system review

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  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: system review

    did you not want 2 of the sharp 24v pvs in series to go into a 24v battery bank or am i missing something here? the cc would down convert the 48v to 24v.
  • MexDogMexDog Solar Expert Posts: 28
    Re: system review
    niel wrote: »
    did you not want 2 of the sharp 24v pvs in series to go into a 24v battery bank or am i missing something here? the cc would down convert the 48v to 24v.

    Oops. Guess I'll be hanging out in the "beginners corner" for a while yet!

    And while I'm here, this may be pretty elementary too, but what's the amperage/wire size for the run from the batt's to the inverter? (probably about 8' total length max). The Trojan t-105's are rates at 225A/hrs. Their spec sheet gives capacity ratings at both 115Amps and 447Amps. Do I work with those ratings, or is there a standard amperage produced by a 24v battery bank used to calculate the wire size?
  • mike95490mike95490 Solar Expert Posts: 8,471 ✭✭✭✭✭
    Re: system review
    MexDog wrote: »
    what's the amperage/wire size for the run from the batt's to the inverter? (probably about 8' total length max). The Trojan t-105's are rates at 225A/hrs. Their spec sheet gives capacity ratings at both 115Amps and 447Amps. Do I work with those ratings, or is there a standard amperage produced by a 24v battery bank used to calculate the wire size?

    That's mostly determined by the power your inverter draws. If you have a 5KW inverter, but only expect to power 1KW of load at any time, you calculate for that size wire, and fuse it appropriately. But if you are going to use that inverter to start a 4KW deep well pump, then you need to use wire that can handle the starting surge of the pump - closer to 8KW, otherwise the voltage drop in the wire, will limit the power your inverter can work with.
    1KW @ 24V = 41.6A
    4KW @ 24V = 166.6A
    8KW @ 24V = 333.3A (surge, not cont)

    So you size the inverter wire to accommodates your anticipated LOADS, not always your nameplate.

    At least that's my opinion. John Wiles likely has a different one, and if you ask him a week later, it may change !
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: system review

    i pretty much agree with mike, but most inverters require a fuse or circuit breaker of a specified value on the dc side and that is kind of a maximum current that you can use for the calculated wire size and set it to the voltage the inverter runs at like 12v, 24v, or 48v. try for a low percentage like 2% or 3% or lower if it's not a problem for you to do so.
  • MexDogMexDog Solar Expert Posts: 28
    Re: system review
    niel wrote: »
    i pretty much agree with mike, but most inverters require a fuse or circuit breaker of a specified value on the dc side and that is kind of a maximum current that you can use for the calculated wire size and set it to the voltage the inverter runs at like 12v, 24v, or 48v. try for a low percentage like 2% or 3% or lower if it's not a problem for you to do so.

    The manual for the G-Power 1000w (2K max surge) inverter specifies using #6 in from the batt's and a 70A fuse. Giaim, who I bought it from specified a 60A fuse for use with this unit.

    So, this raises a couple of new questions:

    1) If I go with the manufacturer spec's and use #6 wire, does that necessitate using #6 ground wire for the system?

    Or would #8 be sufficient for batt to inverter run? (It will likely only be 2-3 foot one-way at the most).

    2) Is it safe to stick with the 60A fusing already purchased, or do I need to bump that up to 70A?
  • mike95490mike95490 Solar Expert Posts: 8,471 ✭✭✭✭✭
    Re: system review

