Growatt SPF 5000 ES 2 units in Parallel- Off Grid / Wiring

[magnathea]

Hi All,
Have been running 1 Growatt SPF 5000 SE off 5400W of panels now for over 5 months. Have decided to expand my system to 2 inverters in parallel and have some questions that I can't find answers to.

New system:
2 x Growatt SPF 5000 SE both powering same loads using parallel kits, 16 x 540w panels, 12 kWh LIfepo4 battery (self built)

Solar array: 2 strings, 1 for each inverter, each string is 8 panels in series. Each inverter will have 4320w (8 x 540w) 12.9A @ 330vDc. Each string on seperate 15 amp fuse.

Battery: will be connected to both inverters (will expand battery in future) Each inverter (2) has a C class breaker between it and the battery. All cables are equal length.

No Utility connection.

240v AC Output: Each inverter is connected to a seperate breaker.

My questions that are not so clear in the user manual:

Parallel setup, Single phase
Step 1. On the AC output side
User Manual: "Ensure all breakers in Line wires of load side are open and each neutral wires of each unit are connected together"
Breakers I have are 2 pole each, break both active and neutral.

Question 1: Do I need to connect both neutrals and Actives together before the individual breakers? or just the Neutrals?

Step 4. AC input.
User Manual: "Switch on all AC breakers of Line wires in AC input. Its better to have all inverters connect to utility at the same time. If not, it will display warning 15."

Question 2: Can I start up the inverters using Solar array or Batteries as I have no AC input? If needed I can start up on AC by running some extension cables, but would prefer not to.

Thanks in advance.
Nick

 

[peteruu]

Hi man how did you resolved the issue with 2 pole breaker ....
did you need to have neutral always connected or it was ok to break it ?

 

[magnathea]

Reply I got from growatt which i followed:

1. I believe both neutral are connected before each individual breakers.

2. Yes you can start them up withouth AC in connection.

 

[gabvalentin]

Hi @magnathea ,

I need to install 2 Growatt 5000 in parallel in single phase, a similar setup to yours.

Do you have a diagram or a picture of your installation that you could share?

I really appreciate any help you can provide.

 

[magnathea]

The diagram for connection is shown in the back of the instruction leaflet. It’s quite straight forward. The connection cables come with both units, 1 set in each box and both are needed. If you don’t have the instructions you need it for the rest of the setup anyway. It’s downloadable from Growatt.

Once the 2 inverters are connected any setting changes made in the settings on one unit are automatically transferred to the other unit. The only important part is the startup of the 2 units as you have to start up one unit first change the setting to parallel, turn it off and do the same on the other, then turn them both on at the same time. They will randomly decide which one is slave and which is master on startup. They can be started on any power source, batt, PV or 240v mains.

On run my 2 units off grid (no change in settings required) just no AC input, only battery or PV. I did my initial start up on batteries.

The only unclear connection in the instructions is the AC output. I emailed Growatt for confirmation. Each inverter needs its own circuit breaker on the AC output. I used 2 pole 25amp breakers on each one, but the neutrals from each inverter must be connected before the breaker so when the either breaker is switched off the neutrals are still connected. I just put a loop wire between the neutrals on the input side of the breakers.

Hope this is clear.

 

[gabvalentin]

Thanks so much @magnathea , your instructions are very clear. I also need to connect AC input, perhaps @peteruu can help me with this. Do I need to connect the same L N and Earth wires to both inverters?

 

[magnathea]

Yes, both inverters need ac input with earth and both inputs should have seperate breakers.

There are 2 cables for each inverter for parallel setup. 1 is data communication and the other (red and black) is named current sharing but due to their small wire gauge they can not share much current. Think this might actually be for matching frequency.

I have noticed on my inverter setup that sometimes one is charging batteries and 1 is discharging batteries this could be how they current share, through the batteries. Not sure. Doesn’t make sense that they would need to share current anyway.

 

[gabvalentin]

Thanks again, one more question. From the breakers output on the AC output side, did you then join the L wires of both breakers, same for N and for Earth to end up with one L one N and one E to connect the cable with 3 wires to the house Consumer Unit?

 

[magnathea]

Yes. After the 2 output breakers (25amp) into 1 breaker (63amp) that supplies my house.