Question on vintage panel replacements

[Fortium]

I am a homeowner in Southern California who has a PV plant which has been in constant operation for 15 years. Recently, one of the two SMA Sunny Boy 2500U inverters finally died, so a wholesale review and assesment of my entire solar plant was performed, with an eye towards replacing the two older inverters with a single newer model. I decided a new inverter complete with AFCI protection and web enabled monitoring was the minimum I would settle for. The SMA SB 6.0 was chosen as I found one on sale (with a deep discount and free shipping).

Sadly, a number of the panels (40 vintage Shell Solar SP 140-PC's) were no longer in top form - some with darkening of their cells and one suffering from outright cracking in it's surface glass (possibly from an airsoft or BB gun fired at it from the ground, though I am not certain).

I began a search for used SP 140-PC's local to me to swap in as replacements. Surprisingly, I could find *none* of these old panels for sale in my area. I did stumble upon a large cache of Shell SQ 150-PC's, which are nearly identical to the older SP 140-PC model.

SO, the question is this:

Understanding that strings of differing models of solar panels should be avoided in almost every occasion, is this an occasion where dropping in a few SQ 150's to replace damaged SP 140's would be agreeable? The loss of such a minor efficiency/production edge (over the older panels) should outweigh the outright loss of the old panel itself.

Is my thinking correct or am I missing something? Thank you for your time and attention.

[ButchDeal]

SO, the question is this:

Understanding that strings of differing models of solar panels should be avoided in almost every occasion, is this an occasion where dropping in a few SQ 150's to replace damaged SP 140's would be agreeable? The loss of such a minor efficiency/production edge (over the older panels) should outweigh the outright loss of the old panel itself.

Is my thinking correct or am I missing something? Thank you for your time and attention.

I think if you upgrade that system then you are going to have to meet current code. If it is rooftop then you are going to have to meet NEC 2017 which means optimizers or micros.
With either you will have no problem with different types of PV modules.

[Mike90250]

If it's called a repair (and using used/compatible form-function parts) does that trigger updating to current standards ? You may have to ask your inspector. When you change a water heater in your house, it doesn't trigger changing all the shower heads to low flow.

Replacing failed inverter, without increasing the exported power, in my mind, should not trigger a demand to update all to current code, again the AHJ would know, but if they will tell is another story.

[ButchDeal]

If it's called a repair (and using used/compatible form-function parts) does that trigger updating to current standards ? You may have to ask your inspector. When you change a water heater in your house, it doesn't trigger changing all the shower heads to low flow.

Replacing failed inverter, without increasing the exported power, in my mind, should not trigger a demand to update all to current code, again the AHJ would know, but if they will tell is another story.

electrical and plumbing are not quite the same.
however if for example you had a water heat that was of such age that it did not have a pressure release valve then replacing the water heater would require bringing that part of the plumbing up to current code (poor example as this is pretty much contained in the water heater but plumbing standards haven't changed as much as electrical around solar).

If OP replaced the inverter with an identical unit, it would not require upgrade
but generally changing the inverter to a current model would require upgrading everything on the circuit to meet current code.

The catch is that the OP likely will have a hard time finding a similar NOS inverter and the other inverter is still just as old anyway.

I agree check with the AHJ.

[littleharbor]

I have some shell SQ 150's in the event you decide to replace your bad panels with like sized and powered panels. I'm in So Cal as well.
shell 150.jpg

[Fortium]

I think if you upgrade that system then you are going to have to meet current code. If it is rooftop then you are going to have to meet NEC 2017 which means optimizers or micros.
With either you will have no problem with different types of PV modules.

A couple questions about this, if I may.
From what I read on a number of NEC related sites and other websites by/for professionals (such as mikeholt.com). California officially has not adopted 2017 NEC code yet. According to their state by state breakdown:

Effective on January 1, 2017. The 2019 building codes for California will be adopted 1/1/2020. This update will include the 2017 NEC (found in the California electrical code) and exams will be based on the 2017 NEC.

https://www.mikeholt.com/necadoptionlist.php

Also,

https://www.ntainc.com/code-update/california-voted-to-adopt-the-2017-national-electrical-code/

While I do agree in theory that optimizers or micro-inverters may be a fair way to approach the subject, I am also approaching this issue from the stance that this is not an upgrade. The SB 2500U inverters are no longer offered or repaired by SMA, requiring a modern replacement of the hardware, and the new SQ 150-PC panels themselves are so substantively similar to the old SP 140-PC's, I can't imagine anyone considering them an "upgrade" - especially when it is clear their fractionally higher wattage and fractionally higher voltage will both be pulled down to the level of the old panels. For additional consideration, both panel types were compliant with UL listing 1703 way back in 2003/2004, based on their spec sheets.

