CCM

Sorry for raising this topic again, I see it's a frequent and well worked through one on this forum across a plethora of threads, but I'd like to try and summarize what I've learned and check if my understanding is correct.
Context:
I recently had my entire system installed - Sunsynk 5.5 kw inverter, 2x Shoto 5.2kWh batteries, 12x 545w Solar panels. Without the earth neutral relay bond I must add, something my installer seems to not be aware of - more on this later. As an engineer myself I like to understand how/why things work so I can fix it or understand why it doesn't work, and this led me down this rabbit hole.
My understanding - please correct if I'm wrong:
1) In the majority of South Africa installations, Neutral is bonded to Earth coming from Eskom at some point prior to entering my house, likely at the meter box, or the transformer. Regardless of this bonding, for the purposes of wiring inside the house, Earth, Neutral and Live are to be treated as distinct lines. I'm not aware of a grid related earth spike on my property, and I only have an earth wire coming from the meter box on the opposite side of the road. 
2) SANS regulations require that in a UPS installation, such as my Sunsynk inverter, split neutrals be used. I.e. The neutral on the non essential (LOAD) side of the inverter shall NOT be connected to the neutral on the essential (LOAD) side of the inverter. I'm sure there is more motivation than just SANS, but for the purpose of my current understanding this is sufficient motivation. Also, both GRID and LOAD side needs their own earth leakage breaker.
3) Within my house wiring earth should be common across the board - I.e all earth (PE) lines can join on the same bar in my main DB. This is in relation to the AC circuitry of course. Panels have their own unique earth spike.
4) When Eskom is on, and the inverter is running in 'normal' mode, the LOAD and GRID live and neutral lines are connected internally in the inverter. This allows the inverter to blend power from multiple sources. 
5) When Eskom goes down, we effectively lose the earth/neutral bond on their side, and we're left with Live and Neutral with no reference to ground, and what people see elevated voltage output on the inverter load output.
6) Because of 5) we need to create that earth/neutral bond in-house dynamically when Eskom power goes out to prevent the elevated voltage, and other funnies. This is where the bonding relay and the Sunsynk islanding mode signal comes into play.
7) Why can't we bond earth and neutral permanently on the inverter load output and take out the need for the bonding relay?
7.1 ) It's not allowed by SANS to have another earth/neutral bond in the home? [citation needed].
7.2 ) Because of the earth neutral bond existing on Eskom side, if we do ANOTHER earth/neutral bond on the house side while Eskom is live, it effectively connects the split neutrals from 2) above via ground. This is a problem because it risks negating/messing with the earth leakage breaker functionality? I'm still fuzzy on why though.
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Theory 101 complete, now to my localized issues:
My installation concern:
My installer has connected the Neutral port on the LOAD side of the inverter to both Neutral for the essential loads, AND to my common earth. He's not connected the Earth (PE) port on the LOAD side of the inverter to anything. When I queried him on this he said without this setup (bonding earth and neutral on the load side) the inverter LOAD output voltage floats high (110v), and "all the Deyes and Sunsynks do this and the engineers have not been able to explain why". If my understanding is correct 5) above would explain what they are seeing, right?
Symptoms in-house:
I have the following problems in-house, that I suspect may be linked to this installation approach, some more than others:
1) When everything is 'on', Eskom, etc, my oven clock light has a weird flicker. Some of the LCD display segments blink on and off intermittently. Setting the clock on the oven takes 'longer' (Normally when you adjust the time, pressing and holding on the + button makes the minutes spin by faster and faster, this isn't happening anymore). The oven is on the non-essential (GRID) side of my setup, and if I disconnect my 'AC TO INVERTER' breaker, the oven returns to normal operation, i.e. Eskom is still on, but the AC link into the GRID port of the inverter is severed. I suspect this might be due to the now not-split neutrals as described in 7.2 )
2) I have 2 aircon units (8000 and 12000 BTU), both on the essential (LOAD) side of the inverter. When either one is on, I hear a buzzing sound on the earth leakage breaker for the essential loads. I've replaced the breaker once already, and the buzzing is reduced but it's still not gone. I'm not convinced this relates to the earth/neutral bond situation, but rather caused by cheap RCD. Going to be replacing them. My essential side RCD doesn't even trip (reliably) when I press the test button on it. 

3) Elevated base power draw, and inaccurate load measurements on my house since the installation. My base load at night when only a bare minimum of lights are active is reporting 400 to 600w, and it 'feels' too high. I'm used to around 300w only. Also when something like my geyser element turns on, the inverter reports its load as adding 4kW to the grid draw, and I was under the impression I had at MOST a 3kW element in the geyser. 
4) Bad house wiring (not my solar installers fault). It would seem the original house wiring took shortcuts and had a few plugs and light circuits on the same neutral line. This proved a headache when splitting the DB during the solar installation and it's not in an ideal state. Some lights are causing RCD trips, even though they have removed the light circuits from the RCD's.
Next steps:
Unless I'm completely daft in my understanding, I'm going to get a earth/neutral relay bond installed on the inverter load side, and see if any of the above issues subside. I'm also going to get an electrician to rewire my house side and fix the joined lights/plugs.
If anybody has read this far through my ramblings they deserve a medal. If you have anything to add or correct to my understanding of the whole sunsynk/earth/neutral/bond/relay topic, please feel free to do so. 

 

Good Morning. Finally bite the bullet with sky soft.
speak to Dinel if you want to get it installed without paying any deposit.
you only pay when they arrive with everything and the job is done. No upfront payment is the best part.
https://skysoftsuppliers.co.za
+27 83 388 6000
Thank You 

Good Morning. Finally bite the bullet with sky soft.
speak to Dinel if you want to get it installed without paying any deposit.
you only pay when they arrive with everything and the job is done. No upfront payment is the best part.
https://skysoftsuppliers.co.za
+27 83 388 6000
Thank You 

More or less. You're a bit imprecise on units and so forth here and there, but the following is your take-away (and I'm using round numbers for ease of calculation):
1. If you're using a single 5kWh 1C battery, it can discharge 100A, at approx 50V, in other words, it's got a 5kW instantaneous power output. If you have a maximum Depth of Discharge of 20%, you will use up the available 4kWh of energy in 48 minutes. The power delivered by the battery is equal to the 5kW power rating of the inverter. 
2. If you have two 5kWh 1C batteries in parallel, the system Voltage remains 48V (call it 50V), and the maximum total instantaneous power from the batteries will be 10kW. You will have 8kWh of energy available, however in this case your power output from the batteries will be limited by the 8kW power rating of the inverter (bottleneck). In this scenario you will use the 8kWh of energy within 1 hour.