Another P&P Vendor - Can plug and play work in the US?

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  • igor1960igor1960 Solar Expert Posts: 85 ✭✭✭✭
    Please, be patient with me.
    Lets discuss my original question.
    We have circuit branch build for 30AMP load: #10AWG wires, 30AMP rated outlets and possibly etc. and we have 15 CB on it. At the end of it we have max.15AMP pnp inverter, so it looks like this

    Main === 15AMP CB ======= 30AMP Outlet1 ==== 30AMP Outlet2 ==== ...... ==== 30AMP OutletN ====<== max.15AMP PNP inverter

    Now, show me vulnerable point in here.
    Where and when you might have more then 30AMP load on that circuit, with 15AMP CB not tripping?

    Feel free to propose different location of 15AMP PNP inverter if you feel it will help to understand possible vulnerability
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    not a vulnerability point, but rather a power reduction when solar is not producing as the circuit would then be limited to the available utility power from its 15a cb. even though 30a of power may be available to the circuit in total with a 15a gt inverter to the circuit, you can only count on the 15a available from the utility as the sun doesn't shine all of the time. ok i guess that is a vulnerability point. that means don't count on being able to draw more than 15a consistently.
  • igor1960igor1960 Solar Expert Posts: 85 ✭✭✭✭
    niel wrote: »
    not a vulnerability point, but rather a power reduction when solar is not producing as the circuit would then be limited to the available utility power from its 15a cb. even though 30a of power may be available to the circuit in total with a 15a gt inverter to the circuit, you can only count on the 15a available from the utility as the sun doesn't shine all of the time. ok i guess that is a vulnerability point. that means don't count on being able to draw more than 15a consistently.

    NIEL,
    So, there is no vulnerability, Right?
    "Vulnerabilty" of not being able to draw 30AMP utility load on that circuit is not that important

    That means you would accept P&P inverters in such configuration?
    Any other/alternative views?
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    most of us were speaking of how things look from the standpoint of laws and such here because of the safety issues, but you still have to be aware of it from a safety standpoint even if russia doesn't care about gt inverters or bus current overloads and i think you now do see it from that standpoint we speak of. so that's what our hubbub was about, safety.
  • bill von novakbill von novak Solar Expert Posts: 891 ✭✭✭✭
    igor1960 wrote: »
    I'm reconsidering my previous agreement with you. I didn't look it through, but your example is not proper. You can not have this situation
    My proposal was to have line rated for 30AMPS, means 30 amp outlets with 30 amp wiring and then 15AMP CIRCUIT BREAKER on this line! That's what my proposal was: circuit braker twice lower then all wiring/outlets and etc.

    Now, show me the scenario how you can overload 30AMP outlet...

    The above example was to show an overload of the WIRING.

    To show an overload of the OUTLET, replace the two 22A undersink water heaters on separate outlets with two 22A water heaters on the same outlet. Load on the outlet - 44 amps. Load as seen at the breaker - 14 amps.
    That also means that yours GT inverters current should be not more then 15AMP (as CB will trip if its more)

    Unless there's a load taking the power - like, say, a water heater used during the day.
  • igor1960igor1960 Solar Expert Posts: 85 ✭✭✭✭
    The above example was to show an overload of the WIRING.

    Listen, sorry, but it's like talking to the wall... I'm saying that your GT Inverter could not be more then 15AMP, as it is sitting on 15AMP CB.
    You yourself said that heaters will turn only for a while, Right?
    Meaing that majority of the time they are OFF, Right?
    When they are OFF all GT Inverter current would go through CB, which is 15AMP, Right?
    Meaning yours GT Inverter current couldn't be mor then 15AMP, Right?

    So, having GT Inverter at 15AMP you cannot have more then 30AMP load in between Inverter and 15AMP CB... That's it. If you have such, your CB will TRIP. End of discussion.
  • igor1960igor1960 Solar Expert Posts: 85 ✭✭✭✭
    So, my conclusion:

    Alternative 1:
    1. P&P inverters in there current implementation are not safe for public usage. While they obviously can be used in DIY projects, they are not safe and dangerous for common person to be able to plug them here and there basically not because they internally are not safe (???), but mostly because of the danger of overloading circuits without "adequate circuit protection" on such circuits;
    2. "Adequate circuit protection" for circuits with any number of P&P inverters connected, should be at least twice the sum of the possible AC currents produced by those inverters, with circuit breaker equal to sum of the possible AC currents produced by those inverters. Meaning, with possible sum of max. production currents from P&P inverters equal to 15AMP, the line should be designed to withstand 30AMP, while installed CB should be 15AMP. This could only be achieved by somehow "marking" this "Adequate circuit line", so P&P inverters will only work on "marked" circuit lines and on ordinary lines will not be able to be turned on;
    3. "Marked" circuit as described above should be able to withstand twice the load of it's CB. Also, "Marked" circuit should be able to "inject" information into the line, that will dsitinquish it as being marked. That could be achieved by different means (unknown yet now): for example by generating some known high frequency on Vac line and/or providing some voltage level on neutral and etc. Each P&P inverter will check for presence of such "marking" and only work if such marking exists;
    4. "Marking" could be performed for example inside special CB. In fact, such CBs could have special "For P&P" labels and while showing "30AMP" on that label in reality implement 15AMP protection inside...
    5. Any circuit "Marking" should be completely isolated for one circuit only and not visible on other circuits from main panel.


    Alternative 2:
    Just change the receptacle (remove ability to plug anywhere) and use "dedicated" lines or "safe" places on existing lines. Inspect just those lines.


    I think 2 is better, but it removes laughable P&P selling point.

    That's it for now...
  • BB.BB. Super Moderators, Administrators Posts: 32,226 admin
    There are some code/customary standards in the US that may not apply in Russia/other regions...

    First, a circuit can only be operated at 80% of its rated power (hardwired devices). So, a 30 amp circuit can only operate at 24 amps continuous. Technically, for plug-in devices, nobody is going to say anything if you plug in 30 amps worth of loads (other than in cities where the fire department enforces building codes).

    Second is the customary part... In the US, the standard AC household appliance plug/cord set/extension cords are rated to be connected/plugged into a 15 (or 20) amp circuit (using fuse or CB rated for branch circuit use).

    If we were to wire in an outlet with 30 Amp 120 VAC power--There is almost nothing that I can think of that I can buy off the shelf with that rated plug cord set short of contractor's tools (i.e., table saw, air compressors, etc.) or specific equipment used in machine shops, food processing, etc.... Most devices using that level of power would either be hardwired and/or running at 240 VAC (or 3 phase or other, higher voltages).

