EDIT: Included suggestion from @iiznh

EDIT: Powering contactor coil from correct neutral (non-essential before E/L)

Hi all

I've been doing some reading, sourcing some parts and planning my installation. I will do this in two phases, the first being battery backup, and the next adding panels. The installation is single phase.

I'm at a point where I'd like some input from the community on topics mostly related to the AC wiring (or re-wiring of my existing DB).

Disclaimer: I am of course aware of the risks and would not expect anyone giving any information to be accountable for any mistakes (either by the information given or any potential misinterpretation thereof on my part).  This project, although necessary to maintain sanity, is also one of personal education and growth.  I'm comfortable with DIY and enjoy a good dive into detail.  All work will of course be checked and a CoC sought. 

All comments, advice, warnings, instruction, judgement, nitpicking etc are welcome and most appreciated .

Some questions (refer to images below for reference):

• As expected, my current flush mount DB has all house circuits, as well as the main input circuit from the prepaid meter box terminate in the cavity the DB is mounted in.  The house circuit cables are all twin and earth, fed into the cavity by 20mm and 25mm PVC pipes.  The first specific question I have is around the legality of mounting two surface mounted DBs over the cavity, and feeding the appropriate circuits to the relevant DB.  Is this allowed in any way?  If so, do the PCV piping have to be lengthened to terminate into the surface mount DB so that the cables are continuously in the pipes, or can they just be guided through a gland?  Note that all house circuits are stripped of the outer white insulation right up to where the original pipes end.
• What should the Amp rating of the contactor be whose job it is to bond the secondary neutral bar (ESP) to earth when Eskom power is interrupted.  If it's 63A, can anyone recommend one that is silent (no humming/buzzing), and takes preferably only up to 2 slots in the DB (35mm)?
• Does the placement of the various components in the board make sense, in particular the lights and SPDs?
• Is the wiring correct considering it's a hybrid inverter and that I'm only doing battery backup for phase one (no CT coil drawn yet, although I'd likely install it anyway)?

 

Existing installation (AC wiring):

Proposed installation (AC wiring)

Some notes to consider:

• I'm generally not too fussed about the cost.  I'm happy to spend extra so that things look neat and uniform.
• Phase 2 will introduce a 3rd surface mount DB, and all 3 DBs will be neatly mounted above each other.
• My existing DB is hideous and I'm happy to go through the effort and cost to replace it with the same looking surface mount than the two additional ones
• The one aircon CB is rated 25A, but with 2.5mm2 wiring, so I believe this breaker must go down to 20A for exceeding the current carrying capacity for the installation method used.
• The current stove breaker is 32A which protects the 4mm2 cable, but our oven was replaced with a unit that has a normal household plug (16A). So, instead of being wired directly onto the stove terminal blocks from the twin and earth, the twin and earth now terminates into a 16A surface mount socket enclosure (hob is gas, so plugged in for starters).  I believe the breaker must go down to a 20A because the breaker may not exceed 25% of the socket's rating.
• 

Thank you if you have read this far, and any input is greatly appreciated.

 

Edited January 11, 20232 yr by SomeOrOther
Included suggestion from @iiznh

Disclaimer: I am not an electrician

The hybrid inverter should be wired directly to mains that has not gone though a RCD (but after the main breaker). You do not want to RCD to trip and the inverter taking over the load supplying power where power should be cut.

@SomeOrOtherLook at the PDF in this post 

 

Edited January 9, 20232 yr by iiznh

52 minutes ago, iiznh said:

Disclaimer: I am not an electrician

The hybrid inverter should be wired directly to mains that has not gone though a RCD (but after the main breaker). You do not want to RCD to trip and the inverter taking over the load supplying power where power should be cut.

@SomeOrOtherLook at the PDF in this post 

 

Thank you @iiznh, that makes perfect sense.  Will adjust and post an update.

Looks good, very similar to my wiring. I have a heatpump so I moved my whole house to the essential loads which made my wiring very simple. 

I believe the The Non-essential loads Neutral busbar that is after the RCD connected to "Geyser" and "GPlugs" must be kept separate from the essential circuits neutral bar. When in islanding mode (loadshedding) then the inverter should disconnect both grid lines completely. This will ensure that the RCD does not trip when switching between and from islanding mode.

It goes without saying that all earths are always connected and shared between essentials and non-essentials. You should also consider a copper rod earthed and connected to your earth should there be any issues when cables are stolen and earth/neutral might be floating.

The sunsynk installation manual does have some good diagrams ( I used those when I did the wiring for my install)

For 40A breakers you should use al least  10mm2 (This is what I used for my 8KW inverter)

For 64A you need 16mm2

I believe there are some SANS cable rating tables on the internet for AC wire sizes.

4 hours ago, iiznh said:

Looks good, very similar to my wiring. I have a heatpump so I moved my whole house to the essential loads which made my wiring very simple. 

I believe the The Non-essential loads Neutral busbar that is after the RCD connected to "Geyser" and "GPlugs" must be kept separate from the essential circuits neutral bar. When in islanding mode (loadshedding) then the inverter should disconnect both grid lines completely. This will ensure that the RCD does not trip when switching between and from islanding mode.

It goes without saying that all earths are always connected and shared between essentials and non-essentials. You should also consider a copper rod earthed and connected to your earth should there be any issues when cables are stolen and earth/neutral might be floating.

The sunsynk installation manual does have some good diagrams ( I used those when I did the wiring for my install)

For 40A breakers you should use al least  10mm2 (This is what I used for my 8KW inverter)

For 64A you need 16mm2

I believe there are some SANS cable rating tables on the internet for AC wire sizes.

Thank you once more for your insights.

Your second paragraph made me realize that I was powering the contactor coil with live before E/L, and neutral after E/L.  It is now set to take power from grid before the non-essential E/L.

Will definitely do the earth spike once I do the panels (which is soon).

I'll have a look at the Sunsynk manuals as well for cross-reference.

I used a 40A Relay as the Earth / Neutral bond.

I also used 40A breakers and 10mm2 wiring to and from my inverter.

My reasoning for using a 40A relay is that in the case a fault the full 40A can be routed to Earth/Neutral and the relay/contactor must not weld itself shut. Anything more than 40A my breakers will disconnect the connection.

 

Finally finished the installation and all is working as expected  - no floating voltages, tripping ELs etc.

Many thanks to @iiznh for your input.

Looking good, I like it. You did a great job documenting this for the next engineer that needs a refresher before diving in.

You should do a load test and check if there are any hot spots when the wiring is pushed to its intended max current. I assume you torqued every screw to spec so everything should run as cool as a cucumber. Chances are that you already did so I am just mentioning this for anyone reading this thread in the future.

Then the only thing missing is the labelling on each circuit and warnings that circuits are powered by alternative power source after which you can get a COC

Sorry I do not know the ins and outs of such labelling   

On 2023/02/04 at 9:02 PM, iiznh said:

Looking good, I like it. You did a great job documenting this for the next engineer that needs a refresher before diving in.

You should do a load test and check if there are any hot spots when the wiring is pushed to its intended max current. I assume you torqued every screw to spec so everything should run as cool as a cucumber. Chances are that you already did so I am just mentioning this for anyone reading this thread in the future.

Then the only thing missing is the labelling on each circuit and warnings that circuits are powered by alternative power source after which you can get a COC

Sorry I do not know the ins and outs of such labelling   

Thanks

Torqued to spec but have not done a load test for hotspots yet.  Labelling on its way (read nicely cut vinyl).