48V Off Grid Setup

mickeymichael

So, I am new to solar in general which will likely be obvious from the diagram I've included. I have been designing a 48V system to run (at the moment) just a pond pump and I have a few questions. Here are core components:

1. 3 X Hyperion 400w Bifacial Panels wired in series

2. Victron 150/35 MPPT Charge Controller

3. EG4 V2 LiFePO4 48V 100ah Battery

4. Victron Phoenix V.E. Direct 48/500 Pure Sine Wave Inverter

For anything not mentioned in the core components, please refer to the diagram which I am hoping is not too sloppy. I drew it in the way that made sense to my brain. Assume that the wire runs are as short as possible and wire gauges are more than sufficient. Here are the questions I currently have:

1. Since it is just a single string array currently, can the surge arrestor just go directly to the positive/negative/ground busbars?

2. The diagram for the Midnite Solar Ground Fault Protection Device was more confusing than helpful so if you have any advice about including a GFPD in my system, including other brands, I would appreciate it.

3. Is it considered "best practice" to bond the neutral to the chassis in my inverter to create a "true neutral" which is listed in the manual as optional depending on local regulations?

4. Should the inverter be wired directly to the battery or to the positive busbar?

5. The portable GFCI plug states that it is rated for 15 amps. Does that mean it will provide ground current protection as well as overcurrent protection up to 15 amps?

6. I am not looking for suggestions about getting rid of the AC pump and inverter and getting a DC pump. Please keep advice in the realm of the questions I have outlined. Thank you in advance.

Graham Parkinson

Re:

1) Surge protectors protect only the circuit they are in, usually there is a protector between the panels and the MPPT to protect the MPPT circuit from lightning or induced currents coming in from the big outdoor antenna produced by the PV panels and their wiring.

If you were on grid you might also want a surge protector on the battery bus side to protect against any surges getting into that circuit from the grid via chargers etc. but off grid the battery itself does a pretty good job of mopping up surges.

2) I don't know anything about the Midnite ground fault device, but I think that they have excellent support you could reach out to.

3) For a residence, the ground-neutral connection is made at the electrical entrance near the panel or in the panel.  In that case it would not be in the inverter.  For off grid it would be in the inverter panel.

4) Generally speaking, most circuits should have breakers or disconnects designed to protect the wire size in each part of the circuit to limit short circuit currents to the wire's carrying capacity so that wires don't melt and start fires.  This usually means that you have a big high current breaker between the batteries and the bus bar then connect loads to the bus bar with smaller breakers specified by each load's wiring size.  Your inverter is a big load, but you usually also want to have a suitable breaker on the inverter to allow isolating it from the battery (aka as a disconnect for testing, setup etc).  Breakers are more convenient than fuses but must be DC rated and installed properly as DC breakers are polarized.  Switching large DC currents under load is a real no-no since DC arcs inside switches and breakers don't self extinguish unlike AC arcs.

5) Yes but the rating only means that it is safe to carry 15 amps.  The ground protection is based on difference in current between neutral return and earth.   If this is over the threshold (around 5mAmps) it trips.