February 10, 20197 yr 15 hours ago, Padwan said: Next was to measure earth and neutral on the inverter out terminal, and it was giving zero reading. Ah, my bad. I took this as an ohms reading, with the inverter off and isolated. Odd that it's intermittent, though. Maybe it depends on a load between the DB and inverter, like the light bulb (circle with an X through it) on @plonkster's diagram. Perhaps your stove, oven, or geyser turning on an off? Or just leakage? Some Axpert models only had the three relays; Weber's speculation is that those omit the inverter output relay. Since you have all single pole relays, and no setting 38, you can't do the proper switchover. I can't see the harm in shorting AC in neutral to AC out neutral. Though doing so does short out one of the "safety" relays.
February 11, 20197 yr Author 5 hours ago, Coulomb said: I took this as an ohms reading, with the inverter off and isolated. Odd that it's intermittent, though. So It turns out this is not intermittent. When the inverter is in battery/PV mode, neutral and earth on out terminal give out 94V. When in bypass mode, reading on neutral & earth on out terminal is 0V. So the real question now is, does this behaviour constitute malfunctioning unit or is it simply way [older] Axperts work? [Have to mention that 2 out of three units I've got from this batch/supplier behave the same way, so is this feature or bug? ]
February 11, 20197 yr Author 5 hours ago, Coulomb said: I can't see the harm in shorting AC in neutral to AC out neutral. Though doing so does short out one of the "safety" relays. What would I be risking trading-off by doing so, at the moment my options were to accept voltage on my neutral [and pray this does not cause harm or damage] bond earth and neutral on out terminal in my db board to get rid of the 94V going to my home circuits [this comes with a tradeoff that inverter will not switch over from battery mode, and if it does somehow end up in grid supply (ac input to inverter goes up), my db board earth leakage trips ]
February 11, 20197 yr 1 hour ago, Padwan said: What would I be risking trading-off by doing so Possible violation of regulations, or at least norms. In South Africa, I seem to see a lot more double pole breakers/isolators than I do here in Australia. I have no idea about the SA regulations.
February 11, 20197 yr 1 hour ago, Padwan said: When the inverter is in battery/PV mode, neutral and earth on out terminal give out 94V. It is going to depend on what loads you have on there. Most old-style appliances are not going to affect this, but the new electronic stuff have stuff wired between live/neutral and earth and that tends to create little voltage dividers that raises earth roughly to the middle of the rail. Different loads... different voltage. 1 hour ago, Padwan said: When in bypass mode, reading on neutral & earth on out terminal is 0V. Because the neutral is now connected to the grid neutral, which is bonded to earth on the supply side. 7 hours ago, Coulomb said: I can't see the harm in shorting AC in neutral to AC out neutral. Though doing so does short out one of the "safety" relays. That would be the easiest way to make it safe... 19 minutes ago, Coulomb said: Possible violation of regulations, or at least norms. In South Africa, I seem to see a lot more double pole breakers/isolators than I do here in Australia. I have no idea about the SA regulations. But there is that. Now the electricians I've spoken to over the years differ on this topic. Some see no problem with it, others say no. From my own understanding of SANS 10142-2-1, on single phase systems all disconnects (including the one in the inverter) must switch both poles, so it would not be legal. There is however a diagram in the old SANS regulations that allows such sharing of a neutral on three phase systems in cases where the backup supply (that is the inverter) is connected at the "entry point", in other words, if the entire house is on the inverter. The moment you supply only a part of the installation, then you're supposed to have a double pole changeover, separate neutral bars, and so on and so forth. I suppose one could always wire a small double-pole 12V relay in parallel to one of those grid switching relays (ie, solder wires onto terminals inside the inverter!) and use the NC side to power a bonding relay... It's a long shot... For now you'd have to choose the lesser of two evils, which I suspect would actually be to bridge the neutral across. Edited February 11, 20197 yr by plonkster
February 12, 20197 yr Hi, bit late to this topic, and I am only saying what I did with the Axpert when I had it running... On the output side of the Axpert (and after the manual changeover when I bypassed the Axpert completely), I bonded the Earth and Neutral. My main reason for this was that I was getting tired of getting zapped by my computer equipment and my CCTV cabinet! After reading a post on this or another forum (I cannot remember where), I risked it and gave it a try. There are probably many reasons above on how you should do it differently than I did, but I kept that Neutral-Earth bond after the output of the Axpert for over 2 years without issue. My Axpert only destroyed itself thanks to a 500V+ surge from municipal or storm that got passed my input protector (it was more smoke than the Axpert when it blew up). My internal UPS's would trip over for about 20s despite the short switchover of the Axpert when I had this configuration (removing the bridge stopped this, but zapping me was not a fun situation - and it threw out certain network cards). I was ok with the 20s tripping of the internal UPS's. Please note: Millage may vary - This is just my input, wrong or right.
