Another P&P Vendor - Can plug and play work in the US?
Options
Comments
-
solar_dave wrote: »SO if you would take the time to read the NEC you would know that it is acceptable to have a 200 amp buss bar with up to a 40 amp solar backfeed. It is called the 120% rule, the breaker needs to be place at the opposite end of the buss bar. Now what do you do if you want to back feed more? You derate the main breaker to something less like 175 amps. That would allow up to a 65 amp backfeed (more probably an even breaker amount of 60 amps).
BTW it is not laughable, it is the electrical code.
Thanx, that is usefull info. Again, some of my questions are due to a different locality we are in. So, this 120% rule applies only to main panel or to anything else? Because, the principal is the same, as in my original proposal: derate CB to 50% of possible line load and then you can install P&P inverters -
Cariboocoot wrote: »There is NO current without a load. If the inverter is back-feeding the grid then the grid is a load. If the inverter is powering a device and back-feeding then both are loads to the inverter. If the device draws more current than the inverter can supply the difference is made up by the grid. The power sources will always act in concert. That is how it is. Physics.
Agree. 100% correct. -
Igor,
For the moment, forget AC--Think of a DC system. You have a 15 amp CB to a battery bank, and you have 15 amp alternator. Circuit:
Battery->15 Amp CB->10 awg cable "A"-> "X" socket for 15 amp Alternator->10 awg cable segment "B"-> "Z" socket->appliance pigtail designed for 15 amp @ 120 VAC outlet
I put a variable load on Z socket. Fire up the alternator and output 15 amps.
The current flowing through 15 amp CB will be equal to [Alternator Output - Load at "Z" Socket]. Correct?
Zero amp load at Z socket will give me 15 amps at CB. Correct?
15 amp load at Z socket will give me "zero current" at CB and 15 amps in "B" cable and "Z" socket? Correct?
30 amp load at Z socket will give me 15 amps at CB, 30 amps at Segment "B", and 30 amps at Z socket and appliance pigtail. Correct?
More than 30 amp load at Z socket... 15 amp Alternator is already current limited, and 15 amp CB limit will be exceeded. CB will trip and alternator will shut down because of "anti-islanding" circuitry in alternator (not true in real life, but is "true" for GT based inverters). Correct?
If this is a "standard" 120 VDC @ 15 amp branch circuit appliance, then its pigtail and UL Listing will be voided in this installation because of the 30 amp available power. If appliance is designed for a 30 amp circuit, then all is OK (other than it will not work if it requires more than 15 amps at night/less than full sun).
Yes, your wiring and outlets are designed for "30 amps"--And nothing inside this DC House wiring example will exceed the 30 amp rating (ignoring the NEC 0.80 or 1.25x derating of wiring, outlets, and breakers).
Do you agree with this as a DC example of your proposal? (forgetting the AC discussion for the above example).
-Bill
YES! Absolutely. -
bill von novak wrote: »Rating on all outlets is 15 amps (i.e. standard NEMA 5-15R's)
No, you still couldn't comprehend: in my proposal all outlets are rated at 30AMPs -
Thanx, that is usefull info. Again, some of my questions are due to a different locality we are in. So, this 120% rule applies only to main panel or to anything else? Because, the principal is the same, as in my original proposal: derate CB to 50% of possible line load and then you can install P&P inverters
No just the main panel buss bar. Your problem is you are trying to work around what is a fairly straight forward installation by using a plug in. I think you have made the complications of using a 30 amp line with a 15 amp breaker just to complex. It will just be so much easier to accept the safety guidance of the NEC and do it to code. You can always try to get your ideas added to the code, but I can almost guarantee that will be an uphill battle.
BTW lots of people do guerrilla installs, problem is they leave themselves open to disconnect from the utility and the code people. They also play into the hands of the insurance companies. I know my utility drives around looking for solar panels and checking if they have the proper interconnection documentation and equipment. It will be really expensive to get a red tag and meter pull corrected, plus they will look up your skirt really hard.
