Question on the 2000W Sun Grid Tie Inverter with Limiter with 240V output

BryanSBryanS Registered Users Posts: 3
I was wanting to buy this 2000 want grid tie inverter with limiter, as it will meet with my current desire to offset my power utility bill without any major hindrance. My question is to those who might be in the know. This grid tie inverter has an output of 240 V (two wires) and not having a neutral conductor. When I tie these two inverter output conductors to my line 1 and line 2 to my incoming grid connectors via a breaker in my electrical panel, what happens when a small 120v load arises on one leg to neutral? Would this grid tie inverter be able to see this 120v load on one leg and supply a current to reduce or negate this load? Or will this inverter just respond to 240 v loads that arise from houseold appliances?

Comments

  • BB.BB. Super Moderators, Administrators Posts: 30,759 admin
    Assuming you are in North America (Alberta, Canada?), you have 120/240 VAC split phase power.

    Your utility meter will take care of accounting for the kWH being used/sent back to the utility. It works with Hot to Neutral loads (and backfeeding of current) and Hot to Hot loads (and backfeeding).

    kWH is calculated as:
    • Energy = kWH = Volts * Current * Time (Hours) * 1kWH/1,000 WH (divide by 1,000 to get "kilo")
    Not an expert, but many (most) split phase utility meters for North America have "four clamps" for electrical connections. Two for L1/L2 in, and another two for L1/L2 to the home/main panel.

    The meter measures the voltage (can only measure 240 VAC, Line to Neutral is assumed to be 240VAC/2=120 VAC nominal). And the meter measures the current in L1 and L2.

    If you have 10 amps on L1 and 10 amps on L2 and zero current on the Neutral, that assumes that you have 10 Amps @ 240 VAC or 2,400 Watts (2.4kWatts).

    If you have 5 amps on L1 and 10 amps on L2, then it is assumed that 5 amps is flowing on Neutral. So, you have 5 amps @ 240 vAC (1,200 Watts) and 5 amps on 120 VAC (600 Watts).

    And similar, if you have 5 amps on L1 and 0 amps on L2, assume 5 amps on Neutral (Neutral is always the "difference between L1 and L2"), then you have 5 amps @ 120 VAC = 600 Watt.

    The meter "knows" which direction the energy is flowing based on the phase between Voltage and Current...

    Think of like peddling a tricycle... You push on the "forward pedal", you go forward. You push on the back pedal, and you slow down/go backwards.

    The GT inverter "knows nothing" about your connected loads and if 120 or 240 VAC... It is just feeding energy back into your main panel. And Utility supplies the 120/240 VAC and "accepts" backfeed energy (like recharging a giant 240 VAC battery bank), or supplies energy when you are using more than you generate (discharging the giant 120/240 VAC utility battery).

    And if you are wondering where the 120/240 Voltage/Current "magic" takes place, it is just the transformer on the pole outside your home. It has L1/Neutral/L2 connections and naturally "balances" current flow based on the loads (and your GT inverter output). The "input" to the transformer is something like 2,000 to 12,000 volts on two terminals for the other set of windings (left side of drawing below).

    And there is always the question--Do you have an GT agreement with your utility and the proper meter installed?

    The question is... Of course, the utility has the right to allow or refuse GT Inverter connections. They may ignore you, or "do something about it" (I have not heard of very many utilities that have pushed against "guerrilla GT inverter installs"--So I cannot tell you what may or may not happen).

    Then there is the issue of using a "non-approved" GT Inverter installation....

    In the very old days, the old mechanical meters would go "forward" if you bought power from the utility. And would go "backwards" if you generate power and feed it back to the utility.

    These days, GT systems are not rare, and utilities are always looking for "flags" that help them identify people stealing electricity. And one of the common methods was to install the meter "upside down" for 1/2 the billing cycle to run the meter backwards to get "free power".

