Blown fuses

stmoloudstmoloud Registered Users Posts: 100 ✭✭
edited January 20 in Solar Beginners Corner #1
My panels output 43 amp continuous but I've manged to blow two 50 amp fuses in as many days. 
This happens after a cloudy start to the day after which the clouds disappear and then very good sun.
I expect the panels are pumping out a surge current which is then blowing the fuse.
The manual says the 45 amp controller can handle up to 130% of (overloaded) rated current.
So, accordingly, would a 100 amp fuse be sufficient to handle the amp surge from the panels?
Thanks.
 
760W panel array, 4 x 6v 220 ah Crown batteries, Tristar TS-45 PWM controller,  no name 600 PSW inverter. 
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Comments

  • mcgivormcgivor Solar Expert Posts: 2,759 ✭✭✭✭✭
    The purpose of the fuse is to protect the conductors, therefore the gauge, or cross sectional area, is required to determine tha appropriate fuse capacity.
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery bank 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah FLA 24V nominal used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
  • stmoloudstmoloud Registered Users Posts: 100 ✭✭
    So the wire is too small, therefore I should increase the sq mm? The solution then will be to increase the amp capacity of the wire to 100, and also fit a 100 amp fuse?
    760W panel array, 4 x 6v 220 ah Crown batteries, Tristar TS-45 PWM controller,  no name 600 PSW inverter. 
  • mcgivormcgivor Solar Expert Posts: 2,759 ✭✭✭✭✭
    edited January 20 #4
    What size do you have and how long is the run? Going by your signature the modules are in parallel, do each have overcurrent protection before the combination point?
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery bank 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah FLA 24V nominal used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
  • stmoloudstmoloud Registered Users Posts: 100 ✭✭
    edited January 20 #5
    The wire is 56 amp and there's about 10 foot of it. Do I need overcurrent protection? I have five panels and the largest current of any of them is 8.88A @ peak power.
    760W panel array, 4 x 6v 220 ah Crown batteries, Tristar TS-45 PWM controller,  no name 600 PSW inverter. 
  • mcgivormcgivor Solar Expert Posts: 2,759 ✭✭✭✭✭
    edited January 20 #6
    stmoloud said:
    The wire is 56 amp and there's about 10 foot of it. 
    So  6 sq.mm?

    stmoloud said:
    The wire is 56 amp and there's about 10 foot of it. Do I need overcurrent protection? I have five panels and the largest current of any of them is 8.88A @ peak power.

    Dose each module have its own protection, typically ~15A fuse or circuit breaker? 
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery bank 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah FLA 24V nominal used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
  • stmoloudstmoloud Registered Users Posts: 100 ✭✭
    edited January 20 #7
    The wire is 8 AWG or 8.31 sq.mm. The second question is no, the modules are wired directly into the combiner. Total combined amps is 42.3.
    760W panel array, 4 x 6v 220 ah Crown batteries, Tristar TS-45 PWM controller,  no name 600 PSW inverter. 
  • mcgivormcgivor Solar Expert Posts: 2,759 ✭✭✭✭✭
    Each module should have its own protection to prevent backfeeding from the other modules in the event of a short in an individual, a DC circuit breaker like this https://www.amazon.com/Low-voltage-Miniature-Circuit-Breaker-Panels/dp/B0746DLP7S?ref_=fsclp_pl_dp_7
    at the controller would provide a means of disconnect as well as protect the conductors. Inline mc4 fuses are available https://www.amazon.com/STETION-20Amp-Waterproof-Holder-Female/dp/B07GGWSPNX/ref=sr_1_7?keywords=Inline+mc4+fuse&qid=1547957110&sr=8-7 though circuit breakers are preferred as they can be switched under load.
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery bank 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah FLA 24V nominal used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
  • stmoloudstmoloud Registered Users Posts: 100 ✭✭
    Thanks. I will individually protect probably with inline auto-type connectors. MC4 stuff (as is most solar) in NZ is way overpriced. I just chop them off and solder. 
    760W panel array, 4 x 6v 220 ah Crown batteries, Tristar TS-45 PWM controller,  no name 600 PSW inverter. 
  • mcnutt13579mcnutt13579 Registered Users Posts: 98 ✭✭✭
    For the record, it is allowable to combine 2 strings into one set of conductors without breakers or fuses.  Reason being, any short in solar module leads will be carrying 21 amps in from one direction, and 21 amps from the other direction, therefore no conductor will be overloaded.

    3+ strings need overcurrent protection.
  • petertearaipetertearai Solar Expert Posts: 390 ✭✭✭
    Although fuses are cheaper ... circuit breakers are s better long term idea .. easy to reset and great for easy switching for fault finding .
    2225 wattts pv . Outback 2kw  fxr pure sine inverter . fm80 charge controller . victron battery monitor . 24 volts 450 ah surette batterys . off grid  holiday home 
  • littleharbor2littleharbor2 Solar Expert Posts: 1,255 ✭✭✭✭
    You're experiencing "Cloud Edge Effect" I've watched panels go considerably over their Imp. rating on Days where fluffy clouds are traveling at a leisurely pace across the sky. The reflected light bouncing off the cloud edges added to the fully exposed sun will momentarily produce over 1000 watts per square meter, which is what panels are tested at for their power rating. If your controller is in bulk charging mode it is allowing all current to flow into your batteries and cause your fuse to blow.

