Conductor insulation type for routing through a building

[isurf]

Hey everyone. I am designing a PV system using a SolarEdge 17.3kus 120/208V-3Ph grid tied inverter with P505 optimizers. I am using USE-2 to route from the panels to the inverter. I will need to route conduit through the building to get to the inverter. My understanding is USE-2 cannot be routed indoors (even if in a raceway).

My question is can I use 600V THWN copper given the max input voltage on the inverter is 600VDC? I believe the optimizers have a maximum allowable voltage of 1000VDC. The voltage for the inverter is given as DC+ to DC- so I am assuming if this was measured between DC+ and ground it would be 300V. Thank you for any input!

 

[LarryFine]

My understanding is USE-2 cannot be routed indoors (even if in a raceway).

It can if it carries a dual rating such as RHW.

 

[don_resqcapt19]

Hey everyone. I am designing a PV system using a SolarEdge 17.3kus 120/208V-3Ph grid tied inverter with P505 optimizers. I am using USE-2 to route from the panels to the inverter. I will need to route conduit through the building to get to the inverter. My understanding is USE-2 cannot be routed indoors (even if in a raceway).

My question is can I use 600V THWN copper given the max input voltage on the inverter is 600VDC? I believe the optimizers have a maximum allowable voltage of 1000VDC. The voltage for the inverter is given as DC+ to DC- so I am assuming if this was measured between DC+ and ground it would be 300V. Thank you for any input!

Yes because that insulation is suitable for a 600 volt ac system. The peak voltage on a 600 volt ac system is ~850 volts.

 

[jaggedben]

Yes because that insulation is suitable for a 600 volt ac system. The peak voltage on a 600 volt ac system is ~850 volts.

I think not. Read his post more carefully.

...

My question is can I use 600V THWN copper given the max input voltage on the inverter is 600VDC? I believe the optimizers have a maximum allowable voltage of 1000VDC. ....

The voltage for the inverter is given as DC+ to DC- so I am assuming if this was measured between DC+ and ground it would be 300V. Thank you for any input!

Voltage to ground in the NEC is defined to include the highest voltage between two conductors in an ungrounded system.

 

[don_resqcapt19]

I think not. Read his post more carefully.




Voltage to ground in the NEC is defined to include the highest voltage between two conductors in an ungrounded system.

He had two statements ...my comment clearly applies to the part that I put in bold when I responded, and that is exactly why I put what I was responding to in bold.

 

[ggunn]

Hey everyone. I am designing a PV system using a SolarEdge 17.3kus 120/208V-3Ph grid tied inverter with P505 optimizers. I am using USE-2 to route from the panels to the inverter. I will need to route conduit through the building to get to the inverter. My understanding is USE-2 cannot be routed indoors (even if in a raceway).

My question is can I use 600V THWN copper given the max input voltage on the inverter is 600VDC? I believe the optimizers have a maximum allowable voltage of 1000VDC. The voltage for the inverter is given as DC+ to DC- so I am assuming if this was measured between DC+ and ground it would be 300V. Thank you for any input!

No, you have to use 1000V (at least) PV wire on the DC side with SolarEdge inverters.

 

[Carultch]

No, you have to use 1000V (at least) PV wire on the DC side with SolarEdge inverters.

Can you substantiate this?

It is only the 3-phase inverters built for the 480V grids or rest-of-world grids, that even involve 1000V circuits. Anything single phase or for the 208V grids, is limited to 600V by the inverter, and the optimizers won't independently produce >600V on their own, even if the "maximum output voltage" adds up to more than 600V.

 

[ggunn]

Can you substantiate this?

It is only the 3-phase inverters built for the 480V grids or rest-of-world grids, that even involve 1000V circuits. Anything single phase or for the 208V grids, is limited to 600V by the inverter, and the optimizers won't independently produce >600V on their own, even if the "maximum output voltage" adds up to more than 600V.

I apologize if I mis (or under) read the OP; I thought he was talking about a 480/277VAC inverter. If the DC voltage between any two conductors is greater than 600V then 1000V wiring must be used.

 

[isurf]

It can if it carries a dual rating such as RHW.

Thank you! Do you know if it is typical for USE-2 to carry a dual rating with RHW or is it something that would need to be specified?

 

[isurf]

Voltage to ground in the NEC is defined to include the highest voltage between two conductors in an ungrounded system.

Ah so it would be 600V then.

 

[isurf]

Yes because that insulation is suitable for a 600 volt ac system. The peak voltage on a 600 volt ac system is ~850 volts.

So it doesn't matter if it's 600VDC or 600VAC?

 

[isurf]

I apologize if I mis (or under) read the OP; I thought he was talking about a 480/277VAC inverter. If the DC voltage between any two conductors is greater than 600V then 1000V wiring must be used.

