690.7 (C)

[david]

SolarEdge holds training seminars in lots of cities and on line. You should attend one.

http://marketing.solaredge.com/acto...his message in a browser window&sid=ZeDFipNIk

I’ll take your recommendation under advisement that might be a nice choice if my employer would be willing to compensate for additional training in this area.

I do however have a different tool at my disposal. I can kick back all solar designs that come in and require that the designed be prepared and stamped by an electrical engineer.

After receiving the stamped drawings if I have any questions I’ll call the electrical engineer and he will answer any questions I might have on the design.

By the way if you click on the links Mike Holt provided to this forum you might review a video where Mike states, it is his opinion that no one is going to be able to read through the solar provisions in this code and understand them unless they get engaged in discussion on the subject.

 

[ggunn]

I’ll take your recommendation under advisement that might be a nice choice if my employer would be willing to compensate for additional training in this area.

I do however have a different tool at my disposal. I can kick back all solar designs that come in and require that the designed be prepared and stamped by an electrical engineer.

After receiving the stamped drawings if I have any questions I’ll call the electrical engineer and he will answer any questions I might have on the design.

By the way if you click on the links Mike Holt provided to this forum you might review a video where Mike states, it is his opinion that no one is going to be able to read through the solar provisions in this code and understand them unless they get engaged in discussion on the subject.

I'm pretty sure SE has on line tutorials that don't cost anything. From what you have been posting I got the impression that you are trying to design Solar Edge systems. If all you are doing is reviewing designs, then get the designer to add a note that the voltage will not exceed 600V. SolarEdge single phase string voltage is constant irrespective of the number of optimizers and is less than 600V, and whoever is doing the designs should know that.

SolarEdge is a different animal from string inverter systems. In whatever capacity you are acting in the design process it could not hurt to learn how it works. With the advent of rapid shutdown enforcement by AHJ's we are likely going to see a lot of it.

 

[david]

I'm pretty sure SE has on line tutorials that don't cost anything. From what you have been posting I got the impression that you are trying to design Solar Edge systems. If all you are doing is reviewing designs, then get the designer to add a note that the voltage will not exceed 600V. SolarEdge single phase string voltage is constant irrespective of the number of optimizers and is less than 600V, and whoever is doing the designs should know that.

SolarEdge is a different animal from string inverter systems. In whatever capacity you are acting in the design process it could not hurt to learn how it works. With the advent of rapid shutdown enforcement by AHJ's we are likely going to see a lot of it.

From a solar edge power optimizer cut sheet I pulled from the on line link you gave.

Output During operation (power optimizer connected to operating inverter)
Maximum Output Current 15 Amps DC.
Operating output voltage between 5 to 60 volts DC.

18 ea. 285 watt panels in a string
18 X 285 = 5130 watts
5130 watts / 15 Amps operating at max current output = 342 volts ( 19 volts per single power optimizer)
5130 watts / 600 volts = 8.55 amp min current output. (33.33 volts per single power optimizer in the string)

So are you saying that the optimizer is calibrated to keep the Min output operating current from falling below 8.55 Amps

 

[jaggedben]

From a solar edge power optimizer cut sheet I pulled from the on line link you gave.

Output During operation (power optimizer connected to operating inverter)
Maximum Output Current 15 Amps DC.
Operating output voltage between 5 to 60 volts DC.

18 ea. 285 watt panels in a string
18 X 285 = 5130 watts
5130 watts / 15 Amps operating at max current output = 342 volts ( 19 volts per single power optimizer)
5130 watts / 600 volts = 8.55 amp min current output. (33.33 volts per single power optimizer in the string)

So are you saying that the optimizer is calibrated to keep the Min output operating current from falling below 8.55 Amps

For single-phase 240V inverters the max voltage for a Solaredge optimizer string is 500V. It says so right on the spec sheet. The nominal operating voltage is 350V. It varies for different grid voltages and phase counts.

