AC control DB

[Tradie]

Now that the crazyness has settled and the grid has been sort of stable for a couple of months, the fly by nights has gone back into the holes they crawled out of, and people are holding dodgy contractors that are still out there conning people are being held accountable.

It time to take a look at common failures in the solar installations.

Things like permanent neutral earth bonds in TN-S installations (make sure you understand your earthing arrangement)

The changeover/bypass switch wiring and the many wiring variations out there.

The current rating of the changeover/bypass switch, which also highlights the pass through confusion

Where to install the indicators lights, (certainly not the trunking cover) and the purpose of the indicator light.

Labels.

Safe isolating procedure and where it should be displayed. How often do you get a call from a customer asking what are where to switch off the power. How often have you arrived on a site after the dodgies have already left the building, and you sit trying to figure out where to isolate the power. Even as a trained, skilled sparkie, with no experience in solar installs, you sit trying to figure out how to isolate the part of the installation you need to work on, making that installation far from reasonably safe.

Anyway lets focus on the AC control box/DB.

[Tradie]

Now that you are upgrading your installation and need to replace the permanent bond with a relay, a note dont forget to remove the permanent bond, once the relay is fitted. I have seen an installation where an inverter was replaced with a Deye unit and the installer has fitted a relay, but didn't remove the N-E bond which was fitted by the previous installer.

[Tradie]

The AC control box/DB.....

You have an 8 kw sunsynk or Deye unit (as the example, because they are the most common) with a pass through current of 50 amps and a load/ups/essential side, rated at 34.8 amps.

You fit a 50/63 amp single pole mcb in the main DB (non essential DB) install a 10 or 16 mm sq 2 core plus earth cable, because I hear you cannot run a 4 core plus earth (maybe GCE will attach a reg if there is one) more jibba jabb to confuse people on the socials and connect it to the double main switch in the AC control box.

Here is where it gets interesting, why because many installers dont install an double pole inverter input breaker, instead they run a cable directly for the bottom of the double pole main switch to the inverter input and directly to the bypass/changeover switch using a 10 or 16 mm sq wire. For the record, if this is what you do, you defeat the objective of keeping the power on while the inverter is bypassed or you have to physically open the panel and disconnect the wires, or leave exposed wire where you removed the inverter, then why waste the money installing the bypass switch in the first place.

Then we move over to the changeover/bypass switch, this is where it gets interesting, most installations I have seen have a 63 amp changeover , why ?

If the inverter is rated to 34.8 amps, why install a 63 amp and not a 40 amp?

Which brings me to the next point of concern with a changeover/bypass switch installed, the wire from the inverter ouptut goes to the top of a 32 amp double combo or circuit breaker and into the gen/ups input and the grid bypass goes into the grid input, that great

On the ouput side of the bypass switch you run a 4 or 6 mm wire and that is where the fight started.

Unless you fit a 32 amp breaker between the output of the bypass switch and the essential DB main switch, the cable has no overload protection when in bypass mode, because it is fed from a 50 amp breaker, if you install a 10 or 16 to and from the AC control box then it is fine, but make sure you rate the essential DB at 50 amps and not 32 amps.

[Tradie]

I believe the AC bypass/changeover DB should scrapped and replaced with a double pole isolator on the inverter input and double pole isolator on the inverter output, or standard wiring configuration must be added to the regs.

At least if double pole isolators are sued then there is not confusion and multi power supplies in one enclosure.

The same with the DC control box/DB, it is certainly not reasonably safe, in fact more dangerous.

If you do feel it is necessary, to fit surge protection, which is already in the inverter and an isolator which isolates all the strings, then each string should be have a separate box or the main switch must be a four pole to isolate the both string connected to the same mppt.

While on the topic of DC strings, the location of the MC 4 connectors which connect the panels and the layout of the panel cabling should available in the document holder next to the inverter. We all knw that nobody wants a DC isolator ay the panels because they say it creates more connection point which could cause hotspots. Then at least clearly identify where the MC connectors are located and leave an mc 4 connector tool clipped onto that panel or clipped to the document holder, in case of an emergency.

I can see a firemans switch being added to future regs.

[Tradie]

Does anyone have an internal schematic for a Sunsynk unit. I would like to see how the contactor and busbar configuration works, so that we can get a better understanding of how each terminal is managed, grid aux and load. Until you understand the internal components, it is difficult to comment.

From my understanding is that the grid, aux and load all all connected to the common busbar.

If the grid power lost, all that happens is it drops out the grid contactor, disconnecting the inverter from the grid, which creates an islanding mode.

The same with aux and the load, if that is the case then there should be power on the aux at all times, then how can you connect a generator and feed into the inverter and if you wan to use the aux for a load controlled by the battery level

The part that I dont understand is if they are just contactors, then how does the aux convert from a generator input to a output for loads controlled by the battery level.

Which then brings me to the load terminal , some people have suggested that the load terminal can carry 50 amps (pass through, another misunderstood topic), for this reason they connect the load terminal to the DB including the geyser stove and all other heavy loads, which results in a warranty claim.

The question, is the load terminal permanently connected to the busbar or does it switch over when grid fails, like a standard ATS ?