I’m a HVAC tech and anytime I run into anything that has to do with electrical I turn to Mike, he always knows how to explain things, cites codes so you know he’s not making things up 😂
The DC-DC converters in your graphic are typically called Power Optimizers, and in the code they are grouped into Module-Level Power Electronics (MLPE). They are there to do something called Maximum Power Point Tracking (MPPT): the Power Optimizer controls the effective impedance of the circuit through itself (including the module/panel) with a DC-DC converter, to keep the string voltage near the maximum, where it will transfer the generated power most efficiently to the load equipment (usually an interactive inverter or charge controller). The other common type of MLPE is "microinverters", which is what's going on with the ‘AC modules’ drawing. The other common DC voltage for DC load systems is 48V, because it's four times as efficient on equivalent conductor sizes.
The multimode inverter is bi-directional, i.e. it can either work as an inverter using battery power, or it will be ac coupled to the grid ac or the other inverter ac and then charge the battery, hence the description ac coupled. DC coupled means the battery is charged from the DC derived from the pv side.
The safety disconnect between the multi mode / inverter and the service MSB / service disconnect is required by a utility (i.e. PG&E). This disconnect is a visible bladed safety fused disconnect.
Good (very) high level intro. May be worth mentioning that besides NEC and AHJ, you also have state codes (e.g. CRC and CFC for California) to consider. For ESS, the NEC is still a bit old-fashioned and doesn't cater well to modern AC-coupled storage battery inverter systems like the Tesla Powerwall. Some AHJ's still scream about not having a giant DC disconnect marked with max short-circuit current (following 480.7(D)) while ignoring 706.7 for the Powerwall (because it has a tiny on/off switch). Then there's the screaming about 110.26 clearances, and somehow 706.7 becomes interpreted as needing a visible knife-style disconnect.
I am an entry level safety plan certifier. It is needed to go out in the field and give us an actual representation or applicable examples. I enjoyed the presentation though and it was very insightful. To go a step further is to actually apply these in real life scenarios and show us how it is applied.
Mike, I support you and your mission as often as I need to learn something. I often suggest others choose your programs. Thank you for what you do, and how you do it. I’m wanting to get Sean to set me up access to 2017 & 2020 online/Capacitor items. UNEC, Solar, Master Exam, etc. I would pay for a lifetime connection if there were one. Thanks. David.
Minor correction, or distinction. Referring to the discussion at 12:01 When grid power goes down, inverters connected to the grid are required to detect the grid going down, and require inverters to go down completly so as to not back feed power to the downed grid are anti-islanding, not islanding. On the other hand, systems that detect the grid going down and disconnect from the grid but continue to operate providing power to the building, with power from solar, battery, wind, and or generator use islanding mode or technology that allows local generation of power without back feeding it to the grid. Maybe we can think of it like a little island of power isolated from everything else.
Keith, my work is based on the National Electrical Code, the NEC uses the term "Interactive Inverter" for what you call 'anti-islanding.' Search the NEC for the terms 'Interactive' so you can better understand my usage of this term. Please watch the video again after you review this term in the NEC and let me know if you still feel that I need a correction.
@@MikeHoltNEC Thank you Mike🙂. I virtually immediately regretted starting with correction, as it was too strong, but was pulled away on an errand before I could remove that part. I reviewed the video discussing the graphic presented upto and including and just after the timestamp 12:01. The discussion and the graphic under discussion were clearly about an interactive system without any battery backup, but moments later the speeker discusses battery backup in conjunction with islanding which is spot on. But, became a source of confusing at that moment in time with the discussion up to this point and the graphic depicted at 12:01 were clearly interactive without battery backup. I'm not an electrician, consequently my knowledge of the NEC code is sparse so maybe you were referencing something else, but I did find this... NEC 690.60 "only inverters and AC modules listed and identified as interactive shall be permitted in interactive systems." Then I found on your website a pdf with a graphic discussing NEC 690 it pointed out "listing means that the equipment is in a list published by a testing laboratory acceptable to the authority having jurisdiction". As an example, on the same graphic I seen an inverter identified as "utility interactive inverter" with its listing UL1741. Looking up UL1741 I found in its scope among other things, section 1.2 for interactive equipment, and it referenced IEEE 1547. Looking up IEEE 1547 I found in the 2018 revision, section 3.1 defined island: A condition in which a portion of an Area utility electric power system (EPS) is energized solely by one or more Local EPSs through the associated point of common couplings (PCC) while that portion of the Area EPS is electrically separated from the rest of the Area EPS on all phases to which the distributed energy resource (DER) is connected. When an island exists, the DER energizing the island may be said to be “islanding” I didn't invent the name anti-islanding inverter. The phrases islanding vs anti islanding or islanding protection, are things that interactive inverters do depending on the situation, and how they are intended to function. like my micro grid tie inverters have anti-islanding technology which means they fall into a subclass of inverters that we call interactive inverters with islanding protection, and contrast with interactive inverters that have islanding technology. 🙂
The key is what kind of inverter you buy. My inverter works off grid,it has solar input,48v battery, an mppt charge controller. It also can input 240v mains or 240v generator. I use a completly separare double wired 240v system. So I have outlets that come from the company and outlets that are my emergency system. Some grid tie inverters have a hybrid off grid system as well that use back up batteries. As someone has said the technology is changing all the time. When my utility goes off I have off grid outlets that I use.Been working well for over 5 years.
Bill does a great job. My concern is also on having PV and batteries on the same bus. How do you control voltage on each and is there a charging circuit? And part of the confusion is how the ESS (batteries) behave during charging, discharging and stand alone modes. We’re working on that in IEEE P1547.9 along with many other ESS challenges.