BTW there have been documented cases where not having the proper meter cause the back feed watts to actually run the meter higher and you end up paying the utility for the watts you push to the grid. If you have a smart meter it is pretty easy for the utility to see the back feed as well. -
BB, you are the smartest here! I am really amazed.
I was showing this to other "professors", who think that LOAD current and INVERTERS current should be added on common load lines, instead of subtracted.
Seriously, what do you think?
Assuming we are doing connection permitted by electrical company with central UL listed inverter. Everything sits on a separate 30AMP circuit. Perfect, and everything kosher.
Assuming, this is all connected to 200AMP main panel with 200AMP main circuit breaker and 200AMP Meter.
Now, we have the same problem here, as according to those "professors" even though we have 200AMP main CB, we might have 230AMP current somewhere inside our main panel, Right? According to them Yes: 200AMP load + 30AMP solar...
Question now: did they upgrade their main panel? Is this required. I don't know, maybe, but this is laughable!!!
Igor,
First--Please stop with the air/scare quotes around knowledgeable and professor. You complain I am putting words in your posts--And I am just trying to understand your proposal. Not one of us has said we were a teacher or professor. And we are actually paying attention to what you said because a different outlook on a system design can result in a new understanding.
Passive aggressive postings just serve to tick people off.
Remember, we have years of looking at the issue and even several companies over the last few years telling us we were wrong and they would have (or already have) UL Listing--And they did everything under the sun to avoid giving us the UL File number (which is public and published for building inspectors to reference at an installation).
And--Instead of learning/discussing--One person came in under multiple user names and a chip on his shoulder--He did not learn anything, we did not find anything new/useful, and it just ended up locking the thread.
We are here to help people build reliable and safe power systems. What you may build on a lab bench may not be what you want built into your walls at home running 24*7 for years with your family inside.
Next--I am not sure I understand where you are coming from regarding AC power theory. You seem to have some confusion about how AC circuit power flow works. And this is very understandable, AC circuit theory is very complex and math heavy. And there are definitions that are used that are not traceable back to fundamental engineering/physical principles.
For example, the polarity of voltage (+/-) source is defined. Based on Electron "Pressure". it has a polarity and a value.
Current is a bit more difficult.... Obviously, it has a value (Amperes) based in physics. However, polarity is not. For example, the output current of a car alternator is defined
as +0 to +100 amps. Current leaving the alternator is defined as a positive value.
For a battery bank, typically, output current flow is defined as a negative value (negative current is discharging a battery). And pushing current back into the battery is a positive value (recharging a battery). However, in a +12 volt (negative grounded system) the current flow is "backwards" from a -48 volt (positive ground) telecom power system.
So--When you looked at the scope picture for voltage vs current on a Texas Instrument reference manual--When you saw a "positive sine wave peak" vs a"negative current peak", it re-enforced your understanding of how AC current flow works. When, as an engineer, I looked at it as simply a the AC Mains voltage being inverted by the push of a button on the oscilloscope. For whatever reason, 1/2 the scope pictures had the AC Main trace inverted, and the other 1/2 of the pictures had the voltage trace not inverted (normal).
Because people tend to define positive current flow sign based on the "black box" function of the device (alternator/generator--positive current flow is normal operation; battery is discharging, negative sign ; and loads with a positive sign as this is their normal operation; yet the current flow is the not same direction between loads and sources, and bidirectional sources/sinks have yet a different convention)--There are many "sign corrections" in power math.
Regarding:Assuming, this is all connected to 200AMP main panel with 200AMP main circuit breaker and 200AMP Meter.
Now, we have the same problem here, as according to those [screw the 3rd party name calling--UNDERSTAND] even though we have 200AMP main CB, we might have 230AMP current somewhere inside our main panel, Right? According to them Yes: 200AMP load + 30AMP solar...
Question now: did they upgrade their main panel? Is this required. I don't know, maybe, but this is laughable!!
Yes--In your example there is 230 Amperes available on the AC bus bar in that mains panel. Since the NEC allows us to "uprate" a panel by 20%, there could be 40 amps of GT solar or 240 Amps average peak current available at any point in the bus bar. This is the fundamental flaw in your design/understanding of a Plug&Play system.
