Preventing reverse current in domestic solar power installation?





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  1. #1
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    Question Preventing reverse current in domestic solar power installation?

    So, my rather ancient prepaid elec. meter (CBI Ecolec 570) trips immediately if it senses even the smallest amount of reverse current. Looks like a known issue courtesy of Google. There is presently no option to have this meter replaced or swopped with anything else.

    I have a Victron installation with their Multiplus II inverter / charger and Venus GX management. When a large load switches off, there is sometimes a tiny overshoot (i.e. power into the grid) as the system tries to compensate, this trips the prepaid immediately. The Victron is set to always use 200W from the grid - initially this was 50W, but then it keeps tripping the prepaid meter very frequently.

    My installer is working on finding a solution, but as this is a major challenge in terms of stability, I am trying to find out as much as possible. I would appreciate any ideas.
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    Default Re: Preventing reverse current in domestic solar power installation?

    Is the load that causes the reverse current inductive?

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    Default Re: Preventing reverse current in domestic solar power installation?

    Quote Originally Posted by Richard Mackay View Post
    Is the load that causes the reverse current inductive?
    Is it the same load that is causing this every time?

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    Default Re: Preventing reverse current in domestic solar power installation?

    Perhaps fit contactors in line with supply ie when Mains drops out, contactor pulls in thus preventing any back feed into the prepaid. You might need two contactors for this or perhaps an automatic or manual change over switch.
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    Default Re: Preventing reverse current in domestic solar power installation?

    Quote Originally Posted by Richard Mackay View Post
    Is the load that causes the reverse current inductive?
    No, should be almost purely resistive - geyser element. Thus far it seems to be the only culprit. I am considering moving the geyser to the "non-critical loads" output of the inverter.

    Ideally of course I would not want to keep the 3kW geyser forever, but some way off going solar on the geyser (budget wise). Looking at a heat pump, but still a future project.

    The system itself has a multitude of control options, but the biggest issue seems to be the prepaid meter that does not tolerate even a very short duration reverse current.
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    Default Re: Preventing reverse current in domestic solar power installation?

    Quote Originally Posted by An3s View Post
    No, should be almost purely resistive - geyser element. Thus far it seems to be the only culprit. I am considering moving the geyser to the "non-critical loads" output of the inverter.

    Ideally of course I would not want to keep the 3kW geyser forever, but some way off going solar on the geyser (budget wise). Looking at a heat pump, but still a future project.

    The system itself has a multitude of control options, but the biggest issue seems to be the prepaid meter that does not tolerate even a very short duration reverse current.
    Where does the circuit trip? Is it on your DB, or is there a breaker on you prepaid meter, or is it the main supply in the box outside?

    The 'very short duration' is most likely plenty to time to bugger with the rhythm of someone working on the line, there is a reason municipalities and Eskom are so stuck on this issue. Where is the essential supply connected to the grid? Why are the two connected at the same time?

    Where this trip is occurring will help give insight into why.
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    Default Re: Preventing reverse current in domestic solar power installation?

    Quote Originally Posted by An3s View Post
    So, my rather ancient prepaid elec. meter (CBI Ecolec 570) trips immediately if it senses even the smallest amount of reverse current. Looks like a known issue courtesy of Google. There is presently no option to have this meter replaced or swopped with anything else.

    I have a Victron installation with their Multiplus II inverter / charger and Venus GX management. When a large load switches off, there is sometimes a tiny overshoot (i.e. power into the grid) as the system tries to compensate, this trips the prepaid immediately. The Victron is set to always use 200W from the grid - initially this was 50W, but then it keeps tripping the prepaid meter very frequently.

    My installer is working on finding a solution, but as this is a major challenge in terms of stability, I am trying to find out as much as possible. I would appreciate any ideas.

    A long shot, but would a dummy load before the inverter not absorb some of this load before it is seen by the meter? Almost like a capacitor in DC circuit :-)

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    Default Re: Preventing reverse current in domestic solar power installation?

    Quote Originally Posted by An3s View Post
    No, should be almost purely resistive - geyser element. Thus far it seems to be the only culprit. I am considering moving the geyser to the "non-critical loads" output of the inverter.

    Ideally of course I would not want to keep the 3kW geyser forever, but some way off going solar on the geyser (budget wise). Looking at a heat pump, but still a future project.

    The system itself has a multitude of control options, but the biggest issue seems to be the prepaid meter that does not tolerate even a very short duration reverse current.
    If your geyser thermostat has contacts you can access then i would use those to switch a contactor/relay and switch both the live and neutral connections.
    It sounds like the pre paid meter is transient sensitive..