Extra info on DC to Dc converters with MPPT, maxium power point tracking. The DC to DC converter continually changes its effective input impedence to keep the PV pannels operating at their maxium power given current solar conditions on each seperate pannel. Consider the following three conditions. 1) A load represents a high effective impedence to the PV power source. This allows very little current to flow while the pannel's output voltage is near max for the pannel. But still almost no current × max rated voltage results in very little power being extracted from the PV pannel. Meaning they are opperateing inefficiently. 2) A load represens a very low impedence to the power source, say a near short. The pannel will push near max current but due to internal resistance in the PV pannel, the output voltage drops to a very low voltage and again, very little power is extracted from the pannel making it operate very inefficently. 3) some where between those two extremes, a DC to DC converter will continously reset its effective input impedence such that maxium power is extracted from the PV pannels under changing light conditions throughout the day. The DC to DC converter regulates its output voltage that go to a combiner and inverter, such that the inverter may draw maxium power from the DC to DC converters. Finally at least with some types of DC to DC converter provide galvanic isolation between the DC to DC input and output.
Can you clarify "non-interactive" PV system NEC requirements? 31:30 - Stand Alone Systems - for instance an extension-cord based 120VAC distribution to only a few appliances. Inverters often have GFCI - are there NEC grounding requirements? Can you clarify what and where Articles are in the NEC for the various subsystems (only 690 is called out on the slide).
Is there a NEC code explaining off grid and grid power in the same building? I would like to run two breaker panels so that I have my 220 appliances on grid and a completely separate breaker panel with all of my 120 appliances tied to off grid power, two power sources in the same house with zero chance of connecting to eachother is what I want.
Mike, I have a problem with all your diagrams that incorporate battery power. Most of them show power coming from the PV panels going to the inverter and also directly to the batteries. If that were the case, the batteries would be immediately fried. PV power is often in the 100 VDC or more range. PV power must go through a DC charge controller before going to the batteries in order to charge them at the correct voltages for the particular batteries being used ( flooded lead acid. AGM, lithium etc.) Many of the inverters on the market also incorporate a solar charge controller but many do not.. There should be a path showing the PV output going to the inverter/charge controller and then controlled DC going to the batteries or the PV output going through a separate charge controller and then to the batteries. Please let me know if I am missing something. Thanks. Paul
Does the NEC address fly back voltage from an inverter on the DC side in respect to disconnects or overcurrent devices? I am thinking in terms of available fault current from a battery bank plus energy what is added to the arc by the collapse of the magnetic field from the inverter transformer. I see this addressed in AC circuits with motors in terms of AIC for fuses/breakers but I can not find anything addressing this on DC, especially in the Canadian Electric Code.
Starting at 18:54 - Mike, the Stand-Alone AC Panel does not need a 'main breaker' OC device noted in the diagram because a partial loads panel can be fed through a back-feed breaker. Since the 'main breaker' or service disconnect is noted in the right panel between the meter and the inverter disconnect, we know this is a partial home backup versus a whole home backup. This is important as the partial loads panel can be anywhere from 20amps to 200amps, and good luck finding a main breaker under 90amps, along with the always important question....why pay for more than needed?
I have a PV system that has a 10 awg ground for electric component grounding in conduit and a 6 ga bare wire connecting the rails /panels outside conduit that goes to the inverter that will connect to a bus bar with the 10 ga and will connect thru the a ground to the other component boxes to the main house AC box/ ground rod. From looking at the plans it shows the bare wire going to the AC ground with no mention of any other grounds. I'm told I need to have 2 additional ground rods installed that will connect to the inverter bus bar then to the 2 new rods and back to the AC ground rod. From all the info I seen this makes no sense or am I totally confused
You are correct, there is no need to have the additional grounding that you were told. That is why it doesn't make sense, the rule for 'grounding' is contained in 690.47 "For PV systems that are not solidly grounded, the equipment grounding conductor for the output of the PV system, connected to associated distribution equipment, shall be permitted to be the connection to ground for ground-fault protection and equipment grounding of the PV array."
I've been thinking of adding an array of ground mounted Pv pannels as opposed to roof mount. I'd be using micro grid tie interactive inverters (AC module) to a breaker on the PV system disconnect. I follow you on your comments on auxiliary ground issues. I get that all the metal parts need to be properly bonded and connected to ground at the service pannel. But I'm wondering if the racking (mounting) system is steel pipes set in concrete, would that potentially act like an auxiliary ground or does proper bonding make it not an auxiliary ground? Or, should I consider using wood post set in concrete to support the PV pannels. Your thoughts on how to be safe here? And, thank you inadvance for your time and consideration.
Hi everyone, I have a couple of question, Can a common switchgear be used for both battery and solar in 3-7 MW َAC-Coupled projects, and then connected to a transformer and grid, or should separate switchgears be considered for the battery and transformer, separate from the solar system? Moreover, the voltage and frequency of the Inverter and PCS systems are exactly the same. Thanks
Is UL1741 compliance the same as UL 1742 listed? Would UL1741 compliance (TUV certified) pass inspection? Looking at the MPP solar LV6548 but not sure if it will pass inspection
The NEC, 690.4(B) requires PV inverters and other PV equipment to be 'listed.' The use of a UL 1741 'compliance' product is a violation of the NEC; unless it's 'listed' for PV systems.
I have a problem with the Graphics as well. There are Missing Components on the Graphic. Between the PV Disconnect and the Energy Storage Disconnect there should be a Charge Controller or Several Charge Controllers that regulates and transform power, then it conditions it into the expected Voltage and currents into a Battery Bank, Cycling the Battery through several charging methods, and prevention from over-charging them ...
You are 100% correct, I'm sorry we didn't include this detail, it will be corrected for the book shortly. Thank you so much for helping me do a better job.
Sir mike, I have a question but not for PV. For Smoke Extract Fan, Is it still needed for Overload Relay? I am confuse because Smoke Extract is intended to operate during fire mode right? i am realy confuse
Hi Mike, do you have a diagram showing a PV system and a standby generator for a house. I have had conflicting advice on a issue. Should the DC feed, from solar panels be installed on the line side of a transfer switch? Thanks in advance!