    So--there is nothing that I can buy at a local store that would even run "legally" from such a socket in the home appliance realm. And any "commercial" equipment I would plug in would not function on a 15 amp + 15 amp GT outlet (i.e., surge current for typical induction motor equipment would expect ~5x30amps=150amp surge current--A 15 amp breaker would trip in 1 second or much less).

    And, I cannot (legally/insurance wise) cut off the 15 amp plug and connect it to a 30 amp @ 120 VAC plug + outlet (without a fuse/breaker in plug or wall outlet to limit the maximum rated current to 15 amps as done in the UK with Ring Circuits).

    So, in this case, it is a solution that has no use for any standard off-the-self electrical equipment the US.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • bill von novakbill von novak Solar Expert Posts: 891 ✭✭✭✭
    igor1960 wrote: »
    Listen, sorry, but it's like talking to the wall... I'm saying that your GT Inverter could not be more then 15AMP, as it is sitting on 15AMP CB.
    What would stop you from plugging two of them into that circuit?
    So, having GT Inverter at 15AMP you cannot have more then 30AMP load in between Inverter and 15AMP CB... That's it. If you have such, your CB will TRIP. End of discussion.
    IF you do not have any sun-synchronous loads (like A/C) on the same line. If you do, you can overload the line because they will only draw when solar is active. No regulator will listen to an explanation that involves "usually no one will . . . ." And THAT, from a safety perspective, is the end of the discussion.
  • igor1960igor1960 Solar Expert Posts: 85 ✭✭✭✭
    What would stop you from plugging two of them into that circuit?

    I can plug in million of them, but sum of there currents would not exceed 15AMPs, as I have CB at 15AMPs that will trip, when I reach 15AMP.
    Seems you can't comprehend that current from inverters goes through the same CB, eventhough in opposite to normal direction.
    IF you do not have any sun-synchronous loads (like A/C) on the same line. If you do, you can overload the line because they will only draw when solar is active. No regulator will listen to an explanation that involves "usually no one will . . . ." And THAT, from a safety perspective, is the end of the discussion.

    Doesn't metter: if you have AC or not. If you have 15AMPS input to the circuit through CB and 15AMPS input to the circuit through inverters, and you don't have any voltage/current transformations, then you can not have more then 30AMPS anywhere in the system. Otherwise, that would be like creating free energy from nothing.
    You have:
    1. Input power equal to: Wcb=Vcb*Icb, where Wcb=WATTS traveling through CB; Vcb-voltage on CB, and Icb-current on CB;
    2. Watts produced by inverter: Winv=Vinv*Iinv, where Winv=WATTS produced by inverter; Vcb-voltage on inverter, and Icb-current produced by inverter
    3. Max power in that circuit W=Wcb+Winv=Vcb*Icb+Vinv*Iinv
    5. Vcb=Vinv=V=110V then W=V*(Icb+Iinv)
    6. Max. Icb=15AMP, max Iinv=15AMP, V=110V, then W=110*(15+15)=3300wt.

    THat's it: if you think that there might be more power in that circuit, then you probably ready to invent bycicle and/or get Nobel prize for free energy.


    Just give me a sequence of events that you think should happen, so this circuit will have more then 30AMPS at any point, with any number of inverters (up currents) and any number of loads (down currents).
  • vtmapsvtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    igor1960 wrote: »
    Just give me a sequence of events that you think should happen, so this circuit will have more then 30AMPS at any point, with any number of inverters (up currents) and any number of loads (down currents).

    That's easy, and its already been explained by others. Lets try again:

    You plug in three inverters (15 amps each) at one end of the line. You plug in a couple of 20 amp loads somewhere in the middle of the line.

    You will have 45 amps running down the line, 40 amps of which will go to the loads and 5 amps of which will go through the circuit breaker to the grid.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • BB.BB. Super Moderators, Administrators Posts: 32,226 admin
    Igor,

    I will see if I can help here--This stuff gets quite complex very quickly if we start going off on tangents.
    igor1960 wrote: »
    Let me explain in ordinary words what I mean by opposite current direction as it relates to tie inverters.
    In a few and ordinary words and this is my understanding and you correct me if I'm wrong.
    Yes, the purpose is to "inject" the power into the AC voltage line.

    Things have changed A LOT over the years... The present "simple" GT Inverters really inject "current" into the utility line. After the AC Voltage and frequency has been "qualified", the system basically injects current on the Parray/Vsine-instant=Isine-instant --- This is much different than the standard synchronizing a generator (alternator) at speed/frequency/voltage/phase so the the grid and generator can connect together and not destroy the smaller genset.

    The GT Inverter is a "current source" (high impedance source) that injecting current into a low impedance "load" (voltage source--Aka "the grid"). This looks very much like the equivalent of a "alternator" recharging the AC version of a Giant Battery Bank with unlimited storage capacity (vs the output of our GT inverter in our home).

    Much different that an AC Genset (voltage source/low impedance) trying to share loads with "the grid" (also an AC voltage source with very low impedance).
    Existing AC voltage line Vac is pure sinusoidal with Vrms=110v for example, which corresponds to Vpeak=~156volts.
    Should we have an active load on this line possible current through this load would be sinusoidal exactly matching in phase with Vac AC voltage sinusoid
    In order to "inject" the power into this line (that has no active load), we need to create the current, opposite to possible current described above.

    It turns out that for a GT Inverter operating as a Current Source, any loads on the local circuits are pretty much irrelevant to the operation of the GT Inverter. The loads have higher impedance than the grid (grid impedance is something on the order of 0.25 ohms in a typical US drop from the distribution transformer--Just a SWAG for discussion). All the loads will have much higher impedance than the grid--So the Grid "swamps" any local effects of loads and wiring (other than voltage drop which can become significant in some cases).

    The direction of the current in the wiring is simply where it will find the lowest impedance. If there are no local loads in the home, the current simply goes out to the utility grid. If there are some loads (off of the main AC panel), some of the current will go to the local loads too.

    If the GT output current is higher than local current requirements, then there is a net outbound power flow to the grid (utility meter "spins backwards"). If there are more local loads than the GT Inverter is supplying, then there is a net power from the grid to the local AC panel and out to the loaded branch circuits. The GT Inverter cannot tell the difference.

    Note it is the Grid that sets the voltage (really sine wave voltage/frequency). GT inverter output is just based on the instantaneous Grid Sine Wave voltage and the available power from the Solar Array.