February 14, 20197 yr On 2019/02/10 at 9:14 AM, Padwan said: Last night, however, after attempting to switch over to a grid supply, every time there was AC in on the inverter it tripped the earth leakage on my sub-board. Because you are feeding the inverter from an E/L circuit in your grid DB, and you have connected N-E on the outputs which is an earth fault. I hope the attached sketch is legible, my CAD skills are a touch lacking (I can do it but it will take the whole day!)
February 14, 20197 yr On 2019/02/10 at 2:22 PM, plonkster said: Doesn't the Axpert's transfer switch disconnect the neutral? I know one suggestion (not legal according to SANS) is to bridge the neutral from the input to the output, so that only the live/active/hot is switched by the transfer switch. That way the TN bond remains active. The other way is, as you say, through setting 38. I tried to get the manual... Voltronic wants me to register and then review the application... this is going to be interesting... I used my work email address 🙂 Can you please quote that section of SANS 10142-1 that says it is not legal? It is strange that it would be legal to connect the neutral to earth a second time, seeing that it is already connected to earth either in the main panel or at the supply transformer assuming a TN-S or a TNC-S system of earthing at the supply of the utility.I use the existing utility neutral with the inverter neutral without problems.No need to feed the inverter from the mains via a RCD. Treat the ac supply to the inverter as a dedicated circuit of the mains supply DB and add your RCD on the inverter output in the inverter AC panel.
February 14, 20197 yr 29 minutes ago, SOLARWIND said: Can you please quote that section of SANS 10142-1 that says it is not legal? And more stuff follows about separate neutrals when there is a UPS, and how your protection devices should not rely on the utility bond to function (ie, it pretty much tells you to install your own bond when running from the alternative supply). It is pretty much a rule that only fault current is allowed on the earth wire. The moment you add a second bond, then you allow operating current to jump across from the neutral to the earth and continue the journey to the second bond where it transfers back onto the neutral... so between the two bonds you have operating current on an earth wire. That is not allowed.
February 14, 20197 yr 43 minutes ago, SOLARWIND said: bridge the neutral from the input to the output Well actually I said that and he quoted it... but I just realised why this is not legal either. Bridging the neutrals so the supply-side earth connection comes back into play... well that would be relying on this connection while switched. So pretty much just one way to be legal: A bonding relay.
February 14, 20197 yr 3 minutes ago, plonkster said: "This earthed neutral bar shall be the only point at which the neutral of the installation is earthed." That sums it up and means that the neutral of the mains supply DB complies and must be used as the common after the earthing point (where they are combined and then run as separate wires, each with its own function).
February 14, 20197 yr 3 minutes ago, plonkster said: Well actually I said that and he quoted it... but I just realised why this is not legal either. Bridging the neutrals so the supply-side earth connection comes back into play... well that would be relying on this connection while switched. So pretty much just one way to be legal: A bonding relay. The bonding relay is then something that switches the neutral only, which is not allowed.
February 14, 20197 yr 2 hours ago, SOLARWIND said: The bonding relay is then something that switches the neutral only, which is not allowed. The bonding relay only connects the earth to the neutral while running disconnected from the grid, so that your RCD might function properly. It is usually electrically interlocked with the changeover switch (which in turn must switch both live and neutral) so that the bond is only engaged after the grid is disconnected (otherwise the RCD will again trip).
February 14, 20197 yr 7 minutes ago, plonkster said: The bonding relay only connects the earth to the neutral while running disconnected from the grid, so that your RCD might function properly. It is usually electrically interlocked with the changeover switch (which in turn must switch both live and neutral) so that the bond is only engaged after the grid is disconnected (otherwise the RCD will again trip). Rather then let the relay connect neutral to neutral instead of to earth, because as you've already said, and that is my point also, you should not connect the neutral to earth other than in the main panel.
February 15, 20197 yr 12 hours ago, SOLARWIND said: Rather then let the relay connect neutral to neutral instead of to earth, because as you've already said, and that is my point also, you should not connect the neutral to earth other than in the main panel. I'm not an electrician, so I only repeat what I learn from others 🙂 What I can tell you is that later Voltronic inverters and all Victron inverters have a bonding relay. They bond the earth and the neutral while the grid is disconnected. It is pretty much the de facto (if not de jure) standard in the industry.
