Lesson Learned - Cheap DC Breaker

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fcwlp
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My RE system: GS8048A, FM80 w/3,600W PV Fixed, FM80 w/2,700W on Zomeworks tracker, Mate3, 24 Trojan 2V L16 1100AH @ C20, Grid-Tied with Kohler 14RESA LPG Generator and MEP-803 Diesel if needed.

I install and maintain grid-tied and off-grid systems in my area and consult on solar system design/operation.
Location: 80 miles NE of Phoenix at 5500'

Lesson Learned - Cheap DC Breaker

Post by fcwlp »

I have been helping a friend that had gone the cheap route with his 24V solar system. The Chinese charge controller was acting very erratically, bouncing between absorb at 29V and 23-24V which was actual battery voltage. Finally found that it was the cheap Chinese breaker to the battery that had a 5-6V drop (~50A at 0.1 ohm) across it when passing current. Also found that breaker was incapable of being tripped manually. Replaced it with a Blue Sea Systems breaker and system works as expected. As I said in a previous post, it is not worth the few dollars you save by going with that cheap breaker. In this case there is a good chance the batteries have been in a PSOC for a long time and will also need to be replaced.
raysun
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Re: Lesson Learned - Cheap DC Breaker

Post by raysun »

Absolutely false economy to use cheap, sub-standard parts.
In this case there is a good chance the batteries have been in a PSOC for a long time and will also need to be replaced.
GC2 type battery?
fcwlp
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Posts: 1163
Joined: Wed Jan 22, 2020 9:40 am
My RE system: GS8048A, FM80 w/3,600W PV Fixed, FM80 w/2,700W on Zomeworks tracker, Mate3, 24 Trojan 2V L16 1100AH @ C20, Grid-Tied with Kohler 14RESA LPG Generator and MEP-803 Diesel if needed.

I install and maintain grid-tied and off-grid systems in my area and consult on solar system design/operation.
Location: 80 miles NE of Phoenix at 5500'

Re: Lesson Learned - Cheap DC Breaker

Post by fcwlp »

raysun wrote: Mon Mar 27, 2023 9:55 am GC2 type battery?
Good guess. :grin: Fortunately this is a "temporary" system until they get the house built. They did buy good hardware already for the house.
raysun
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Joined: Tue Jul 26, 2016 5:57 am
My RE system: Flexpower Two: (2) FXR3048A-01 - Series Stacked, (2) FM80, MATE3s, FlexNetDC
6 SimpliPhi 3.8-48 (48v @ 75AH. 450AH total)
Outback IBR3 battery enclosure
REC Alpha 440W panels - 2 arrays: each of 4 strings of 2 in series
2 Midnite Solar MNPV6 combiners w/20A DC disconnects.
Honda EU7000is gas fuel generator
Off-Grid

Re: Lesson Learned - Cheap DC Breaker

Post by raysun »

Just more temporary than they hoped for...
If the GC2s are less than a year old, have your friend take them back to Costco for replacements.
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SandyP
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Re: Lesson Learned - Cheap DC Breaker

Post by SandyP »

In Aus DC breakers are required on each string on the roof.
Array1_DCBBox.JPG
I'm not sure if it was because these were cheap breakers or if a weather "event" damaged these or even of they were undersized for the max string output but something major occurred to result in this.
Array1_DCBreakers.JPG
I somehow expect they were undersized as on another array the 10A one failed but the 16A was OK.
Array2_DCBreakers.JPG
All of the breakers were recently replaced with new 16A ones.
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raysun
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My RE system: Flexpower Two: (2) FXR3048A-01 - Series Stacked, (2) FM80, MATE3s, FlexNetDC
6 SimpliPhi 3.8-48 (48v @ 75AH. 450AH total)
Outback IBR3 battery enclosure
REC Alpha 440W panels - 2 arrays: each of 4 strings of 2 in series
2 Midnite Solar MNPV6 combiners w/20A DC disconnects.
Honda EU7000is gas fuel generator
Off-Grid