    This very much the same as the electrical system on the car. The battery sets the system voltage. The charge controller for the alternator determines the average voltage (~14 volts) by adjusting the amount of output current. And the loads determine the current flow at any point in the circuit.

    Alternator not running, the battery supplies all current. Alternator running and battery voltage a bit low, Alternator Controller generates XX amount of current to recharge the battery bank. If there are some loads, some of the current naturally flows through the car wiring from the alternator to the loads. If the loads are greater than the alternator, then the battery stops charging and actually supplies additional current to the loads.

    There is no "active current steering" going on... It is simple circuit theory.
    To do that our inverter produces AC output exactly matching AC voltage line, but with absolute values for Virms a little bit above Vrms=110v and Vipeak=166V above Vpeak=~156volts.

    That increase in voltage at the generator source (alternator/GT inverter/etc.) is simply because wires have resistance and there needs to be a voltage drop to cause voltage to flow. Heavier wire, lower voltage drop... But it does not change the basic behavior of the system.
    For example, let's assume that inverter produces pure sine wave exactly matching AC wave in phase, but an amplitude of that wave is just 10volts higher at Vpeak, so it's not 156, but instead 166. That would cause opposite to normal AC current flow from inverter to the AC.

    In the case of the GT inverter--It is a voltage source with very high impedance. If the GT source voltage is too low--Current will simply not flow backwards in the GT inverter (other than a bit of leakage current/tare current).

    When a current source drives current to a Voltage Source (or sink)--The voltage drop is simply V=I*R (or =Z*R if you want to do the vector math). All that is happening is a little I^2R heating losses.
    If we can achieve this then difference between Vac and Vi would be sinusoidal exactly matching Vac and Vi. Because Vi at any moment is larger then Vac (excluding 0 points on sinusoid) we get sinusoidal current between Vi to Vac. If you draw sinusoid of this current you will get obviuously same phase, but it would be 180degress rotated relative to Vac(AC voltage sinusod) and Vi(inverters sinusoid)...

    Relative to the GT inverter when it is outputting current (sun on solar array). The Current phase angle is always zero degrees (PF=1.0 in a standard implementation). No (appreciable current flows back into a GT inverter except when it is dark out--tare losses to run a bit of the electronics/capacitive leakage, etc.). At very low currents, current phase and amplitude become soft of "muddy" (tiny changes make large sign and phase changes--but current is still very small and is usually assumed to be near zero amps).

    At the Main Breaker--you will see large current changes (as loads and amount of solar power vary). And you will see 0 to 180 degree phase changes at the main breaker--But the breaker is not sensitive to direction of power flow (or even phase angle)--It is just responding to the RMS current flowing through it (there are direction sensitive protection devices used by utiltiies, but they are not usually found in homes and small businesses).

    Just like the car battery--It may see -100 amps while cranking, then in second flip to +100 amps as the alternator supplies initial charging current, then quickly settle down to 10 amps or less charging current. And the alternator will (on average) keep ~14.0 volts on the battery bus and supply current to the ignition system, head lights, radio, etc.
    Now, the power we will be feeding back into AC would be equal to P=(Vrms-Virms)*Irms*PF, where

    Not really--You have mixed several AC power concepts together. 1) wire loss which is usually resistive on smaller scales at this frequency (I^2R or V*I losses for a segment of a wire which is the Vrms-Virms--If I understand you correctly) and Power Factor which is a load characteristic (a pure voltage source has Z impedance very near zero at 50/60 Hz--So does not really have much to do with "defining/causing phase or non-linear current wave forms--Poor PF).

    The loads are what accept/define the current "response" to the Sine Wave Voltage (transfer function of the load). That may be linear (some combination of capacitive, inductive, and resistive--I.e., Z or complex impedance)... Or it may be non-linear (the typical input for a Rectifier with a Capacitor storage element found in many electronic power supplies) as below:

    Attachment not found.

    Again, because the typical GT inverter is a high impedance device outputting current proportional to the amplitude (and polarity) of the sine wave, it can only output 1.0 PF current. The "complex" or imaginary/non-linear current has to all come from the Voltage source (the Utility Grid--A big issue for them and another discussion).

    Pretty much how the battery supplies (or sinks) (i.e., Battery=Voltage Source) all energy that the alternator is not able to source (and can never sink) in a vehicle.
    Irms -- RMS of sinusoidal Ii, that our inverter can sustain to perform above using current DC input power

    Not sure what your point is here--RMS can be measured/calculated for any arbitrary Linear (aka sine wave) or non-linear wave form. For off grid systems, MSW (modified square wave) inverters are quite common, because they are cheap.
    PF -- power factor due to the possible shift between Vac and Irms (which is equal to shift beween possible Iac and Ii)

    For Linear waveforms with repeating cycles (aka sine waves in this case), Power Factor = Cosine of the phase angle between Vsine and Isine.

    However, Power Factor can also represent the RMS value vs Sine Wave value of an arbitrary wave form too (like the current trace in the above scope trace).

    For specifically GT Inverters with Current Source output (high impedance)--The output current wave form will be as linear (pure sine wave) as the voltage sine wave from the utility grid. Ideally, then the output current of the GT Inverter will be a sine wave (perhaps some filtering too).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • igor1960igor1960 Solar Expert Posts: 85 ✭✭✭✭
    BB. wrote: »
    Keep it simple is always a good place to start. It does not take much to make to NEC safety confusing (grounding and neutral bonding is one of the common questions that generate long and complicated posts/threads).
    ....
    I don't think you could reliably trigger anything (such as a GT 1 minute shutdown) on a suspicious voltage drop on an AC branch circuit...
    ...
    A 2x overload will trip the breaker in ~7-35 seconds--May not be "fast enough" to meet UL/NRTL/NEC current protection requirements for arbitrary wire heating (insulation, ROMEX, conduit, ambient temperatures, etc.).

    BB/Bill,
    How about the following approach:

    1. As any active load will force circuits Neutral Voltage to go up a little bit;
    2. As Neutral is connected to Ground in main panel and therefore that circuits Neutral small voltage is isolated from other circuits;

    Then we can get a signal of extra active load connected/disconnected by simply constantly looking/checking voltage in Neutral vs. Ground. The moment that voltage increases compared to some previos accumulated/averaged value -- means new active load got connected to the circuit. If at any moment that voltage decreases compared to some previos accumulated/averaged value -- means active load has been disconnected from the circuit.