You are wrong. And ticking people off that are trying to help you is not winning friends or furthering your education... I try really hard to respond to the post, not attack the poster (Internet forum etiquiette rule #1). We want to keep people from killing themselves and others. This are fundamental principles (both safety and AC/DC power flow). Please ask, discuss, and learn. You are making this (moderating the forum) much more difficult than it needs to be.
Which do you want to discuss... The fact there is 230 Amperes available on the bus bar in your example, and discuss the AC power theory behind that? The layered protection provided by circuit breakers and the maximum ratings (like AIC rating of circuit breakers/fuses)? Or what...
Look at my DC example... The AC circuitry follows the exact same rules when PF=1.0 (forget all of the other non PF=1.0 stuff for the moment--It is just confusing you).
-BillNear San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset -
Here I agree, better to do permitted stuff. The problem is, in order just to try 1 panel, someone has to go through not that cheap process of approval. My friend in LA told me that his utility company charges $600 just to look into interconnection diagram (SCE I think) and before that installation should be permitted by the city, which is another $300-$400 dollars. Someone should come up with the design (another $$$), properly fill papaers and etc., then "Net Metering" application + $10 charge each month for NEM...solar_dave wrote: »BTW lots of people do guerrilla installs, problem is they leave themselves open to disconnect from the utility and the code people. They also play into the hands of the insurance companies. I know my utility drives around looking for solar panels and checking if they have the proper interconnection documentation and equipment. It will be really expensive to get a red tag and meter pull corrected, plus they will look up your skirt really hard.solar_dave wrote: »BTW there have been documented cases where not having the proper meter cause the back feed watts to actually run the meter higher and you end up paying the utility for the watts you push to the grid. If you have a smart meter it is pretty easy for the utility to see the back feed as well.
Yes, I know, those SmartMeters by default integrate both delivered and received power. It's just a pressing check box somewhere in the electrical company office to remotely reprogramm it to measure NET usage, but in order to do that you have to go through so much headache... -
Igor,
Which do you want to discuss... The fact there is 230 Amperes available on the bus bar in your example, and discuss the AC power theory behind that?
Yes, please. Having 200AMP active load and 30AMP solar input, could you please show me where is the particular place in the main panel where we have 200+30AMPS=230AMPS current.
I'm showing you the point where we will have 200-30AMP=170AMP -- that would be the METER and Main CB. If you disagree on that: there is nothing else to discuss.
You are saying it's a bus bar: where can I read the theory behind that? -
No, you still couldn't comprehend: in my proposal all outlets are rated at 30AMPs
You still have that problem whenever you can plug both loads and sources into the same line. Doesn't matter what the rating of the breaker, outlets or wiring is; if you can use the internal wiring to send GT power to loads on the line with no circuit breaker between the two, you can have this problem, because no one is stopping you from putting too much power through that section. (And history has demonstrated that if a device/line can be overloaded, it will be overloaded.) You can decrease the odds of overload by increasing ratings of the wiring and connectors, but you cannot eliminate the problem. -
Yes, please. Having 200AMP active load and 30AMP solar input, could you please show me where is the particular place in the main panel where we have 200+30AMPS=230AMPS current.
In that case your maximum load is 200 amps. The problematic case is 230 amp load, 30 amp solar input. Now you can have 230 amps flowing through busbars with a 200 amp load on the breaker (which means it won't blow.) -
bill von novak wrote: »In that case your maximum load is 200 amps. The problematic case is 230 amp load, 30 amp solar input. Now you can have 230 amps flowing through busbars with a 200 amp load on the breaker (which means it won't blow.)
But you will not be able to connect 230AMP load, as all loads are sitting on smaller circuit breakers, sum of which is less then 200amps, Right?
Actually it's even less then 200AMP, as one space is occupied by 30AMP breaker going to solar -- so it is max 170AMP...
