BritishRacingGreen

Another note to self: that power monitor must indicate flow direction as well, thanks.

@Coulomb, @87 Dream Ok so today setup a a DSO to check vector relations between current and voltage on the grid incoming. By setting it up I probably violated 0.6 COC rules per square inch of layout.😁 Note to myself : listen to people on this forum, be carefull, be safe, specially ⚠️⚠️that blikemse High tension solar DC.!!! Added a pure resistive load , kettle, drawing 8.5 amps and checked voltage and current nearly 0 degrees difference . Then removed load and checked the infamous 1.9 amp flow. Interesting the phase shift nearly approaches 90 degrees , which infers 100 % virtual power ( powder puff!) . Cannot really tell if current was lagging or advancing. But I suppose it was capacitive if anything else. So coulomb , you were spot on , near pure apparent power . So I am stepping down on this one. lessons learned: one thing I want in my future solar toolbox is an instantaneous real and apparent power monitor. Yes please, let's leave nothing to the imagination. Maybe the problem with us engineers is we pedantic, and as a result we don't sleep well. ! But hey that's how we roll. so no it's not power exporting. I have another discussion regarding blending , but will leave it for another day.

Good to know that thank you, I think it will not hurt to insert them anyways, so I put them on my installation BOM. Yes , unless someone correct me there will be movs in DC surge devices. Maybe gas arrestors as well , but they are used invariably to block leakage to earth from the movs. Maybe a bit of inductors as well to smooth rate of current change. But I cannot fathom why a good DC arrestor must cost in the order of 1000 rands. Because my take on them is to replace them every 2 years (consumables) , in order to reduce the probabilty of a faulty open circuit MOV ( bad undetected failure mode ) not being able to provide defence in the next round. We have learned these lessons in the railway , where qualative measures needs to prevail over quantative measures ( where you cannot measure a failure). If COC is going to require me to put on a commercial arrestor, then fine , but I will put my own devices also in place . Oh and I think your diode steering has another advantage , that is blocking reverse voltages in panels that are not exactly same output. Though I do think there is some block in the panel moulds themselves. But I like the idea , plus you can measure individual panel voltages at the combiner.

Thank you 87 , for valuable response. I have been so far avoiding the inevitable , ie. Flashing new firmware. But I suppose that going forward, I'll have to learn to do that sooner than later.

Thank you for your valuable response, Coloumb . I have no battery connected, so only grid,solar and load. I'll tell what I will do Tommorow . I will connect both voltage and current( via CT) and measure the phase relationships on two channel DSO. That will give me a measure of (a) how apparent the power is , and (b) direction of power transfer .

At the same time realized yesterday a simple characteristic of AC , that is , because of alternating current flow , we cannot detect the direction of power flow without calculating the vector relationship between current and voltage. Damn , this solar thing is getting complicated . But to see the sun operating my pool pump , whilst my middle finger is pointing towards Escom HQ , makes all effort worth it !!!

@Coulomb @87 Dream Curious Case of Serious Energy Waste , or is it? Hi guys , sorry for so many questions , but I have noticed a rather peculiar phenomena whilst testing. As you will recall , I have attached ammeter to the inverter grid input on my test jig. 1. Before the inverter is turned on , there a small quiescent current , which is normal, id say. 2. When I switch the inverter on , with zero load , the ammeter reads 1.9A . Huh? That's 427W of power ! . Is it coming in or going out? What is it? 3. That unaccounted 1.9Amps energy diminishes and vanishes as I introduce and increase load. pump , 2kw kettle , 2kw kettle and pump etc. 4. Remove grid , solar takes on all 800wats of pump power. pretty efficient transfer of energy from solar to load = 95.2%. This is not random behavior , pretty systematic / deterministic . I am battling with readout sequences on the kodak screen , so I am going to introduce a logger by next week in order to provide detailed logs. PS : I have stumbled upon this Spanish thread where the MAX is reviewed (I think this info also applicable to the VMIII and MKSIII). It would appear that energy are released onto grid when the load cannot handle it . This stuff is really above my paygrade. https://www.solarweb.net/forosolar/fotovoltaica-sistemas-aislados-la-red/48226-voltronic-axpert-max-review-profundidad-2.html In SUB, that is, when it is coupled with the network to add with it towards the loads, it also turns back (discharges) a lot of active power. We are not talking about a few watts .... In the following graph you will see it clearly: The discharge measurements are made with an EASTRON SDM230 network monitor connected to the AC INPUT of the MAX. The other active power measurement is with another EASTRON SDM230 connected to the AC OUTPUT of the MAX. Solar power measurements come from the MAX. It seems to me that it pours a lot into SUB. Too. In SBU it does not pour anything since it does not connect with the network. Is this what I fear it is , grid tied issues? Kind Regards dropkick

Good to copy your input , rclegg. If I may what do you use as automation controller? That sensor is cool ,(no pun intended), it is already calibrated and exposes its reading over i2c one wire bus. I bought them last week at microrobotics for 25 rand each. Value for money. Cheers

Valuable post , Sarel . Just shows to me the scalability of solar PV vs solar thermal (tubes) and the fine granularity by which one can scale and adjust load / consumption management. I have attached a 18b20 temp sensor at the neck if the outgoing hot water pipe , just for evaluation purposes. What powerfull little sensor. I am wandering about a profile where you heat up geyser during the day to say 60 degrees. Then you program that Arduino to go in geyser survival mode after no more sun.that is , use mains to maintain losses, but only up to 55 degrees Celsius. This is in the context of a system with no batteries, only solar, and objective is to decrease Eskom cost. No backup. Think this will be too little of a gain, or worth an evaluation shot?