    So, then:

    3. P&P inverter checks Neutral vs. Ground voltage, performs accumulation/averaging and compares current reading with accumulated/averaged value, calculates delta beween them and if delta is above threashold, conclusion is made that the new active load has been connected to the circuit;
    4. If describe in (3) has been determined P&P inverter stops production for example for 1 minute. As, all possible P&P inverters on that circuit are doing that: for 1 full minute we would have only active load current on CB, so it has enough time to trip if such active loads current is above CB rating.
    5. To be able to work described algorithm can only be implemented on perfectly grounded outlet, therfore P&P inverter should also check for proper grounding by checking active resistance between Neutral and Ground (should be > 0)

    What do you think?
  • igor1960igor1960 Solar Expert Posts: 85 ✭✭✭✭
    vtmaps wrote: »
    You plug in three inverters (15 amps each) at one end of the line. You plug in a couple of 20 amp loads somewhere in the middle of the line.

    How do you plug three inverters? OK, you plug first one and on plugging second, or third one your CB will break, as it is 15AMP CB.
    Or, you first plug first 20amp load with no inverters attached? Then again your CB will break, as it is 15AMP CB. OK, if it doesn't break on first load for some reason, it will break on second.
    OR, you might say we connect 3 inverters at night, when there is no sun? And connect load in the middle of the day.

    Actually, I don't want to argue about this anymore, as obviously someone can come up with some weird and unprobable hypothetical scenarios, as if people just connecting and disconnecting stuff each day around, including P&P inverters...
  • BB.BB. Super Moderators, Administrators Posts: 32,226 admin
    igor1960 wrote: »
    How about the following approach:

    1. As any active load will force circuits Neutral Voltage to go up a little bit;
    2. As Neutral is connected to Ground in main panel and therefore that circuits Neutral small voltage is isolated from other circuits;

    Then we can get a signal of extra active load connected/disconnected by simply constantly looking/checking voltage in Neutral vs. Ground. The moment that voltage increases compared to some previos accumulated/averaged value -- means new active load got connected to the circuit. If at any moment that voltage decreases compared to some previos accumulated/averaged value -- means active load has been disconnected from the circuit.

    Would not be reliable for an arbitrary system. "Zeros/calibrations" would shift with loads, temperatures, grid conditions, surge currents, etc.

    If you are looking a "cheap dirty" rule of thumb... In engineering terms (in general), things that are within a factor of 2 or less of each other are about the same. Things that are a factor of 10x different or more--You can pretty much ignore the smaller item.

    What ever effect you are looking to measure, it should be something like 10x larger than the rest of the "noise" out there to even have "hope" as a reliable trigger signal.

    Since grid voltage can vary by +/- 10% or so--You would be looking for a +/- 100% signal to be above the "noise". Obviously not very practical. And very difficult to pick out a ~2 volt neutral shift from a +/- 20 volt nominal voltage range.
    So, then:

    3. P&P inverter checks Neutral vs. Ground voltage, performs accumulation/averaging and compares current reading with accumulated/averaged value, calculates delta beween them and if delta is above threashold, conclusion is made that the new active load has been connected to the circuit;
    4. If describe in (3) has been determined P&P inverter stops production for example for 1 minute. As, all possible P&P inverters on that circuit are doing that: for 1 full minute we would have only active load current on CB, so it has enough time to trip if such active loads current is above CB rating.

    What do you think?

    Would be much easier (and more accurate) to put a CT (current transformer) and a data processor/transmitter on the lines you want to monitor AC current on. Very accurate and very cheap (relatively speaking).

    Still does not address the issue of an arbitrary issue where the GT inverter can be plugged into any outlet anywhere along a branch circuit and an arbitrary load.

    Note, as an engineer (or as an inspector), I reserve the right to configure what I believe to be the worst case "legal" system/wiring configuration out there. And the implementation has to be "safe" (interestingly, the system does not have to work--UL does not usually "care" if the computer "computes"--It just cares it does not melt down and catch fire or electrocute somebody).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • vtmapsvtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    igor1960 wrote: »
    Actually, I don't want to argue about this anymore
    Thank heavens!
    igor1960 wrote: »
    as obviously someone can come up with some weird and unprobable hypothetical scenarios, as if people just connecting and disconnecting stuff each day around, including P&P inverters...

    That's what code is all about... protecting people from unintentionally burning down the house. For example, one aspect of the building code is that electrical outlets must be no more than 8 ft apart on the wall. This rule makes no sense from an electrical circuit perspective, but the rule means that people will need to use fewer extension cords, and fewer cords means fewer fires.

    As far as P&P inverters, there's a lot of folks out there who figure that if one P&P is good, three is better. Remember, if someone can come up with some "weird and unprobable hypothetical scenarios", they will.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • igor1960igor1960 Solar Expert Posts: 85 ✭✭✭✭
    BB. wrote: »
    Since grid voltage can vary by +/- 10% or so--You would be looking for a +/- 100% signal to be above the "noise". Obviously not very practical. And very difficult to pick out a ~2 volt neutral shift from a +/- 20 volt nominal voltage range.

    I agree, that this require testing, but I dissagree that this couldn't be done. And why are you saying +/-20v and 2 volts, why so high?
    We are talking about voltage drop between Neutral and Ground. So, we have 0 Ground at main panel and some voltage on Neutral at receptacle just due to the wire run between receptacle and main panel. This voltage drop shouldn't be more then 5v IMO...
    So, at 15amp current and 100ft run of #12 this would give us drop of 15*0.2=3volts
    In fact, P&P inverter measures R between N and G and can easily calculate active current on neutral by dividing Vn/R.... Based on that it can perform shut down when it sees increase in Vn... Doesn't any amp meter that uses shunt to measure current perform the same thing?
  • igor1960igor1960 Solar Expert Posts: 85 ✭✭✭✭
    vtmaps wrote: »
    Thank heavens!

    Enough! Looks like wrong forum for technical discussions.
    I didn't know that this forum if for a bunch of electrical contractors that only know how to follow/enforce the code (at least while talking about that).
  • BB.BB. Super Moderators, Administrators Posts: 32,226 admin
    igor1960 wrote: »
    I agree, that this require testing, but I disagree that this couldn't be done. And why are you saying +/-20v and 2 volts, why so high?

    I was refering to +/- 10% of your 230 VAC line... With actual numbers, we do get stuck on the assumed difference (I use Russian/240 VAC for our Micro GT inverters/You use Southern California Edison and US number of ~115 VAC +/-10%).
    We are talking about voltage drop between Neutral and Ground. So, we have 0 Ground at main panel and some voltage on Neutral at receptacle just due to the wire run between receptacle and main panel. This voltage drop shouldn't be more then 5v IMO...

