Solar edge inverter require full size neutral

hhsting

Senior Member
I have install which uses Solaredge inverter SE43.2KUS 208V three phase.

From inverter AC side to AC panelboard wire size used is (3)#1/0 + (1)#6 AWG NU + (1)#6GND

From AC panelboard to the AC fused disco the wire size is

(3)#400kcmil +(1)#2/0 AWG NU + (1)#2/0 AWG Gnd

The neutral provided in both cases is same size as EGC.


The AC fused disco is taped off building main service supply side and the same cable that is tapped off feeds the building main service disco which is used for storage.

Questions:

1. Does Solaredge inverter require full size neutral?

2. How does one size neutral for solar edge inverter?

3. Would it be acceptable to provide just neutral for instrumentation, controls ? Would not Solar feeds the building loads would that not create huge unbalanced load? Anyone know or have any experience
 

jaggedben

Senior Member
Questions:

1. Does Solaredge inverter require full size neutral?
Ask them.

2. How does one size neutral for solar edge inverter?




3. Would it be acceptable to provide just neutral for instrumentation, controls ?
That depends on whether it satisfies 705.95(B).
Would not Solar feeds the building loads would that not create huge unbalanced load?
No. That is not how interactive solar inverters typically work. The system transformer balances current as it normally does.
 

hhsting

Senior Member
Ask them.



That depends on whether it satisfies 705.95(B).


No. That is not how interactive solar inverters typically work. The system transformer balances current as it normally does.

Ok thanks

Last question response: What system transformer in inverter? It’s all 208/120V three phase. I don’t follow where would system transformer be?

First question response: I looked in their website it says requires neutral was wondering if anyone here came across any document for sizing neutral or they need full size neutral??

Second question response: NEC 2014 section 705.95(B) is confusing not sure if it satisfies or not. If conductor is coming from inverter to AC panel and from AC panel to supply side connection the. how can that conductor be used solely for instrumentation, voltage detection or phase detection?
 

jaggedben

Senior Member
Ok thanks

Last question response: What system transformer in inverter? It’s all 208/120V three phase. I don’t follow where would system transformer be?
The system transformer is either the utility transformer or the transformer in a separately derived systems that the inverters are connected to.

First question response: I looked in their website it says requires neutral was wondering if anyone here came across any document for sizing neutral or they need full size neutral??
Ask SolarEdge directly about " instrumentation, voltage detection or phase detection", or 705.95(B). You cannot deduce answers from documentts that don't address the question. Lacking an answer from them you''d need a full size neutral.

Second question response: NEC 2014 section 705.95(B) is confusing not sure if it satisfies or not. If conductor is coming from inverter to AC panel and from AC panel to supply side connection the. how can that conductor be used solely for instrumentation, voltage detection or phase detection?
Many solar inverters use the neutral to determine what type of system they are connected to in order to stay in the correct voltage range. For example a single phase inverter can look at the phase angle of the hots-to-neutral to determine if the nominal system voltage is supposed to be 240V or 208V. This affects the voltage at which the inverter will shut off for having too high or too low a voltage. This does not mean that the inverter is designed to output any current on the neutral.
 

wwhitney

Senior Member
Location
Berkeley, CA
Occupation
Retired
FWIW, the data sheets for both SE43.2kUS and SE14.4kUS list acceptable grid connections as either 4-wire wye or 3-wire delta. So the neutral connection is optional. The only reconfiguration shown in the installation manuals is moving a fuse (not exactly clear on what this about).

Cheers, Wayne
 

hhsting

Senior Member
FWIW, the data sheets for both SE43.2kUS and SE14.4kUS list acceptable grid connections as either 4-wire wye or 3-wire delta. So the neutral connection is optional. The only reconfiguration shown in the installation manuals is moving a fuse (not exactly clear on what this about).

Cheers, Wayne
That only shows neural is not for instrumentation voltage detection. Wye grid produces neutral but delta grid does not. If neutral was for instrumentation or voltage detection it would be required delta grid

It only shows on wye grid neutral is required Not neutral is optional.
 

hhsting

Senior Member
The system transformer is either the utility transformer or the transformer in a separately derived systems that the inverters are connected to.



Ask SolarEdge directly about " instrumentation, voltage detection or phase detection", or 705.95(B). You cannot deduce answers from documentts that don't address the question. Lacking an answer from them you''d need a full size neutral.



Many solar inverters use the neutral to determine what type of system they are connected to in order to stay in the correct voltage range. For example a single phase inverter can look at the phase angle of the hots-to-neutral to determine if the nominal system voltage is supposed to be 240V or 208V. This affects the voltage at which the inverter will shut off for having too high or too low a voltage. This does not mean that the inverter is designed to output any current on the neutral.
The first question: I think your assume all power goes to grid. The solar system is tied to grid and building loads. Assume utility power is out then solar elders the building loads Not the grid at which point you are going to have unbalanced loads since power produced from solar goes back to solar Not the grid. What do you think?

Last question: would email from sales rep Solaredge saying for models used neutral is used for solely instrumentation, voltage detection and 795.95(B) can be used to size neutral or it has to be in Solaredge documentation on their website?
 

hhsting

Senior Member
The first question: I think your assume all power goes to grid. The solar system is tied to grid and building loads. Assume utility power is out or when utility power is on then solar will feed some or all power to the building loads Not the grid unless power produce is greater than meter usage at which point you are going to have unbalanced loads since power produced from solar goes back to solar Not the grid. What do you think?