Re: Lesson Learned - Cheap DC Breaker

Post by raysun »

It's certainly a very good idea to have the PV strings protected by circuit breakers - of the proper size to protect the wiring.
One issue that seems to crop up in PV array fires is arc faults, rather than overloads, being the ignition source. A bad connection or damaged conductor can permit an electric arc at fairly low current.
Arc Fault Interruptors are the newest trend in electrical safety requirements to address just such hazards. The AFDI technology is not without its own challenges, however. Just ask boat owners hooking up to shore power at modern marinas, or homeowners beset by nuisance tripping of the latest circuit protection. For as modern as the AF electrical codes are, the technology employed is straight out of Marconi's lab notes. The AFDI circuitry relies on electric arcs emitting low radio frequency impulses. The detectors are not much more than that employed by cheap AM radio receivers. False positive detection is common.
But that's not your problem, perhaps, though it would be interesting to disassemble some of the failed circuit breakers to see if there's evidence of arcing in the internals.
fcwlp
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My RE system: GS8048A, FM80 w/3,600W PV Fixed, FM80 w/2,700W on Zomeworks tracker, Mate3, 24 Trojan 2V L16 1100AH @ C20, Grid-Tied with Kohler 14RESA LPG Generator and MEP-803 Diesel if needed.

I install and maintain grid-tied and off-grid systems in my area and consult on solar system design/operation.
Location: 80 miles NE of Phoenix at 5500'

Re: Lesson Learned - Cheap DC Breaker

Post by fcwlp »

SandyP wrote: Fri May 19, 2023 11:01 pm I somehow expect they were undersized as on another array the 10A one failed but the 16A was OK.
I would not call breakers from ABB "cheap breakers." I cannot say the same about Noark breakers which appear to be typical Chinese breakers, some of which are good and other are ?? If you still have the 10A ABB breaker, take it apart and see if there is evidence of thermal damage. It could also be mechanical damage from the installation process.
raysun wrote: Sat May 20, 2023 12:14 am It's certainly a very good idea to have the PV strings protected by circuit breakers - of the proper size to protect the wiring.
Per the 2017 NEC 690.8 and 690.9 it is not necessary to have breakers on each string as solar panels are "current limited sources," provided the conductors are properly sized per 690.8(B). From 690.8(D), when connected to higher current sources (e.g., parallel strings of modules) there must be protection at the higher current source.
.
In other words:
1) Make sure your conductor is sized to be greater than the string's short circuit current and
2) If you have two strings combined in parallel there is no need for individual string breakers/fuses, but if you have three strings in parallel, string breakers/fuses are likely needed.
.
In today's market, I usually have one string or at most two strings of modules in parallel. Granted I am typically designing systems with string voltages of ~400VDC.
Last edited by fcwlp on Sun May 21, 2023 6:18 pm, edited 2 times in total.
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SandyP
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Posts: 522
Joined: Tue Jun 21, 2011 4:44 am
My RE system: 8 x 190W 24V Suntech panels (4 strings of 2) July 2011
4 x 325W 24V Suntech panels (2 strings of 2) added Sept2018
Mate2
Outback FM60 MPPT (max output lowered to 55amps)
12 x 2V Hoppecke GEL 612 Ah C24 - 24V System (June 2011)
Outback VFX3024 Inverter/Charger
Victron BMV-602s
Honda 5.5kW Genset
Location: Victoria, Australia

Re: Lesson Learned - Cheap DC Breaker

Post by SandyP »

fcwlp wrote: Sat May 20, 2023 8:11 am ../.. If you still have the 10A ABB breaker, take it apart and see if there is evidence of thermal damage. It could also be mechanical damage from the installation process.
Shall do.
The ABB breakers looked like this 4 years after they were installed and just prior to another 2s2p array being installed on the roof with a separate circuit - however I suspect the installers did access this breaker enclosure when running the wires from the new array.
ABB_CB_2015.JPG
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