How you connect 230AMP load? -
bill von novak wrote: »You still have that problem whenever you can plug both loads and sources into the same line. Doesn't matter what the rating of the breaker, outlets or wiring is; if you can use the internal wiring to send GT power to loads on the line with no circuit breaker between the two, you can have this problem, because no one is stopping you from putting too much power through that section. (And history has demonstrated that if a device/line can be overloaded, it will be overloaded.) You can decrease the odds of overload by increasing ratings of the wiring and connectors, but you cannot eliminate the problem.
Could you repeat the problem on example with 30AMP outlet. So, both Inverter and Load connected to it? Give me example in AMPs please. -
But you will not be able to connect 230AMP load, as all loads are sitting on smaller circuit breakers, sum of which is less then 200amps
In many main circuit breaker boxes, the sum of the smaller breakers is greater than the main breaker. --vtMaps4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i -
In many main circuit breaker boxes, the sum of the smaller breakers is greater than the main breaker. --vtMaps
Is this legal? Where can I read NEC and/or other materials allowing this? -
Not at all. I have a relatively "normal" panel (200 amp service) and the sum of all my breakers is 540 amps. The breakers are rated to protect the wiring, not to limit power drawn from the main breaker.But you will not be able to connect 230AMP load, as all loads are sitting on smaller circuit breakers, sum of which is less then 200amps, Right?
Let's take a very simple case - a GE PowerMark Gold 200 AMP 32 space 40 circuit load center. If you put 30 20 amp breakers in there, you are at 600 amps max load that can be drawn. Naturally the 200 amp breaker will trip before that happens. If you add a 30 amp breaker to feed back grid tie solar, now the panel can supply 230 amps.Actually it's even less then 200AMP, as one space is occupied by 30AMP breaker going to solar -- so it is max 170AMP...
How you connect 230AMP load?Could you repeat the problem on example with 30AMP outlet. So, both Inverter and Load connected to it? Give me example in AMPs please.
OK, example for 30 amp outlets with 30 amp wiring:
Two undersink hot water heaters, each drawing 22 amps when on, each plugged into a 30 amp outlet on the same string. A 30 amp GT inverter at the beginning of the run. Max load in the wiring between GT and first heater - 44 amps.
Since the undersink heaters are demand driven, they are almost never both on at night - so no trip of a 30 amp breaker. In the morning the sun comes up and starts providing power, only 14 amps at first. Both heaters come on as people wake up and use sinks/hot water spigots. The additional GT generation prevents breaker trip. In the middle of the day people use the sinks. 44 amp load, 30 coming from solar, 14 coming from breaker. -
Could you repeat the problem on example with 30AMP outlet. So, both Inverter and Load connected to it? Give me example in AMPs please.
If you wire up the circuit with all 30 amp receptacles what is to stop someone from plugging in multiple inverters and multiple loads? Are you planning to put all new 30 amp plugs on all your lamps, blenders, vacuum cleaners, etc? If you leave the standard plugs on them the receptacle that receives them will not be rated 30 amps.
--vtMaps4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i -
It is the same issue as in my DC Example, post 94. If you have a 15/20 amp maximum rated pigtail/power cord on your laptop, hair drier, etc., and plug it into a 30 amp rated outlet (with 15 amps from main, and 15 amps from GT inverter) (and cut off the 15 amp plug and put a 30 amp plug on the power cord), the UL Listing and safety will be compromised on the appliance.
The only way to "make it legal" (simple, relatively cheap), is to put a fuse/breaker in the 30 amp device plug itself (like UK does because of "Ring Circuits", see earlier post), or to put a 15 amp fuse/breaker in the wall outlet itself for each socket (two sockets, two 15 amp fuses--or variations of same idea).
Regarding:Yes, please. Having 200AMP active load and 30AMP solar input, could you please show me where is the particular place in the main panel where we have 200+30AMPS=230AMPS current.
I'm showing you the point where we will have 200-30AMP=170AMP -- that would be the METER and Main CB. If you disagree on that: there is nothing else to discuss.
You are saying it's a bus bar: where can I read the theory behind that?