    For a ~120 VAC circuit--That would be a typical maximum--I would guess.
    So, at 15amp current and 100ft run of #12 this would give us drop of 15*0.2=3volts

    Yes--And you could measure Vac across line to line (or line to neutral) and double the drop and therefore double the resolution.

    It is possible that the Neutral to earth bond reference would remove the much (if not most) of the +/-10% differential Power Line tolerances/variation.

    Copper wire resistance is temperature sensitive--on the order of 1.5:1 to perhaps 2:1 for extreme conditions. That would have to be accounted for somehow. But, the variation would seem to swamp the effect you are looking for... A 1.2:1 difference in current to current limit P&P GT inverter output vs a 1.5:1 difference just based on temperature (ignoring other sources of "noise").
    In fact, P&P inverter measures R between N and G and can easily calculate active current on neutral by dividing Vn/R.... Based on that it can perform shut down when it sees increase in Vn... Doesn't any amp meter that uses shunt to measure current perform the same thing?

    A DMM current shunt would be chosen based on having a near zero temperature offset--Plus it would be easy to measure the shunt temperature (or ambient in area of shunt) to better linearize the accuracy of the shunt.

    I have used wiring to and DMM's to estimate current flow and direction in vehicle wiring and parallel battery banks with a DMM (when I was too cheap to buy a DC current clamp meter) and looking for 'unbalanced circuit/current flow". Much different when trying to estimate an actual absolute current measurement.

    In the end, it would still rely on a known circuit topology to (possibly) estimate the current through the worst case wire segment in a distributed power/load power system.

    I have done many distributed DC Power systems and looked at some simple distributed AC power systems (N+1 redundant telecom/networking systems)... It is difficult to ensure a single factory built as designed configuration is safe.... I just don't see how a distributed power system on an arbitrary/unknown residential branch circuit would work as desired.

    If you want to do this by replacing all of the AC outlets--It might be doable--We already use GFI (ground fault interrupting) outlets which are reliable/accurate down to the 0.005 amp level (trip the GFCI outlet). I think that is the model you have to look at to do P&P current protection. Still not "cheap" and requires installing current measuring/controlling on the entire branch circuit. Still not a P&P because building upgrades would still be required.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • bill von novakbill von novak Solar Expert Posts: 891 ✭✭✭✭
    igor1960 wrote: »
    I can plug in million of them, but sum of there currents would not exceed 15AMPs, as I have CB at 15AMPs that will trip, when I reach 15AMP.

    1) Not if you are adding loads at the same time. We have people here all the time asking how to do exactly that. They want to do it for a slightly different purpose - to "fool" their GT inverter so it continues to operate - but the desire is there. You would not believe the schemes people have proposed to get loads added at the same rate that production climbs; they are quite intricate.

    2) Not if your wiring is poor. GT inverters are designed to trip off-line when voltage ranges are exceeded. So you could well see something like this:
    -You plug in one 15 amp inverter via a long extension cord. It fires up. Voltage rises to 130 volts as current is added. Cool, you think; if one is good, two must be better.
    -You plug in a second 15 amp inverter to the end of the same extension cord. Voltage goes up to 140 volts. One of the inverters (the more sensitive one) trips and goes off-line. No breaker event since the current did not last very long. "Hmm" you think. "Maybe the inverter is bad."
    -You plug in an air conditioner to the end of the home run line. Its compressor starts, and it pulls down the voltage. Now when both inverters try to start they see only 131 volts - and both start up. "Excellent!" you think. "I have fixed it."
    -The A/C compressor cycles off. Voltage goes back up to 140 volts. One inverter trips off line and voltage drops again. Again no steady currents greater than 15 amps, so no breaker trip.

    Just give me a sequence of events that you think should happen, so this circuit will have more then 30AMPS at any point, with any number of inverters (up currents) and any number of loads (down currents).
    See above.

    Take a step back for a second. Here's the basic problem:

    Normal power distribution systems take power from a source or send it to a load. If the circuit does just that then protecting it is straightforward - rate everything for X amps then have circuit protection that trips above X amps. That way no matter what you do you cannot exceed the current rating in any segment of the circuit.

    You propose a different system - one that uses the circuit as a power bus. Some can inject current into the bus, some can remove it. Now the above does not hold. If you have a 15 amp breaker, and you inject 40 amps into the circuit, and take 30 out, then the breaker does not trip - and a segment can carry 40 amps. You cannot choose a breaker value to prevent this. You can make it less likely but you cannot eliminate the possibility with a standard distribution (i.e. home run) circuit.

    If this is a research project then no problem. You can calculate what the maximum load will be in each part of the line and attach a series of loads and sources, ensuring that you never exceed that rating. I have done this back in the Trace Microsine days, and I am sure many people here have done this.

    However if this is intended as a consumer product, then:
    1) it will get used on circuits where the user does not understand how the circuit is wired.
    2) it will get used contrary to instructions.

    That is why it's not approved for consumer usage.

    Want to change this? There are many ways to do this, some of which have been discussed. Wiring devices with 15 amp fuses at EVERY connection point, so no one segment can carry more than 15 amps. Dedicated lines and outlets - if there is only one outlet at the end of a dedicated run, then most of these problems disappear. Current sensors at each point, so the inverters can throttle themselves. A "lost power" measurement system so the circuit breaker can know how many inverters are really on the home run circuit.

    But you cannot come up with a clever arrangement of breakers and standard wiring/connectors to ensure that a consumer cannot overload his system.
  • igor1960igor1960 Solar Expert Posts: 85 ✭✭✭✭
    You propose a different system - one that uses the circuit as a power bus. Some can inject current into the bus, some can remove it. Now the above does not hold. If you have a 15 amp breaker, and you inject 40 amps into the circuit, and take 30 out, then the breaker does not trip - and a segment can carry 40 amps. You cannot choose a breaker value to prevent this. You can make it less likely but you cannot eliminate the possibility with a standard distribution (i.e. home run) circuit.

    If this is a research project then no problem. You can calculate what the maximum load will be in each part of the line and attach a series of loads and sources, ensuring that you never exceed that rating. I have done this back in the Trace Microsine days, and I am sure many people here have done this.

    However if this is intended as a consumer product, then:
    1) it will get used on circuits where the user does not understand how the circuit is wired.
    2) it will get used contrary to instructions.

    That is why it's not approved for consumer usage.

    Want to change this? There are many ways to do this, some of which have been discussed. Wiring devices with 15 amp fuses at EVERY connection point, so no one segment can carry more than 15 amps. Dedicated lines and outlets - if there is only one outlet at the end of a dedicated run, then most of these problems disappear. Current sensors at each point, so the inverters can throttle themselves. A "lost power" measurement system so the circuit breaker can know how many inverters are really on the home run circuit.