Last question: would email from sales rep Solaredge saying for models used neutral is used for solely instrumentation, voltage detection and 795.95(B) can be used to size neutral or it has to be in Solaredge documentation on their website?
Questions edited as follow: Assume utility power is out or when utility power is on then solar will feed some or all power to the building loads Not the grid unless power produce is greater than meter usage

Please see revised above
 

jaggedben

Senior Member
The first question: I think your assume all power goes to grid. The solar system is tied to grid and building loads. Assume utility power is out then solar elders the building loads Not the grid at which point you are going to have unbalanced loads since power produced from solar goes back to solar Not the grid. What do you think?
I did not make any assumptions about where the power is going. The utility transformer balances the neutral current even when the solar only outputs on the line conductors. Just the same as the transformer balances neutral current when the source is the utility primary. It does not matter what the loads are doing, they essentially can't tell the difference.

Last question: would email from sales rep Solaredge saying for models used neutral is used for solely instrumentation, voltage detection and 795.95(B) can be used to size neutral or it has to be in Solaredge documentation on their website?
Yes I think an e-mail qualifies.
 

jaggedben

Senior Member
That only shows neural is not for instrumentation voltage detection. Wye grid produces neutral but delta grid does not. If neutral was for instrumentation or voltage detection it would be required delta grid
...
What you're saying here only applies to instrumentation, not voltage detection. I think you could put the question to any inverter manufacturer "is the neutral used as a current carrying conductor for the inverter output?" If the answer is no then it can be sized smaller.
 

Carultch

Senior Member
Location
Massachusetts
Last question: would email from sales rep Solaredge saying for models used neutral is used for solely instrumentation, voltage detection and 795.95(B) can be used to size neutral or it has to be in Solaredge documentation on their website?
They have a document addressing this question, that spells out model numbers for which it applies. Ask them to email you that document. For the customer's convenience, it is best if it is on the manufacturer's website, but it doesn't necessarily need to be on their website for you to take credit for it. In any case, you should get it in writing so you have more than just hearsay, if someone questions you on it.
 

hhsting

Senior Member
They have a document addressing this question, that spells out model numbers for which it applies. Ask them to email you that document. For the customer's convenience, it is best if it is on the manufacturer's website, but it doesn't necessarily need to be on their website for you to take credit for it. In any case, you should get it in writing so you have more than just hearsay, if someone questions you on it.
They do have document? Can please you send that link?
 

wwhitney

Senior Member
Location
Berkeley, CA
Occupation
Retired
FWIW, the data sheets for both SE43.2kUS and SE14.4kUS list acceptable grid connections as either 4-wire wye or 3-wire delta. So the neutral connection is optional.
I should clarify that the neutral connection is shown as optional on a 4-wire wye grid.

Cheers, Wayne
 

wwhitney

Senior Member
Location
Berkeley, CA
Occupation
Retired

hhsting

Senior Member
Doesn't the part about "or 3-wire Delta" mean you can hook it up to a 208Y/120V without a neutral, and it will still generate power?

Page 17 of this installation manual shows the neutral as optional for 280Y/120V:


There's a similar diagram in the installation manual of the SE42.2KUS.

Cheers, Wayne
Neutral is required for 480/277V but optional for 208/120V four wire according to that diagram? I have four wire wye 208/120V three phase wye Not delta from utility. So neutral would not be required for that? I don’t get it both are wye. Why optional for one and not the other?
 

Carultch

Senior Member
Location
Massachusetts
Neutral is required for 480/277V but optional for 208/120V four wire according to that diagram? I have four wire wye 208/120V three phase wye Not delta from utility. So neutral would not be required for that? I don’t get it both are wye. Why optional for one and not the other?
It has to do with whether the inverter puts its power across each combination of two phases, or across each phase and the neutral. In order to use a similar power electronics design for both inverters it is of interest to plan on generating waveforms that are as close as possible in their voltage amplitude. It therefore will use the higher voltage phase-to-phase option for the 120/280V inverter, and the lower voltage phase-to-neutral option for the 277/480V inverter. The 120/208V inverter is a delta source so that the inverter can supply power to 208V phase-to-phase connections. The 277/480V inverter is a WYE source, so that by contrast, it supplies power to the 277V phase-to-neutral connections.
 

hhsting

Senior Member
It has to do with whether the inverter puts its power across each combination of two phases, or across each phase and the neutral. In order to use a similar power electronics design for both inverters it is of interest to plan on generating waveforms that are as close as possible in their voltage amplitude. It therefore will use the higher voltage phase-to-phase option for the 120/280V inverter, and the lower voltage phase-to-neutral option for the 277/480V inverter. The 120/208V inverter is a delta source so that the inverter can supply power to 208V phase-to-phase connections. The 277/480V inverter is a WYE source, so that by contrast, it supplies power to the 277V phase-to-neutral connections.
So wait install manual says for 208V three phase inverter can be wye or delta and one can interchange page 44 and 17. So if I set for 208V wye configuration Regardless no neutral is require? Confused?
 
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