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mod con on PV power

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hot_rod
hot_rod Member Posts: 22,498
a friend that lives off grid has installed a mod con, spark ignition. It will not light off, it has two wire 120V feed hot and neutral.
He claims it is grounded thru the inverters, if runs a third wire to the inverter? There is no actual ground connection to earth in the system.
Is it possible to "ground" through and inverter? Or does it need an earth ground, a copper rod, driven into the earth to ground the unit to?
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream

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  • FranklinD
    FranklinD Member Posts: 399
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    My PV system has the AC side grounded to an 8' copper ground rod. I've never had any issues with any equipment caused by the ground, though. Some inverters internally bond neutral and ground, some don't, and some allow you to decide using a jumper.

    That said, what type of inverter is it? I only ask because I'd be willing to bet that a modcon, with its variable speed fan control, wouldn't like modified sinewave power. Variable speed controls HATE mod-sine. I had to upgrade to a pure sinewave inverter for my boiler...the inducer fan made a horrible buzzing sound, and my bumblebee circ ran alarmingly hot on my modified sine inverter.

    Pure sine units have come down in price over the last ten years, but they're still significantly more than the mod-sine units.

    I'd look at that before worrying about the ground issue.
    Ford Master Technician, "Tinkerer of Terror"
    Police & Fire Equipment Lead Mechanic, NW WI
    Lover of Old Homes & Gravity Hot Water Systems
    Solid_Fuel_Man
  • FranklinD
    FranklinD Member Posts: 399
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    In addition to the above, anything transformer-based will run hot and less efficiently on modified sinewave as well. We used to have to use capacitor banks to smooth out the waveform enough just to run a few specific appliances...anything with an electric motor, really.
    Ford Master Technician, "Tinkerer of Terror"
    Police & Fire Equipment Lead Mechanic, NW WI
    Lover of Old Homes & Gravity Hot Water Systems
  • Harvey Ramer
    Harvey Ramer Member Posts: 2,261
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    There should be an equipment ground lug bonded to the neutral at the power source. Connecting at this point, the equipment ground should be connected to a ground rod, bonded to the water system and connected to any appliance that uses power.
  • Solid_Fuel_Man
    Solid_Fuel_Man Member Posts: 2,646
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    I agree with all of the above. I don't however think it has anything to do with being grounded. My bet is the lass than optimal sine wave the inverter is producing. A ground is only there to keep cases of appliances from becoming energized. That said, if the inverter has no ground reference, the neutral will float which shouldn't have any I'll effects on equipment but can cause an unsafe condition.

    I'd drive several ground rods and bond them to the inverter with a #6 copper minimum. I am assuming this I stall is completely off grid.

    SFM
    Serving Northern Maine HVAC & Controls. I burn wood, it smells good!
    Zman