NotDave

Hi All. I've got a nagging issue with the RCD on my DB sporadically tripping when switching between on-grid and off-grid. My setup consists of two 5kva Kodak / Axpert inverters running in parallel, each hooked up to a different solar array and a single stack of pylontech batteries. The system is off-grid by default, and then on-gird in case the batteries drop too low (which happens about 12 or so days a year). The tricky bit is that I have two db boards that can be fed independently from the inverters or the grid. Each of the DB has a 63A 2N0,2NC contactor to switch between on-grid (eskom) and off-grid (inverters). The contactors have 220v AC coils which are actuated by a relay with two independent contacts and supplied from the inverters (there is no point in switching off-grid if there is no power off-grid). The second set of contacts on the relay switches the earth between grid and inverters. The output from the contactors feed into an RCD and then to the rest of the circuit breakers. The only difference between the primary and secondary DBs is that the secondary also has a smartswitch that switches the geyser on and off. Like I said: the RCD on the primary board trips sporadically when switching between gird and offgrid, and from what I can tell, the cause doesn't seem to be the relays / contactors as switching between batteries and gird on the inverters themselves cause the same issue. I have no idea where to even start with this one. Any advice or tips would be greatly appreciated.

This puzzle has been boggling my mind since yesterday. More Napkin Math (probably very wrong, so feel free to point it out) The specific heat (the amount of energy stored per unit) of water is about 4.18 Joule per gram per degree Celsius. Working backwards, if the temperature difference in the water is 33 degrees (22 minimum temperature in the house, 55 max water temperature in the storage tank) with an 800L water tank, the system will store roughly = (specific heat in joule) x (temperature difference in Celsius) x (weight of water per litre in grams) x (storage capacity in litre) = 4.18 * 33 * 1000 * 800 = 110 million joules. 1Kwh of energy = 1 joule * 60 seconds * 60 minutes * 1000 (kilo) = 3,6 million joule. Thus, a 2.8Kwh lipo is going to be around 10 million joules (2.8 as opposed to 3.5 as there is a 80% depth of discharge limit). Even if the lipo battery -> inverter -> air-air heatpump / aircon is 100% efficient, and the heatpump / aircon has a coefficient of performance of 1:4 (generoud in cold climates), its only going to deliver about 40 million joules of heat, which is only about 36%, which works out to almost exactly 3 pylontech US3000s (R54k) or 4x 200L geysers from chamberlains (R26k). Granted, I have not taken into account the loss of heat due to insufficient system insulation, but at the same time I didn't take into account the loss of energy as part of the charge-discharge cycle in batteries. TL;DR: it seems like storing heat in a 'hot water battery" is roughly half the cost compared to storing it in Lipo Batteries, at the expense of not being able to use said energy for anything other than heating purposes.

There are some 11kw commercial units out there. They are not common in residential installations, but I get your point, there not that many situations where you need to boil a 150L geyser in the middle of winter in 45min or less. During the winter I run my 150L geyser in cycles from 10h00 to 15h30 to avoid drawing on the batteries and it consumes about 5kw per day. If a heatpump uses half the draw, it should extend the usage window from 09h00 to 16h30. From my current usage patterns, I have about 10kwh of unused solar potential after the batteries are full and the geyser is boiled, which would probably increase to 12kw or 13kw with a heatpump. With napkin math, its close to an additional 800L in hot water that can be used to take the edge off in heating the house in the winter, though that's probably a whole different can of worms.

I was wondering if people could give me a little advice before I take the plunge and install a heatpump. My chief reason is to cut down on the consumption on my off-grid PV system and hopefully increase the capacity of the hot water system. Noise: Looking at heat-pump datasheets, they list things like 52dB. Looking at what 52dB means, you get: "normal level of speech, rainfall, refrigerator, light traffic and a residential street.", which is about as descriptive as softer than a hairdryer but louder than rustling leaves. Since the unit has to be installed outside, the most ideal place to mount it would be under the eaves of the upstairs bathroom close to the geyser: a spot that is unfortunately pointing directly at neighbours and right next to the bedroom and lounge windows which will end up with a particularly low "Wife Approval Factor" and high "Neighbour annoyance factor". Currently I am considering either mounting it in the utility room and then building a massive amount of ducting to try and vent it to the outside, or mounting it on the wall and putting some sort of fibre-cement board and insertion rubber sound shroud around it. Anyone have any advice or other suggestions? Size: The current geyser is around 3kw, so I have room for around a 11kw heatpump (looking at the power consumption numbers from datasheets). Should I install one 11kw unit, or 2x 5.4kw units? I am aware that there is a price difference, but it will allow me to run a single unit in the event that my PV panels are experiencing low production. If i install 2 units, do i run them in series or parallel?