    2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old  but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric, 700 ah @24 volt AGM battery bank. Plenty of Baja Sea of Cortez sunshine.

  • softdownsoftdown Solar Expert Posts: 2,148 ✭✭✭✭
    The purpose of the fuse is to protect the  wiring and equipment, behind the fuse, from catastrophic power and surges. The "purists" will howl but I would probably try an ~75 amp fuse. Not surprised that a 50 blew with 43 amps continuous. I'm no expert on this. I have found that some "lines" simply require a larger fuse than the manufacturer used. My late father worked with medical equipment repair for over 4 decades and was generally not averse to going up a bit in fuse size. Its not a perfect world with perfect equipment.

    Perhaps somebody will produce a formula. 50 amps of 12 volt power is broadly akin to 5 amps of 120 volt power. DC circuit breakers are much stouter than AC circuit breakers rated for the same amperage by the way. That might be  clue. And I'm no expert.
    First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
  • stmoloudstmoloud Registered Users Posts: 100 ✭✭
    littleharbor2 said:
    You're experiencing "Cloud Edge Effect" I've watched panels go considerably over their Imp. rating on Days where fluffy clouds are traveling at a leisurely pace across the sky. The reflected light bouncing off the cloud edges added to the fully exposed sun will momentarily produce over 1000 watts per square meter, which is what panels are tested at for their power rating. If your controller is in bulk charging mode it is allowing all current to flow into your batteries and cause your fuse to blow.
    Yes I'm still going with the theory of a surge. And your description of "cloud edge effect" describes exactly how it has been the last couple of days. 

    softdown said:
    The purpose of the fuse is to protect the  wiring and equipment, behind the fuse, from catastrophic power and surges. The "purists" will howl but I would probably try an ~75 amp fuse. Not surprised that a 50 blew with 43 amps continuous. I'm no expert on this. I have found that some "lines" simply require a larger fuse than the manufacturer used. My late father worked with medical equipment repair for over 4 decades and was generally not averse to going up a bit in fuse size. Its not a perfect world with perfect equipment.

    Perhaps somebody will produce a formula. 50 amps of 12 volt power is broadly akin to 5 amps of 120 volt power. DC circuit breakers are much stouter than AC circuit breakers rated for the same amperage by the way. That might be  clue. And I'm no expert.
    OK thanks. I'll keep upping the fuse in increments of ten to find the sweet spot. And then install the nearest breaker
     
    760W panel array, 4 x 6v 220 ah Crown batteries, Tristar TS-45 PWM controller,  no name 600 PSW inverter. 
  • mcgivormcgivor Solar Expert Posts: 2,759 ✭✭✭✭✭
    The expression " A chain is only as strong as it's weakest link" applies to a fuse or circuit breaker, it is the weakest link in a circuit, used to prevent the conductors from themselves becoming the fuse. Current capacity ratings are very conservative, usually derated to ~80% to provide a margin of safety and prevent heating, the actual value is also determined by conductor material, insulation type, conduit fill, ambient temperature etcetera.

    When selecting an over current device, sizing is usually calculated by multiplying the maximum allowable current by 120%, this prevents nuisance failure or tripping. As the OCP is the weak link, heat is generated, if current too close to its maximum capacity the heat generated will cause the fuse to increase in resistance and eventually fail. So in the case of 8 gauge, the current rating of 50A multiplied by 120% is 60A, or the next closest value eg. 63A, so that would be the preferred value, note, this is a general calculation.

    Automotive fuses/circuit breakers are not the best fit for solar power applications, they are not designed to carry close to maximum current for extended time, but rather to protect against short circuit and support intermittant loads. Often they rely in interference connection rather than screw terminals which are a more reliable method of connection.

    DC circuit breakers are available  at very reasonable prices outside New Zealand, the equipment  availabie in Thailand is generally the same product as Aliexpress but 3-5 times the price, so I order directly. 

     https://m.aliexpress.com/item/623939178.html?pid=808_0000_0101&spm=a2g0n.search-amp.list.623939178&aff_trace_key=a5610d1f37fd4899a687a76cf182b72b-1542768906153-07210-UneMJZVf&aff_platform=msite&m_page_id=3729amp-ZXkLFFJjLTwwvWd9Q8WQJQ1548032677744
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery bank 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah FLA 24V nominal used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
  • stmoloudstmoloud Registered Users Posts: 100 ✭✭
    Thanks. Was tempted to purchase a 70A circuit breaker today but in the small print it "will trip within 1 minute of a 90A load" So can I assume then that this will trip at 70A but it will take longer than 1 minute to do so, and is that an acceptable amount of time in an over current situation?
    760W panel array, 4 x 6v 220 ah Crown batteries, Tristar TS-45 PWM controller,  no name 600 PSW inverter. 
  • mike95490mike95490 Solar Expert Posts: 8,204 ✭✭✭✭✭
    Spend the $22 and get the Switch Rated DC breakers from Midnight Solar.   They are magnetically activated and don't have the heating up and thermal issues conventional breakers have

    Today the sun has be popping out between clouds and have been varying between 200W and +5000.  i've had 6 days of clouds
    and batteries are quite thirsty, this sort of event needs to be allowed for so your breakers don't trip off incorrectly.
     Size your wire properly, then chose the breakers to protect the wire gauge.



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