SolarEdge DC Terminal Rating

[Zyb]

Hi,

Does anyone knows what the DC Terminal rating of SolarEdge Inverter? 90° or 75° Thank you.
If I use 75° rating I can only place up to 9 conductors in a conduit, if 90° up to 20 conductors

 

[jaggedben]

...
If I use 75° rating I can only place up to 9 conductors in a conduit, if 90° up to 20 conductors

That is incorrect. Terminal ratings do not affect the derating of conductors in a conduit. If you are using 90C rated wire then your derating can be based on 90C. You must also size the wire appropriately for the terminals, and the number of conductors in the conduit has nothing to do with that.

I always assumed that Solaredge terminals had a 75 C rating and have never seen otherwise. I'm pretty doubtful they are 90C rated, just not 100% sure.

 

[ggunn]

That is incorrect. Terminal ratings do not affect the derating of conductors in a conduit. If you are using 90C rated wire then your derating can be based on 90C. You must also size the wire appropriately for the terminals, and the number of conductors in the conduit has nothing to do with that.

I always assumed that Solaredge terminals had a 75 C rating and have never seen otherwise. I'm pretty doubtful they are 90C rated, just not 100% sure.

Agreed. This is a common error, and I have encountered inspectors and plan reviewers who still don't get it.

125% of the inverter current cannot exceed the 75 degree ampacity of the conductors in continuous use for more than three hours; this ensures that the conductors do not get hot enough to damage the 75 degree terminals in continuous use conditions, i.e., when the system is running.

In a separate calculation the ampacity of the conductors must be derated for conditions of use, which are ambient temperature and conduit fill; this protects the conductor insulation from overheating, and it is based on the 90 degree column of the ampacity chart if 90 degree conductors are used.

Conductors must be chosen which satisfy both parameters but the calculations are separate. If you fold in conduit fill to the continuous use calculation, you are derating the conductors twice. Incidentally, it is the conditions of use ampacity of the conductors that must be considered in determing if they are protected by an OCPD in a fault condition, not the continuous use calculation, which is to protect the terminals under normal operation.

 

[Zyb]

Thank you @jaggedben @ggunn. This answer my question.

 

[msi99]

Are the AC terminations on a solaredge inverter also rated for 75 degree. While calculating the AC conductor size we always check for 75 and 90 degeee calculation, however, I am wondering why the conductors are not checked for 60 degrees as well.
Solaredge tech note shows that the temp is 60

 

[jaggedben]

Do you have a link to this tech note?

 

[msi99]

chrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/https://knowledge-center.solaredge.com/sites/kc/files/se-temperature-derating-note-na.pdf
- This is the manufacturer for AC terminals on SolarEdge - https://www.wago.com/us/material-specifications
Per 110.14(C) we would need to chose a conductor that passes 60 degree check as well unless we can prove that the AC terminals is 75 degree

 

[jaggedben]

The first link is not about termination ratings.
The Wago link does not have specific information stating that any terminals are rated 60C, nor does it confirm which terminals are used by Solaredge. I also don't know if a rating from a third party supplier necessarily establishes termination ratings once it's part of listed quipment.

Without further info the terminal ratings remain undetermined.

 

[pv_n00b]

Most inverter manufacturers just don't publish this information. When inverters have an AC circuit breaker you can usually get the terminal temperature for the CB.

 

[wwhitney]

Are there examples of installations with string inverters in which it would be a savings to be able to use the 90C rating of DC conductors if the termination ratings could be determined to be rated 90C?

I assume that when 690.9(A)(1) applies (OCPD not required), then 240.4(D) is moot, and a #12 Cu, say, could be utilized at 25A (75C) or 30A (90C).

Cheers, Wayne

 

[jaggedben]

Are there examples of installations with string inverters in which it would be a savings to be able to use the 90C rating of DC conductors if the termination ratings could be determined to be rated 90C?

...

I think we're more concerned here with whether we can use 75C instead of 60C for termination. For AC as well as DC.