Apologies for the wall of text. This past year has left me with a pretty amazing experience as far as going solar is concerned. What started out as a UPS to run a couple of utilities during loadshedding has turned into an obsession to rid the house from the grid completely to the point where we're normally unaware of any eskom outages. My accumulated setup consists of 2x 5kw Axpert clone inverters, 8x US3000 Pylontech batteries and 2x 4kw pv arrays installed on the roof. I opted to plumb everything straight into 2 DB boards (Essential: plugs, lights, stove and Non-Essential: Geysers, Aircons, Underfloor heating) with managed contactors that allows the loads to run either on grid or local. So far everything is running fine- I have optimised the geyser with a timer to run short cycles between 10h00 and 16h00, and most of the days we start with the batteries at 60% and have them charged by 12h00. I calculated my grid reliance and it came down to less than 4% of my total annual consumption. This is mostly because I switch to grid the moment the batteries reach about 40% capacity- my reasoning behind it is that I want to stay well above the maximum depth of discharge in case Wapadrand Substation decides to spontaneously combust again (of which there is probably a 50% chance on any given day). The cut-over to grid has only happened once since October last year, and it basically requires 2 solid days of rainy weather and almost no sunshine. Some back-of the envelope math suggests another 2X US3000 batteries, an additional inverter, and another 4kw of solar will help, but it will only get me down to about 1% reliance- so the law of diminishing returns has a pretty prominent effect here. Another thought was to install a secondary geyser ahead of the primary, so water gets heated before it goes into the primary. The advantage of this is that the primary would run much shorter cycles, and the secondary would only be run on excess electricity after the primary has been heated and the batteries are fully charged. It should save about 3 to 4kwh on the first day of bad weather and be half the cost of a battery, but it wont do anything for the second or third day. The last idea is to forego the inverters and batteries and just install some more panels. I have plenty of storage, but the generation is the issue. The inverters max out at 4000w of pv, but in low light a 4000w array will produce less than 2000w. Would it be possible to run a auxiliary array that can be controlled with a contactor? Eg, the moment solar production falls below 2000w, activate in the auxiliary array, and then the moment it goes over 3000w, cut the auxiliary array? I am aware that there are going to be a couple of issues (voltage will have to match very closely, the contactors will have to fail-open, and there will have to be a snubber circuit to reduce arcing in the contactor). EDIT: now that I've put it in writing, it might be safer to just get the third inverter and hook it up to another 4kw array and shut down the inverter between sunset and sunrise to avoid the overhead standby power usage... EDIT2: Its probably not a bad idea to shut down the second inverter between 21h30 and 05h30 either (should save about ~0.5kwh) So my question is this: how does one cater for that 4%? After addressing the usual suspects (note: gas and solar water heating are not options at this point in time), what other solutions are out there, commercial or otherwise? (I own an angle grinder and I am not afraid to use it)

Okay, so I have made 3 different cables now. Sadly none of them seem to work. The cable that was supplied: 3 - 8, 5 - 7, 7 - 5, 8 - 3 Custom cable 1: 1 - 3, 2 - 5, 3 - 1, 5 - 2 Custom cable 2: 1 - 4, 2 - 5, 4 - 1, 5 - 2 I see Coulomb has done some work with firmware updates... Is there a specific version you can recommend? Thanks for the settings, Panther.

Hi Everyone. The story is pretty much what it says on the tin: The dreaded "Error 61: Communications Failure between a 5kw Kodak / Axpert King and a stack of Pylontech us3000's The Setup: 1x Kodak branded King 5kw inverter, running firmware 71.90 4x Pylontech US3000 batteries. No solar panels (yet) Everything is new and got delivered from the supplier about a week ago. What I have tried: I have tried to set up everything as was specified in the manual and as I have gathered from the various sources online (mostly on here) The inverter came delivered with an RJ45 cable to connect between the Inverter and the batteries and I verified that the pin-outs matched what I have seen mentioned on the forum a couple of times. I have checked the cable to make sure there was no breaks or twists in it. I even made up my own using some RJ45 connectors and UTP cable in case the connectors was a little dodgy. The cable was plugged into the RS485 port on the master battery (checked and rechecked). I made sure the dip switches were using the sequence: 1-0-0-0 on the master and 0-0-0-0 on the slave batteries. On the inverter the cable was plugged into the Battery Monitor port, and I changed the inverter settings OPTION 5 to PYL. Sadly, no dice. What I think the problem might be: A setting somewhere might not be applied - I power-cycle the batteries and the inverter every time after changing the settings to ensure that if a setting is applied to the inverter when it gets switched on, the change is persisted. I also verify that it changed on Watchpower (Via Bluetooth), but I get the feeling that this is in all likelihood not the problem. Some coms electronics got fried. The pylontechs came with a data cable which I briefly attempted to use (It has RJ45 connectors on it!). In my attempts to get it working, I had it plugged into the CAN bus on the batteries. I am not sure about the voltages on the data lines, and all likelihood this is probably not the problem either as most designs probably has some built-in protection (one would hope) The firmware is out of date- Currently the inverter is running 71.90 but I have seen it mention on the forum that the 71.93 firmware is available. I haven't looked into upgrading it yet, but this seems like the only real option available to me at this point, as I am drawing a blank on any potential hardware related issues. An intermittent solution If all else fails, I'll probably have to configure the inverter with Option 5: USR batteries. From what I understand, the only benefit of the coms cable is that the BMS takes over responsibility of monitoring the batteries rather than the inverter attempting to do it via its own sensors and a bit of guessing. If I go this route, what are the currently recommended settings for these batteries to not void warranties, observe safety margins and maximize the battery lifespan? Apologies for the long-winded explanation, or if I missed something blindingly obvious in the manual, and thank you in advance for any advice and suggestions I should try. -NotDave