    But you cannot come up with a clever arrangement of breakers and standard wiring/connectors to ensure that a consumer cannot overload his system.

    Bill,

    Finally, and you are the first one that gave an extremely clever explanation, which is difficult and impossible to argue with!
    I was waiting for that, and I was looking for someone to just describe that sequence, as simply sequentially adding on suny day 5AMPS of inveters followed by 5AMPS of load, and then repeating the sequence again and again and again, without CB trip (even 5AMP CB).
    However, no one did, except finally you. Great!
    Anyway, I agree with you.
    The question is: could we come up with "a clever arrangement" to protect the circuit. IMO: "clever arrangement" would be to come up with some solution that would not require modifications to existing home lines, but instead some "special" electronics inside of P&P Inverter.
    Obviously, one answer would be just different receptacle.
    However, as I said that means: removing the most advantageous/selling point of those "P&P inverters" and it is "P&P".
    Thats why I'm looking into possible solutions:
    -- of measuring max.Current on the circuit from "P&P inverter" site;
    -- sync. turn off/on those inverters for some time on determination of extra load connected and etc...
  • igor1960igor1960 Solar Expert Posts: 85 ✭✭✭✭
    BB. wrote: »
    I was refering to +/- 10% of your 230 VAC line... With actual numbers, we do get stuck on the assumed difference (I use Russian/240 VAC for our Micro GT inverters/You use Southern California Edison and US number of ~115 VAC +/-10%).
    For a ~120 VAC circuit--That would be a typical maximum--I would guess.
    -Bill

    Bill,
    I have great news! (Maybe it's not news for you)
    I'm currently at my friends house in Palos Verdes, CA. I've just checked real stuff and it works! At least it works here!

    So, idea is to measure Current on Neutral from any arbitrary free outlet on that circuit, while active load is sitting on some other outlets.

    So we have:
    == Main == CB == Outlet1 === Outlet2 ==== OutletN
    Neutral
    Gnd

    Let's start with no load:
    1. OutletN is our Test Outlet;
    2. We measure Neutral-Gnd Resistance on Test Outlet (OutletN): My real measuremnt: 1ohm ==> that resistance is due to the run of Neutral from Test Outlet to Main Box and back through Gnd to Test Outlet. So we have Rng=1ohm. As it's about the same length and the same gauge/type of wire for Neutral and GND, we can assume that those wires have equal resitance and then:
    Neutral Resistance=Ground Resistance=1ohm/2=0.5ohm, and Rng=Rn+Rg and Rn=~0.5ohm and Rg=~0.5ohm, Agree?
    3. Now we measure Voltage between Neutral and Ground. Theoretically, it should be 0, as there is no load on that circuit, but in reality it's not probably because there is some extra shift in Neutral due to existance of other circuits in Main and as they are not isolated of our Neutral, there is some shift in a Voltage value, which is explainable. So, we measure Vng with no load on any outlet on our circuit. Real number: Vng0=0.015V.

    So, we done our preparation. Now, I'm adding load on Outlet1.
    4. Connect/turn ON 75watts on Outlet1. I'm using just plugged 75watt bulb and 75watts output with 0.6AMP consumption is confirmed by WattMeter.So we get:
    == Main == CB == Outlet1=75Watts === Outlet2 ==== OutletN
    5. Now we repeat Step (3) described above and perform Voltage reading between Neutral and Ground (difference with (3) is that we now do it with 60wt load on Outlet1).
    Real Number: I'm getting Vng1=0.315V
    6. So, by adding 75wt load on Outlet 1 we got increase in Voltage in Neutral by dVng=Vng1-Vng0: Real number dVng=0.315-0.015=0.3v, Agree?
    7. Now, we can find current in Neutral due to the load using Ohm's law: Ing1=dVng/Rn, Right? So, real number: Ing1=0.3/0.5=0.6AMP. Do you see this is the same current as reported by Watt Meter on step 4... Hahahaha

    Do you want to write patent?
  • BB.BB. Super Moderators, Administrators Posts: 32,226 admin
    You can write patent applications for anything... Using the "natural voltage" drop in a power wire to estimate current has been used forever (I had a 1970 pickup that use 4' of battery cable and a millivolt meter to drive the amp meter on the dash).

    Can you do this--Yes. Can it give you a "NEC"/Code Safe understanding of the current in the neutral in a distributed power system... The answer is still no. It is not something that is going to be accurate enough for code use (I don't believe).

    For example just using simple round numbers. Assume that 30 amps in wiring or in load pigtail is a "failure" of the power system. Note that 0, +1, -2, etc. is 1 unit of 15 amps and + is voltage rise, - is voltage drop (note tables below use fix font and display properly (for the most part) on PCs--Note sure how well it works on other operating systems):
    [FONT=fixedsys]               zero amps              15 amps
    15 amp CB =============== Outlet A =============== Outlet B
                                 []                       []
                           15 amp GT source (0)       15 amp load
    
    [FONT=fixedsys]              -15 amps              Zero amps
    15 amp CB =============== Outlet A =============== Outlet B
                                 []                       []
                           15 amp GT source (+1)    Zero amp load[/FONT]
    
                   15 amps                  30 amps
    [FONT=fixedsys]15 amp CB =============== Outlet A =============== Outlet B
                                 []                       []
                           15 amp GT source (-1)      30 amp load [/FONT]       [/FONT]
    
    
    You can program the GT Source to adjust its output to output inversely to the voltage drop in the first segment.

    [FONT=fixedsys]               zero amps              -15 amps
    15 amp CB =============== Outlet A =============== Outlet B
                                 []                       []
                           15 amp Load           15 amp GT Source (+1)
    
    [FONT=fixedsys]              -15 amps                  -15 amps
    [FONT=fixedsys]15 amp CB =============== Outlet A =============== Outlet B
                                 []                       []
                           zero amp Load           15 amp GT Source (+2)[/FONT][/FONT]
    
                   15 amps                  -15 amps
    [FONT=fixedsys]15 amp CB =============== Outlet A =============== Outlet B (0)
                                 []                       []
                           30 amp Load           15 amp GT Source[/FONT]     [/FONT]
    
    

    So, now you have two topologies, 0 or 15 amp current, and loads that draw 0, 15, or 30 amps of current (0/15 amps OK, 30 amps not OK).

    Create a truth table with GT inverter output = 15 amps and various load combination. You can now program the plug and play GT inverter to turn off its output if the truth table says that it is a dangerous situation.