Hi Mike, Thank you for helping me to have a detail view on the PV system interconnection. But i have a question on the synchronization? How is the utility supply and the PV system inverted AC synchronized together?
@@MikeHoltNEC I was thinking less current, thus forcing my voltage up, something closer to 60v at 4 amps at the panel. So my panel won't be in scope of 720 but everything else would.
Multi-mode inverters are intended to supply the power in a bidirectional fashion( You may observe the energy flow arrows) which was not clearly highlighted in this great video.
19 minutes in. Yellow panel. Why would it need a Main disconnect switch? I have a reliance manual tranfer box to bypass the inverter if it failed which it feed 4 seperate circuits. This subpanel/stand alone/tranfer switch panel is next to main breaker panel. Part number reliance trb1005c.
Hi Mike - I bought your book on the 2020 NEC for Solar Voltaics. I have an island system running several things across extension cords. The "Island System" chapter illustrations are much too small to make out. What are the requirements for GFCI vs floating (return pin not tied to ground) 120VAC power? The third pin is tied to the inverter case ground, so is the inverter required to have a separate earth-grounded stake or just tied to the same ground-stake as the city-power junction block? There are people who argue about where grounding should take place in island systems and others who say floating is fine because there's no current-fault path (say, through a wet cement floor) that can cause an unexpected shock - but I'm not sure I believe this. In your book - there's only a few pages on Island Systems - why is the NEC ignoring this? My MultiPlus inverter has the option of either tying the return pin to case ground or leaving it floating (at ~60VAC relative to the inverter case ground). Will GFCI's work with a "floating" return pin? (at about 60VAC)
interesting question, i just got my multiplus, but i had no idea that the multiplus allow you to use floating ground like the smaller phoenix inverters from same company (Victron)
Video suggestion: I have not watched the 2020 Solar yet, but I would really appreciate a video explaining if 705 12(B)(2)(3) is also applied to each and every up stream load centers of downstream solar interconnect. If you tell me, I will believe it. Lots of back and forth on this topic. Thank you
@@MikeHoltNEC Mike, it’s fun to get your replies, thank you! I’ve watched the video you suggested twice, I have not noticed it speak to the upstream load centers, if they also need to follow load side interconnection rules? Meaning, if I interconnect solar to a sub panel using 705.12(B)(2)(3) (NEC 2017) Does the main panel upstream of the sub panel also have to follow 705.12(B)(2)(3)? It would seem the arguments might be: 1. that current (solar or utility) will flow towards the load (house more often than not) Thus We won’t see an excess of heat being applied on the upstream, main panel busing as it might do on the interconnection bussing. Counter argument… If it is a bright sunny day, and there is no load in the sub panel, yet there is heavy load in the main panel, you might get full amperage/heat being supplied to the main panel busing which could be excessive. Reply…But the Utility supply at that main panel bussing will only be the difference of the needed house load minus the solar supply,…right? In the end, I still don’t see why the main panel bussing would be required to follow load side interconnection rules. Maybe I’m missing something? Thanks.
PV produces current via the photovoltaic process. The discussion was about 'interactive' PV mode where the Utility and PV where both in parallel with each other supplying the 'loads.' The PV in the 'interactive mode' (parallel with utility) does not directly supply any given load. That only occurs in the 'off grid' mode (stand-alone).
Hey Mike thanks for the info. I work in the HV monitoring industry, and I wanted to know if there are plans for implementing NEC standards with regards to phase angle conditioning/monitoring for dc-to-ac Distributed systems?
The "stand alone system" needs revision. The solar array shown feeding both directly to the battery and the dc loads panel could be any volts DC. The drawing needs a DC/DC convertor after the array disconnect and have array feeding DC/DC convertor then to the battery and DC loads panel. Once that is corrected you wont be flowing high voltage DC to the DC loads it will be regulated by the DC/DC convertor and battery voltage. May also need some revision on the invertor disconnect circuit for the same reason as above, if the invertor can accept high voltage DC and is accepting converted/battery limited DC it needs to show those connections separately. We need to distinguish the difference where high voltage dc flows and convertor/battery limited voltage flows.. Lets say for example the array is putting out 1000volts at 10-20 amps then that is what the DC loads panel and battery are getting as well as the invertor. That cannot be right... So we dont have to label the specific voltages just need adjust the legs and input the DC/DC conversion took place. Again if the invertor has the MPPT capability it still needs to show that convertor/battery limited DC and array high voltage DC enter on separate circuits. Color coding the arrays DCVA and the batteries DCVA could also help. We also have to assume to much here like the DC loads are 12volt due to most DC devises being 12volt, but many people have batteries at 24/48volt and some higher so might need optional DC/DC conversion right before the DC loads panel. I hope that makes sense. This particular drawing is very confusing and i understand the want to simplify it but not at risk of a deadly mistake by the end user. Also thanks for the videos i have learn much and sadly have much more to learn before i can take on my solar project.
You can check out Alencon based in Hatboro PA. They make DC DC converters too. I have a close relationship with them but can't seem to use their product in typical project applications. Mostly for Repowering
SolarEdge is a manufacturer whose system by design, uses DC-to-DC converters, also known as optimizers. One reason you would want to use them in a design, is to accommodate diversity in tilt/orientation and shading. Another reason you do this, is to satisfy rapid shutdown requirements, as optimizers default to a shutdown standby output voltage, and stop the module open circuit voltage at the source. Optimizers work by solving an algebra problem, in order to satisfy Kirchhoff's laws. Like a transformer, they trade voltage for current. They dynamically adjust the buck/boost ratio to adapt to the conditions, and cooperate with each other to solve the algebra problem. Voltage adds up to an inverter-governed input voltage, and current is the same in each unit. Individual voltage is free to vary as needed, and ends up being proportional to what each one can do. Each module can operate independently of all the others, unlike when wired in series in a standard source circuit. Example: 20 optimizers in series. First 15 output 300W, remaining 5 output 100W. Inverter-governed total voltage = 400V. Solution: the first 15 produce 12.5A at 24V. The remaining 5 produce 12.5A at 8V.
