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JustinSchoeman

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Everything posted by JustinSchoeman

  1. Technically, I suppose they could just keep the grid relay open. That way the inverter could still control the frequency. But then you could not provide power to the non-essentials.
  2. You can only control the micro inverter output power by frequency shifting the AC line it is feeding. But, if the grid relays are closed, there is no way you can shift the frequency of the entire grid to throttle the micro inverter.
  3. Sort of - On the Sunsynk you can configure the Aux input (NOT AC in) as a micro inverter input. Micro-inverters are grid-following, not grid-forming, so they require an existing AC signal to 'boost'. It is a limited setup suitable for feeding in extra panels over an AC link, but can only produce power when grid is present. OOPS - I see the Sunsynk can do grid forming for micro-invertres - so they can work off-grid. BUT on-grid is an issue, as the Sunsynk can not control production on micro-inverters on-grid, and they will run at full power permanently, exporting all additional power to the grid. Generally not acceptable unless you have a feed-in agreement... So DC coupling will definitely be the best option.
  4. Most GP wire is DC rated (although it is best to double check the specific brand with the supplier/manufacturer). So it is fine to use for long haul DC connections (just make sure of your voltage drop limitations - you will probably require thicker wire than the current limit would suggest). Solar wire is primarily for environmental exposure, which you do not need in a protected conduit. Otherwise, a micro-inverter on the panels with AC coupling to the Aux input should do it (but you won't get PV power when grid is off).
  5. Interesting... They sell on Takealot too, so unlikely to be a complete scam. If you buy there at least you get 30 days to do proper testing with some security. Might actually be interesting to try these.
  6. A balancer is always a good idea. But the symptoms seem to be related to a start-up current surge. Bypass the breaker with a 24v lamp (or even 250v incandescent lamp if this is all you have). Let this charge the inverter input a bit before closing the breaker.
  7. I don't know what is worse. That I remember when these were still common, or that no one else seems to know about them...
  8. Will probably be the 5A BS546: Was commonly used for low power/lighting plugs in the 70s (and probably before).
  9. Easy test. If you can get the cable into a 50mm² lug with only a moderate amount of swearing, then it is 50mm² cable. But seriously, it is virtually impossible to get cable that is not labelled. Shine a light parallel to the surface of the cable, and you will probably see some lightly embossed markings.
  10. Also: Pretty much, if it is metal, and it is exposed, it must be earthed - that applies to pretty much everything in SANS 10142-1.
  11. In my opinion (for what it is worth), I think mostly correct: AC and DC cannot run in the same conduit Correct. DC and DC also can not run in the same conduit, unless all cables are rated to the highest voltage in the conduit. All MCB’s (Micro Circuit Breakers) must be correctly sized for both Grid & Load Correct. If the inverter manual specifies breaker size, you must never go higher than that, although you can go lower. Must also never be higher than the wire rating. Each Solar Installation must have a separate Earth spike which must read less than 10 ohms (if not then add a 2nd or 3rd spike approx. 1m away and join them) - The DC DB / Combiner box / Solar Panels would be connected to this newly installed earth spike Only required if the inverter requires this (depends on the type of internal surge protection). Every Panel must be joined to the next panel by 6mm earth wire (you cannot just earth the Rails) Only if required by the rail or panel manufacturer, otherwise the rails (aluminium rails only - other materials may be different) meet all the legal requirements of earth conductors. You must run the positive (Red) wires in a separate conduit and must include the earth in that conduit. If you have multiple strings and have separate conduit for each strings positive wire, then you must include the earth wire in each conduit. Never seen anything like this before? Within the Combiner Box, you need to fit Bootlace Ferrules at the end of each Solar wire (stranded wire). This is required for both single wires (single wire bootlace ferrule) and where 2 wires are going into a MCB (twin wire bootlace ferrule) As far as I can tell, not yet a legal requirement in SA, but will be shortly, and is a really good idea. For your Inverter installation (Grid and Load connections), you cannot just use the earth wire (normally a single copper wire) contained within the flat Twin & Earth wire, as this is normally thinner than the actual load carrying wires (e.g. 6mm or 10mm). To be compliant you would need to run a separate earth, which is the same thickness as the current carrying wires, between your Main DB board as well as your Essential DB board. Sort-of correct. For fixed installation, the earth must be min 10mm² copper - but not necessarily the same size as the phase conductor. For your Inverter connections (Grid & Load), the earth of the Load input (in the inverter) must be bridged (I presume bridged to the Grid earth). From what I was told, if you do not do this you may have a floating voltage between Neutral & Earth especially prevalent during load shedding) Must definitely be bonded - but using a bonding relay (some say to use a permanent bond, but this seems to be against SANS regs - many arguments about this). Your Inverter casing must be earthed to this same earth Correct Your batteries must also be earthed to this same earth Correct
  12. The Neutral wire is switched. Depending on operating mode, it is either connected, or not. Hybrid converters it remains connected until grid power is lost. Off-grid inverters only connect when drawing power from grid. Neutrals connected to the wrong circuit will cause earth leakage trips when affected appliances/plugs are used. This is probably the most common installation issue in older houses.