As a plan checker one thing you should note is that nominal short circuit current is higher for a Solaredge output circuit (15A vs typical 10A or less from a series string of modules). However in the 2014 code you are allowed to use this value without the first 125% factor (690.8(A)(5) vs 690.8(A)(1)). This is less clear in previous code cycles where DC-to-DC converters simply aren't addressed, so I suggest using the 2014 NEC as a guideline. 690.8(B) requires an additional 125% factor, among other things.

 

[david]

For single-phase 240V inverters the max voltage for a Solaredge optimizer string is 500V. It says so right on the spec sheet. The nominal operating voltage is 350V. It varies for different grid voltages and phase counts.

As a plan checker one thing you should note is that nominal short circuit current is higher for a Solaredge output circuit (15A vs typical 10A or less from a series string of modules). However in the 2014 code you are allowed to use this value without the first 125% factor (690.8(A)(5) vs 690.8(A)(1)). This is less clear in previous code cycles where DC-to-DC converters simply aren't addressed, so I suggest using the 2014 NEC as a guideline. 690.8(B) requires an additional 125% factor, among other things.

I have to apply the 2008 NEC to the design. I took it upon myself to research the 2014 NEC so I could try and understand how you guys are applying the NEC to these systems

I will use the 2014 in applying my own understanding in an attempt to have common ground in discussing these systems with solar contractors

Just the other day i went on with a big discussion here over 225.30 only to realize the feeder language changed in 2011 code cycle. Here the Ohio installers are installing under more current codes, it’s frustrating

 

[david]

For single-phase 240V inverters the max voltage for a Solaredge optimizer string is 500V. It says so right on the spec sheet. The nominal operating voltage is 350V. It varies for different grid voltages and phase counts.

The construction documents submitter did not include any information about the power optimizer .

I was able to clean from you guys that all solar edge inverters are supplied through a power optimizer.
Solar edge has a video showing each solar panel with individual optimizers instead of a junction box.

When I first looked at the SolarEdge Power optimizer Module Add-ON for North America, I thought the Optimizer technology was an option you could add to your DC Voltage supply to the inverter

 

[ggunn]

The construction documents submitter did not include any information about the power optimizer .

I was able to clean from you guys that all solar edge inverters are supplied through a power optimizer.
Solar edge has a video showing each solar panel with individual optimizers instead of a junction box.

When I first looked at the SolarEdge Power optimizer Module Add-ON for North America, I thought the Optimizer technology was an option you could add to your DC Voltage supply to the inverter

Yes, SolarEdge inverters only operate with their proprietary optimizers. The optimizers swap voltage for current to keep individually shaded modules from dragging down a whole string and to maintain a constant voltage to the inverter no matter how many modules are in a string within their published limits. Each optimizer has its own MPPT capacity and you can combine strings of different lengths. SE also claims that you can combine three strings without string fuses but none of the AHJ's I work with will let me do that.

There are other optimizers which are designed to work with "normal" string inverters but they are a different animal.

 

[GoldDigger]

There are other optimizers which are designed to work with "normal" string inverters but they are a different animal.

And in addition, the SE optimizers rely on control commands from the SE inverter to set their output. If no inverter is sensed the optimizer clamps its output voltage to a non-threatening and useless 1V per module

 

[ggunn]

And in addition, the SE optimizers rely on control commands from the SE inverter to set their output. If no inverter is sensed the optimizer clamps its output voltage to a non-threatening and useless 1V per module

Not entirely useless, though. The 1V per optimizer lets you test string continuity and tells you how many optimizers are in a string.

SE qualifies for rapid shutdown per 690.12, but there are a couple of things one needs to know about it. In order for the system to fulfill the 10 second time requirement for getting the voltage below 30V the inverter needs to have rapid shutdown enabled and the DC disco on the inverter must be switched off. Simply shutting off the AC connection to the inverter won't bring the voltage down fast enough.

 

[GoldDigger]

...
... Simply shutting off the AC connection to the inverter won't bring the voltage down fast enough.

Even with newer optimizer hardware or the addition of the Rapid Shutdown Kit (bleeder resistor) to each opmtimzer?