Also, and forgive me if I'm completely off target here, but if the need for modern optimizers is to make panels/strings compliant with NEC 2017 requirements revolved around the "rapid shutdown" elements listed in the new code... If so, according to SMA, the new inverter model that I have purchased and has already been installed and functioning flawlessly (the SMA Sunny Boy SB6.0-1SP-US-40) speaks to the requirements on page 18 & 19 of the 1.5 edition of the install manual.

PV Rapid Shutdown System Equipment

The inverter is a PV Rapid Shutdown System Equipment and performs the function of voltage reduction according to UL 1741 CRD PV Rapid Shutdown Systems 2015. When a rapid shutdown is triggered by disconnecting the utility grid, the inverter discharges independently on the AC side to ≤ 30 V within 30 seconds. If a disconnection device is used in addition between the inverter and the PV array that disconnects the PV array in the case of a rapid shutdown, the inverter discharges independently on the DC side to ≤ 30 V within 30 seconds. The electric discharge on the DC side is deactivated by default and must be activated manually after commissioning of the inverter via the user interface.

NOTICE - The inverter's Rapid Shutdown function is initiated by disconnecting the inverter from the AC grid voltage, for example, by opening the main PV system AC disconnect. The AC disconnect that serves as the Rapid Shutdown initiation device must be readily accessible and clearly marked in accordance with National Electrical Code® . The Rapid Shutdown status of the PV system will be indicated by the On/Off (Closed/Open) position of this AC disconnect. The Off (Open) position indicates that Rapid Shutdown has been initiated.

From what I understand, this would necessitate the purchase and installation of three SMA TS4-R-F rapid shutdown boxes (one for each string) which will coordinate with the inverter to shut down from the panel side .... I'd be more agreeable to buy those instead of 40 power optimizers. (ack!)

Also, and asking out of genuine curiosity - and not trying to dodge responsibilities, but if NEC 2017 isn't officially in effect until January 1, 2020 here in California; wouldn't these remediations to my PV plant technically be allowed - similar to how currently functioning systems would be "grandfathered"?

Thanks everyone for your comments and info. Please feel free to correct any misinterpretations I've made.

[peakbagger]

Its likely that the reason that they are "drop in" is they were made on the same production line.When panels are assembled they are then tested for output and graded. There may be three or four grades of the same panel differing only in the actual output. The lower rated panels are usually a bit less expensive.when new. I would not worry about swapping in the slightly higher grade panel..

[Ampster]

............
While I do agree in theory that optimizers or micro-inverters may be a fair way to approach the subject, I am also approaching this issue from the stance that this is not an upgrade. The SB 2500U inverters are no longer offered or repaired by SMA, requiring a modern replacement of the hardware, and the new SQ 150-PC panels themselves are so substantively similar to the old SP 140-PC's, I can't imagine anyone considering them an "upgrade" - especially when it is clear their fractionally higher wattage and fractionally higher voltage will both be pulled down to the level of the old panels. For additional consideration, both panel types were compliant with UL listing 1703 way back in 2003/2004, based on their spec sheets.
......
Also, and asking out of genuine curiosity - and not trying to dodge responsibilities, but if NEC 2017 isn't officially in effect until January 1, 2020 here in California; wouldn't these remediations to my PV plant technically be allowed - similar to how currently functioning systems would be "grandfathered"?
........

Yes that would be my interpretation. I had a warranty repair of BP solar panels with Canadian Solar panels in 2014 and did not obtain a permit. Three years later my Xantrex inverter died and I replaced that with a SolarEdge with optimizers. While technically in compliance with NEC 2017 I did not pull a permit. I do not pull a permit when I change out water heaters either although that is technically required. I do upgrade the earthquake straps. Next time I do it I will bond water lines to the gas lines which is a new requirement.

Risk management decisions should never be made based on some anonymous poster from California. I am just sharing my experience and not endorsing any building code violation. I did this with full knowledge of the code requirements and I would recommend that you familiarize yourself with your local code as well.

[ButchDeal]

Yes that would be my interpretation. I had a warranty repair of BP solar panels with Canadian Solar panels in 2014 and did not obtain a permit. Three years later my Xantrex inverter died and I replaced that with a SolarEdge with optimizers. While technically in compliance with NEC 2017 I did not pull a permit.

I would agree that you do not need a permit to replace a PV module
you likely should have had a permit for your replacement of Xantrex bimodal with SolarEdge grid tie but this is still a smaller change than OPs reconfiguration of two older inverters with a single inverter.
Many people do not pull permits when they should; it has no difference on if OP should pull a permit, or if OP should (regardless of permit) meet the code.