    Next, you have to now do the same thing with the GT inverter at zero amp output--To decide when to "turn on" again (15 amps).

    [FONT=fixedsys]               15 amps              15 amps
    15 amp CB =============== Outlet A =============== Outlet B
                                 []                       []
                            0 amp GT source (-1)       15 amp load
    
    [FONT=fixedsys]               0 amps               0 amps
    15 amp CB =============== Outlet A =============== Outlet B
                                 []                       []
                            0 amp GT source (0)     Zero amp load[/FONT]
    
                   40 amps                  30 amps
    [FONT=fixedsys]15 amp CB =============== Outlet A =============== Outlet B
                                 []                       []
                            0 amp GT source (-2)      30 amp load [/FONT] (trip breaker)      [/FONT]
    
    
    [FONT=fixedsys]               15 amps                0 amps
    15 amp CB =============== Outlet A =============== Outlet B
                                 []                       []
                           15 amp Load            0 amp GT Source (-1)
    
    [FONT=fixedsys]                0 amps                    0 amps
    [FONT=fixedsys]15 amp CB =============== Outlet A =============== Outlet B
                                 []                       []
                           zero amp Load           0 amp GT Source (0)[/FONT][/FONT]
    
                   30 amps                    0 amps
    [FONT=fixedsys]15 amp CB =============== Outlet A =============== Outlet B (0)
                                 []                       []
                        30 amp Load (won't happen)  0 amp GT Source[/FONT] (-2)    [/FONT]
    
    

    So you now have a second truth table when the GT Inverter can turn on.

    Then you have to have a learn mode to figure out the resistance between the GT inverter and the Neutral/Ground Bond, etc...

    Next, you have to look at other common fault conditions. For example, the green wire ground may carry up to rated CB current and offset the ground reference too... So you will have to have a logic table to determine when to "fault" the GT inverter because of failed Green Wire Reference (broken ground, offset grounds, other equipment/miss-wiring failures, etc.).

    Anyway--That is the beginnings of how I would characterize a P&P distributed power system to understand how to use active feedback to modulate the GT Inverter output to reduce the chance of over current causing a fire hazard due to arbitrary configurations by a customer in an arbitrary home wiring system.

    The above is just a first level SWAG--I would have to work much longer and document the tables to see what else may be an issue.

    Just be aware, that different signaling is used because it has much better resistance to noise. Common mode signally (measuring voltage drop between neutral and ground) would normally be assumed to have much larger "noise" values.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • bill von novakbill von novak Solar Expert Posts: 891 ✭✭✭✭
    igor1960 wrote: »
    Do you want to write patent?

    Not to discourage you, but a prior public disclosure of a patentable idea renders any such idea indefensible. (But don't let that stop you; there is plenty of work to be done in distributed generation systems.)
  • igor1960igor1960 Solar Expert Posts: 85 ✭✭✭✭
    BB. wrote: »
    Then you have to have a learn mode to figure out the resistance between the GT inverter and the Neutral/Ground Bond, etc...

    ....
    The above is just a first level SWAG--I would have to work much longer and document the tables to see what else may be an issue.

    Bill,
    I appreciate your time and efforts you are puting into those "stupid" ideas! Obviously, your knowledge and way of thinking is just remarkable.
    However, what I'm thinking is not really properly "adjusting" GT to current load, but instead just way to avoiding, what everybody here and code consider "dangerous situation". And, as I said before, I agree that safety is #1 priority.
    So, what I'm thinking here is pretty simple: just P&P inverter by looking into voltage between Gnd-Neutral and constantly monitoring this voltage can easily determine the moment of some extra load turning ON. So, at this moment and based on timer P&P inverter can just turn its output OFF for example for a period of just 1 minute. As, all possible P&P inverters on the same CB will do the same, CB will be loaded with real active load for 1 minute and therefore would have enough time to react to possibly over limit active load current. Remember, at that period we would have no "injection" of power into circuit bus. So, basically P&P inverters will goto "islanding" mode for 1 minute.
    That's it.

    Alternatively, obviously we could investigate possibility of regulating GT output, based on some specified threashold Voltage level between GND-NEUTRAL and if mantained -- that would obviously be smart. That specified Voltage would be obviously equal to CBamps/Rn => the problem is we don't know precisely Rn, as it is changing depending on current flow, but who knows, maybe there is a solution...
  • igor1960igor1960 Solar Expert Posts: 85 ✭✭✭✭
    Not to discourage you, but a prior public disclosure of a patentable idea renders any such idea indefensible. (But don't let that stop you; there is plenty of work to be done in distributed generation systems.)

    C'mon... It was just a joke..
  • igor1960igor1960 Solar Expert Posts: 85 ✭✭✭✭
    Bill/Others,

    I think I have figured "Safe" solution that would probably make you guys happy as well as really make P&P Inverters installation Safe.
    It's actually very easy.
    The purpose is just to find that P&P invetrter(s) is/are installed on dedicated circuit devoted only to RECEIVE power and there are no active loads on that circuit and if there is such load it's insignificantly small. So, if P&P invetrter finds that it's not dedicated line, it stops producing power and displays something "Not Dedicated Circuit".

    1. P&P Inverter starts working and looks into Line, Neutral and Ground wires.
    2. Instantaneous voltage drop/rise read is performed between Line and Ground, while inverter outputs power: result stored in Vlg (including sign of it) should be exactly equal to main supply voltage wave;
    3. Instantaneous drop/rise read is performed between Neutral and Ground: result stored in Vng (including sign of it), should be equal to (Sum of currents going through neutral to ground)/(Resistance of Neutral);
    4. If only inverters are installed on that circuit then sign of Vng would be opposite to sign of Vlg, meaning that direction of the current is opposite to normal -- current is travelling from Ground in the main box to output of inveters through Neutral. So, Vng is 180 degrees shifted relative to Vlg(Vac). This is OK mode. P&P inverter(s) continue working.
    5. However, if sign of Vng is equal to sign of Vlg, meaning that Vng is in phase with Vlg -- means that current goes in normal load direction (through CB into Neutral and then to Ground) -- then conclusion is made that this is not RECIEVING circuit, but instead normal LOAD circuit and therefore P&P inverter(s) should stop supplying power.
    6. If 5 is TRUE: P&P inverter(s) stop producing power and display something like "Not Dedicated Circuit".

    1-6 sequence might be repeated based on timer and/or (if 6 occured) some reset button and/or reconnect.