 

[ggunn]

Even with newer optimizer hardware or the addition of the Rapid Shutdown Kit (bleeder resistor) to each opmtimzer?

Yes. Our AHJ (Austin Energy) has started enforcing rapid shutdown, and they conducted their own testing of the 10 second rule on an installed system of ours. It failed because all they did was cut the AC to the inverter. We didn't know about the necessary inverter configuration and the need to cut the DC disco. Panic ensued.

We contacted SE and they filled us in; we instituted the changes and it passed. Big ol' WHEW.

 

[ggunn]

Even with newer optimizer hardware or the addition of the Rapid Shutdown Kit (bleeder resistor) to each opmtimzer?

BTW, the rapid shutdown kit is an addition to the inverter, not the optimizers. All SE inverters now being made now have it already.

 

[jaggedben]

The construction documents submitter did not include any information about the power optimizer .

Well then reject it for that reason! I mean c'mon, they want to install specialized equipment and can't be bothered to give you the specs...

BTW Solaredge inverters shipping from the factory now come with the rapid shutdown parts installed, but distributors may still have stock of the older ones that require the retrofit kit.

Edit: and for the second time in this thread, ggunn beats me to posting something while I was in progress. . :roll:

 

[GoldDigger]

BTW, the rapid shutdown kit is an addition to the inverter, not the optimizers. All SE inverters now being made now have it already.

If the DC disconnect is open the bleed down in the inverter should have no effect, right?

 

[Carultch]

Yes. Our AHJ (Austin Energy) has started enforcing rapid shutdown, and they conducted their own testing of the 10 second rule on an installed system of ours. It failed because all they did was cut the AC to the inverter. We didn't know about the necessary inverter configuration and the need to cut the DC disco. Panic ensued.

We contacted SE and they filled us in; we instituted the changes and it passed. Big ol' WHEW.

So what exactly is one supposed to do for rapid shutdown if they have a group of a dozen Solaredge inverters?

Obviously it would take longer than 10 seconds to shut off the DC switch on all of them. Does the rapid shutdown kit help you pass, if all that gets shut off is the AC side of the system?

 

[jaggedben]

If the DC disconnect is open the bleed down in the inverter should have no effect, right?

That's not my understanding. Bleed down happens through a resistor, not the array, and comes from the inverter side of the DC disco.

So what exactly is one supposed to do for rapid shutdown if they have a group of a dozen Solaredge inverters?

Buy a dozen kits. This will cost you roughly $1200 btw.

Obviously it would take longer than 10 seconds to shut off the DC switch on all of them. Does the rapid shutdown kit help you pass, if all that gets shut off is the AC side of the system?

Yes.

 

[GoldDigger]

That's not my understanding. Bleed down happens through a resistor, not the array, and comes from the inverter side of the DC disco.

That is my understanding too.
So I do not understand what is going on in the situation that ggunn describes, namely that the optimizer output does not go down fast enough to meet the 10 second requirement unless the inverter DC disconnect is opened.

 

[ggunn]

That is my understanding too.
So I do not understand what is going on in the situation that ggunn describes, namely that the optimizer output does not go down fast enough to meet the 10 second requirement unless the inverter DC disconnect is opened.

The bleed down kit is a resistor that bypasses the DC disco. It allows the voltage that is trapped between the switch and the optimizers to equalize in under the ten seconds dictated by the NEC. My understanding is that the residual voltage is on capacitance in the optimizers and the inverter, and opening the DC disco takes the capacitance in the inverter out of the circuit.

 

[ggunn]

Buy a dozen kits. This will cost you roughly $1200 btw.

Once the old stock inverters that do not have the kit factory installed get moved through the supply chain it will not be necessary. The SE inverters that we are getting now all have it.

 

[ggunn]

Does the rapid shutdown kit help you pass, if all that gets shut off is the AC side of the system?

It helps but according to the tests that our AHJ ran it doesn't get you all the way down in the ten seconds allotted.