    The modern electronic utility meters are programmed by the utility to behave they way they want/need/per PUC regulations. Old mechanical meters can have a "one way" clutch or ratchet installed. So... The meter may:
    • Run forward when you buy power, run backwards when you sell power (and may flag the utility if power is being sold and not GT Plan). Of course, they have the option of different "registers" (one for buying kWH, another for selling kWH -- If different rates).
    • Run forward when you buy power, not move when selling power.
    • Run forward when you buy power, run forward when you sell power.
    • Various other registers and functions are possible, and out there (my meter phones home once per hour so utility can charge me different rates for morning/afternoon/evenings/weekends--Time of Use TOU metering).
    If you do not have a GT inverter rate plan/approved meter--You have to watch that you do not generate more power than you are using at any time... It is possible that your meter may charge you for feeding back into the utility (third bullet).

    I do not know which GT Inverter you have, and you say it has a "limiter"... One of the most desired options wanted is a GT inverter that measures power usage by the home, and cranks back on the GT Inverter power output so that the energy never feeds back energy to the utility (for places were GT Inverters are not allowed--Common request).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • BryanSBryanS Registered Users Posts: 3
    @Bill Yes, I am in Alberta Canada. I have read your reply and it is spot on. I have not yet bought this solar inverter with a limiter just yet as I want to make sure that I purchase correctly. There are numerous companies selling them on the major website stores such as Ali Express, Amazon, and eBay. Here is one that I am looking at 

    https://www.ebay.ca/itm/2000W-Solar-Panels-on-Grid-Tie-Inverter-with-Limiter-Battery-Power-Home-PV-2000G/202020786543?var=502023108496

    They do exactly what you state is your common request is with grid tie inverters in your last statement. They just measure power usage in the home and make just enough power to cover what is needed in the home but not so much as to export excess power back onto the grid.

    That way the power company does not get back fed power whatsoever, and thus there should be no problem from their perspective and should not raise any red flags. With a few solar panels a person may be able to offset some of their utility costs. I see a few people on you tube that have purchased and installed the 120v version and I see it working in real time with one leg of power in the home. I've also seen on you tube where people have installed two separate 120v units and put one one each leg. That seems to work just fine. I have not seen as of yet on the web here in North America, an inverter of this type, a single 240v outputing unit with just two wires servicing a spit phase system such as is common at least in Canada. This would be more cost effective for my application.

    I was kind of hoping someone on this site would have tried this style of grid tie inverter already here in North America with our grid system to see exactly how it would work. Hopefully this clarifies my question a bit further.

    Cheers,
    Bryan



  • BB.BB. Super Moderators, Administrators Posts: 30,759 admin
    Bryan,

    I have no experience, but hopefully somebody(ies) here has.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • BryanSBryanS Registered Users Posts: 3
    @Bill I appreciate your input and feedback to my question. Cheers
  • eboxebox Registered Users Posts: 2
    @BryanS I have a few years experience using 240v  GTIs with limiters on 240v split voltage systems. I have installed 2 at 2different locations and they do work. 

    Some details you need to pay attention are:
    1. You will need to use 2 CT connected to your limiter input. 

    2. The CTs are clamped around your L1 and L2, in series with one of the CTs pointing in the opposite direction

    3. Keep the limiter cable as short as possible, use Cat7 or other high quality shielded cable and ground one end in order for the limited to read your power usage accurately as possible.

    I bought my initial GTIs from eBay but then discovered Alibaba and found them to be 1/2 the price for the same item.

    I recently purchased 2 new GTIs with limiter which allow me to connect 2 PV strings to capture morning and afternoon sun as lm blessed with trees everywhere.

    My intention is not to hijack the thread, but these new GTis have settings for reactive power and we'll as PF. I am finding that most of my home loads in both locations are inductive...ie air conditioning, washing machines, pumps etc.. and so my GTIs aren't seeing true power used and are under producing by 1/3 or more with these inductive loads. I have verified with test equipment.

    Maybe some can point me in the right direction to a thread which would give me some guidance as to what I should set the reactive and PF settings to?

    Other than that if anyone has any questions regarding 240 v GTIs with limiters, send me a message and I'll do my best to point you in the right direction.
  • aleks2aaleks2a Registered Users Posts: 1
    found this video:
    https://www.youtube.com/watch?v=gek4x4sh9MA

    Looks like many questions resolved there.. 
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