges. I just hooked up the SMA and turned on the AC and DC disconnect switches. I have thoroughly read the installer manuals but have no idea what you mean by Installer Webpage or DC measurements page.

All strings have almost exactly the same voltage. There are slight variations due to aging of the panels.

I pulled the fuse in the combiner box for one string only because the SMA tech told me reducing the input would help keep the inverter from derating. Later in the day, when there was less light, I reinstalled the fuse because the input had lowered (less direct sunlight). The inverter didn't derate because of less sunlight (I am assuming). Neither the fuse nor the fuse holder showed any signs of corrosion.

The next day I returned from a bike ride at noon and the inverter was not derating.

The inverter has worked perfectly since (3 days now). I contacted Youlovesolar and asked them if these inverters reprogram themselves. The woman texted me back and said these inverters reboot every night. So, I am assuming the reboot is the reason the new inverted is no longer derating.

[oregon_phil]

My mistake, the older SMA 7000 US inverters do not have a web interface, just the inverter display. Now that your setup is working, I'm not sure if you are going to find root cause. You have 4 strings of 10 panels with each string at 430VDC. Troubleshooting would require you to connect and disconnect each string and/or each panel. Working/experimenting around high voltage DC isn't something in my wheelhouse.

[Joseph.Unden]

On the morning of July 15 I tested each of my 4 panel arrays (ten panels per array). The panels in array #4 are a year older and are tilted differently than the others. I tested the voltage at the combiner box and the current as it leaves each array using a clamp meter. Here is what I got:

#1 4.12 A ... 411 V
#2 3.30 A ... 410 V
#3 3.01 A ... 396 V
#4 2.17 A ... 396 V

My question ... am I getting the most I can from each array?

[DanS26]

If you're handy and your panels are accessible, and you have the inclination, then you can fully test your panels by following these instructions. The test kit using an auto battery and cheap charge controller is very DIY........

https://footprinthero.com/how-to-test-solar-panels

Good luck.

[bcroe]

A basic sanity test of a panel, is
1. check Open Circuit voltage,
2. with no sun, short the output leads together. Then
with good sun observe the short circuit current with
a clamp on ammeter.

The above is NOT a complete test, because a weak section
(often there are 3 each having a bypass diode) will allow the
good sections to bypass it with their full current capacity.
Even the weak section will probably be capable of normal OC V.

3. for a power test you need an MPPT control and a suitable load.
That link might be OK for 12V stuff, rather reckless for a 400V
system. A grid tie inverter with enough capacity would work.
If it does not display V and I, use the votmeter and the clamp
on ammeter. I NEVER connect/disconnect DC wiring under
power at that voltage, the sun will set.

A great test is running 2 strings with identical panels and identical
orientation under sun. The outputs should be nearly identical. I
previously posted a step by step method of tracking down a weak
panel in a large system. Bruce Roe

[oregon_phil]

On the morning of July 15 I tested each of my 4 panel arrays (ten panels per array). The panels in array #4 are a year older and are tilted differently than the others. I tested the voltage at the combiner box and the current as it leaves each array using a clamp meter. Here is what I got:

#1 4.12 A ... 411 V
#2 3.30 A ... 410 V
#3 3.01 A ... 396 V
#4 2.17 A ... 396 V

My question ... am I getting the most I can from each array?

Did you make the measurements above with all strings attached at the same time?

FWIW, your inverter has DC inputs for 4 strings that are paralleled into 1 MPPT input.

I'm not an expert on how one MPPT input would operate with 4 parallel strings (different orientations and panel age), but others might.

[J.P.M.]

On the morning of July 15 I tested each of my 4 panel arrays (ten panels per array). The panels in array #4 are a year older and are tilted differently than the others. I tested the voltage at the combiner box and the current as it leaves each array using a clamp meter. Here is what I got:

#1 4.12 A ... 411 V
#2 3.30 A ... 410 V
#3 3.01 A ... 396 V
#4 2.17 A ... 396 V

My question ... am I getting the most I can from each array?

To add to Oregon Phil's last post:

Were all arrays tested at the same time ?
If not, how much time between readings ?
Also, what were the sky conditions ? any clouds ?

What's the orientation of array # 4 ?
What's the orientation of the other 3 arrays ?

[Joseph.Unden]

Thanks everyone for your advice. Here is the information you have asked for:

All 4 arrays are pointed exactly at the azimuth.

Arrays 1,2, & 3 are ground mounted and are tilted at approximately 30 degrees (my latitude) while the panels in array #4 are on my carport and are tilted at 17 degrees.

All readings were taken within a few minutes of each other and the skies were clear.

[oregon_phil]

This implies that all arrays were connected to the DC interconnect terminal block at the same time. You moved meter test leads from the + and - terminals on the DC interconnect terminal strip from array 1, then to array 2, etc. Correct?