[Ampster]

Yes, the importantant issue is to be code compliant. I inadvertantly accomplished compliance with a future code requirement when I replaced the Xantrex with a Solar Edge system.

[J.P.M.]

Yes, the importantant issue is to be code compliant. I inadvertantly accomplished compliance with a future code requirement when I replaced the Xantrex with a Solar Edge system.

It's important but to my experience not the only important issue. Code compliance is always good and necessary, but I'd think of it as a step - and not the first, most important one or the only one - to a safe and fit for purpose design.

I'd suggest the larger issue is safety with one of the major but not the sole component of a safe(r) design being following and complying with a recognized code.

Another component of a safe(r) design, and often/usually a part of building code conformance is an inspection by a third party or parties.
PITA ? Yup.
Cheap insurance ? Fur sure.

I might have the best of intentions and think I'm following the NEC for example, and in my hubris, duck out of getting any required building permits. But while I may be sincere and well intentioned in my attempts at code conformance, I may well be ignorant of all the codes I'm required to conform to, much less the finer points of such conformance.

One of the big advantages of building codes is to have another (hopefully more) experienced set of eyes looking at a project.

I bet we've all seen stuff done by folks who think they know what they were doing and we look at the results and wonder "what were you thinking ?".

[Ampster]

It's important but to my experience not the only important issue. Code compliance is always good and necessary, but I'd think of it as a step - and not the first, most important one or the only one - to a safe and fit for purpose design.

I'd suggest the larger issue is safety with one of the major but not the sole component of a safe(r) design being following and complying with a recognized code.

Yes, I agree. Because the mods are so paranoid about liability for the owners of this forum I always try to include a general statement about code compliance. Safety would include a safe process of installing whatever is being installed. I guess if we want to cover all bases maybe we should remind them about all the warnings printed on ladders if they are going to use a ladder.

Another component of a safe(r) design, and often/usually a part of building code conformance is an inspection by a third party or parties.
PITA ? Yup.
Cheap insurance ? Fur sure.

That doesn't insure that it is either safe or code compliance. It all depends on how thorough the individual inspector is. I have had a number of building inspectors take my word for how things were done either because they were to lazy to climb a ladder or too lazy to walk through the premises. I got a final inspection on a major home remodel once and the inspector asked if I had any complaints about my contractor. The permit was taken out by me as an owner builder. LOL

[J.P.M.]

That doesn't insure that it is either safe or code compliance. It depends on how thorough the individual inspector is. I have had a number of building inspectors take my word for how things were done either because they were to lazy to climb a ladder or too lazy to walk through the premises. I got a final inspection on a major home remodel once and the inspector asked if I had any complaints about my contractor. The permit was taken out by me as an owner builder. LOL

Assuming that the inspector is competent and knowledgeable. for once I couldn't agree more with what you write. I've dealt w/inspectors around here and elsewhere and found it's sometimes a hit/miss thing on the time they have available and laziness rather than competence. Fortunately, and to my experience only, more hit/thoroughness than miss. Unfortunately, it only takes one miss to lead to an unsafe condition.

Goes without saying there is no 100 % fail save, either in design or inspection. But, my point is, and working on the premise that code compliance will result in a safer project/installation, another set of experienced eyes and area knowledge will increase the probability that more, and hopefully all snafus, and glitches and dumb stuff that can lead to an unsafe situation/condition will be found and corrected.

Every place I ever drew a paycheck had more than one engineer, usually at least several. As an expected part of job responsibilities, written down or not, we were always checking each other's work and were almost without exception glad for more eyes looking at a design with a devil's advocate attitude to find possibly unsafe conditions before inspections done during fabrication/installation/erection/startup/operation. Bad crap still got through once in a while. Competent surveillance is one of the cornerstones of a good project.

I suppose we both again drifted off topic.

[brycenesbitt]

While I do agree in theory that optimizers or micro-inverters may be a fair way to approach the subject, I am also approaching this issue from the stance that this is not an upgrade. The SB 2500U inverters are no longer offered or repaired by SMA, requiring a modern replacement of the hardware.

Well, not really. The 2500U show up on eBay all the time as refurbs. They're simple devices, and several people out there refurbish them.

[Ampster]

Well, not really. The 2500U show up on eBay all the time as refurbs. They're simple devices, and several people out there refurbish them.

A lot has changed since 2019 when the OP first posted. I for one would rather spend the money on a modern UL1741SA inverter. Based on trends in my area including the likelihood of power outages, adding a hybrid inverter may be a way to leverage a modern GT system and get a hedge against further rate increases and erosion of benefits. My comments are not for the benefit of the OP, who has not posted since 2019, but for the benefit of subsequent readers now that this thread has been bumped to the top.