Introduction/Questions

Joe J
Joe J Solar Expert Posts: 49 ✭✭
in Off Grid Solar & Battery Systems #1
Hello everyone!
This is my first post on this forum although I have been reading it for a while. Nice to be here. I have a passed background in industrial refrigeration so A/C wiring is not a problem for me. Can't say the same thing for the solar D/C side of things. I have two general question without going into specifics of controllers and panels ect...


1) To keep wire size down, I was thinking of going directly though the roof to my controller instead of running conduit down my roof and to the side of my house. What is the best way to to this? I'm worried about waterproofing more than anything else. How have other done this?


2) I'm running my panels....two in series than in parallel. 24 volts. I was going to go with a 12 volt battery bank and 12 volt inverter, a 5 foot run. What would be the advantage to go 24 volt inverter and battery bank? My controller is a mppt so it adjust foe 24 into 12. (panel array 1000 watts) (also using 6 volt golf cart batteries)


Thanks


Joe
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Comments

  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
    Re: Introduction/Questions

    Welcome to the forum.

    I'm going to pass on question #1 because I don't like putting holes in roofs! But there are some good installers on this forum who can tell you exactly what sort of connection is needed for this. Yes, it can be done.

    Question #2 has a "ready made" answer: http://forum.solar-electric.com/showthread.php?15989-Battery-System-Voltages-and-equivalent-power
    In detail, much depends on how much power you need to supply (both in terms of Watt hours and maximum Watts). The 24 Volt system will be slightly more efficient than the 12 Volt for the same amount of power.

    How are we doing so far? :D
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  • unicornio
    unicornio Solar Expert Posts: 217 ✭✭
    #3
    Re: Introduction/Questions

    if you up the volts, you get amperes down, and everything in life will be much better... ;-)

    welcome to forum!... :-)
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  • Joe J
    Joe J Solar Expert Posts: 49 ✭✭
    #4
    Re: Introduction/Questions

    O.K. Great link. Brings another question. 12 volt inverter (looking at a Xantrex pro watt 2000) Vs a 24 watt prue sine wave inverter cost wise. Is there a 24 volt inverter out there that is in the same price range as the Pro Watt? (around $325 street?) Alternatives? Or what's a descent priced 24 volt inverter?
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #5
    Re: Introduction/Questions

    Probably not.
    Usually when you go for pure sine you pay more, because they are more complex to build. When you go up to 24 Volts you add another layer of complexity. By this time the manufacturers figure you're going for an "up market" unit and will start to add on the bells and whistles, which further increases the price.

    About the least expensive 2kW 24 Volt sine inverter you'll find new is the Samlex (or its cousin Cotek): http://www.solar-electric.com/sa2wa24vosiw1.html They have a hard-wired version too: http://www.solar-electric.com/sa2wa24vosiw.html These are not top-of-the-line quality, but certainly usable (as opposed to a no-name brand). Another 'entry level' unit would be the Exeltech XP2000, but that's more money: http://www.solar-electric.com/exxp1224vo20.html

    You can sometimes find used inverters for good price from people who are increasing system capacity, but make sure you can check the unit out first; it's easy to destroy one.
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  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    #6
    Re: Introduction/Questions
    Joe J wrote: »
    1) To keep wire size down, I was thinking of going directly though the roof to my controller instead of running conduit down my roof and to the side of my house. What is the best way to to this? I'm worried about waterproofing more than anything else. How have other done this?

    If lightning strikes on your roof, do you want to wire up a path that brings it into your house on its way to the ground rod? Better to bring it down the side of your house to the inverter and ground rod.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
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  • Joe J
    Joe J Solar Expert Posts: 49 ✭✭
    #7
    Re: Introduction/Questions

    Thanks for the info Cariboocoot. Now I have some options to think about.:p
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  • Joe J
    Joe J Solar Expert Posts: 49 ✭✭
    #8
    Re: Introduction/Questions

    Yes, I am very familiar with grounding and lightning. I'm a Ham operator and have done lots of antenna systems and lightning protection. So your point is well taken. But if you take a direct strike to the roof panels I really don't think your going to be in good shape either way. I really haven't done my home work on solar lightning protection. I'm assuming that basically the solar lightning arrestor is a capacitor that bleeds to ground so the static doesn't build up. So the lightning is not attracted. In the electrical world and Ham world you really get a lot of opinions about how to ground. (or not ground) Myself, I think you can't ever have enough grounds. Thanks vtMaps for your input.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #9
    Re: Introduction/Questions

    The typical PV array install involves directly grounding the panel frames/mounts to prevent charge build-up in them. The lightning arrestors http://www.solar-electric.com/suprde.html are wired to the output leads to bleed off any high Voltage that occurs there before it does damage (hopefully) or travels inside.

    As you know, you can't do anything about a direct strike accept keep your insurance premiums paid. :p
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #10
    Re: Introduction/Questions

    joej,
    hi and welcome. i too am a ham and electrically grounding base antennas when possible is, imho, a necessity. the act of electrically grounding can bleed off static buildup charges making a direct strike less likely and your radio can also be a tad quieter as a result as long as you don't create any ground loops. in the case of a direct strike i definitely prefer a path to ground outside as i've seen what happens without it. anyway, my point is your pvs should be grounding as that is allot of metal sitting high above that if lightning should strike it you would want a path for that lightning to follow that is less likely to do you or your property in. just the fact that the metal is in the air, the attraction to the lightning is already present.

    i recommend the midnite spd and it is a bank of movs and they are very heavy duty. there's also leds in it for operation indication on the 2 available legs. you could get a gas discharge tube to do this quicker, but once fired they're fried and lightning often gets multiple strokes occurring. i thought of using the reverse breakdown voltage (piv) of heavy duty diodes to trip lower voltage spikes faster from lightning emp. i employ both at my qth as the more you do to thwart lightning or emp, the better.
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  • Joe J
    Joe J Solar Expert Posts: 49 ✭✭
    #11
    Re: Introduction/Questions

    On the same page Niel. Totally agree! I have 8- 8 foot ground rods at my QTH. All connected together with the electric main ground. Number 4 wire. I have in the shack a copper buss bar with all equiment hooked to it. Inside I have all Delta switches with the replacable gas discharge tubes inline. Outside on the beam and wire antenna I have I.C.E protucts to bleed the static from the LMR cable. Some old timers tell me " why do they put wing nuts on back of the rig"?? :confused:

    Joe
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