Solar systems

[Isetech]

As hundreds of thousands of inverters are installed, going into the billions spent in SA, we still can’t seem to find a common basic guideline for installations where everyone interprets the regs the same and the installations are done according to a standard, yes many will say the regs don’t need to be updated, it’s all there in the book, many will argue.

Like we have done with smaller installations, is create a basic setup, for example.
5 kw inverter, with a 5-kwh battery and 6 solar panels is pretty much your standard entry level system being installed. Creating a basic guideline would help improve the standard of installation.

I see there is a new one popped up, fuses for solar panels and where they should be located.

Some will say you need a DC isolator, a set of fuses and SPD in what some refer to as a DC combiner box others call it a DC control box, a DC protection box, there are many names for it.

The latest chatter is where to install the DC fuses for the solar panels, some will say, close to the inverter, others are saying in the roof as close to the panels as possible.

What I have learnt from designing and building many control systems for water and wastewater treatment plants, simple is better. The less buttons and options the safer and better the plant functions.

The same thing with the solar system, simple is better, you want a simple accessible layout which makes access to the components as easy as possible for everyone.

Isolating these systems should be a quick easily accessible action.

For example, there should be isolators built into the inverter:
A 4 pole for the input output of the AC power, you switch it off the power is off going in and coming out, with lights to indicate when the power is off, no confusion.
A multiple pole DC isolator for the solar panels, which isolates all DC power going into the inverter and prevents DC power from leaving the inverter while in the off position (Sunsynk already has one of these fitted to their small inverters)
A DC isolator for the battery.
Each battery should be fitted with fuse protection and an isolator, plug in terminals which are insulated and easy to remove from the battery,
Where the solar panel wires enter the building and connect to the inverter of DC combiner/control/fuse box, there should always be MC 4 connectors, so that no matter what happens with the box or inverter, there are no exposed live wires. Just like the panels have Mc 4 connectors, so the extended wire should also be fitted with connectors to prevent them being left live in the building. IF you look at commercially made DC boxes, you will notice most of them have MC 4 connectors under the box, which are then connected to the fuse-SPD/DC isolator- inverter.

[Isetech]

100 % word (casual) editor score rate, making it a better expereince for people to read.

It seems we are creating this complicated system which requires a manual (safe isolation Procedure) just to identify how to carry out what should be a simple one switch operation in case of an emergency.
Let’s look at why I say this, imagine there is an emergency, as per the old regs you would have a label on the DB which clearly states in bold red writing “in case of accidently….switch off the main switch” just imagine in a panic state of mind trying to find the safe isolation procedure which should be mounted next to the inverter, then trying to locate and identify which isolators to switch off. That old reg and label should be the first update. Now you need a data sheet stuck to the DB in red writing.

I stripped a solar system yesterday to do some work on the wireways and cabling, basically tidy up. As many of you are aware I have a bit of electrical experience and have installed a few solar systems, even after switching off every single isolator, mcb, fuse disconnector, plug you name it, I still checked and checked and checked again to make sure there were no live wires. After getting nailed by the silly DC combiner box error, I am very nervous working on these systems. I am used to switching off isolators and the power is off, not back feeding via other parallel circuits. Just imagine how it feels for someone who has no idea about these solar setups, not just the end user but other electricians just wanting to do some basic electrical maintenance on the property.

That why I am going to be looking at a way to make our installations a lot simpler for the end user and safer for teams to work on them.

[Isetech]

Starting with making sure the wire from the panels has MC 4 connectors up to the point where there is an isolator., for example:

If we install a 5 kw Sunsynk inverter which has MC4 plugs fitted to the inverter, with a DC isolator on the side of the inverter and surge protection built in, why complicate the system with a silly combiner box, just creating more bad connections. Some might say but you have to install an isolator next to the inverter, then you should be installing an isolator next to every socket outlet.
The reason there is an MC 4 connector below the inverter, to safely isolate the panel wires once you have shut down the load and switch off the multi pole DC isolator on the side of the inverter.

Let’s look at the 8-kw Sunsynk inverter which doesn’t come with MC4 connectors but is fitted with a multi pole DC isolator on the inverter.
Chances are they didn’t fit MC 4 connectors on the inverter was because they assume you are going to install a commercially purchased DC combiner box (containing fuses and SPD’s, not isolators), fitted with MC4 connectors at the bottom of the box for safe isolation of the wires. Much easier and safer than having to go onto the roof to unplug the MC 4 connector if you need to remove the box or any components in the box.
What are your thoughts on the SA trend of fitting multiple DC isolators in DC combiner boxes, dangerous due to the false sense of isolation caused by the parallel connections at the MPPT?

[Isetech]

It would be good to see the isolators mounted on the inverter and batteries enclosures, it is slowly becoming a reality, I see certain battery manufacturers have already started, but the SA clan seem to feel our 3 rd. world regs are far superior than more modern countries 1 set world countries. So, let’s see what direction that takes. Fortunately, customers in SA have lots more money to waste on extra nice to haves.

I believe installing a simple 4 pole AC isolator below the inverter which isolates both the AC input and output of the inverter would be a better option for creating a safer environment. If you have the budget to add an AC bypass box next to the inverter with a pile of extras, then that would be your choice. The only reason we fit the AC bypass box is to bypass the inverter in case you have to work on to or remove it. In most cases they are wired incorrectly and don’t have the correct equipment installed to bypass the grid to the essential supply.

The next time you are working on a site with solar, try bypass the grid and work on the inverter. You will notice that there is no main switch and inverter input isolator, just the inverter input isolator, so your essential power is off if you need to remove the inverter, waste of customers money. Or you will have live wires hanging loose, or you have to disconnect the cabling in the DB, which just doesn’t make practical sense.

A box which attached to the bottom of the inverter which has 3 isolators in separated compartments, would just make the entire setup simple and safe.

IF you have extra cash to through at a project, then go wild with all the nice to haves.

[Isetech]

At least creating the post in word then pasting here, saves my sanity dealing with the pops up and ads Maybe I should just install ad blocker again, or find another soap box to make a noise.

[Dylboy]

At least creating the post in word then pasting here, saves my sanity dealing with the pops up and ads Maybe I should just install ad blocker again, or find another soap box to make a noise.

Hey uncle, so I use TAPATALK on my phone and then I pay yearly for no ads, I think it's R125 or something. But the site seems to work quicker, it is now an app on my phone and there is no ads. So maybe worth a try perhaps on the phone or a tablet that you have or something : )

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[Dylboy]

With regards to the 4pole to isolate both, I too have thought of that and I think is a good solution. Correct labelling with it I think it's a solution.

Only thing is for 3phase, maybe doing 2x4pole breakers and a rod joining them so they can switch all 8 at the same time.


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