Remember, in generic terms, solar and wind power sources are not interchangeable. Each requires its own separate controller. But they are certainly a good combo for taking advantage of differing weather conditions. (Not an electrician.)
690.33 "Mating connectors can be used as a disconnect if not readily accessible or require a tool. " So I guess we can place MC4 connectors inside an enclosure that has a screw down lid? or link me to an approved connector....
Very bad advice to tell people that a molded case breaker can be used as the pv disconnect. It's important to explain the reasoning that utilities have to require a visible break even if not in the NEC. Iny opinion molded case breakers should not be allowed per nec because of this extremely common requirement (for safety!)
This video only covers what is required to make the system comply with the NEC. Utility requirements are another set of standards entirely, and are utility-specific. A molded-case circuit breaker can be used for PV disconnects in general, where electrically rated for the details and direction of electric power, and where their purpose doesn't concern the utility. Commonly used when ganging up multiple inverter output circuits in a subpanel dedicated to the PV system, or interconnecting to the main panel.
@@carultch ok yes that's certainly true. I think the NEC should adopt similar nomenclature as IEEE 1547 regarding POI and require this in the NEC. If the molded case breaker is counterfeit and fails closed, rapid shutdown doesn't operate
The wiring for almost all PV systems terminate to a circuit breaker (which has the 'required' overcurrent protection for the PV system), which is the PV system disconnect. If the utility wants an 'additional' disconnect (without overcurrent protection, like a knife switch) that their call. I'm not giving advice, I'm explaining the NEC requirements.
@@MikeHoltNEC fair enough! I love the UA-cam content and this format, starting from the basics and developing to a specific end goal discussion. It's easy to get caught up in specifics like what I brought up here.
this video is DONE BACKwards. Instead of explaing how the code applies to real life situation, they look at some theoretical diagram and work backwards to figure out what section of code applies to that. Maybe inspectors will gets their jollies watching this , but every solar installer is rolling their eyes. Try explaining some stuff in layman terms. When half the of words coming out of your mouth are numbers it doenst help. What's next giving us the page number the code is on? It's like teaching bible class and getting people to remember the number of the verse instead of the meaning of it.
Mark, this video is discussing the 'first' rule contained in Article 690 and how this article applies. It's not a 'solar course' - this I have at MikeHolt.com/Solar. It's not designed for those that actually are experts on Article 690 like you. I'm sorry that you wasted your time and had negative feelings of my free content. Over 98% gave this a thumbs up and less than 2% (you included) gave it a thumbs down. Have a great life.
@@sunshine5349 Mark, the video is an 'introduction' video on the 'Scope' of Article 690. To cover all of Article 690 before the introduction is just not possible in a matter of minutes. My video style just might not be what your looking for. Let me know if you do find what your looking for on the Internet so that I can better understand your comments.
![Solar Photovoltaic (PV) Systems, Rapid Shutdown, NEC 2020 - [690.12], (31min:43sec)](http://i.ytimg.com/vi/GiWiaGeZ79c/mqdefault.jpg)
![Solar Photovoltaic (PV) Systems, Rapid Shutdown, NEC 2020 - [690.12], (31min:43sec)](/img/tr.png)
![Solar Photovoltaic (PV) Systems, Grounding Electrode System, NEC 2020 - [690.47], (9min:30sec)](http://i.ytimg.com/vi/cZo8ict33_I/mqdefault.jpg)
![Lp. Сердце Вселенной #60 РОЖДЕНИЕ ЛОЛОЛОШКИ [Финал] • Майнкрафт](http://i.ytimg.com/vi/YoR0pAV9FVQ/mqdefault.jpg)
I’m a HVAC tech and anytime I run into anything that has to do with electrical I turn to Mike, he always knows how to explain things, cites codes so you know he’s not making things up 😂
The DC-DC converters in your graphic are typically called Power Optimizers, and in the code they are grouped into Module-Level Power Electronics (MLPE).
They are there to do something called Maximum Power Point Tracking (MPPT): the Power Optimizer controls the effective impedance of the circuit through itself (including the module/panel) with a DC-DC converter, to keep the string voltage near the maximum, where it will transfer the generated power most efficiently to the load equipment (usually an interactive inverter or charge controller).
The other common type of MLPE is "microinverters", which is what's going on with the ‘AC modules’ drawing.
The other common DC voltage for DC load systems is 48V, because it's four times as efficient on equivalent conductor sizes.
The multimode inverter is bi-directional, i.e. it can either work as an inverter using battery power, or it will be ac coupled to the grid ac or the other inverter ac and then charge the battery, hence the description ac coupled. DC coupled means the battery is charged from the DC derived from the pv side.
The safety disconnect between the multi mode / inverter and the service MSB / service disconnect is required by a utility (i.e. PG&E). This disconnect is a visible bladed safety fused disconnect.
Good (very) high level intro. May be worth mentioning that besides NEC and AHJ, you also have state codes (e.g. CRC and CFC for California) to consider.
For ESS, the NEC is still a bit old-fashioned and doesn't cater well to modern AC-coupled storage battery inverter systems like the Tesla Powerwall. Some AHJ's still scream about not having a giant DC disconnect marked with max short-circuit current (following 480.7(D)) while ignoring 706.7 for the Powerwall (because it has a tiny on/off switch). Then there's the screaming about 110.26 clearances, and somehow 706.7 becomes interpreted as needing a visible knife-style disconnect.
Wow, you know what your talking about!...
the struggle is real!
Thanks for the detailed intro. Kindly make a video only on article 705 with installed examples.
I have a book and DVD that covers all of solar. Visit MikeHolt.com/Solar
I am an entry level safety plan certifier. It is needed to go out in the field and give us an actual representation or applicable examples. I enjoyed the presentation though and it was very insightful. To go a step further is to actually apply these in real life scenarios and show us how it is applied.