    As, the result P&P inverters might only work only on "dedicated" for them circuits, eventhough you might install several number of them on the same "dedicated" circuit.
    The same "dedicated" circuit will accept any normal load at any time, but should this happen, and normal load current reaches/exceeeds production current of the all P&P inverters on the circuit: P&P inverters will stop producing power and display "Not Dedicated Circuit" till circuit returns to "dedicated" condition.

    What yoiu tnink? Is this safe?
  • BB.BB. Super Moderators, Administrators Posts: 32,226 admin
    It can work in some situations (ignoring surge/ground noise).

    1) Must be Neutral+Earth ground in the Main Panel.
    2) Must be 120 VAC + Neutral (in US) or must be a country with ~230 VAC that has a Neutral+Earth bond in Main Panel
    3) Must have ground wire and Neutral wires from main panels

    It may not work in this situations:

    1) If there are sub panes off of main panel (common neutral from main to sub panel will give "false load" report). Not real common.
    2) Older homes in US may not have ground wire at outlet (two wire plug) or ground wire from main panel). Homes over 50 years old, very common unless upgraded in remodel.
    3) If there are separate green wire grounds different than "Main Panel" grounds (some industrial types of circuits allow/require this). Not common in homes.
    4) If the local 120 VAC circuit is really 120/240 VAC split phase (2 hots+Neutral+ground) with "equal 120 VAC loads" (equal loads on split phase loads have no current through neutrals). Common to have 4+1 AC wiring in newer homes. Easy to fool circuit (two electric heaters plugged into 120/240 VAC on Red and Black hots, shared neutral). Common--probably not. But not fool proof either.
    5) If plug and play is 240 VAC circuit (like drier plug, etc.), 240 VAC loads will have no neutral current. Some 240 VAC GT inverters have no neutral connections. Plug & Play is not aiming at these installations?
    6) Only allowed to install/use 80% of circuit rating. Installing GT inverters >80% of circuit rating (i.e., over 12 amps on a 15 circuit) is against code and can cause breaker/fuse trips (argue if this is "dangerous or not"--Is not to code).

    So, while the circuit could do what you ask, in some circumstances (ignoring electrical noise/surge issues)--It is still not "fool proof". Certain installations will probably have "false trips" (bothersome, but not unsafe). And in some installations, it is possible to get a "fail to trip" (#4, #5, #6).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • igor1960igor1960 Solar Expert Posts: 85 ✭✭✭✭
    BB. wrote: »
    1) Must be Neutral+Earth ground in the Main Panel
    Yes, required by code
    BB. wrote: »
    2) Must be 120 VAC + Neutral (in US) or must be a country with ~230 VAC that has a Neutral+Earth bond in Main Panel
    Yes, required by code
    BB. wrote: »
    3) Must have ground wire and Neutral wires from main panels
    Yes, required by code
    BB. wrote: »
    1) If there are sub panes off of main panel (common neutral from main to sub panel will give "false load" report). Not real common.
    But sub panels by code shouldn't have Neutral+Earth bond. So, assume that done by code and Neutral+Earth bond in Main Panel.
    But even if not: we are talking about one circuit. OK, Neutral+Earth in Sub panel, so what: we just need a run of Neutral wire to provide us some valuable resistance + we need Earth as an absolute 0 voltage, Right? So, even if not in Main Panel, but 0 ground and Neutral Resistance -- we are OK:
    BB. wrote: »
    2) Older homes in US may not have ground wire at outlet (two wire plug) or ground wire from main panel). Homes over 50 years old, very common unless upgraded in remodel.
    OK, easily resolved: P&P inverter check for valid resistance between N and G, they should be connected. Not connected: "N and G not connected/Check receptacle/circuit" message and stop output;

    BB. wrote: »
    3) If there are separate green wire grounds different than "Main Panel" grounds (some industrial types of circuits allow/require this). Not common in homes.
    We are talknig about P&P inverters with the standard 110v plug/outlet installed on resedintial 15AMP-20AMP lines. Are we? As I understand, that was the original concern -- ability to safely install into standard outlet. So, lets assume we are talking only about "common in homes" installations.

    BB. wrote: »
    4) If the local 120 VAC circuit is really 120/240 VAC split phase (2 hots+Neutral+ground) with "equal 120 VAC loads" (equal loads on split phase loads have no current through neutrals). Common to have 4+1 AC wiring in newer homes. Easy to fool circuit (two electric heaters plugged into 120/240 VAC on Red and Black hots, shared neutral). Common--probably not. But not fool proof either.
    Aren't those heaters by code require special plug/outlets and dedicated lines? Again, we are talking about relatively small P&P inverters (probably max.1200wt, like SUN-GT or similar), that are using computer type power plugs for ordinary outlets. So, you will be fooling the system and obviously ignoring the code if you don't properly connect standard 15AMP outlet (L1,N,G), possibly GFCI or not...

    BB. wrote: »
    5) If plug and play is 240 VAC circuit (like drier plug, etc.), 240 VAC loads will have no neutral current. Some 240 VAC GT inverters have no neutral connections. Plug & Play is not aiming at these installations?
    Again, the same as for 4). Also, by your code: are you allowed to mix on one circuit different type of equipment/outlets? Could you use standard outlet with L,N,G (that is only type of P&Ps we are talking about) on L1,L2 line? I don't think so -- at least here: you are not allowed. Not to say that usually for such cases ampearge is much higher on L!/L2 double breaker, isn't it?
    BB. wrote: »
    6) Only allowed to install/use 80% of circuit rating. Installing GT inverters >80% of circuit rating (i.e., over 12 amps on a 15 circuit) is against code and can cause breaker/fuse trips (argue if this is "dangerous or not"--Is not to code).

    Our circuit works in RCEIVING mode only, with no LOAD. All RECEIEVED current goes through CB. In that sense we are not different from standard LOAD circuit. So, we would obviously design it, so sum of installed P&P inverters currents use 80% of circuit rating. However, obviously user might increase installation and/or production would intermitently go above designed. Therefore, we have CB and in such situations it will trip. Same as currently on standard LOAD circuits -- you might design it, but user may overload it at anytime and CB will trip. No, difference on that issue here, CB will trip the same way, eventhough due to opposite direction of the current.


    Thanx, Bill.
  • vtmapsvtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    igor1960 wrote: »
    I think I have figured "Safe" solution that would probably make you guys happy as well as really make P&P Inverters installation Safe.
    <snip>
    As, the result P&P inverters might only work only on "dedicated" for them circuits, even though you might install several number of them on the same "dedicated" circuit.

    Well then, you still have a problem: Start inverter. Add loads to circuit, start another inverter, add more loads, start another inverter, add more loads, call fire department.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
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