Utility Interactive Photovoltiac Inverters

[marsac]

Re: NEC 705.40 and NEC 705.42





In our jurisdiction, we are encountering PV solar installations on 3-phase systems in which the PV inverter is a single phase production source.



Our position is that both of the above code references requires a single phase PV source when attached to a 3-phase system to cease exporting power when the primary source loses one or all phases. This would include the phase that the single phase PV inverter is not connected to.



We would appreciate your analysis and opinion.



Thank you,

 

[highvolts582]

Inverters

Inverters

You need to just make sure the equipment is listed and labeled for the system. Im trying to get a big solar job i know most of the sunny boy sma inverters are field convertible for different voltages. its ok to have single phase 208 volt circuits in a 3 phase system this includes solar. im not an inspector but i do install a lot of solar systems. The inverter is guaranteed to stop producing when power is lost to one of its connected phase as for the unconnected phase in that system losing power... now that is something i would like to know to.

 

[marsac]

PV Inverters and NEC 705.40

PV Inverters and NEC 705.40

Thanks for the input.
It is my understanding that to be a listed "Utility-Interactive Inverter" it shall comply with UL Std. 1741, part of which is the capability to cease exporting power upon loss of primary source. If you install the inverter per it's listing it should be a safe and legal installtion.
The the question remains, if a single phase inverter is installed in the 3 phase system, "upon loss of primry source, an electric power production source shall be automatically disconnected........, (or cease exporting power per exception). This is per NEC 705.40 (and 705.42), what is you opinion of this code section?

 

[highvolts582]

Hey info from my engineer i asked him

Hey info from my engineer i asked him

Michael,



705.42 would apply in this case. However, you don?t have to worry about how to make this happen.

This is something the inverter manufacture has provided inside the inverter.

Hope this helps.



Warmest Regards,

Brian Tannenhaus, PE

President

Description: cid:image001.png@01CB7685.D547EDE0 BD Engineering, LLC

1825 Swarthmore Ave, Unit B

Lakewood, NJ 08701-4540

 

[raider1]

Thanks for the input.
It is my understanding that to be a listed "Utility-Interactive Inverter" it shall comply with UL Std. 1741, part of which is the capability to cease exporting power upon loss of primary source. If you install the inverter per it's listing it should be a safe and legal installtion.
The the question remains, if a single phase inverter is installed in the 3 phase system, "upon loss of primry source, an electric power production source shall be automatically disconnected........, (or cease exporting power per exception). This is per NEC 705.40 (and 705.42), what is you opinion of this code section?

As I read 705.42 this section applies to 3 phase power production sources (Inverters) so 705.42 would not apply if you are using a single phase inverter.

705.40 is the general requirement for the inverter to disconnect upon loss of the primary source. If you are using a listed utility interactive inverter it will shut off supply whenever the source it is connected too is interupted.

Chris