 

[wwhitney]

Most inverter manufacturers just don't publish this information. When inverters have an AC circuit breaker you can usually get the terminal temperature for the CB.

Most inverter manufacturers don't document that their terminations are 75C rated? If so, 110.14(C) is very clear about the necessity of using the 60C termination ampacity unless 110.14(C)(1)(b) applies (>100A or >#1 AWG).

Cheers, Wayne

 

[jaggedben]

The Solaredge HD Wave manual says to use only copper conductors with minimum 75C rating. That seems to fit the language of 110.14(C)(1)(3).

 

[pv_n00b]

Most inverter manufacturers don't document that their terminations are 75C rated? If so, 110.14(C) is very clear about the necessity of using the 60C termination ampacity unless 110.14(C)(1)(b) applies (>100A or >#1 AWG).

Cheers, Wayne

I agree, but no one I know in the PV industry does this as it would require sizing a 90deg conductor like it was 60deg rated. Everyone just assumes the DC terminals are rated for 90deg and holds their nose. Luckily the DC string conductors are usually way oversized for the current anyway.
Fun fact, DC combiner manufacturers often list the terminal temperature for the combiner as 90deg but do not tell us that the rating is only for the output terminals. The input terminals into the fuses are often 75deg or 60deg rated. I've been pointing this out for a long time and get little traction. People want to do what helps them and engineers and installers assuming all the terminals are 90deg helps them.

The Solaredge HD Wave manual says to use only copper conductors with minimum 75C rating. That seems to fit the language of 110.14(C)(1)(3).

This is a bit wishy-washy, they won't say the terminals are rated for 75deg only that 75deg conductor or greater needs to be used. We can use 75deg conductor on 60deg rated terminals so the way they phrase it does not give the terminal temperature rating.

 

[ggunn]

I agree, but no one I know in the PV industry does this as it would require sizing a 90deg conductor like it was 60deg rated. Everyone just assumes the DC terminals are rated for 90deg and holds their nose.

I don't. I assume and design for 75 degree terminals.

 

[jaggedben]

...


This is a bit wishy-washy, they won't say the terminals are rated for 75deg only that 75deg conductor or greater needs to be used. We can use 75deg conductor on 60deg rated terminals so the way they phrase it does not give the terminal temperature rating.

Yeah, I hear what you're saying. But specifically given the language used in 110.14(C)(1)(3), it allows the 75C rating to be used when the equipment is listed (no dispute there) and 'identified for use with such conductors'. A minimum requirement, weirdly, seems to qualify as identifying for use with such.

 

[msi99]

Doesn't 110.14(C) state that the conductors rated at 100A or less can only use 60 degree Ampacity rating of the conductor size in 310.16? So you should size your wires for 60 degrees.
The 110.14(C)(1)(3) talks about the temperature rating and not the ampacity rating. Is there a section that states that we should be able to size the conductors for 75 and 90 degrees on 310.16

 

[jaggedben]

Doesn't 110.14(C) state that the conductors rated at 100A or less can only use 60 degree Ampacity rating of the conductor size in 310.16?

No, not across the board. It gives four options, (a)(1) thru (a)(4). Using the 60C ampacity option is (2). This option allows you to comply without verifying anything else about the equipment, but it's only one option.

...
The 110.14(C)(1)(3) talks about the temperature rating and not the ampacity rating.

Okay, true, but that means it neither requires or prohibits the use of any particular ampacity ratings from 310. Rather, it says the ampacity rating you can use depends on the terminal rating temperature, if the equipment being listed and 'identified for use' with such conductors.

The last part is where things get genuinely muddy, because you see all sorts of language in install manuals and you could debate the meaning of 'identified for use.' However if the install manual clearly states 'terminals are rated 75C and may used with 75C conductors at their 75C ampacity rating', then there would be no debate that doing so complies with 110.14(C)(1)(a)(3).

Is there a section that states that we should be able to size the conductors for 75 and 90 degrees on 310.16

Again, 110.114(C)(1)(a)(3) is the section. If the equipment instructions 'identify for use' with such conductors. *(Accidentally left out the '(a)' in previous replies.)