Thank you, but can you confirm that while the Aluminum frame needs to grounded, the DC feeds are not grounded at any end, ie. Floating? On the note of MOV , I would dearly like to think that the DC surge arrestors available commercially also employ movs . If not can anyone confirm what technology is used.? Kind regards

Very valuable and interesting info. So if I read correctly, then if one is ok with no parraleling option, as well as lower charging current, then the Kodak vmiii is just as good as mksiii. And if so then vmiii is a lot of bang for your buck. I see here on the forum shop it's going for like 7700 rand.

Geez Sarel , just when I think I beginning to understand heavy current rollout philosophies, you come with this micro grids and AC and coupled system. Sigh. So much to learn. But I am following this thread with interest, a bit above my pay grade , but nonetheless. I have particular interest in your solid state element chopper. I will , weather,covid and funds permitting , invest in additional geyser, to act as what I call a 'water battery'. So I will drive both geysers with 5kva inverter, downgrade elements to 2kw each and then multiplex the power with something like you have here. So I am looking forward to your sessions on this product as you promised. I have a question so long for you. Instead of slicing/multiplexing the power cycles between geysers as you explained, would it be viable to chop energy on a per cycle basis , ie triac phase control. It will allow me to turn a 3kw element into a continuously variable element between 0 and 3 kW. Like a house dimmer. But this is a powerful one, will it upset the inverter , and will the resultant EMI/RFI issues be hell to deal with? My rationale is based on the fact this arrangement will have a lesser impact on instantaneous inverter power demand. Or am I wrong.? Kind regards Dropkick Murphy.

Yes, my Vmp is 170vdc and max open circuit is 250V DC. Because the axpert range is 450V , I reckon they clamping at 500v upwards. So knowing that I will not exceed 250v , I want my protection to be ideally 300v upwards , so I am going to suck up the garbage surges before it even enters the surge protection stage of the machine itself. To ensure that , I need to clamp between 300v and 450v . Unfortunately , as good as MOV s are, they possess a sloppy characteristic in terms of where they will start clamping in the real world. For instance a 280v MOV may not be suitable for my 250v , as the tolerance of the MOV is too big. Currently I am using two back to back epcos 20mm 115v movs , which combined will clamp at 328v . And of course they are placed between the DC fuses and the inverter, to ensure the fuse will protect the MOV and inverter when there is sustained surge energy. Of course a number of assumptions is made by me, experienced users must please correct me where I am wrong: 1 the PV output is regarded as floating, ie. No earthing on any PV leg, only PV frames are earthed. Therefore no protection required to earth. The movs employed only serves to protect the differential surges between plus and minus feed conductors. 2. The leakage current and capacitance disadvantage of MOV is not applicable here , so no need for gas arresting assistance to block leakages to earth. Hence the need for a simple MOV only arrangement. Kind regards

Thank you , it confirms that I will not unneccessary duplicate resources if I employ current xformer and RMS converter, and to some extent , as a semi-retired light-current engineer, I feel worthy again! For my configuration it is important , as I need a power blending percentage monitor , which gives instantaneous measure of what energy I am importing from Eskom , in relation to load. Or in other words , to what degree is solar helping to pay the bill .

Sadly , I do not see incoming mains current as a monitoring parameter on serial or WiFi watchtower. Also looked at axpert comms protocol qpigs commands, no mains power or amps offered, only volts and Hz. At the moment wired in fluke ammeter, but that's eating from the floor.

Yesterday I have performed a load test of a different kind. That is 800w pool pump over plus minus 25m cable. Very surprised and happy with results. Added an Ellies 8/20 13500 amp surge protector to the load side, and then I threw the kitchen sink at the inverter,including , inter alias , abrupt interruption of load, abrupt interruption of incoming mains. Very happy. Also , because if lack of sun yesterday , I observed power blending at work. At times 380w available from solar , and the inverter imported the balance from Eskom. Exactly what I needed. Magic.

Hi 87, thank you so much for inspiring words from a guru. Have been following you in coloumb for a while and got some really good insight. I am trying to following the manual as much I can , learning curve still. But I will try those inputs of yours soon as I can. Please find below the requested image of inverter. Regards dropkick

That begs a question. Where is neutral officially grounded. On my premise , or anywhere outside of my immediate proximity?

Hi, awesome forum this . Disclaimer : absolute beginner. I am busy test benching 5kw inverter and 2 x 5 x 465w panels. Panels are on ground but I have cloned my roof tilt angle and direction. I have single requirement, that is to augment solar energy with mains in order to reduce Eskom consumption. No batteries. Loads are limited to geyser and swimming pool pump for now. When mains is not available, and little sun like today here in Germiston, the inverter will limp with the small amount of energy that comes from solar, it actually adjust AC output voltage to xfer as much input power to output. My load is old oven plates for testing, but I don't like this lower AC voltage for say swimming pool pump. Can this be disabled? Or should I detect this and cut it out with external device. Inverter is in SUB mode. Also, my absolute max open circuited DC voltage is 250 volt DC . At the moment I have worked a MOV arrangement on the fuse to start clamping at 428v . That would allow me not to invite the inverter to clamp. But commercial offerings is in the order of 600v and 1000v DC, is this fine? Also they pretty expensive, so I want buy right. Thanking you.