# Solar Power Optimizers and Maximum Inverter Voltage



## Nearly-Complete (Jul 5, 2019)

SolarEdge tells their designers to design a system based on the maximum power because their optimizers keep everything at the right voltage for the system.
https://www.solaredge.com/us/guide-designing-with-solaredge

Is this supported by code? CEC 690.7 (a) states that the maximum voltage shall be calculated as the sum of the open-circuit voltage of the series-connected PV modules corrected for the lowest expected ambient temperature, and this voltage shall be used to determine the voltage rating of equipment.


----------



## Paul Sweet (Jul 6, 2019)

I'd use the voltage of the inverter output.  CEC 690.7 (a) is for DC, so it probably applies to wiring between the solar array and inverter, which is the system manufacturer's worry.


----------



## Nearly-Complete (Jul 6, 2019)

How is it the manufacturer’s worry if there is a code requirement specifically for this scope?

So because this is listed equipment it just has to be installed per the manufacturer’s instructions and this discrepancy with the code must have been worked out by the listing agency and deemed safe and meeting the intent of the code?


----------



## cda (Jul 6, 2019)

Nearly-Complete said:


> How is it the manufacturer’s worry if there is a code requirement specifically for this scope?
> 
> So because this is listed equipment it just has to be installed per the manufacturer’s instructions and this discrepancy with the code must have been worked out by the listing agency and deemed safe and meeting the intent of the code?




Not sure your reply

“”Manufactures installation instructions and listing””,,,


And

“Code”

Do not always meet.

Sometimes one requires more than the other.


----------



## Nearly-Complete (Jul 6, 2019)

Sorry. My post was really poorly written and I couldn’t figure out how to edit on my phone.

There is a code provision that states how to calculate the voltage of the circuit between the panels and inverter. That provision is not met when installing the system per the listed equipment’s installation instructions. I am trying to determine if the fact that this equipment is listed means that the intent of the code has been met through the use of optimizers. Or do I have to reject these plans because the sum of the series voltages exceeds the input voltage of the inverter?


----------



## Nearly-Complete (Jul 6, 2019)

What happens when optimizers fail?


----------



## cda (Jul 6, 2019)

“””the fact that this equipment is listed means that the intent of the code has been met“”””


I cannot answer for the equipment you are looking at,,,,

But just because an item is listed,     Does not mean it will meet all codes for the equipment or installation.


----------



## ICE (Jul 7, 2019)

cda said:


> “””the fact that this equipment is listed means that the intent of the code has been met“”””
> 
> 
> I cannot answer for the equipment you are looking at,,,,
> ...


The solar industry is like the Wild West. There’s too much money to be made. The premise that an NRTL listing is a testament for a safe product isn’t always valid. 
I am not speculating.


----------



## ADAguy (Jul 8, 2019)

Points well taken


----------



## Rick18071 (Jul 9, 2019)

No different than a simple listed light fixture that has #16 wires in it.


----------



## tmurray (Jul 9, 2019)

typically, where manufacturer's instructions and code differs, the code governs. I would say the onus is on the manufacturer to provide justification as to why they do not need to comply with the code.


----------



## ICE (Jul 9, 2019)

tmurray said:


> typically, where manufacturer's instructions and code differs, the code governs. I would say the onus is on the manufacturer to provide justification as to why they do not need to comply with the code.


You can put the anus anywhere you want but good luck with the manufacturer.


----------



## classicT (Jul 9, 2019)

ICE said:


> You can put the anus anywhere you want but good luck with the manufacturer.


Lets all agree that we shouldn't be placing "anuses" anywhere..... 

Joking aside, the most restrictive requirement shall apply. Exemption would be where a specific listing permits a less restrictive application. This would understandably be justified by in-depth testing and analysis.


----------



## Mark K (Jul 10, 2019)

Use the output voltage from the optimizer.  The device is designed to produce the same output voltage irrespective of the load.


----------



## jar546 (Jul 10, 2019)

Rick18071 said:


> No different than a simple listed light fixture that has #16 wires in it.



Actually no, not the same.  NEC Article 402 does cover fixture wire sizes so, although a fixture has a listing with an NRTL approved agency (or should), the actual fixture wire sizes are covered by the prescriptive code.


----------



## jar546 (Jul 10, 2019)

Nearly-Complete said:


> SolarEdge tells their designers to design a system based on the maximum power because their optimizers keep everything at the right voltage for the system.
> https://www.solaredge.com/us/guide-designing-with-solaredge
> 
> Is this supported by code? CEC 690.7 (a) states that the maximum voltage shall be calculated as the sum of the open-circuit voltage of the series-connected PV modules corrected for the lowest expected ambient temperature, and this voltage shall be used to determine the voltage rating of equipment.



Your question is confusing because the code requirement has to do with voltage and you are referencing 'power' in your comment about the manufacturer's design guidelines.  I believe the real issue with the wires and system are designed or rated for the correct voltage, ie 600v, 1000v etc as stated in 690.7.  Maybe I am confused by your concern.  In the past I always contact the manufacturer to ask technical questions and they are always helpful and knowledgeable.


----------



## Nearly-Complete (Jul 10, 2019)

jar546 said:


> Your question is confusing because the code requirement has to do with voltage and you are referencing 'power' in your comment about the manufacturer's design guidelines.  I believe the real issue with the wires and system are designed or rated for the correct voltage, ie 600v, 1000v etc as stated in 690.7.  Maybe I am confused by your concern.  In the past I always contact the manufacturer to ask technical questions and they are always helpful and knowledgeable.



Now you know my confusion. In this portion of the circuit the code says to use equipment listed for the voltage output of the string and says to calculate it by summing the open circuit voltages of the series panels. 

I check that and the voltage is exceeded. 593 Volts into an inverter with max input of 480 Volts.

I ask the manufacturer about it and they say not to worry about the voltage because the optimizers maintain the voltage at 400 Volts where it needs to be for the inverter’s sweet spot and the max string length is based on total power output of the string, not voltage.

This answer would be fine except for two issues: 1) Is this explanation supported by code and/or covered by their listing? and 

2) what happens if an optimized fails? If optimizers never fail, or if when they fail there is no voltage, then it should be a safe setup. If they apply open circuit voltage there will be a problem.

I had to give them a response so I decided that the voltage limitation is not applicable because these panels are not simply wired in series. It is a dynamic system with feedback loops, and this complicated system is not covered by this paragraph of code as long as the equipment is listed for the specified use.

Let me know if I was wrong.


----------



## jar546 (Jul 10, 2019)

I understand your situation a little better now.  I think the bottom line is that if they have a maximum input voltage labeled and listed as 480v then you cannot exceed that input voltage.  They will need a smaller array to handle it or add another inverter/optimizer


----------

