Piet_de _Pad
The sun: a free natural large nuclear reactor
Dear readers,
I'm planning to install a SPF3000 inverter as a backup in and existing house. I would like to have feedback from people who have experience working with the SPF3000 or a similar inverter and who understand electrical installations for housings. The location is Querétaro, Mexico and the grid considered single phase grid. I have seen many videos of people installing this inverter and many have problems with the concept of Neutral-Earth bonding. Others have problems with RDS leak currents. I have investigated the architecture of the SPF3000 to better understand how this inverter is interacting with the wiring of the house.
My first question is: who knows something about the internal architecture of this SPF3000 inverter and is my suggested architecture, see fig1 top, correct.
My second question can some confirm the table see fig1 bottom what is connected with what during backup or utility mode
I watched various videos where some measured the connect state of the line neutral and Ground of the ACin and ACout puts this is what I found see table fig1.
Lp Np Gp stand for LNG protection and represents the ACout of the inverter. Lg Ng Gg are the LNG grid cables of the ACin of the inverter. The relays are single contact, normally on SPST NO types. You can see them on the PCB in fig3
The table of fig1 below I copied from a video in which someone tested the connect state of the various wires. When the Grid is available, the relays are in the utility mode. When no grid is available, the relays are in backup mode. The inverter is switched on when no grid is detected and off then the grid is available.
Fig1 suggested architecture Fig2 schematic of the house with backup
My question is: Is the design see fig2 correct and is a Np-Gp relay really needed.
Figure2, a schematic representation of the house. The original electricity groups in the house I have split in two groups. Protected and non protected groups. There is a Ng-Gg bonding available at the entrance of the house. The protected groups are connected on the ACout and the Grid with it unprotected groups are connected at the ACin.
The problem with this SPF3000 inverter is that it assume to have an island group at the ACout (Lp Np Gp) when in backup mode. The point here is that there is never and island, the neutrals and the grounds of both ACin and ACout are interconnected with each other and rewiring the house is no option.
In side the SPF3000 see the architecture schematic, exist a bonding between Ng-Gg this makes that in utility mode two N-G bonding exist and that is not allowed or suggested. To my knowledge that bond can be removed by removing two screw in side of the SPF3000
My question is : Does GroWatt permit to have these screws removed?
Assuming the internal N-G bonding is removed. When the inverter goes in backup mode N-G bonding at the entrance exist in the network but it has some issues. 1) is not close to the source and second, the return path of a leak/short current goes through the main interrupter I1 not a good idea. That is why I have proposed using a Np-Gp relay. I wish that was not needed, but I don't see any other solution. Any suggestions what is good practice here.
I leave it here I hope someone can give me some tips and tricks. for the ones who are looking for a similar solution I hope this info helps.
Thanks Pied de pad
Fig 3 Internal section of the inverter with the two Ng-Gg bonding screws and the three relays.
I'm planning to install a SPF3000 inverter as a backup in and existing house. I would like to have feedback from people who have experience working with the SPF3000 or a similar inverter and who understand electrical installations for housings. The location is Querétaro, Mexico and the grid considered single phase grid. I have seen many videos of people installing this inverter and many have problems with the concept of Neutral-Earth bonding. Others have problems with RDS leak currents. I have investigated the architecture of the SPF3000 to better understand how this inverter is interacting with the wiring of the house.
My first question is: who knows something about the internal architecture of this SPF3000 inverter and is my suggested architecture, see fig1 top, correct.
My second question can some confirm the table see fig1 bottom what is connected with what during backup or utility mode
I watched various videos where some measured the connect state of the line neutral and Ground of the ACin and ACout puts this is what I found see table fig1.
Lp Np Gp stand for LNG protection and represents the ACout of the inverter. Lg Ng Gg are the LNG grid cables of the ACin of the inverter. The relays are single contact, normally on SPST NO types. You can see them on the PCB in fig3
The table of fig1 below I copied from a video in which someone tested the connect state of the various wires. When the Grid is available, the relays are in the utility mode. When no grid is available, the relays are in backup mode. The inverter is switched on when no grid is detected and off then the grid is available.
Fig1 suggested architecture Fig2 schematic of the house with backup
My question is: Is the design see fig2 correct and is a Np-Gp relay really needed.
Figure2, a schematic representation of the house. The original electricity groups in the house I have split in two groups. Protected and non protected groups. There is a Ng-Gg bonding available at the entrance of the house. The protected groups are connected on the ACout and the Grid with it unprotected groups are connected at the ACin.
The problem with this SPF3000 inverter is that it assume to have an island group at the ACout (Lp Np Gp) when in backup mode. The point here is that there is never and island, the neutrals and the grounds of both ACin and ACout are interconnected with each other and rewiring the house is no option.
In side the SPF3000 see the architecture schematic, exist a bonding between Ng-Gg this makes that in utility mode two N-G bonding exist and that is not allowed or suggested. To my knowledge that bond can be removed by removing two screw in side of the SPF3000
My question is : Does GroWatt permit to have these screws removed?
Assuming the internal N-G bonding is removed. When the inverter goes in backup mode N-G bonding at the entrance exist in the network but it has some issues. 1) is not close to the source and second, the return path of a leak/short current goes through the main interrupter I1 not a good idea. That is why I have proposed using a Np-Gp relay. I wish that was not needed, but I don't see any other solution. Any suggestions what is good practice here.
I leave it here I hope someone can give me some tips and tricks. for the ones who are looking for a similar solution I hope this info helps.
Thanks Pied de pad
Fig 3 Internal section of the inverter with the two Ng-Gg bonding screws and the three relays.
