Morningstar SureSine earth conductor

_OS_
_OS_ Solar Expert Posts: 207 ✭✭✭
in Off Grid Solar & Battery Systems #1
Hi,

I have ordered a SureSine inverter and while waiting for it to arrive I have read the installation instructions where it reads:
Wire Earth Ground as shown in Figure 5 using UL Listed 4 AWG (25 mm2) or larger green wire. The Earth Ground conductor must be larger than the battery power conductors.

Would someone explain why such a tick ground cable is needed? On my 1200VA Victron inverter I have a 2.5mm2 ground wire connected to a 2m (6 feet), 12mm diameter ground rod that I have inserted into the ground right outside my tool shed. The SureSine calls for a wire ten times this in mm2.

Regards,
OS
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Comments

  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #2
    Re: Morningstar SureSine earth conductor

    ole,
    you might want to check with your country's regulations on grounding as you are seeing us regulations reflected in that. wiles tends to err way over the side of caution.
    btw, i wouldn't go smaller than 3.25 mm in any case for a ground lead so it would be that or larger in general. 3.25 mm is roughly equal to our #8 gauge and note that i am not familiar with the size standards your wire may come in. i use #6 around my house and that's about 4.1 mm, but my inverter is also 300w. he(wiles) is basing things i believe from a dc current potential and not an ac current potential.
    i do understand your feelings on this for we shouldn't have to have ground wires as large as or larger than a utility pole's ground for an inverter of that small of a size.
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  • _OS_
    _OS_ Solar Expert Posts: 207 ✭✭✭
    #3
    Re: Morningstar SureSine earth conductor
    niel wrote: »
    ole,
    you might want to check with your country's regulations on grounding as you are seeing us regulations reflected in that. wiles tends to err way over the side of caution.
    btw, i wouldn't go smaller than 3.25 mm in any case for a ground lead so it would be that or larger in general. 3.25mm is roughly equal to our #8 gauge. i use #6 around my house and that's about 4.1 mm, but my inverter is also 300w. he is basing things i believe from a dc current potential and not an ac current potential.

    Hi Niel,

    Thank you very much! I will use the thickest ground cable (green/yellow) cable I can find over here. My local dealer has 4mm2 and he has never heard of a 25mm2 ground cable.

    Ole
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #4
    Re: Morningstar SureSine earth conductor

    i added this here for i am a bit confused why they say 25 mm for 25mm does not correspond to #4 wire as that is about 5.2 mm. this chart may help you. know that 25 mm is almost equal to 1 inch in diameter and would be off of the scale for most wire sizes.
    http://en.wikipedia.org/wiki/American_wire_gauge
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  • _OS_
    _OS_ Solar Expert Posts: 207 ✭✭✭
    #5
    Re: Morningstar SureSine earth conductor
    niel wrote: »
    i added this here for i am a bit confused why they say 25 mm for 25mm does not correspond to #4 wire as that is about 5.2 mm. this chart may help you. know that 25 mm is almost equal to 1 inch in diameter and would be off of the scale for most wire sizes.
    http://en.wikipedia.org/wiki/American_wire_gauge

    Hi Niel,

    I checked the chart and if AWG 4 is the same as #4 then 25mm2 is the cable with closest area; in the chart it says 21.2mm2. Maybe you looked under diameter (mm) instead of area (mm2)?

    The standard cables in my country are 1.5, 2.5, 4, 6, 10, 16 and 25. All mm2

    Ole
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #6
    Re: Morningstar SureSine earth conductor

    ok that's where i went wrongly as it was in area. #4 is awg 4 and the # sign just means number in this case. it's up to you if you would put in wire that large and i don't know how your country feels about grounding in this regard for as i later mentioned in my other previous post, "i do understand your feelings on this for we shouldn't have to have ground wires as large as or larger than a utility pole's ground for an inverter of that small of a size."
    i guess i should add utility poles here are grounded with the same #6, but utility poles carry far more power than a few hundreds watts as we would see by the inverter. they are calling for thicker wire than a utility pole must have here and i think wiles gets so lost in his regulations that common sense goes out of the window sometimes.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #7
    Re: Morningstar SureSine earth conductor

    Maybe it's a typo in the manual. Try putting a decimal point between the 2 and the 5 in 25mm. :D
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  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
    #8
    Re: Morningstar SureSine earth conductor

    The SureSine ground carry's minimal current, its to ground the case and possible a cap or two for filtering. For your cabin, a wire the size of the AC wiring for the ground connection is more than adequate.

    I've alerted MS to the wording in the manual ... FYI, the Xantrex XW-6048 ( a 6Kw inverter ) uses a 4 AWG wire, and that's 20X the rating of the SureSine.
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  • _OS_
    _OS_ Solar Expert Posts: 207 ✭✭✭
    #9
    Re: Morningstar SureSine earth conductor
    Solar Guppy wrote: »
    The SureSine ground carry's minimal current, its to ground the case and possible a cap or two for filtering. For your cabin, a wire the size of the AC wiring for the ground connection is more than adequate.

    I've alerted MS to the wording in the manual ... FYI, the Xantrex XW-6048 ( a 6Kw inverter ) uses a 4 AWG wire, and that's 20X the rating of the SureSine.

    Thanks! I will use a 2.5mm2 or 4mm2 conductor then.

    Ole
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #10
    Re: Morningstar SureSine earth conductor

    careful ole that you don't make the same mistake as the 4mm i cited for our #6 was the diameter and not the area.
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