Inverter swap

[SAP]

I'm swapping out 4 2800 pv power with 4 sunny boy 3.0-us inverters, existing inverters did not utilize a neutral , my new inverters manual says I don't need a neatral if my grid is 208 delta connection I'm not to good with transformers. I know I don't have a high leg. I believe we have a 208 wye. What is 208 delta connection thank you

 

[Carultch]

I'm swapping out 4 2800 pv power with 4 sunny boy 3.0-us inverters, existing inverters did not utilize a neutral , my new inverters manual says I don't need a neatral if my grid is 208 delta connection I'm not to good with transformers. I know I don't have a high leg. I believe we have a 208 wye. What is 208 delta connection thank you

A 208 delta connection means that you wire your circuits across adjacent phases, instead of from phase to neutral.

The first inverter connects on a 2-pole breaker to A & B.
The second inverter connects on a 2-pole breaker to B & C.
The third inverter connects on a 2-pole breaker to C & A.

To calculate the combined current of many inverters wired in such a manner, add up all connected to AB, then BC, then CA.
Ia = sqrt(Iab^2 + Ica^2 + Iab*Ica) + Ian
Ib = sqrt(Iab^2 + Ibc^2 + Iab*Ibc) + Ibn
Ic = sqrt(Ibc^2 + Ica^2 + Ibc*Ica) + Icn

Iab = current on circuits connected between phases A & B
Ian = current on circuits connected between phase A & the neutral

Size all aggregate equipment for the maximum of the above.

 

[pv_n00b]

I looked through an old PV Powered 2800 install manual and that inverter requires a neutral. So you have a neutral or whoever installed did it wrong. Assuming that you already checked this and there was no neutral connected to the inverters check the service entrance. It would be really unusual to have a 208V delta 3 wire service, 208/120 4 wire services are the usual.

In addition to the neutral issue you will also need to deal with changing the PV array from grounded to ungrounded to use the SMA inverters unless you have a stash of old transformer based 3000s.

 

[GoldDigger]

They are not really telling you that you need a 208 delta, just that you make a delta connection to it.
The only difference visible to the outside of a black box between a 208 delta and 208Y/120 wye is the absence of a neutral terminal on the former.

Sent from my XT1585 using Tapatalk

 

[ggunn]

In addition to the neutral issue you will also need to deal with changing the PV array from grounded to ungrounded to use the SMA inverters unless you have a stash of old transformer based 3000s.

What's to change? Normally in a grounded PV array the connection to ground is in the inverter and the array itself is ungrounded once it is disconnected from the inverter.

 

[SAP]

A 208 delta connection means that you wire your circuits across adjacent phases, instead of from phase to neutral.

The first inverter connects on a 2-pole breaker to A & B.
The second inverter connects on a 2-pole breaker to B & C.
The third inverter connects on a 2-pole breaker to C & A.

To calculate the combined current of many inverters wired in such a manner, add up all connected to AB, then BC, then CA.
Ia = sqrt(Iab^2 + Ica^2 + Iab*Ica) + Ian
Ib = sqrt(Iab^2 + Ibc^2 + Iab*Ibc) + Ibn
Ic = sqrt(Ibc^2 + Ica^2 + Ibc*Ica) + Icn

Iab = current on circuits connected between phases A & B
Ian = current on circuits connected between phase A & the neutral

Size all aggregate equipment for the maximum of the above.

So your saying all I had to do was hook it up with out a neutral that would have been so much easier. I ran a neutral to both subpanel, I guess I just panicked because it said compatible grid configuration 208 delta L1 L2 no neutral. My grid was 208 wye 4 wire

 

[summitville]

deleted

 

[jaggedben]

For what it's worth, I've been quoting a similar project and have decided to go with a single Fronius that's approved for a 208wye. Sounds like you're too far along to take advice on inverter purchases, but I do think a single three phase inverter is a simpler, cheaper, and safer way to go, when the array specs allow it. And you don't have to calculate those unbalanced currents.

 

[GoldDigger]

A not immediately obvious difference is that for three separate single phase inverters you will need to divide the PV into three separate sub arrays, while a three phase inverter will take a single set of PV inputs for all phases, possibly allowing for better balance.
But with three inverters a failure will not bring the entire production down.

Sent from my XT1585 using Tapatalk

 

[ggunn]

A not immediately obvious difference is that for three separate single phase inverters you will need to divide the PV into three separate sub arrays, while a three phase inverter will take a single set of PV inputs for all phases, possibly allowing for better balance.
But with three inverters a failure will not bring the entire production down.

And the utility may or may not be OK with that.

 

[jaggedben]

And the utility may or may not be OK with that.

Although if the original interconnection was for single phase, they ought to be okay with a 'repair' that doesn't change that. Changing out a previously existing 3-phase inverter for single phase inverters might be different.

 

[pv_n00b]

What's to change? Normally in a grounded PV array the connection to ground is in the inverter and the array itself is ungrounded once it is disconnected from the inverter.

No white grounded conductor.
USE-2 not allowed in ungrounded PV arrays until 2017 NEC.
If there are DC disconnects or combiners they will need to be changed out for ungrounded units.

It’s not a drop in replacement to go from grounded to ungrounded.

 

[ggunn]

No white grounded conductor.
USE-2 not allowed in ungrounded PV arrays until 2017 NEC.
If there are DC disconnects or combiners they will need to be changed out for ungrounded units.

It’s not a drop in replacement to go from grounded to ungrounded.

I see, not the array itself but the BOS that accompanies it. FWIW, most of the grounded arrays I worked on didn't use a white conductor but just white tape to mark the negative.

I agree with whomever said that a three phase inverter as a replacement is a better idea than using three single phase inverters.