  13. Sorry - missed the 'recommended': "Recommended Max. Continuous Discharge Current: 37.5A" I see absolute max continuous is indeed ~2.5kW. So you have 7.5kW available - but you also need to remember that the inverters have no way to communicate among themselves, so you should set one up for 5kW max discharge, and the other for 2.5kW, or you may get BMS trips which take down everything.
  14. That should work - but just remember the max load of the battery. Max continuous discharge is only 5.4kW - it can only keep one inverter running at full load anyway. I also have no idea what the Sunsynk will do when the BMS is reporting substantially different charge/discharge to what it is measuring. You may need to disconnect both BMS cables to keep the inverters happy.
  15. Unfortunately, this is entirely wallbox dependent. Volvo provides a Garo wallbox with a very simple JSON protocol which I have hooked up to Node Red for automation. If you want a more 'off the shelf' solution, have a look at OpenEVSE on the OpenEnergyMonitor community. Designed for automation, and lots of support available.
  16. The SANS standards quite explicitly cover low voltage DC systems, and for good reasons: "SANS 10142-1:2017 Edition 2 Introduction In this edition an attempt has been made to move towards the IEC codes: extra low voltage (below 50 V) and d.c. applications (up to 1,5 kV) have been introduced as new requirements owing to the extensive usage of, and increased fire risk that result from, high load currents." Sunsynk: Luxpower: (2AWG = 33mm²) Growatt: etc. All 5kW inverters rated for 10kW surges (5 or 10 seconds). All specified to use wire that can not be safely used at 10kW. Victron is indeed the exception - but it is NOT related to safety. Victron is a Low Frequency inverter (single conversion), and is extremely intolerant of ripple on the DC bus (which is directly connected to the batteries). The Victron wiring is instead specified in terms of maximum voltage drop, which must be very low to meet the minimum THD requirements. High frequency inverters run their DC bus from a DC-DC converter which can regulate the DC bus (relatively) independently of the battery voltage. Their wiring is specified in terms of safety and regulatory compliance only. The original question is in regards to a Deye inverter (high frequency).
  17. Gives you an idea of the cell quality if they feel the need to ship a 4A active balancer with new, matched cells...
  18. I had one of those. Did not work very well, and eventually died. Replaced it with one of these: https://www.aliexpress.com/item/1005005233850655.html Only marginally more expensive, and has bluetooth monitoring (but only 1A balance current).
  19. No where, anywhere, ever does 'RMS' limit something to a single wave period average. Pretty much the only time you will ever see that, is in a mathematical analysis of a perfect waveform, in order to determine the theoretical RMS value of that wave form. You can happily plug a true RMS meter into a noise source, and it will tell you the RMS value of that signal, even although there are no repeating periods. Which is pretty much what I was saying. Thermostat or TRIAC - they both work by zeroing the waveform for a period. The periods are just shorter in one case. And in both cases, the source (inverter) can be called upon to provide the full instantaneous power of the load. I am not sure why you keep dragging energy into this. We are, and always have been, discussing power.