Do you agree, if I have a 200 amp main breaker connected to the grid, and have a 30 amp load (through 30 amp breaker), that there is 30 amps flowing from the grid through the main breaker, through the bus bar, and out the 30 amp branch circuit?
If I have two 30 amp breakers/loads running, then I have 60 amps through main 200 amp breaker and bus bars?
And if I change one of the 30 amp loads to a 30 Amp GT inverter, I now have zero amps running through the main 200 amp breaker (from the utility) and 30 amp running out the load circuit? And 30 amps flowing through a portion of the bus bar?
-BillNear San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset -
Do you agree, if I have a 200 amp main breaker connected to the grid, and have a 30 amp load (through 30 amp breaker), that there is 30 amps flowing from the grid through the main breaker, through the bus bar, and out the 30 amp branch circuit?
If I have two 30 amp breakers/loads running, then I have 60 amps through main 200 amp breaker and bus bars?
And if I change one of the 30 amp loads to a 30 Amp GT inverter, I now have zero amps running through the main 200 amp breaker (from the utility) and 30 amp running out the load circuit? And 30 amps flowing through a portion of the bus bar?
Agree, absolutely. -
Is this legal? Where can I read NEC and/or other materials allowing this?
There is a difference between residential and commercial code (at least in times past).
Residential you are allowed to have branch circuits that exceed the rating of the main breaker. It is assumed that not all loads are running at the same time (a few people running around doing their thing at different locations in the home).
In commercial, the main panel rating and main breaker rated current must meet or exceed the sum of the breakers in the panel. In commercial, it is assumed that all loads may operate at the same time. All the workers are at their stations using their allotted power (as I understand the reasoning).
There has been some recent changes (I think) to NEC regarding GT solar and Commercial installations--But I am not sure. The last time I worked with code was decades ago (and it was not house/building wiring).
-BillNear San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset -
Agree, absolutely.Do you agree, if I have a 200 amp main breaker connected to the grid, and have a 30 amp load (through 30 amp breaker), that there is 30 amps flowing from the grid through the main breaker, through the bus bar, and out the 30 amp branch circuit?
If I have two 30 amp breakers/loads running, then I have 60 amps through main 200 amp breaker and bus bars?
And if I change one of the 30 amp loads to a 30 Amp GT inverter, I now have zero amps running through the main 200 amp breaker (from the utility) and 30 amp running out the load circuit? And 30 amps flowing through a portion of the bus bar?
Then, the total available current on the bus bar is 200 Amps from the main breaker plus the 30 amps from the GT breaker, and you get 230 Amps available on the main bus. This has been what these pages and pages of discussions have been about.
You put two or more power sources (distributed power sources) in a single circuit, and the maximum available current from each adds (assuming PF=1.0). And the various safety checks/ratings now have to be done on the worst case assumption that each of these sources will output its rated load at some time during the day.
And at some point either a person will plug in too much stuff, something will short circuit and fail, or something else, and those failures have to be matched against the total available current in the distributed power system.
It is that simple.
-BillNear San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset -
bill von novak wrote: »Two undersink hot water heaters, each drawing 22 amps when on, each plugged into a 30 amp outlet on the same string. A 30 amp GT inverter at the beginning of the run. Max load in the wiring between GT and first heater - 44 amps.
Since the undersink heaters are demand driven, they are almost never both on at night - so no trip of a 30 amp breaker. In the morning the sun comes up and starts providing power, only 14 amps at first. Both heaters come on as people wake up and use sinks/hot water spigots. The additional GT generation prevents breaker trip. In the middle of the day people use the sinks. 44 amp load, 30 coming from solar, 14 coming from breaker.
Here, theoretically I agree. Vulnerable system. Except, probably in documenaton for heaters it is probably mentioned that each has to be connected to a dedicated circuit (as each is around 15amps) and not doing that would void warranty and etc. and you do it at your own risk. Plus, probably they might have special plug and etc. to dissalow simple connection. -
Then, the total available current on the bus bar is 200 Amps from the main breaker plus the 30 amps from the GT breaker, and you get 230 Amps available on the main bus. This has been what these pages and pages of discussions have been about.
