Watthour Meter to measure inverter output?

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James
James Solar Expert Posts: 250 ✭✭
in Advanced Solar Electric Technical Forum #1
Hello folks,
I had the idea to add a conventional watthour meter to my setup in order to measure my actual inverter output/electrical usage.
I ordered and installed new (factory refurbished) unit. I wired it correctly according to the detailed instructions for 120 vac usage.

Here's the issue...it passes power no problem, but has not registered any readings at all. It's been installed a week.
Is it possible that the meter doesn't operate off the stepped sinewave from the sw4024? I tried swapping another meter just to verify in case the meter was defective. I thought about hooking up a quick test set up to try running grid ac through it....i'm guessing that would confirm if the meter doesnt like inverter ac.

Anyone with direct experience regarding this?
I've seen plenty of photos in Home Power magazine in the old days showing meters passing power from the 4024 inverters.

?????
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  • RCinFLA
    RCinFLA Solar Expert Posts: 1,484 ✭✭✭✭
    #2
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    Re: Watthour Meter to measure inverter output?

    It is unlikely the stepped sinewave from SW inverter would not work. SW does have higher harmonic components due to stepped sinewave however worse case you might get a slight error in watt hour reading.

    Does the watt hour meter work on regular grid service?

    I have put a Kill-A-Watt meter on a refrig running on an SW inverter with no issue.
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #3
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    Re: Watthour Meter to measure inverter output?

    gotta ask, are you feeding the INPUT legs of the meter ?
    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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  • James
    James Solar Expert Posts: 250 ✭✭
    #4
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    Re: Watthour Meter to measure inverter output?

    yes, absolutely. wired exactly as noted on mfg. wiring diagram for use as 120 volt meter.
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  • Windsun
    Windsun Solar Expert Posts: 1,164 ✭✭
    #5
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    Re: Watthour Meter to measure inverter output?

    I don't know about your particular meter, but in the past we have used the newer digital models with installs with Outback and Xantrex sine wave inverter setups and they work.
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  • James
    James Solar Expert Posts: 250 ✭✭
    #6
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    Re: Watthour Meter to measure inverter output?

    Hello folks, problem has been solved. Although I wired it correctly according to the supplier, their info was not totally clear.
    I found information on the internet that the meter supplier did not clairify.

    I tied the neutral terminal to the small screw/slider plate on the back of the meter.....it is now spinning in my grid test setup. I should note that the slider tab must be slid "open", and then hook up the neutral wire to it.
    Otherwise they said it might trip a breaker.

    A light gage wire (18-22) is all that is needed.
    As soon as my accuracy test is complete I will add the wire to my system meter box and see what happens. i'm guessing it should work fine.
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  • James
    James Solar Expert Posts: 250 ✭✭
    #7
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    Re: Watthour Meter to measure inverter output?

    Follow up:
    The meter tested fine now that I made the neutral wire modification in my test set up.
    I have re-installed the meter back into my system and am happy to report it's working fine.

    I can finally now document my actual kilowatt usage, as generated by my system.
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  • silvertop
    silvertop Solar Expert Posts: 155 ✭✭✭✭✭
    #8
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    Re: Watthour Meter to measure inverter output?

    I just thought I would let you know that there is a slight watt draw with these meters. I had one running for about a year, and when I switched to an inverter with search mode the meter sent the inverter into run mode; I've also found that power strips with an indicator light would also kick the inverter into run mode. Mine is a ABB glass meter, and appears to pull about 1-3 watts , so I pulled the meter.
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  • James
    James Solar Expert Posts: 250 ✭✭
    #9
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    Re: Watthour Meter to measure inverter output?

    hello. mine is also a ABB meter. i havent yet mesured the draw, but i'm guessing it's about the same draw. With my present settings, it does not trigger the search mode to on mode. for the purposes of research use and production, i'm planning on running it for quite a while unless i find it's present a major issue.
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  • john p
    john p Solar Expert Posts: 814 ✭✭✭
    #10
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    Re: Watthour Meter to measure inverter output?

    I personally think watthour merers ans any other type of device to measure an inverters output will be in most cases misleading. Devices connected to it with power factors of less than one will give you a false reading .Another is very small loads use more battery current then you would be expecting because inverters are inneficient at low loads.
    I believe the only accurate way to measure an inverters current consumption is by measuring the battery current into the inverter.Then everything is accounted for
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,439 admin
    #11
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    Re: Watthour Meter to measure inverter output?

    I am not sure... Square Wave issues aside... A US kWHr meter is supposed to only measure power and not KVA. A mechanical meter may be better at reading RMS current/voltage anyway. I have no idea if an electronic kWH meter reads RMS or simply assumes sine wave power.

    Using a WH meter on the input to the inverter may be better, or not--The issues of 120 Hz ripple on the DC battery leg from the inverter could introduce its own set of errors unless you can get a RMS reading DC WH meter with a high enough sample rate.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • James
    James Solar Expert Posts: 250 ✭✭
    #12
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    Re: Watthour Meter to measure inverter output?

    I agree. I just wanted a quick and easy reference to use for computing aprox. how many dollars I'm not paying the electric ultility. I don't plan on the meter being installed indefintely.
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  • chevenstein
    chevenstein Solar Expert Posts: 100 ✭✭
    #13
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    Re: Watthour Meter to measure inverter output?

    I've had an ABB watthour meter on my off grid setup (see signature) for nearly two years now and would contribute the following observations:

    - There is a little pendulum in it to prevent the meter from running backwards when installed upside down. When I first installed mine the pendulum was stuck up, presumably from being shipped upside down, and did not register much usage for some amount of time until it passed 1 kWh.
    - My inverter will go into search (10 watt setting) with this meter connected
    - I regret not installing meters to also measure the generator's cumulative contribution as well as that of the solar array (measure solar versus fossil sourcing and battery efficiency)
    - In another month or so I will crack 1MWh! 500 kWh per year aint bad.
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  • silvertop
    silvertop Solar Expert Posts: 155 ✭✭✭✭✭
    #14
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    Re: Watthour Meter to measure inverter output?

    All in all I liked running the ABB meter. Mine is the mechanical model. Installed on the 110 inverter output, it functioned flawlessly. I think the only draw back with the Cotek S 1500 pure sine wave inverter, is that this particular model doesn't have adjustable set points. Their other Cotek 1500 model did have set points, but consumed more idle draw, so I went with this one for conservation. Still, I am very happy with this inverter. It has a 3 minute 2000 watt rating. I will have to function without my ABB meter for now.:cry:
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  • James
    James Solar Expert Posts: 250 ✭✭
    #15
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    Re: Watthour Meter to measure inverter output?

    My ABB meter is marked as a 3 watt unit.
    at my current 4024 settings, it is not enough load to trigger from search mode to run mode.
    Thanks for the added info about the systems performance with a meter installed
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