Mike, I support you and your mission as often as I need to learn something.
I often suggest others choose your programs.
Thank you for what you do, and how you do it.
I’m wanting to get Sean to set me up access to 2017 & 2020 online/Capacitor items. UNEC, Solar, Master Exam, etc.
I would pay for a lifetime connection if there were one.
Thanks.
David.
Sean will get you taken care of.
Minor correction, or distinction. Referring to the discussion at 12:01 When grid power goes down, inverters connected to the grid are required to detect the grid going down, and require inverters to go down completly so as to not back feed power to the downed grid are anti-islanding, not islanding.
On the other hand, systems that detect the grid going down and disconnect from the grid but continue to operate providing power to the building, with power from solar, battery, wind, and or generator use islanding mode or technology that allows local generation of power without back feeding it to the grid. Maybe we can think of it like a little island of power isolated from everything else.
Keith, my work is based on the National Electrical Code, the NEC uses the term "Interactive Inverter" for what you call 'anti-islanding.' Search the NEC for the terms 'Interactive' so you can better understand my usage of this term. Please watch the video again after you review this term in the NEC and let me know if you still feel that I need a correction.
@@MikeHoltNEC Thank you Mike🙂. I virtually immediately regretted starting with correction, as it was too strong, but was pulled away on an errand before I could remove that part.
I reviewed the video discussing the graphic presented upto and including and just after the timestamp 12:01. The discussion and the graphic under discussion were clearly about an interactive system without any battery backup, but moments later the speeker discusses battery backup in conjunction with islanding which is spot on. But, became a source of confusing at that moment in time with the discussion up to this point and the graphic depicted at 12:01 were clearly interactive without battery backup.
I'm not an electrician, consequently my knowledge of the NEC code is sparse so maybe you were referencing something else, but I did find this... NEC 690.60 "only inverters and AC modules listed and identified as interactive shall be permitted in interactive systems."
Then I found on your website a pdf with a graphic discussing NEC 690 it pointed out "listing means that the equipment is in a list published by a testing laboratory acceptable to the authority having jurisdiction". As an example, on the same graphic I seen an inverter identified as "utility interactive inverter" with its listing UL1741.
Looking up UL1741 I found in its scope among other things, section 1.2 for interactive equipment, and it referenced IEEE 1547.
Looking up IEEE 1547 I found in the 2018 revision, section 3.1 defined island: A condition in which a portion of an Area utility electric power system (EPS) is energized solely by one or more Local EPSs through the associated point of common couplings (PCC) while that portion of the Area EPS is electrically separated from the rest of the Area EPS on all phases to which the distributed energy resource (DER) is connected. When an island exists, the DER energizing the island may be said to be “islanding”
I didn't invent the name anti-islanding inverter. The phrases islanding vs anti islanding or islanding protection, are things that interactive inverters do depending on the situation, and how they are intended to function. like my micro grid tie inverters have anti-islanding technology which means they fall into a subclass of inverters that we call interactive inverters with islanding protection, and contrast with interactive inverters that have islanding technology. 🙂
The key is what kind of inverter you buy. My inverter works off grid,it has solar input,48v battery, an mppt charge controller. It also can input 240v mains or 240v generator. I use a completly separare double wired 240v system. So I have outlets that come from the company and outlets that are my emergency system. Some grid tie inverters have a hybrid off grid system as well that use back up batteries. As someone has said the technology is changing all the time. When my utility goes off I have off grid outlets that I use.Been working well for over 5 years.
Bill does a great job. My concern is also on having PV and batteries on the same bus. How do you control voltage on each and is there a charging circuit? And part of the confusion is how the ESS (batteries) behave during charging, discharging and stand alone modes. We’re working on that in IEEE P1547.9 along with many other ESS challenges.
I revised the graphic to show a 'charge controller' between the PV and batteries. Sorry for not doing a better job.
Extra info on DC to Dc converters with MPPT, maxium power point tracking. The DC to DC converter continually changes its effective input impedence to keep the PV pannels operating at their maxium power given current solar conditions on each seperate pannel. Consider the following three conditions.
1) A load represents a high effective impedence to the PV power source. This allows very little current to flow while the pannel's output voltage is near max for the pannel. But still almost no current × max rated voltage results in very little power being extracted from the PV pannel. Meaning they are opperateing inefficiently.
2) A load represens a very low impedence to the power source, say a near short. The pannel will push near max current but due to internal resistance in the PV pannel, the output voltage drops to a very low voltage and again, very little power is extracted from the pannel making it operate very inefficently.
3) some where between those two extremes, a DC to DC converter will continously reset its effective input impedence such that maxium power is extracted from the PV pannels under changing light conditions throughout the day.
The DC to DC converter regulates its output voltage that go to a combiner and inverter, such that the inverter may draw maxium power from the DC to DC converters.
Finally at least with some types of DC to DC converter provide galvanic isolation between the DC to DC input and output.
Whenever you have battery you have to have charge controller which not appearing in the diagrams can you please clarify this.
Sorry for the lack of clarity, we added a charge controler to the graphic for it's next use.
Can you clarify "non-interactive" PV system NEC requirements? 31:30 - Stand Alone Systems - for instance an extension-cord based 120VAC distribution to only a few appliances. Inverters often have GFCI - are there NEC grounding requirements? Can you clarify what and where Articles are in the NEC for the various subsystems (only 690 is called out on the slide).
Please post your question on MikeHolt.com/Forum.
@ 31:07 ( see also @15:28) Do AC generator inputs into the inverter need a disconnect ?
Is there a way that an ac module PCA system can have an inverter off the main Mabel to store battery backup?
Where in the code does it say about. Using emt vs pvc pipe. For the solar installation. ????? Please lmk
EMT or PVC is fine...
Is there a NEC code explaining off grid and grid power in the same building? I would like to run two breaker panels so that I have my 220 appliances on grid and a completely separate breaker panel with all of my 120 appliances tied to off grid power, two power sources in the same house with zero chance of connecting to eachother is what I want.