  20. Somewhat sloppy use of language that most engineers suffer from. Poster probably meant to say 'frequency component': https://math.stackexchange.com/questions/1920602/how-does-one-derive-the-fourier-transform-of-the-ramp-function Whenever you are dealing with electronics, you pretty much always look at the Fourier decomposition of the wave form, as you need to be able to handle all the significant frequency components of the wave form.
  21. IGBT turn off is ridiculously slow - they need all the help they can get to turn off...
  22. I think you may not understand how RMS works. RMS is a technique for time-averaging a changing reading in such a way that it preserves the effective power transmitted. If you look at your typical AC sine wave, and you measure power at the zero crossing, you will see V=0V, I=0A and P=0W. If you measure at the peak, you will see V=325V, I=25A and P=8125W. 100 times every second, power is 0W and 100 times every second, power is 8125W. If you take the RMS average over one second though, then you will see an average power of 4000Wrms. RMS is an average power over time, whether you take that average over 1 second or 10 minutes does not change it from power to energy.
  23. OK - Let's try an absurdly over simplified example. I have a 3kW inverter. I also have an old-fashioned, thermostat controlled 2 plate stove. Each plate is rated at 2kW. I turn one of the plates to setting '1', and use an accurate power meter to measure the RMS average power over 10 minutes, and it is 200W. I use another power meter which measures instantaneous power, and it shows something like: 2kW ... 0kW ............2kW ... 0kW............2kW ... I can clearly see the plate turning on for a few seconds, and then off again to maintain the target temperature. I turn the first plate off, and do the same test with the other plate, with the same results. (Now I need to cheat a little and assume both plates are still at operating temperature to avoid a long 'on' period to heat up the plates...) I now turn both plates on. I can see the instantaneous power goes: 2kW ... 0kW ..... 2kW ... 0kW ... 4kW - and the inverter trips. Each plate individually only uses 200W, but the combination trips a 3kW inverter because the instantaneous load is 4kW. Exactly the same thing happens in triac controlled loads - just in much shorter intervals. The average RMS power may be 200W, but there are still short 2kW peaks. In reality, things are a little easier in the triac case, as the inverter output IGBTs typically have almost double the pulse rating vs continuous rating (although some of that margin is used for DC bus regulation). As a side note, the above example is a little better if we use capacitor dropping to reduce the plate power to 200W. The would result in a PF of 0.31, and the inverter would need to deliver 300/0.31 = 632W per plate, or nearly 1300W for the two plates combined. No where near the reduction you would expect. If you are relying on derating (triac or capacitor) to connect bigger total loads than what the inverter is rated for, then the results may not be entirely what you expect - even if the RMS average power of the total load is less than the inverter rating. This does not only affect inverters. Many utilities will bill large industrial users based on load harmonics and PF to compensate for the effective power they need to deliver to meet the real load requirements.
  24. This is what a triac limited waveform looks like: For big chunks of the input waveform, the output is 0 - but for the rest the output exactly matches the input. So, unless you reduce power to less than 50% you will still get the maximum positive and negative peak output values. If you look at the unmodified sine wave, then the instantaneous peak voltage of the output is ~324V. If you consider a 4kW element (13 Ohm / 230V), then the instantaneous peak current will be ~25A for an instantaneous peak power of ~8kW. RMS average voltage is 230V, current ~17A and power is 4kW. As you start blanking the waveform with the triac, you immediately reduce the RMS values. But until you reduce power to <50% you will not have trimmed off the peak of the sine wave, and the inverter will still be outputting an instantaneous 8kW at the peak. The output IGBTs have both RMS and pulse limits for current. Loss calculations for power are ridiculously complex, but will also give different continuous/pulsed limits. The problem is, which of those two limits will bite first? If it is RMS current, then you are fine. If it is pulsed current then the magic smoke comes out.
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