You put two or more power sources (distributed power sources) in a single circuit, and the maximum available current from each adds (assuming PF=1.0). And the various safety checks/ratings now have to be done on the worst case assumption that each of these sources will output its rated load at some time during the day.
And at some point either a person will plug in too much stuff, something will short circuit and fail, or something else, and those failures have to be matched against the total available current in the distributed power system.
Bill, here I understand the problem: it is misscommunication. In my jurisdiction (Russia) it states that rated sum of all CBs on the main panel should be not more then rating of main CB/Meter. Thus here there is no way to legally connect overall load which is more then main CB rating, because sum of all circuits ratings is less then main CB (so smaller CB will trip before main CB and main CB is used as a secondary protection to protect utility line/meter).
Looks like, where you are (US?), you can. -
Bill, here I understand the problem: it is misscommunication. In my jurisdiction it states that rated sum of all CBs on the main panel should be not more then rating of main CB/Meter. Thus here there is no way to legally connect load in access of main CB rating.
Looks like, where you are, you can.
If that is the case, then the usual fix would be to take your 200 amp panel, put in a 175 Amp Main Breaker and a 25 amp maximum GT breaker, and the rest of the installed load breakers cannot add up to more than 200 amps (as I understand the commercial code).
Of course, if you have more GT power, you would down side the main breaker more, and/or tear out the 200 amp box and install a larger one.
That is odd that you cannot install more than the rated main breaker/panel capacity in a residential install. That is (from what little I know), not typical... Where are you located? Are you looking at commercial or residential?
-BillNear San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset -
That is odd that you cannot install more than the rated main breaker/panel capacity in a residential install. That is (from what little I know), not typical... Where are you located? Are you looking a commercial or residential?
I can install anything I want -- this is the beauty of living here (Moscow). The problem is, the first thing inspector does (when he is not drunk and usually he is) he checks the main panel (and mostly that's it) by counting sum of rating on CBs and comparing that sum with main CB. Mine is 200amps, which is not usual here (just 50-100AMPS) is the norm. Only very rich people have 300AMPS.LOL... At least voltage is 220v, so you can do more with less current. -
Here, theoretically I agree. Vulnerable system. Except, probably in documenaton for heaters it is probably mentioned that each has to be connected to a dedicated circuit (as each is around 15amps) and not doing that would void warranty and etc. and you do it at your own risk.
Probably! And if you followed such a similar precaution when installing grid tie solar you wouldn't have this specific problem either even if you used an outlet. However
1) with home run wiring it's hard to tell if you are on a dedicated circuit
2) if it's commonly sold it WILL (not might) get misused. Within weeks someone on a message board would post "I just found a way to keep my circuit breaker from blowing all the time - put my grid tied solar on that circuit! My clever solution lets my solar reduce the load on my heavily loaded circuits, and increases convenience and safety."Plus, probably they might have special plug and etc. to dissalow simple connection.
Most small undersink heaters have pretty standard NEMA 5-15R plugs. Fortunately they usually plug into the garbage disposal plug, and that's often a dedicated circuit. (Unless you have both, in which case you are back to the problem.) -
Technically speaking--Notice that channel 3 is actually "inverted" from its measured amplitude (see bottom of scope picture--INVERT "ON").
Not that really matters, all is takes is the reversing the connections of the CT, M-FET/Hall current probe, or shunt to reverse the current polarity on the display (or use the "INVERT Trace" button).
It just depends on how you define "positive and negative" current flow direction.
In any case, if the 500 Watt inverter is outputting (for example) the positive sine wave, then the current flow has to be out from the AC inverter into an arbitrary load. If the current flow is into the Inverter as the wave from goes positive, then the Inverter is a Load--Something that would not be a GT inverter that we would want to use.
It appears, for what ever reason, they chose to inverter the current direction to indicate the Inverter is outputting energy into the branch circuit rather than consuming it. The sign of the current flow is all "relative" to how you assume the device operates.