February 15, 20197 yr 11 hours ago, SOLARWIND said: Rather then let the relay connect neutral to neutral instead of to earth, because as you've already said, and that is my point also, you should not connect the neutral to earth other than in the main panel. Both proposed earthing systems are not code compliant but In my opinion the Lesser of the evils, by quite a long margin, is to rather connect the inverter output Neutral to earth. Relying on the earthed connection of the main incoming supply will be risky and dangerous due to the following: 1) Isolation of the DB main switch (2 pole or 4 pole) will break the neutral and you will lose your N - E connection. 2) Isolation of the supply to your inverter (2 pole or 4 pole) will break the neutral and you will lose your N - E connection. 3) In a TNS system you are relying on the N - E connection at the supply transformer. This connection could be impacted by Maintenance personnel or theft and would not be self monitoring. 4) The earth fault return path will be long and you will you have to consider the impact of the increased impedance (Resistance & Inductance) of the earth loop on the operation of your protection devices. On 2019/02/11 at 8:30 AM, plonkster said: It is going to depend on what loads you have on there. Most old-style appliances are not going to affect this, but the new electronic stuff have stuff wired between live/neutral and earth and that tends to create little voltage dividers that raises earth roughly to the middle of the rail. Different loads... different voltage. The parasitic capacitances between the cables is also enough to create a floating voltage between N - E and L - E even with no load connected.
February 15, 20197 yr 5 minutes ago, Carl said: The parasitic capacitances between the cables is also enough to create a floating voltage between N - E and L - E even with no load connected. Indeed! But I should atually make a video of this one EMI filter i have here. That thing passes enough current that I can make sparks if I brush the floating earth on a neutral screw... How did I find out? Well, I tried to make a test case with an RCD, an EMI filter which I know caused some trouble, and tried to see if I can make it trip by intermittently disconnecting the earth/neutral bond (I simulated one... I could not use a real one, that would trip the house breaker). I couldn't get the breaker to trip... but I did make some cool sparkies. Not of the black-mark-on-the-screw kind, but clearly visible to the naked eye even in sunlight. Edited February 15, 20197 yr by plonkster
February 15, 20197 yr 1 hour ago, Carl said: 4) The earth fault return path will be long and you will you have to consider the impact of the increased impedance (Resistance & Inductance) of the earth loop on the operation of your protection devices. The earth fault return path is there to conduct the phase to earth fault back to the source of supply. When you have grid power your source of supply is the minisubstation, hence why the starpoint of the secondary winding is bonded to earth. When you are in UPS / Inverter mode and disconnected from the grid the minisub is not your source of supply anymore, your inverter is. So in a phase to earth fault the fault current will only flow back to the inverter and not back to the minisubstation. The earth leakage device installed at the inverter supply will protect you here.
February 15, 20197 yr 9 hours ago, Jaws said: The earth fault return path is there to conduct the phase to earth fault back to the source of supply. When you have grid power your source of supply is the minisubstation, hence why the starpoint of the secondary winding is bonded to earth. When you are in UPS / Inverter mode and disconnected from the grid the minisub is not your source of supply anymore, your inverter is. So in a phase to earth fault the fault current will only flow back to the inverter and not back to the minisubstation. The earth leakage device installed at the inverter supply will protect you here. Agreed 100%. My comment was referring to the case where you connect Neutral Input and the Neutral output of the inverter together and you then rely on the N-E connection of the main supply as your earth return path for fault currents. Now in a TNS system this will be at the Council supply transformer. So any earth fault current downstream of the inverter would have to flow all the way back to the supply transformer N-E connection and then all the way along the neutral conductor back to the Inverter Neutral.
February 15, 20197 yr Just another reason to stay away from these inverters. If you have to start making plans to create your own star point for all your protection to work on your circuits it can become quite dangerous. If you create an additonal star point on the network while connected to the grid, you basically take over the earthing role for everyone connected to your network(minisub) when the network loses its star point. Ideal situation for things to go blowy blowy.
January 6, 20215 yr Almost a year later and I have a similar problem except in my case the fault is in only one of the socket circuit, all other sockets circuits are fine according to MT310 Socket Earth Tester. Initially I was measuring 24V between Neutral and Earth and later it was 97V! How did the OP overcome this problem?
January 6, 20215 yr 3 hours ago, Tim003 said: the fault is in only one of the socket circuit It is possible that the tester neutral is not making contact inside of the socket outlet, sometimes if you wiggle the 3-pin plug top it might come right. I often find this when the socket outlet contacts are worn. It could also be just a loose neutral.
January 6, 20215 yr 17 minutes ago, Gerrie said: It is possible that the tester neutral is not making contact inside of the socket outlet, sometimes if you wiggle the 3-pin plug top it might come right. I often find this when the socket outlet contacts are worn. It could also be just a loose neutral. Thank you for your input. The tester and sockets are still brand new. The last sentence is a likely possibility and I will investigate further.
May 16, 20215 yr Can I use the grid-in on the coil of a relay for the neutral earth bond on inverter out? This is as an alternative to the dry contact on the inverter?
May 17, 20215 yr 16 hours ago, l3ok said: Can I use the grid-in on the coil of a relay for the neutral earth bond on inverter out? Not really. You want the connection only when the inverter is running in battery mode. It might do that because of the lack of AC-in, but it might do that for other reasons, e.g. if the output source priority (setting 01) is other than UTi. But I suppose if you strictly only ever use UTi priority, then that would be OK.
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