Yep, Article 690. You need to get with a Solar Contractor that is familiar with such a system.
Mike, I have a problem with all your diagrams that incorporate battery power. Most of them show power coming from the PV panels going to the inverter and also directly to the batteries. If that were the case, the batteries would be immediately fried. PV power is often in the 100 VDC or more range. PV power must go through a DC charge controller before going to the batteries in order to charge them at the correct voltages for the particular batteries being used ( flooded lead acid. AGM, lithium etc.) Many of the inverters on the market also incorporate a solar charge controller but many do not.. There should be a path showing the PV output going to the inverter/charge controller and then controlled DC going to the batteries or the PV output going through a separate charge controller and then to the batteries. Please let me know if I am missing something. Thanks.
Paul
I"m working on improving this graphic, send email so I can send you the updated images (Mike@MikeHolt.com).
Does the NEC address fly back voltage from an inverter on the DC side in respect to disconnects or overcurrent devices? I am thinking in terms of available fault current from a battery bank plus energy what is added to the arc by the collapse of the magnetic field from the inverter transformer. I see this addressed in AC circuits with motors in terms of AIC for fuses/breakers but I can not find anything addressing this on DC, especially in the Canadian Electric Code.
No clue.
shall i couple the dc with battry sourc ebefore inverter or couple the ac
12:58 uh... that's what a transfer switch or interlock kit is for.
Starting at 18:54 - Mike, the Stand-Alone AC Panel does not need a 'main breaker' OC device noted in the diagram because a partial loads panel can be fed through a back-feed breaker. Since the 'main breaker' or service disconnect is noted in the right panel between the meter and the inverter disconnect, we know this is a partial home backup versus a whole home backup. This is important as the partial loads panel can be anywhere from 20amps to 200amps, and good luck finding a main breaker under 90amps, along with the always important question....why pay for more than needed?
All panels need overcurrent protection, see 408.36!
thank you for breaking this down.
I have a PV system that has a 10 awg ground for electric component grounding in conduit and a 6 ga bare wire connecting the rails /panels outside conduit that goes to the inverter that will connect to a bus bar with the 10 ga and will connect thru the a ground to the other component boxes to the main house AC box/ ground rod. From looking at the plans it shows the bare wire going to the AC ground with no mention of any other grounds. I'm told I need to have 2 additional ground rods installed that will connect to the inverter bus bar then to the 2 new rods and back to the AC ground rod. From all the info I seen this makes no sense or am I totally confused
You are correct, there is no need to have the additional grounding that you were told. That is why it doesn't make sense, the rule for 'grounding' is contained in 690.47 "For PV systems that are not solidly grounded, the equipment grounding conductor for the output of the PV system, connected to associated distribution equipment, shall be permitted to be the connection to ground for ground-fault protection and equipment grounding of the PV array."
Do energy storage systems need to be UL listed for systems that are off grid/grid tie systems (i think its called ac coupled)
Yep, see NEC 706.5.
I've been thinking of adding an array of ground mounted Pv pannels as opposed to roof mount. I'd be using micro grid tie interactive inverters (AC module) to a breaker on the PV system disconnect.
I follow you on your comments on auxiliary ground issues. I get that all the metal parts need to be properly bonded and connected to ground at the service pannel. But I'm wondering if the racking (mounting) system is steel pipes set in concrete, would that potentially act like an auxiliary ground or does proper bonding make it not an auxiliary ground? Or, should I consider using wood post set in concrete to support the PV pannels.
Your thoughts on how to be safe here? And, thank you inadvance for your time and consideration.
Since you are using a/c modules, it doesn't matter that the metal racking is connected to the earth via the steel pipes.
Good intro, there is much more to cover in the solar world. I hope you have time soon to dive in. thank you
Dive into what? I have a book and DVDs on Solar NEC requirements. Visit MikeHolt.com/Solar
Hi everyone,
I have a couple of question, Can a common switchgear be used for both battery and solar in 3-7 MW َAC-Coupled projects, and then connected to a transformer and grid, or should separate switchgears be considered for the battery and transformer, separate from the solar system?
Moreover, the voltage and frequency of the Inverter and PCS systems are exactly the same.
Thanks
Is UL1741 compliance the same as UL 1742 listed? Would UL1741 compliance (TUV certified) pass inspection? Looking at the MPP solar LV6548 but not sure if it will pass inspection
The NEC, 690.4(B) requires PV inverters and other PV equipment to be 'listed.' The use of a UL 1741 'compliance' product is a violation of the NEC; unless it's 'listed' for PV systems.
@@MikeHoltNEC im not seeing it in that section, do you have a link that shows it please
@@todamnbad I'm not sure how to help you, since at least 2014, the NEC has required PV equipment to be listed.
I have a problem with the Graphics as well. There are Missing Components on the Graphic. Between the PV Disconnect and the Energy Storage Disconnect there should be a Charge Controller or Several Charge Controllers that regulates and transform power, then it conditions it into the expected Voltage and currents into a Battery Bank, Cycling the Battery through several charging methods, and prevention from over-charging them ...
You are 100% correct, I'm sorry we didn't include this detail, it will be corrected for the book shortly. Thank you so much for helping me do a better job.
Awesome video.
Sir mike, I have a question but not for PV. For Smoke Extract Fan, Is it still needed for Overload Relay? I am confuse because Smoke Extract is intended to operate during fire mode right? i am realy confuse
@MikeHoltNEC
Post technical questions on MikeHolt.com/Forum.
Hi Mike, do you have a diagram showing a PV system and a standby generator for a house. I have had conflicting advice on a issue. Should the DC feed, from solar panels be installed on the line side of a transfer switch? Thanks in advance!
should be on the side for the transfer switch before main
DC to DC converter is added after combiner box unless you are using optimizers on panels.
Not before!