If you look at page 20 section 4.2, you see the Hall transistor feedback loop--And their they have the Voltage in Phase with the Current wave form (and scope INVERT Trace "OFF").
This does not do a good job of explaining power flow in an AC circuit and how phasing/polarity of current (0/180 degrees) "works".
-Bill
Note for exactness--Channel 3 is the Grid Voltage Channel that is inverted in the last set of pictures. Again--Whether the Voltage (ch3) trace or the Current (ch2) trace is inverted does not really matter... There was a sign (or effectively a phase) swap.
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.
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.
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. 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. 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)...
Now, the power we will be feeding back into AC would be equal to P=(Vrms-Virms)*Irms*PF, where
Irms -- RMS of sinusoidal Ii, that our inverter can sustain to perform above using current DC input power
PF -- power factor due to the possible shift between Vac and Irms (which is equal to shift beween possible Iac and Ii) -
In the "olden days"--Homes had screw in fuses (just like electric light bulbs with an "Edison" base). You could get anything from 10 amp to 30 amp fuses that fit the same fuse panel. And, my Dad, when the saw blew the 15 amp fuse, put in a 20 amp slow blow, and when that still blew (as I recall) he put in a 30 amp fuse (~5 decades ago--Home is still standing and has not burned down yet).
And, people if they did not have a fuse handy, they simply put a copper penny in the socket and replaced the failed fuse. And there are stories of people wrapping aluminum foil around fuse holders and such too (I did that with a chewing gum wrapper and a blown fuse on my motorcycle to get home).
The new systems are designed to be more "fool resistant" (i.e., a 15 amp fuse will only fit a 15 amp socket and no fuse socket will fit a penny).
What is done in other countries sometimes works for them. And when I was designing equipment--We usually could design the equipment to connect to a wide variety of electrical code standards. You just had to be conservative in how you made the design choices (which adds expenses, and frequently makes J-Boxes a little bigger, more expensive power supplies with wide range / Power Factor Corrected inputs, etc.).
In the US, there is no way (that I can see, in my humble opinion) that existing code will ever allow P&P GT inverters (for reasons discussed). So the option is hard-wire and pay the fees (makes small systems uneconomic), or change the code. Either a "physical" change (something new and improved in wiring/GT inverters), or something on the paperwork side (i.e., only allow 300 watt maximum GT inverter per home).
Because much of the world uses ~230 VAC wiring for home appliances--You already start out with a ~2x greater amount of power per Ampere of current. That makes it "more intersting" to see if you can figure out P&P for existing home wiring.
In the US--Even converting an entire branch circuit (14 amps @ ~110 volts) only lets us install a bit more than 1,000 watt of solar--Not really that much--Cut the "P&P back to 1/2 current", and 500-600 watts is really not even worth it for the pennies per day of power saved (yes, cities and utilities pay a lot to just shuffle paper work and change out a meter/update a billing plan).
-BillNear San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset -
bill von novak wrote: »1) with home run wiring it's hard to tell if you are on a dedicated circuit
2) if it's commonly sold it WILL (not might) get misused. Within weeks someone on a message board would post "I just found a way to keep my circuit breaker from blowing all the time - put my grid tied solar on that circuit! My clever solution lets my solar reduce the load on my heavily loaded circuits, and increases convenience and safety."
Guys,I might be missundertood. It's not like I'm arguing with you, as if those P&Ps are my business and I'm trying to promote them. They are for sure BS in there current form.
I mostly completely agree with what you are saying. And I'm for safety. I'm just trying to undertsand and evaluate if P&Ps are visible. Doing that mostly for technical/ideas reasons and not even for my own installation. Just thinking loud if the idea of P&Ps has the future. For now I do see more reasons against them, but maybe there is some idea somewhere... -
igor,
now that i see you are from russia you may very well be able to legally connect pnp stuff as i don't know russian laws. from a safety standpoint you now understand why it is illegal here. now you have 230vac and it really is not as radically different than our 240vac split for 2 legs of 120vac. think of it as similar to your 230vac, but transformed voltage from a transformer that would be if center tapped. the pnp inverters made to plug into our 120vac sockets (illegally used here, but legally imported) are only feeding 1/2 of the 240vac main panel as our 240vac main panel when split opts for twice the current in a sense.
