Transfer switch issues

sunnyskies
sunnyskies Registered Users Posts: 14 ✭✭
in Off Grid Solar & Battery Systems #1
So i have a single pole transfer switch (no neutral switching) that i want to use to transfer between my honda 2000i and my 1500 watt 24 volt sine wave inverter (Aims power)  then feed my breaker panel (no grid) the breaker panel has a neutral / ground jumper installed. my question is will the inverter tolerate its neutral and ground being tied together at the panel and will the honda tolerate its neutral and ground tied together also. Me thinks there is potential to let some smoke outta somthing here! any thoughts?
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #2
    Let's hope it's a " break before make " style
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #3
    Check your Honda manual, you should find that the generator frame ground does not attach to the AC neutral output (neutral/white wire is not ground bonded). So the generator will simply follow the grounding on the system side (your AC panel neutral to ground bonding).

    In general, smaller gensets "float" the AC output. And larger generators (3,500 watt and above???) generally ground reference the neutral to the generator frame/ground lug (as I understand--Always confirm with manual/testing).

    For the Aims 1,500 Watt Sine Wave inverter, is this the manual?

    http://www.aimscorp.net/documents/PWRI150024S.pdf

    Normally, Pure Sine Wave/True Sine Wave AC inverters have a full transformer isolated output (isolated from the DC input) and both the DC Battery bank can be negative (or even positive grounded in some cases) grounded and one of the AC outputs (normally the white wire) is ground bonded to your local safety ground.

    And Modified Square/Sine Wave AC inverters generally do not have transformer isolation, and they will be damaged if you ground reference the DC Battery bank and the AC "white/neutral" lead (bonding both DC and AC creates a short through the inverter).

    And, with many manuals, they do not mention Neutral Bonding at all (I did not see anything in the AIMS manual about AC neutral/grounding/grounding). Again, I would guess that smaller AC TSW/PSW inverters have floating outputs and the larger ones have the White Wire/Neutral ground bonded to the case/inverter ground lug.

    In some of the inverters I have seen, the AC neutral bonding is done in the AC output wiring box/behind the AC outlet (if present) and pretty obvious (again, only TSW/PSW inverters--MSW inverters are almost never capable of having a ground bonded neutral).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • sunnyskies
    sunnyskies Registered Users Posts: 14 ✭✭
    #4
    Thanks for your comments Did some testing and my Aims 24 volt 1500 watt pure sine inverter has 60 volts to gnd on the hot and the neutral wont be hooking that to my bonded panel. Anyone know of a reasonable hardwire 24 volt inverter 300-1000 watt 
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #5
    That may actually be OK. If you are using a DMM, they will take very small amounts of current to read voltage.

    Use an incandescent bulb between neutral and ground (4-40 watt) and see if it lights/then measure the voltage. My guess is you will see zero volts across the light.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • sunnyskies
    sunnyskies Registered Users Posts: 14 ✭✭
    #6
    stray voltage is your thought? I have the 12 volt 600 watt version it reads the same will try your idea with that since its on the test bench will report back
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  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    #7
    My bet is as Bill has explained, ghost voltage, digital mulltimeters have a high impedance, which often mislead.
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS 
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  • sunnyskies
    sunnyskies Registered Users Posts: 14 ✭✭
    #8
    Hooked up a 40 watt incandescent between neutral and ground took a bit to find one in my cf/led home, and low and behold no light! measuring a few stray mv neutral to gnd with my fluke 43 and some pretty funky waveforms but output steady at 119v and sinewave looks good! i would imagine the same results with the higher power unit will check next time i am at the cabin you are a genius:)  so what was i measuring? 
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  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    #9
    What you are probably reading is reverse bias voltage in the electronics, an analog meter probably would read nothing due to its lower ohm per volt internal circuitry.
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    edited July 2017 #10
    Your meter can have as high as 10,000,000 Ohms input resistance.

    And overall you can have 10,000 Ohms of stray resistance, that "floats" the line voltage 1/2 way between 0 and 120 vac.

    When you connect the light, its relatively low resistance swamps the stray resistance (and capacitance) and pulls the neutral to near ground.

    And using a light bulb, if there is real voltage (msw oe non-isolated inverter), the bulb will light vs shorting something out.

    Note the battery negative needs to be attached to the same ground to "prove" this is an isolated ac output PAW inverter.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • sunnyskies
    sunnyskies Registered Users Posts: 14 ✭✭
    #11
    Thanks for all your input guys will use a single pole xfer switch and rest easy knowing that the system is neutral bonded the way it should be
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  • sunnyskies
    sunnyskies Registered Users Posts: 14 ✭✭
    #12
    wire nutted neutral and ground together and connected the light bulb from neutral/gnd to battery negative. no issues so safe to say that the Aims power #pwr/150024s can be neutral bonded. Hopefully this helps someone  else. it seems to be priced right and has a remote good to know it can be connected to a standard ac mains panel
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