The god father of Electricity, ! Excellent presentation!
Lol, I'm blessed that my work has some value to you. God Bless
Great u made it super clear!! Thanks
Hi Mike, Thank you for helping me to have a detail view on the PV system interconnection. But i have a question on the synchronization? How is the utility supply and the PV system inverted AC synchronized together?
The equipment takes care of this.
Are there any codes that pertain to a completely DC residence? (No inverter, no electric utility connection.)
The NEC, Chapter 1 - 4, and Article 720.
@@MikeHoltNEC Fair enough, definitions and part of the PV sections ... that narrows it down, I'll still review 690. Thank you.
@@MikeHoltNEC I was thinking less current, thus forcing my voltage up, something closer to 60v at 4 amps at the panel. So my panel won't be in scope of 720 but everything else would.
Multi-mode inverters are intended to supply the power in a bidirectional fashion( You may observe the energy flow arrows) which was not clearly highlighted in this great video.
19 minutes in. Yellow panel. Why would it need a Main disconnect switch? I have a reliance manual tranfer box to bypass the inverter if it failed which it feed 4 seperate circuits. This subpanel/stand alone/tranfer switch panel is next to main breaker panel. Part number reliance trb1005c.
A transfer switch is a 'switch.'
Hi Mike - I bought your book on the 2020 NEC for Solar Voltaics. I have an island system running several things across extension cords. The "Island System" chapter illustrations are much too small to make out. What are the requirements for GFCI vs floating (return pin not tied to ground) 120VAC power? The third pin is tied to the inverter case ground, so is the inverter required to have a separate earth-grounded stake or just tied to the same ground-stake as the city-power junction block?
There are people who argue about where grounding should take place in island systems and others who say floating is fine because there's no current-fault path (say, through a wet cement floor) that can cause an unexpected shock - but I'm not sure I believe this.
In your book - there's only a few pages on Island Systems - why is the NEC ignoring this? My MultiPlus inverter has the option of either tying the return pin to case ground or leaving it floating (at ~60VAC relative to the inverter case ground). Will GFCI's work with a "floating" return pin? (at about 60VAC)
Email me this question, and I'll work to help you understand (and do a better job with my book).
Mike@MikeHolt.com
interesting question, i just got my multiplus, but i had no idea that the multiplus allow you to use floating ground like the smaller phoenix inverters from same company (Victron)
Where is your charge controller from the panels?
Video suggestion:
I have not watched the 2020 Solar yet, but I would really appreciate a video explaining if 705 12(B)(2)(3) is also applied to each and every up stream load centers of downstream solar interconnect.
If you tell me, I will believe it.
Lots of back and forth on this topic.
Thank you
Watch this video to get your answers! ua-cam.com/video/7vD0r_bVjuo/v-deo.html
@@MikeHoltNEC Mike, it’s fun to get your replies, thank you!
I’ve watched the video you suggested twice, I have not noticed it speak to the upstream load centers, if they also need to follow load side interconnection rules?
Meaning, if I interconnect solar to a sub panel using 705.12(B)(2)(3) (NEC 2017)
Does the main panel upstream of the sub panel also have to follow 705.12(B)(2)(3)?
It would seem the arguments might be:
1. that current (solar or utility) will flow towards the load
(house more often than not)
Thus We won’t see an excess of heat being applied on the upstream, main panel busing as it might do on the interconnection bussing.
Counter argument…
If it is a bright sunny day, and there is no load in the sub panel, yet there is heavy load in the main panel, you might get full amperage/heat being supplied to the main panel busing which could be excessive.
Reply…But the Utility supply at that main panel bussing will only be the difference of the needed house load minus the solar supply,…right?
In the end, I still don’t see why the main panel bussing would be required to follow load side interconnection rules.
Maybe I’m missing something? Thanks.
@@davidorcutt9246 Please post your question on MikeHolt.com/Forum.
26:29 how does it produce current without the load?
PV produces current via the photovoltaic process. The discussion was about 'interactive' PV mode where the Utility and PV where both in parallel with each other supplying the 'loads.' The PV in the 'interactive mode' (parallel with utility) does not directly supply any given load. That only occurs in the 'off grid' mode (stand-alone).
27:00 Interesting point on Multimodal Inverters
what are the pros and cone between coupling dc vs ac
This is a 'design' function. For more information post you question on MikeHolt.Ai.
Do you have any info/vídeos on RV solar systems?
Nope, sorry.
DC Coupled Multimode System needs a charge controller to the energy storage batteries.
Hey Mike thanks for the info. I work in the HV monitoring industry, and I wanted to know if there are plans for implementing NEC standards with regards to phase angle conditioning/monitoring for dc-to-ac Distributed systems?
The NEC has no such standard.
Bill knows what he is talking about....
The ac coupled and dc coupled would be better displayed as sources along a bus bar.
Multi mode inverter means it will convert from DC to AC and AC to DC.
Solar Photovoltaic or PV solar system deals with energy taken from sun radiations, what is the avaerange power effeciency we got from PV
I have no clue.
The "stand alone system" needs revision. The solar array shown feeding both directly to the battery and the dc loads panel could be any volts DC. The drawing needs a DC/DC convertor after the array disconnect and have array feeding DC/DC convertor then to the battery and DC loads panel. Once that is corrected you wont be flowing high voltage DC to the DC loads it will be regulated by the DC/DC convertor and battery voltage. May also need some revision on the invertor disconnect circuit for the same reason as above, if the invertor can accept high voltage DC and is accepting converted/battery limited DC it needs to show those connections separately. We need to distinguish the difference where high voltage dc flows and convertor/battery limited voltage flows.. Lets say for example the array is putting out 1000volts at 10-20 amps then that is what the DC loads panel and battery are getting as well as the invertor. That cannot be right... So we dont have to label the specific voltages just need adjust the legs and input the DC/DC conversion took place. Again if the invertor has the MPPT capability it still needs to show that convertor/battery limited DC and array high voltage DC enter on separate circuits. Color coding the arrays DCVA and the batteries DCVA could also help. We also have to assume to much here like the DC loads are 12volt due to most DC devises being 12volt, but many people have batteries at 24/48volt and some higher so might need optional DC/DC conversion right before the DC loads panel. I hope that makes sense. This particular drawing is very confusing and i understand the want to simplify it but not at risk of a deadly mistake by the end user. Also thanks for the videos i have learn much and sadly have much more to learn before i can take on my solar project.
