Grounding rod

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BoFuller
BoFuller Solar Expert Posts: 187 ✭✭✭
in Off Grid Solar & Battery Systems #1
Will a piece of #5 rebar (5/8 inch) suffice as a grounding rod?
12 Kyocera 235 panels, 3 Gyll LiFePO4 batteries (previously 16 Trojan L16 RE-B batteries), Outback 3600W 48V system, Generac 11K propane backup generator, NW AZ, off grid, 6,000 ft (system installed in April 2015)

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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #2
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    Re: Grounding rod

    not if going by nec rules.
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  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    #3
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    Re: Grounding rod

    Doesn't NEC allow for rebar 'Ufer" grounds?
    http://forum.solar-electric.com/showthread.php?3583
    http://forum.solar-electric.com/showthread.php?10650

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #4
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    Re: Grounding rod

    a piece of rebar would never pass as the ufer arrangements contain allot of rebar and to be honest i never thought the concrete as good enough to sink as grounding material. imo the nec made an exception because of too many in the construction field complaining.

    if you think it's good enough then go ask a local inspector or an electrician what he thinks of driving a piece of rebar into the ground to act as a ground rod. if it were that easy then any pipe of any length would be allowed and this is definitely not the case.
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  • Photowhit
    Photowhit Solar Expert Posts: 6,003 ✭✭✭✭✭
    #5
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    Re: Grounding rod

    I live in Missouri, and pipe(not rebar) can still be used for grounding here, but the grounding rod wasn't expensive at all, worried more about driving in the first couple feet! As I recall it was just $12-15... 8' copper coated maybe 5/8th"
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
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  • BoFuller
    BoFuller Solar Expert Posts: 187 ✭✭✭
    #6
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    Re: Grounding rod

    Personally I think the majority of any code ( electrical, building, zoning, etc.) is about control, with the excuse of safety. Here are my reasons for code; fund raising, control, job security, and then safety.
    But due to the fact that I know less about electrical than all the others, I will go with code on an "official" grounding rod.
    12 Kyocera 235 panels, 3 Gyll LiFePO4 batteries (previously 16 Trojan L16 RE-B batteries), Outback 3600W 48V system, Generac 11K propane backup generator, NW AZ, off grid, 6,000 ft (system installed in April 2015)

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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #7
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    Re: Grounding rod

    No, the majority of code is about safety. How it is applied interpreted in different areas is another matter.

    The grounding issue is one of having sufficient contact between the conductor and the earth to handle the expected current in a failure situation. The Ufer grounding has a lot more contact area than a single piece of rebar would. That is why it is accepted now.

    Different soil conditions in different areas require different solutions to achieve the right level of ground contact. Some areas only require one 5' copper rod. Others want 10' or more. The dryer or more sandy/rocky the soil is the more difficult it is to achieve proper conductance. There are even ground plates which are used in areas where you don't have good soil depth. Sometimes wire grids are used.

    It may seem like a hassle, but proper grounding is one of the simplest things you can do to protect yourself.

    Can't say I feel the same way about certain other aspects of the code. :roll:
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #8
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    Re: Grounding rod

    bofuller,
    believe it not i agree with you, but there is an advantage in driving in one of those copper coated 8ft pieces of steel. these will drive through some rocks and hard soils while maintaining some better electrical connectivity with the copper coating. these rods are much stronger than rebar. if your soil is free of obstructions then you could even drive a 8ft piece off 1/2in copper pipe, but it is softer and may bend on you, not to mention more expensive.

    coot you beat me to the reply again. i do differ with you that i don't know of anyone allowing less than an 8ft rod. i also don't consider grounding to be all that simple.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #9
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    Re: Grounding rod

    Simple protection, Niel; but not necessarily simple to achieve. ;)
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  • Vic
    Vic Solar Expert Posts: 3,208 ✭✭✭✭
    #10
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    Re: Grounding rod

    A UFER is a largish bare copper wire or cable, that is tied to Re-Bar and (usually) encased in concrete. The copper is attempting to bond the rebar together. But, IMHO, rebar is not the grounding conductor or rod.

    We also use copper wire/cable trench grounds here, but tie these to a ground rod where it emerges from the soil. This is a convenient tie point, and is present for an inspector to inspect. YMMV, 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.
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #11
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    Re: Grounding rod
    BoFuller wrote: »
    Will a piece of #5 rebar (5/8 inch) suffice as a grounding rod?

    Only if it is 20' long, and encased in cement. (in a foundation)

    About a foot of rebar comes up from the slab, and the power panel is tied to it with a fancy clamp.

    Copper should NOT go into concrete, it will quickly dissolve in the akaline enviroment. If rebar sections need to be electrically tied together, they are welded, according to the inspector doing my place.
    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

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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #12
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    Re: Grounding rod

    Of course, I have to wonder how well the slab works, with the 5 mil moisture barrier, 4" of sand, and 8" of gravel !

    When the slabs were in native dirt, and could wick up moisture, all the ions in the concrete made the soil very conductive and it IS a good ground. Then the building departments over time, "improved" the drainage of the slab, to where it's likely ineffectual.
    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 ,

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  • Vic
    Vic Solar Expert Posts: 3,208 ✭✭✭✭
    #13
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    Re: Grounding rod

    mike,

    All of the UFERs on the projects that I'ce been involved with have used large copper cable in the pour, and tightly tied to the rebar. The point where this copper cable emerges from the pour uses PVC conduit, as some spalling can occur at that point. Have seen some of the rebar tacked at some of the joints, but many feel that rebar should never be welded. Have seen copper meshed at 12- inch OC under a pour without protection and so on. If the copper is large guage things are probably fine re corrosion. I do like perimeter trench grounds which are tied to a UFER, as each has some advantages.

    But, as you noted, it is ALL up to the inspector. Perhaps the implementation requirements are local preferences. Will continue doing what is required by THE inspector.

    These things do change over time. 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.
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  • Jigme Urgyen
    Jigme Urgyen Registered Users Posts: 13 ✭
    #14
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    Re: Grounding rod

    Its all great that is passes code, but is the ground resistance actually OK?

    If you drive a piece of rebar into the ground and the earth resistance meter tells you its good, then Ok, use it. If you spend 10 thousand bucks on a copper mesh with exo-thermic bonds and the resisteance is 400 ohms per square meter, its a beautifully useless ground.

    What about the joint quality? If you get a decent ground fault, it might blow the joint apart and the ground is useless again.
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