This is the part that's confusing me. The inverter has a max input of 600VDC so I am assuming it will communicate that to the power optimizers to not exceed that voltage, but the optimizers themselves are rated for 1000V. I don't think the inverter will let them go that high though.

I have worked on some projects with 480/277 Solaredge inverters and spec'd 600/1kV USE-2 cable from the optimizers to the inverter (all on the roof).

 

[isurf]

Can you substantiate this?

It is only the 3-phase inverters built for the 480V grids or rest-of-world grids, that even involve 1000V circuits. Anything single phase or for the 208V grids, is limited to 600V by the inverter, and the optimizers won't independently produce >600V on their own, even if the "maximum output voltage" adds up to more than 600V.

Thank you! This was exactly my thought but I was being thrown off on the optimizers being rated for 1kV. I have done some 480V projects where I spec'd 600/1kV USE-2 from the optimizers to the inverter (all on the roof).

 

[LarryFine]

Thank you! Do you know if it is typical for USE-2 to carry a dual rating with RHW or is it something that would need to be specified?

Typical, but not always.

 

[ggunn]

So it doesn't matter if it's 600VDC or 600VAC?

No.

 

[ggunn]

Thank you! This was exactly my thought but I was being thrown off on the optimizers being rated for 1kV. I have done some 480V projects where I spec'd 600/1kV USE-2 from the optimizers to the inverter (all on the roof).

That's because the same optimizers are used for 208/120VAC inverters and 480/277VAC inverters. They have to be rated for the higher voltage inverters.

 

[isurf]

That's because the same optimizers are used for 208/120VAC inverters and 480/277VAC inverters. They have to be rated for the higher voltage inverters.

Thank you for confirming this!

 

[ggunn]

Thank you for confirming this!

Don't take my word for it; pull up a data sheet for, say, the SolarEdge P1101 optimizer. In the chart at the bottom of the page you will find stringing information for 208/120V and 480/277V inverters. The rules are different for the two types of inverters.

Incidentally, SE makes several different optimizers with different input specs; make sure you use one that is compatible with the modules you will be using.

 

[Carultch]

So it doesn't matter if it's 600VDC or 600VAC?

Product ratings are meant to work with nominal voltages, unless otherwise specified. You generally don't need to think about the fact that AC peak voltages are 41% higher than the nominal voltage, when determining compatibility, or standard tolerances of grid voltages that are slightly above nominal. Wire, connector, and distribution equipment voltage ratings are compatible for any circuit with a nominal voltage not exceeding the product rating.

Thank you! This was exactly my thought but I was being thrown off on the optimizers being rated for 1kV. I have done some 480V projects where I spec'd 600/1kV USE-2 from the optimizers to the inverter (all on the roof).

The optimizers are 1kV rated, because they are built to be part of 1kV strings when used in 480V applications. They won't produce 1kV on their own, without being part of a system that enables them to do so. The inverter determines the typical operating voltage and maximum operating voltage. If part of a 600V and less system, the maximum they will produce is their share of that system's voltage, in proportion to the available power at each one. Optimizers work by solving an algebra problem, so that current is the same in each one, voltage adds up to the requisite total, and each voltage is proportional to available power.

Do you have a datasheet that shows the 1kV USE-2 you had in mind? I'm skeptical USE-2 as the primary designation has a 1kV rating. It's very common that USE-2 also carries an RHW-2 rating, as a single conductor, enabling its use inside a building.

 

[isurf]

Product ratings are meant to work with nominal voltages, unless otherwise specified. You generally don't need to think about the fact that AC peak voltages are 41% higher than the nominal voltage, when determining compatibility, or standard tolerances of grid voltages that are slightly above nominal. Wire, connector, and distribution equipment voltage ratings are compatible for any circuit with a nominal voltage not exceeding the product rating.



The optimizers are 1kV rated, because they are built to be part of 1kV strings when used in 480V applications. They won't produce 1kV on their own, without being part of a system that enables them to do so. The inverter determines the typical operating voltage and maximum operating voltage. If part of a 600V and less system, the maximum they will produce is their share of that system's voltage, in proportion to the available power at each one. Optimizers work by solving an algebra problem, so that current is the same in each one, voltage adds up to the requisite total, and each voltage is proportional to available power.

Do you have a datasheet that shows the 1kV USE-2 you had in mind? I'm skeptical USE-2 as the primary designation has a 1kV rating. It's very common that USE-2 also carries an RHW-2 rating, as a single conductor, enabling its use inside a building.

Yes, I was referencing this sheet for the 600/1kV USE-2 https://www.servicewire.com/Products/USE-CT.htm A Solaredge rep is recommending to use this type of cable for the 480V project.