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KendallP's avatar
KendallP
Explorer
May 28, 2014

Kill-a-Watt & 1986 Onan 4.0 BFA

Good afternoon,

So the other day I plugged the KAW into a Rat Shack MSW inverter and got something like 135 volts. Of course my cheap meters were reading between 90 and 100, so I thought it should be in the 115v ballpark.

I've read that the KAW may be an RMS machine. If so, if functioning to spec, it should be accurate with an MSW inverter, yes?

Also...

Any thoughts on how a KAW would react to the waveform of a 1986 Onan 4.0 BFA? Should a properly functioning unit be considered accurate on a generator like this?

How about cheap meters? I was thinking they should be, but while I'm here...
  • KendallP's avatar
    KendallP
    Explorer
    May 29, 2014
    Hi SCVJeff,

    According to the KAW, the frequency remains between 59.9 and 60.1 between zero and nearly 4000 watts.

    Hey PT,

    Hmmm. It appears that it may be hit or miss with the MSW inverters. Yours reads low, mine reads high and I've read that others are within the proper range. Perhaps it depends on the inverter.
  • pianotuna's avatar
    pianotuna
    Nomad III
    May 29, 2014
    Hi KendallP,


    The Kill-a-watt is not accurate with MSW inverter power. In my case it under reads the wattage by as much as 25% In my case, the Hertz reading says 25.
  • SCVJeff's avatar
    SCVJeff
    Explorer
    May 29, 2014
    The BFA sounds like the Onan I had on my 85' Pace. It's clean (because its a real generator), but look at the voltage while its loaded with something like 1000W or so. I have a little box with an AC Voltmeter and Freq meter that I used to set the generator, and all I would worry about is proper frequency. If the output was @ 130V, so be it. Within reason, equipment gets way more upset with lousy frequency control than a few volts one way or the other.
  • jmcgsd's avatar
    jmcgsd
    Explorer
    May 28, 2014
    Find a friend with an oscilloscope so you can take a look at the waveform.
  • KendallP's avatar
    KendallP
    Explorer
    May 28, 2014
    j-d wrote:
    Secondhand info in a way, but I asked if I should run electronics in the RV from power from the ONAN genset or from an Inverter off the batteries. My electronics genius friend said GenSet, clean sine wave.

    What era is that genset? I believe newer ones can have cleaner waveforms. However... I think your friend is correct, regardless. Not all electronics are super thrilled with modified sine waves.
  • KendallP's avatar
    KendallP
    Explorer
    May 28, 2014
    Gale Hawkins wrote:
    Ours read well from grid or our 5000 Kohler Confidant. What load were you running? If it is normal (125v or less) with the AC running you should be fine.

    With A/C running, it shows more like 127v or so. But also 60 hz and 1.0 power factor.

    I had posted something about my proud generator tuning a week or 2 ago. The Kill-a-Watt pretty well shows steady voltage until I max out the load. Then it actually climbs above 130... which doesn't thrill me. But I virtually never need to run that kind of load, i.e. the A/C and electric heater on at the same time.

    The KAW also shows a very steady frequency between 59.9 and 60.1, again, regardless of load. So if the KAW is accurate, then the genny is performing pretty dang well.
  • j-d's avatar
    j-d
    Explorer II
    May 28, 2014
    Secondhand info in a way, but I asked if I should run electronics in the RV from power from the ONAN genset or from an Inverter off the batteries. My electronics genius friend said GenSet, clean sine wave.
  • Gale_Hawkins's avatar
    Gale_Hawkins
    Explorer
    May 28, 2014
    Ours read well from grid or our 5000 Kohler Confidant. What load were you running? If it is normal (125v or less) with the AC running you should be fine.

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