Wire & Fuses, what size and where

RCI
RCI Registered Users Posts: 4
I need some help with fusing my beginner system and the correct wire size between the CC & battery, then between the battery and inverter. I want to begin with a very small system to get my feet wet and understand how to proceed before I jump in with both feet. I'm starting with:
1 ea. 100W 12V panel (Renogy 100W x 12V x 5.75 Short-Circuit Curr) / 30' x 8 ga wire using MC4 connectors to a 40A x 500W MPPT charge controller (Tracer 4210RN w/meter) / wire & fuse to be determined / to an AGM Deep Cycle 12v 125ah SLA battery (Vmaxtanks Vmaxslr125) / wire and fuse to be determined / to a Xantrex PROwatt SW 1000 inverter...... I need help sizing the wire I don't have picked out and the fuses I need to protect the current beginner system. I've purposely increased the CC & inverter so I can add panels in the future after I feel confident about proceeding....... things I have that could be used: 10' x 2 ea. 8 ga coated wire (red & black) / 2 ea. ANL x 100W fuse with holder / 15 ea. 4 AWG Battery Cable 3/8" Tubular Lug Ring / 15 Amp Mini ANL Fuses (2 Pack) / 25 Amp Mini ANL Fuses (2 Pack) / 3 ea ANL Inline Fuse Holder with 4/8 Gauge Inputs and Outputs....... TIA, RCI

Comments

  • oil pan 4
    oil pan 4 Solar Expert Posts: 767 ✭✭✭✭
    I put a 100 amp breaker on my 1000 watt Kisae inverter.
    My latest inverter I picked was the same Xanterx proWatt 1000 watt inverter and it came with a 80 amp breaker.
    So any where between 80 and 100 amps should be good. Locate the fuse or breaker close to the battery.
    I hooked up the 1000 watt Kisae with 4 gauge THWN cable to the battery.
    The Xanterx has not been hooked up yet and I will likely use 4 gauge THWN once again.

    Solar hybrid gasoline generator, 7kw gas, 180 watts of solar, Morningstar 15 amp MPPT, group 31 AGM, 900 watt kisae inverter.

    Solar roof top GMC suburban, a normal 3/4 ton suburban with 180 watts of panels on the roof and 10 amp genasun MPPT, 2000w samlex pure sine wave inverter, 12v gast and ARB air compressors.

  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Welcome to the forum RCI.
    RCI wrote: »
    I need some help with fusing my beginner system and the correct wire size between the CC & battery, then between the battery and inverter. I want to begin with a very small system to get my feet wet and understand how to proceed before I jump in with both feet.

    Remember that small system components usually cannot be added on to make a large system (you can increase capacity about 2-3x before you have to make major changes in design, battery bank voltage, size/number/voltage of solar panels/different AC inverter/different batteries/etc...

    The math/design behind solar power systems is pretty will understood these days--You can design a system that will actually meet your needs, and (if appropreate) get cheap batteries (like "golf cart" batteries) for your first bank.

    For the most part, people "murder" there first set or two of batteries and starting out with "training batteries" is a good place to start. Once you have the system (and users) under control, you can look at better batteries (or different chemistries) down the road.
    I'm starting with:
    1 ea. 100W 12V panel (Renogy 100W x 12V x 5.75 Short-Circuit Curr) / 30' x 8 ga wire using MC4 connectors to a 40A x 500W MPPT charge controller (Tracer 4210RN w/meter) / wire & fuse to be determined / to an AGM Deep Cycle 12v 125ah SLA battery (Vmaxtanks Vmaxslr125) / wire and fuse to be determined / to a Xantrex PROwatt SW 1000 inverter.....

    I am a big believer in designing a "balanced" system.... Too small of battery bank, you cannot supply your loads properly. Too big of battery bank, you need a relatively large battery bank just to keep the bank properly charged--And when you kill your first set, you have more expense to replace the over sized bank... etc.

    Start with the battery, that is the "heart" of your system. Personally, I would probably suggest a flooded cell battery as your first bank. AGMs, while a nice/clean/low maintenance type battery--Are a bit difficult to "understand" and operate correctly. Flooded Cell batteries, you can get a good Hydrometer and measure/log the specific gravity of your cells--That is the "gold standard" for operating a lead acid type battery bank.

    AGM batteries, being sealed and no "free liquid" electrolyte--It is a bit difficult to measure what is happening to your battery. A pair of 6 volt @ ~220 AH golf cart batteries at ~$84 from Costco/Sams Club/etc. are a great starter pair. Plus a 220 AH @ 12 volt battery bank is a bit more capable of system (of course, it depends on your needs--If you do not need much power, then a smaller system is nice too).

    Nominally, suggest a 5% to 13% rate of charge--And if you are going to use the system daily, I would suggest a 10% or greater rate of charge. For a 125 AH @ 12 volt battery bank, that would be:
    • 125 AH * 14.4 volts charging * 1/0.77 panel+controller deratings * 0.05 rate of charge = 117 Watt panel minimum
    • 125 AH * 14.4 volts charging * 1/0.77 panel+controller deratings * 0.10 rate of charge = 234 Watt array nominal
    • 125 AH * 14.4 volts charging * 1/0.77 panel+controller deratings * 0.13 rate of charge = 304 Watt array "cost effective" maximum
    For weekend use/experimenting, a 100 Watt panel is a bit on the small side--But could be OK for you.