    I'd say install the 60, and buy a 70 as your spare.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: system review

    sorry for the delay in replying.
    what the manufacturer states is the max fuse that can be used to get the most from your inverter (and is best 70a) without compromising safety or your equipment. now for a reduced power ability to the inverter and thus a slight reduction in max power out of the inverter, a 60a fuse could be used.
    with a 3ft run of #6 (or a total of 6ft of copper wire) the voltage drop will be .8% and for #8 it will be 1.27% and both are low. try to add all of the percents from the pvs right through to the inverter and see if that adds up to 5% or less as this would be from generation to load with a max of 5% on the voltage drops. now if it is a matter of which gauge of wire to use that you have on hand then by all means use the #6 and to be sure here know that just like the fuse going to 60a rather than 70a the #8 could compromise the system a bit. if the inverter has been limited to that 60a by fusing then you might get away with the #8, but my recommendation would be the #6 in spite of the short run allowing for #8 to possibly be used even if using a 60a fuse for you may upgrade the fuse later necessitating a wiring upgrade.
  • MexDogMexDog Solar Expert Posts: 28
    Re: system review
    niel wrote: »
    sorry for the delay in replying.
    what the manufacturer states is the max fuse that can be used to get the most from your inverter (and is best 70a) without compromising safety or your equipment. now for a reduced power ability to the inverter and thus a slight reduction in max power out of the inverter, a 60a fuse could be used.
    with a 3ft run of #6 (or a total of 6ft of copper wire) the voltage drop will be .8% and for #8 it will be 1.27% and both are low. try to add all of the percents from the pvs right through to the inverter and see if that adds up to 5% or less as this would be from generation to load with a max of 5% on the voltage drops. now if it is a matter of which gauge of wire to use that you have on hand then by all means use the #6 and to be sure here know that just like the fuse going to 60a rather than 70a the #8 could compromise the system a bit. if the inverter has been limited to that 60a by fusing then you might get away with the #8, but my recommendation would be the #6 in spite of the short run allowing for #8 to possibly be used even if using a 60a fuse for you may upgrade the fuse later necessitating a wiring upgrade.

    Here is a link to the diagram of the system for review: http://www.blinddogphoto.com/PVsystemdiagram.PDF
    Note that I have eliminated the AC Load center for the initial set-up as the Inverter has two GFI outlets which will be plenty for me for the time being. If you all can give this one last check, particularly the wire sizing, it would be greatly appreciated as I leave for Mexico this week and need to have everything with me when I go.
    Thank you!
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: system review

    looking it over i'm not seeing anything wrong off hand. i'm assuming that in the run for the pvs to the combiner that the interconnecting pv wire was also included as many forget it takes wire to interconnect seriesed pvs. (seriesed batteries too) i do think you could place a smaller fuse from the cc to the batteries (located near the batteries) if you wish as the pvs will not output anywhere near 60a to the batteries. as such this is to protect the wires in case of a short circuit from the batteries and as long as the current provided from the pvs through the cc have no chance of popping the fuse then the value may be lowered to facilitate an earlier pop in case of a short. adding the sc values for each string + an addition 5a for leeway and mppt action would give a value of about 25a. if you intend on expanding the pv system you may not want to go that low so between 25a and the cc max of 60a would suffice.
    now if you intend on running the inverter at max for any lengthy times you could use a larger wire to the inverter, but otherwise that is fine too.
    as to the grounds on the pvs you don't need to individually run them to ground from each pv as you could daisy chain them to ground keeping 1 solid wire run to the ground rod through each pv's ground connection as shown in the link provided here with a proper pv ground connector.
    http://store.solar-electric.com/gbdbtsopagrl.html
    if one ground lead takes too many bends or zig zags between the pvs too much (sharp bends and deviations from the straight line path to ground isn't advisable) you can then have 2 runs to ground being 1 for each string. if at any point the ground runs are running close to each other, but only from a certain point and on then one could splice them together, with say a split bolt or 2 if stressed, and continue on with one wire from the splice point to the ground rod.
    your highest % loss is showing on the 24v fan wiring and that turns out to be 1.83% which is acceptable for your system.
    all of the voltage drop percents were calculated and checked by me with 60 degrees c and if you suspect you may have wiring going higher than that you may need to recalculate for it. wires with current going through them and the sun beating down on them with high ambient temperatures, especially with confined wires, may cause higher temperatures to materialize which will increase the wire's resistance and the amount of the voltage drop seen.
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