[J.P.M.]

Thanks everyone for your advice. Here is the information you have asked for:

All 4 arrays are pointed exactly at the azimuth.

Arrays 1,2, & 3 are ground mounted and are tilted at approximately 30 degrees (my latitude) while the panels in array #4 are on my carport and are tilted at 17 degrees.

All readings were taken within a few minutes of each other and the skies were clear.

Thank you. Just wondering if P.O.A. irradiance was causing cell temp. differences and so voltage differences but given those orientations and times, probably not.

[curtis-r]

So glad to find this forum and thread, as I also have a failing Sunpower spr-7000m inverter. As others have reported, Sunpower has been absolutely horrible! I'll spare the details except their customer portal has been down for 6+ months, so if it weren't from my local utility utilization, I'd have no way to know when my inverter failed. I also have some cracked panels, and without production data, they won't claim it's a warranty issue (they're out of normal warranty and now in a production warranty period).

My installer wants to put in an SPR-8000m @ $4500 ($2k more than normal they say), plus labor, totaling $7850 on a 12y old system. Not worth it to me. I'm hopeful with the concept of finding a new, old-stock SPR-7000m (or Sunny Boy), but youlovesolar.com is out of them right now.

Two questions:
1) Those that have done their own SPR swap are doing fine and stable, and would you do it again?
2) Is there another inverter that would be a reasonably easy swap? I have a 6kW AC / 6.75kW DC system.

[J.P.M.]

So glad to find this forum and thread, as I also have a failing Sunpower spr-7000m inverter. As others have reported, Sunpower has been absolutely horrible! I'll spare the details except their customer portal has been down for 6+ months, so if it weren't from my local utility utilization, I'd have no way to know when my inverter failed. I also have some cracked panels, and without production data, they won't claim it's a warranty issue (they're out of normal warranty and now in a production warranty period).

My installer wants to put in an SPR-8000m @ $4500 ($2k more than normal they say), plus labor, totaling $7850 on a 12y old system. Not worth it to me. I'm hopeful with the concept of finding a new, old-stock SPR-7000m (or Sunny Boy), but youlovesolar.com is out of them right now.

Two questions:
1) Those that have done their own SPR swap are doing fine and stable, and would you do it again?
2) Is there another inverter that would be a reasonably easy swap? I have a 6kW AC / 6.75kW DC system.

From the FWIW dept: I don't recommend vendors "but",
1.) I too have a Sunpower system, panels and rebranded PVI -5000 inverter that's positive ground. All's well but at 9 yrs. old the inverter, which hasn't missed a beat, is getting a bit long in the tooth. Problem is, my inverter is no longer being made.
2.) About a yr. ago, there was a thread or two here about inverter replacements for Sunpower panels of the type like mine that are positive ground.
3.) The upshot of the threads was that a poster found an outfit called "Solar Cowboys" that also goes by the name of "You Love Solar" (youlovesolar.com).
4.) They had/have a lot of equipment for sale, a lot of which is refurbished and some (so they claim) new stuff as well. They had an exact replacement for my rebadged PowerOne inverter. I ordered a replacement for my current inverter last Sept. The unit came in a sealed box, packing material, manuals, warranty cards and all, and as best as I can tell, is unused.
5.) It will sit in my garage until the current inverter fails.
6.) The old retail price for an SP-5000 was about $2K or so. I paid <$700 to You Love Solar.
Service was good and the folks there seemed knowledgeable. They were also helpful.

I know I might have bought a pig in a poke but things look legit, and given the situation and Sunpower's unprofessional customer service but formerly top quality equipment, I figured for $700, it was the gamble. At worst I'll have some spare parts.

Might be worth giving them a call.

[curtis-r]

Forgot to mention, I also have "Disturbance Imax" fault code as the post that started this thread. My installer changed the AC-side shutoff fuses & says that the readings were within range. When they contacted Sunpower, they were simply told to replace the inverter. They're kind of hating Sunpower these days also, and say Sunpower is going to be partnering with Ikea.

youlovesolar.com is currently out of stock with the Sunny Boy SMA's, but may get some in.

I had turned the invert back on earlier & got the fault, but then restarted it. Before sending this I was going to open up the inverter but when I returned, it's now producing. 3.4kWh in the past 15+ minutes. Probably a temporary thing but I'll cross my fingers.

[frankdp23]

I see this is an older thread. But I was having some similar kind of issues (now for 2.5 years). My system is from 2011 and it needed 2 new inverters that after fighting Sunpower did replace. They were SPR 7000s. I had an outside guy come look, and it turns out when they installed the 2 new inverters, they grounded them neg instead of positive. So they were generating a lot less kwh. The guy fixed it now to positive, so hopefully that helps the productivity. I was only getting about 55% of what I should.