    Next--Sending your solar power ~30 feet is a bit far for a 12 volt system... Possible voltage drop issue. Using a generic drop calculator and using 1-3% voltage drop:
    • 17.5 volts Vmp * 0.01 = 0.18 volts minimum needed drop
    • 17.5 volts Vmp * 0.03 = 0.53 volts max suggested drop
    • 100 Watts / 17.5 volts Vmp = 5.71 Amps Imp
    • 30' @ 5.71 volts @ 0.18 volt drop => 6 AWG
      • Voltage drop: 0.14
      • Voltage drop percentage: 0.80%
      • Voltage at the end: 17.36
    • 30' @ 5.71 v @ 0.53 drop => 12 AWG
      • Voltage drop: 0.54
      • Voltage drop percentage: 3.09%
      • Voltage at the end: 16.96
    I would suggest with the MPPT controller that you get 2x 100 Watt panel and put them in series... Larger array, and you can use much smaller wire (Vmp-array ~ 35 volts).
    I need help sizing the wire I don't have picked out and the fuses I need to protect the current beginner system. I've purposely increased the CC & inverter so I can add panels in the future after I feel confident about proceeding......

    A 40 amp MPPT charge controller, the wiring/breaker needed to support that current:
    • 40 amps * 1.25 NEC derating for wiring+breakers = 50 amp fusing and branch circuit (to meet maximum controller current)
    Suggest getting a small Midnite breaker box + breakers. Very handy for turning on/off controller/devices as needed. I am not a big fan of ANL fuses and holders--They have been reported to melt the holders when ran at less than rated current.

    Each + wire that leaves the battery bank needs a fuse/breaker sized to the wire. Lead Acid and AGM Batteries can output a very surprising about amount of current into a dead short.

    Sizing, here are a couple of tables. The NEC is quite conservative. The Marine tables are not:

    http://lugsdirect.com/WireCurrentAmp...ble-301-16.htm
    http://www.boatus.com/boattech/artic...-terminals.asp

    For 12 volt systems, you want to design for 0.5 volt maximum drop from Battery bank to your DC loads. And you want 0.05 to 0.10 volt maximum drop from battery bank to charge controller (short/heavy leads between charge controller and battery bank).

    If you are going use an AC inverter.. this 12 volt MorningStar inverter--Very nice. Has features that very few 12 volt inverters come with.
    things I have that could be used: 10' x 2 ea. 8 ga coated wire (red & black) / 2 ea. ANL x 100W fuse with holder / 15 ea. 4 AWG Battery Cable 3/8" Tubular Lug Ring / 15 Amp Mini ANL Fuses (2 Pack) / 25 Amp Mini ANL Fuses (2 Pack) / 3 ea ANL Inline Fuse Holder with 4/8 Gauge Inputs and Outputs.

    Remember for solar array wiring, you need to use UV resistant wire where exposed to sunlight... How are you planning on running the cable from the array back to the charge controller (exposed, conduit, buried, etc.)?

    Other things to think about--If you live in an area with lightning--You need surge suppressors, ground rods, etc. to keep your home safe. A solar panel on a roof is prime strike point.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • RCI
    RCI Registered Users Posts: 4
    Thank you both for replying, I'll use the 100A fuse I already have, between my AGM battery and the inverter I already have (Tracer4210RN). If I understood correctly a 50A fuse is appropriate to use between the Charge Controller and the AGM battery.. I have a 25A fuse I could use to get started with and may do that until I get a 50A fuse and hope it doesn't burn up before I get it changed out. I'm placing the battery in my basement and have no way to vent it so an AGM battery is what I chose for now. I'm going to use 6' x 2ea. of the 8 ga wire between the CC and the AGM battery. If this is incorrect I can get another 6' x 2ea. of the 4 ga. wire when I go to Home Depot to buy some 4ga. wire for the run between the battery and inverter. I'm confused about one thing though- the 8 ga x 30' run between the solar panel and the charge controller is already supposed to be over sized and even 10 ga. is supposed to be adequate for that run. Am I missing something here or making a mistake ? As I upgrade in the future I'll go over everything again to make sure I'm not missing something. Thanks for the reminder about grounding wire, I had it planned but it's easy to forget because of being new to this kind of stuff...... TIA, RCI
  • Vic
    Vic Solar Expert Posts: 3,208 ✭✭✭✭
    RCI,

    As BB Bill mentioned, you WILL WANT a circuit breaker between the battery and the Inverter, at the very least. This IS a safety issue. In an emergency, do you want to be looking around for your insulated wrenches to disconnect an inverter that is ON FIRE??

    Also, as noted, you need to size circuit protection -- breakers and fuses -- to the size of the cable that these protective devices are there to protect. So with a 100 A protective device (the recommended breaker in this case), you really should use larger diameter cable than #4 AWG that you are referring to.

