So what does a typical solar installation looking like if we have the following:

1. Grid
2. Solar panels
3. Inverter
4. Load (DB)

Where should there be isolators, fuses, etc?

 

 

OK, I feel it is important to point out that there is a difference between an isolator and a current protection device, although they are sometimes combined.

An isolator's job is to be a switch. It removes the power from that part of the installation. An isolator will not trip if you exceed ratings, unless it is designed to be a combined isolator/overcurrent device. You get RCDs (earth leakage) devices that have both overcurrent and earth leakage in the same device, and that switches both the live and neutral (it also acts as an isolator) which saves you the space of an additional breaker, for example.

Wherever there is a run of cable, you need overcurrent protection to protect that cable. Since there is a cable running to the input of the inverter, you need overcurrent protection on this. In my case I have a combination RCD/isolator/overcurrent device on this input side in the form of a 300mA RCBO.

On the output of the inverter you must have overcurrent protection, again to protect the cables. If the output also feeds (non-dedicated) sockets, you must also have an RCD.

My recipe on the DC side is 1) Mersen disconnects between the battery and the DC busbars, 2) another fuse between the busbar and the inverter, 3) DC-rated breakers between the DC busbars and the MPPTs, 4) DIN-mount fuses between the MPPT and the PV arrays, which also serves as another disconnection point.

If you connect the PV side to the top of the fuse-holders, you will see that you cannot actually touch the PV side when it disconnects. I have however been told that these fuse holders are not themselves rated as disconnects, especially at higher voltages.

Hi Antony,

if I remember correctly you have purchased a ES series Goodwe inverter. I have the same and found the wiring diagram in the manual very accurate and helpful. The only thing it does not show is the isolators and fuses on the DC side (Panel array and Batteries). As Plonkster advised you need both. For the panel array I have used Noark Ex9BP-N 10A  (isolator and fuse combined). Attached is my wiring diagram (not yet approved by the engineer)

1 hour ago, plonkster said:

current protection device

How do you rate your SP's on the DC side? Is it for each strings voltage total sum or Inverters MPPT max voltage rating or expected/assumed max voltage induction from spikes ?

On the AC side I can only assume a rating of say 380v and whatever induced voltage you would receive from Eskom or a lightning strike?

I am only asking these questions as the "wizard" that installed my solar system never installed or mentioned anything of sort and I want to implement these necessary changes.

4 minutes ago, flamegrilled said:

How do you rate your SP's on the DC side?

I rated them for the battery voltage, because they sit on the battery side of the MPPT, that is the voltage they work at. Otherwise I'd assume you rate them for the actual Voc of the PV panels if they live on the other side.

7 minutes ago, flamegrilled said:

Eskom or a lightning strike?

There is a second rating on most breakers, a peak withstand current/voltage, which is usually in the thousands and is meant for surges and stuff. No need to rate the breaker's normal operating parameters for abnormal conditions.

I would prefer that an actual electrician crit my statements on this thread though :-)

You guys are just awesome.

 

I guess then there is no standard DB board/cabinet with glands and with all the necessary breakers, etc. already installed... just bring in your cables from the PV, Inverter, Grid, Load and Boom, well not boom, but you get what I'm, saying.

11 minutes ago, Antony said:

no standard DB board/cabinet with glands and with all the necessary breakers

I think that's where sparkies make half their money. Knowing what you can and cannot do and how to put it together :-)