picture it this way,
240vac at 100a=120vac at 200a total as we have 2 legs of 100a at 120vac.
even though you have cbs that add up to the main cb power, that same power coming in from the utility will add to any power fed to the panel from solar. the main cb won't care and nor will any individual cb being fed solar care, but inside the panel the bus will have more power available if one doesn't make a change as now a smaller cb is adding power rather than subtracting for a load. over here the change is to reduce the size of the main cb so that the sum of the solar power and that which is available from utility power on the bus do not exceed the bus rating. here a 100a panel as an example with a 100a main cb will typically have a bus rating of 20% higher so the bus in the 100a panel is good for 120a. we safely can feed 20a solar into our panel with keeping the 100a main cb. anything higher would make it necessary to reduce the size of the main cb in so keeping with the max 120a the bus would see.
main panels are probably similar where you are, but i can't say for sure.
so this means you have to find out russian laws on the connectivity of such pnp inverters and you need to know if the bus in the main panel can handle the extra current available and that's by finding out if it is rated the same way in your country as it is here. if russian law allows pnp and you have a 200a panel that is rated on its bus like ours is at 20% above the design then you could add up to 40a of solar to that panel safely without changing the main cb. note that i am talking up to a 40a 230vac gt inverter, and not the cheap pnp ones made to plug into our 120vac outlets, for both yours and others reading benefits. you will need to add your own caution with the circuit selected too as we've already discussed as a dedicated circuit for the solar feed to the main panel would be easiest and best to do.
edit to add--if you put a cb of 15a in your main panel to your circuit which is rated for 30a and a gt inverter rated up to 15a with its own cb of 15a to that same 30a circuit wiring then any other taps on the circuit can have up to 30a of power available, but only when solar is producing power. when solar is down the 15a main cb will be the only source of power available to the 30a circuit. -
bill von novak wrote: »OK, example for 30 amp outlets with 30 amp wiring:
Two undersink hot water heaters, each drawing 22 amps when on, each plugged into a 30 amp outlet on the same string. A 30 amp GT inverter at the beginning of the run. Max load in the wiring between GT and first heater - 44 amps.
Since the undersink heaters are demand driven, they are almost never both on at night - so no trip of a 30 amp breaker. In the morning the sun comes up and starts providing power, only 14 amps at first. Both heaters come on as people wake up and use sinks/hot water spigots. The additional GT generation prevents breaker trip. In the middle of the day people use the sinks. 44 amp load, 30 coming from solar, 14 coming from breaker.
bill von novak,
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.
That also means that yours GT inverters current should be not more then 15AMP (as CB will trip if its more)
Now, show me the scenario how you can overload 30AMP outlet...
Categories
- All Categories
- 243 Forum & Website
- 150 Solar Forum News and Announcements
- 1.4K Solar News, Reviews, & Product Announcements
- 191 Solar Information links & sources, event announcements
- 919 Solar Product Reviews & Opinions
- 256 Solar Skeptics, Hype, & Scams Corner
- 22.5K Solar Electric Power, Wind Power & Balance of System
- 3.6K General Solar Power Topics
- 6.7K Solar Beginners Corner
- 1K PV Installers Forum - NEC, Wiring, Installation
- 2.1K Advanced Solar Electric Technical Forum
- 5.5K Off Grid Solar & Battery Systems
- 438 Caravan, Recreational Vehicle, and Marine Power Systems
- 1.1K Grid Tie and Grid Interactive Systems
- 652 Solar Water Pumping
- 829 Wind Power Generation
- 626 Energy Use & Conservation
- 626 Discussion Forums/Café
- 303 In the Weeds--Member's Choice
- 91 Construction
- 124 New Battery Technologies
- 108 Old Battery Tech Discussions
- 3.8K Solar News - Automatic Feed
- 3.8K Solar Energy News RSS Feed