    Here is a dandy breaker:
    http://www.solar-electric.com/installation-parts-and-equipment/midnite/cipr1/high-amperage-inverter-breakers/obdc-100.html

    And, another:
    http://www.solar-electric.com/installation-parts-and-equipment/midnite/cipr1/high-amperage-inverter-breakers/mnedc125.html

    Those are Large Frame breakers, and really should be mounted in an appropriate metal enclosure.

    Here some other breakers that may suit your needs ..

    This is the standard breaker for PV Combiners (which you will not need at this point, probably):
    http://www.solar-electric.com/installation-parts-and-equipment/midnite/cipr1/stfubr1/mnepv.html

    Here are other MidNite breakers, that should also be OK for your Inverter:
    http://www.solar-electric.com/installation-parts-and-equipment/midnite/cipr1/stfubr1/pamodccibr.html

    Would AVOID the MRCB Thermal breakers, they generally do not have the Fault Interrupt current rating of the breakers listed above, and probably have a limited cycle-life.

    BB Bill may well have listed some of these items above ... My unsolicited advice, is, that for your starter system, Please start at a good, safe place, with quality circuit protective devices -- circuit breakers in this instance -- that combine a safety Disconnect, along with circuit protection. And, choose equipment and devices that will set you on a good path for the future. This way, you can avoid problems brought on by sub-standard items and techniques, that will need to be unlearned and corrected later.

    FWIW, Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
  • oil pan 4
    oil pan 4 Solar Expert Posts: 767 ✭✭✭✭
    I use eaton MS25361-100
    I use them as breakers and as battery isolation. Pull the button to pop it. This is how I store my 7kw generator with 1000w Kisae inverter. I pop the breaker I installed to isolate power from both the generator and the inverter.
    Actually if you search for MS25361-___ and fill in the last 1, 2 or 3 numbers with the amperage you want you can find them in 5 amp increments up to 200 amps I believe.
    I don't know what the voltage was rated for but have seen that they are used in 28 volt systems.
    These breakers last many years under daily use.

    Solar hybrid gasoline generator, 7kw gas, 180 watts of solar, Morningstar 15 amp MPPT, group 31 AGM, 900 watt kisae inverter.

    Solar roof top GMC suburban, a normal 3/4 ton suburban with 180 watts of panels on the roof and 10 amp genasun MPPT, 2000w samlex pure sine wave inverter, 12v gast and ARB air compressors.

  • RCI
    RCI Registered Users Posts: 4
    Thanks for the specific items, that's what I need, a little hand holding at this point. I'll check out these items and pick them or the equivalent up where ever I can. Oil Pan, I checked out this first item on Amazon and I'm afraid it's a little out of my price range to experiment with. I'll look at Vic's links and see what they look like..... thanks for the feedback...... RCI
  • Vic
    Vic Solar Expert Posts: 3,208 ✭✭✭✭
    OK RCl,

    Several advantages to the breakers Linked to the Wind-Sun site are;

    Magnetic-Hydraulic, a heavy duty design with repeatable trip.
    Designed specifically for use in Solar and battery applications.
    Rated for 10,000 operations, either as switches at rated current, or for over-current trips.
    Generally, rated for at least 5,000 Amp current interruptions at rated voltage.
    Fit available Listed boxes and enclosures. The Large Frame breakers have few available enclosures that are fairly small, for only several breakers, however.

    Basically they are all very inexpensive, have very good ratings for DC applications, and generally fit available and inexpensive Agency-Listed boxes.

    And, RCl, you may want to look at the MidNite Mini DC or e-Panels for your current needs, or think about them for an expanded system:
    e-Panels:
    http://www.solar-electric.com/instal...ite/misoe.html

    Mini DC:
    http://www.solar-electric.com/instal...idcdipoce.html

    Many of these may be fairly far beyond what you want or need, at this point, but ...

    Have Fun, Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
  • RCI
    RCI Registered Users Posts: 4
    thanks Vic, I'll take my time and look over everything you listed...... I'll eventually add to this initial system and when I do I'll pay a little closer attention to what I purchase. Thanks, , RCI
  • oil pan 4
    oil pan 4 Solar Expert Posts: 767 ✭✭✭✭
    I forgot, those are avation grade breakers. There was a change to some equipment I work on that called for upping the breaker from 100 amps to 125. Normally the old 100 amp breakers get removed and tossed in the trash but I collected them. I had no idea they were so expensive.
    I have seen this type of breaker on ebay for a lot cheaper used, but they were smaller than 100 amp.
    $400, used, I can not believe it. I don't plan on selling mine.

    Solar hybrid gasoline generator, 7kw gas, 180 watts of solar, Morningstar 15 amp MPPT, group 31 AGM, 900 watt kisae inverter.

    Solar roof top GMC suburban, a normal 3/4 ton suburban with 180 watts of panels on the roof and 10 amp genasun MPPT, 2000w samlex pure sine wave inverter, 12v gast and ARB air compressors.