Thanks for the feedback, I'll make the necessary corrections.
Who puts DC-DC convertors on the panels before they go into the inverter? Nobody does that... Doesn't make any sense.
I suggest you do some research on dc-to-dc converters and their applicaiton. This is covered in my book and video program.
Isn’t a module optimizer a DC-DC converter
@@Yuroon360 Yep.
You can check out Alencon based in Hatboro PA. They make DC DC converters too. I have a close relationship with them but can't seem to use their product in typical project applications. Mostly for Repowering
SolarEdge is a manufacturer whose system by design, uses DC-to-DC converters, also known as optimizers. One reason you would want to use them in a design, is to accommodate diversity in tilt/orientation and shading. Another reason you do this, is to satisfy rapid shutdown requirements, as optimizers default to a shutdown standby output voltage, and stop the module open circuit voltage at the source.
Optimizers work by solving an algebra problem, in order to satisfy Kirchhoff's laws. Like a transformer, they trade voltage for current. They dynamically adjust the buck/boost ratio to adapt to the conditions, and cooperate with each other to solve the algebra problem. Voltage adds up to an inverter-governed input voltage, and current is the same in each unit. Individual voltage is free to vary as needed, and ends up being proportional to what each one can do. Each module can operate independently of all the others, unlike when wired in series in a standard source circuit.
Example:
20 optimizers in series. First 15 output 300W, remaining 5 output 100W. Inverter-governed total voltage = 400V.
Solution: the first 15 produce 12.5A at 24V. The remaining 5 produce 12.5A at 8V.
Viva land of enchantment!
Thank you!
Remember, in generic terms, solar and wind power sources are not interchangeable. Each requires its own separate controller. But they are certainly a good combo for taking advantage of differing weather conditions. (Not an electrician.)
I do believe they make controllers/ hybrid inverters that can take in multiple R.E. flavors. (Neither an electrician.)
48 volt is way more common for stand alone. It is the desired size.
Send how to wire an inverter
Are you an electrician?
Mike Holt got away with murder.....Code Killer like no other man, assassin of an instructor lol
@38 minutes. There is still an pv array disconnect.
690.33 "Mating connectors can be used as a disconnect if not readily accessible or require a tool. " So I guess we can place MC4 connectors inside an enclosure that has a screw down lid? or link me to an approved connector....
Very bad advice to tell people that a molded case breaker can be used as the pv disconnect. It's important to explain the reasoning that utilities have to require a visible break even if not in the NEC. Iny opinion molded case breakers should not be allowed per nec because of this extremely common requirement (for safety!)
This video only covers what is required to make the system comply with the NEC. Utility requirements are another set of standards entirely, and are utility-specific.
A molded-case circuit breaker can be used for PV disconnects in general, where electrically rated for the details and direction of electric power, and where their purpose doesn't concern the utility. Commonly used when ganging up multiple inverter output circuits in a subpanel dedicated to the PV system, or interconnecting to the main panel.
@@carultch ok yes that's certainly true. I think the NEC should adopt similar nomenclature as IEEE 1547 regarding POI and require this in the NEC. If the molded case breaker is counterfeit and fails closed, rapid shutdown doesn't operate
The wiring for almost all PV systems terminate to a circuit breaker (which has the 'required' overcurrent protection for the PV system), which is the PV system disconnect. If the utility wants an 'additional' disconnect (without overcurrent protection, like a knife switch) that their call. I'm not giving advice, I'm explaining the NEC requirements.
@@MikeHoltNEC fair enough! I love the UA-cam content and this format, starting from the basics and developing to a specific end goal discussion. It's easy to get caught up in specifics like what I brought up here.
Maybe instead of writing UA-cam comments I'll write to the CMP next time and give it a bit more thought and thoroughness...
Three minutes in, I'm beginning to catch on that this is not on the level of Stanford PhD material. Well, we'll see how it goes.
Mike should have a button to shock panelists when they say something he doesn't like.
They keep me on my toes!
@@MikeHoltNEC You keep us all on ours,Thanks.
The local electricians test has 18 questions on this article
What state/city exam?
@@MikeHoltNEC Maricopa county arizona
Eric the Contrarian
Lol...
This is the lamest explanation of Solar PV systems have heard.
this video is DONE BACKwards. Instead of explaing how the code applies to real life situation, they look at some theoretical diagram and work backwards to figure out what section of code applies to that. Maybe inspectors will gets their jollies watching this , but every solar installer is rolling their eyes. Try explaining some stuff in layman terms. When half the of words coming out of your mouth are numbers it doenst help. What's next giving us the page number the code is on? It's like teaching bible class and getting people to remember the number of the verse instead of the meaning of it.
Mark, this video is discussing the 'first' rule contained in Article 690 and how this article applies. It's not a 'solar course' - this I have at MikeHolt.com/Solar. It's not designed for those that actually are experts on Article 690 like you. I'm sorry that you wasted your time and had negative feelings of my free content. Over 98% gave this a thumbs up and less than 2% (you included) gave it a thumbs down. Have a great life.
@@MikeHoltNEC maybe I was a little harsh, but my comments overall are accurate.
@@sunshine5349 Mark, the video is an 'introduction' video on the 'Scope' of Article 690. To cover all of Article 690 before the introduction is just not possible in a matter of minutes. My video style just might not be what your looking for. Let me know if you do find what your looking for on the Internet so that I can better understand your comments.
@@sunshine5349 solar installers are hacks