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    Default Re: Preventing reverse current in domestic solar power installation?

    Thanks for all the replies!

    I would not like to mess with additional contactors or outboard control logic at this point, unless it is really unavoidable;

    It is the prepaid meter itself that trips, it has a built-in breaker on it. Googling "Ecolec 570 reverse current trip" brings up a few hits. I fully understand the need not to ever feed anything back, but this only happens while there is also an active grid supply. There is built-in control logic and interlocks to prevent this if the grid supply has failed.

    The prepaid meter is located inside the house, i.e. right where the municipal supply enters;

    The system is a Victron setup running in ESS mode. I am confident the installation is according to standard. The prepaid meter in question was installed in 2003/4 as far as I can see, no option to swop it.

    The solar setup supplies the house from the grid and also from solar, as long as the grid is present - so say the geyser wants 3000W, it will take (say) 2000W from the PV and 1000W from the grid. There is a grid setpoint value that tells it to always use a minimum load of X Watt from the grid. It is presently set at 200W.

    If it was the prepaid meter that was too sensitive to any transients, then the trip would have happened without the PV installation?

    On the monitoring system one can see a tiny negative spike (negative Wattage) at the moment that a large load switches off. I believe at that same moment, the prepaid meter trips on detecting reverse current.

    The idea of an artificial load has merit, just not sure how to implement it in a way that is fast enough to prevent the prepaid meter seeing anything going back.
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    Default Re: Preventing reverse current in domestic solar power installation?

    How about speaking to the installer and using some AC capacitors to help with the sudden load drop and disturbance that the prepaid meter might see. Further may be the 200W load at all times could be upped to say 400W from the grid. It does seem when it was changed from 50W to 200W things did improve as far as the tripping is concerned.

    I hope you can perhaps get someone to alter the setting that causes the trip on reverse power. I have just looked at a prepaid meter I want to install for sub letting and it actually stores the reverse power for life but does not trip in any way.

    A simple question. Is the CT clamp ratio set up at the correct ratio on the inverter?

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    Default Re: Preventing reverse current in domestic solar power installation?

    It's a real problem.

    Fact is the system is trying to prevent reverse power/current as best it can within the laws of physics. Reality is that it can only be reactive. It can only intervene once it senses reverse power, it can't predict when it is going to happen.

    Just like Electronic Traction Control on a 4x4. It can only intervene once you detect loss of traction.

    BIG BIG universal problem. Only real solution - Momentary reverse power tolerant meters.
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    Default Re: Preventing reverse current in domestic solar power installation?

    Quote Originally Posted by Fluffy View Post
    It's a real problem.

    BIG BIG universal problem. Only real solution - Momentary reverse power tolerant meters.
    Thanks for the reply! Yup, and with our municipality sinking fast and having abandoned the previous prepaid meters for unknown Chinese "smart" ones that are even worse, this has me worried.
    ZS6VL


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    Default Re: Preventing reverse current in domestic solar power installation?

    Quote Originally Posted by ekkekan View Post
    How about speaking to the installer and using some AC capacitors to help with the sudden load drop and disturbance that the prepaid meter might see. Further may be the 200W load at all times could be upped to say 400W from the grid. It does seem when it was changed from 50W to 200W things did improve as far as the tripping is concerned.

    I hope you can perhaps get someone to alter the setting that causes the trip on reverse power. I have just looked at a prepaid meter I want to install for sub letting and it actually stores the reverse power for life but does not trip in any way.

    A simple question. Is the CT clamp ratio set up at the correct ratio on the inverter?
    Thanks for the reply. I believe the CT is set up / configured correctly, it is internal to the inverter, will double-check. The unit does have the option of adding an external CT, but having read a lot about this, it seems the ever so slightly improved accuracy by measuring directly at the supply will make no difference to my problem.

    My biggest concern is having the added risk of power failure / another possible point of failure due to the prepaid being so sensitive.

    The thing with adding anything else for "load dumping" purposes is how to get this to happen fast enough.

    The prepaid is a 2003 model, long discontinued and not configurable AFAIK.
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    Default Re: Preventing reverse current in domestic solar power installation?

    This is common in most pre-paid meters.

    My modern one has a code which I can set to allegedly stop the meter from tripping. Have not tried as yet!

    It seems that many are factory set to trip which is a safety feature.

    Only real solution as Fluffy says are reverse power tolerant meters. When last I looked these were expensive and clearly you would have to comply with municipal regulations.

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    Default Re: Preventing reverse current in domestic solar power installation?

    Quote Originally Posted by An3s View Post
    Thanks for the reply! Yup, and with our municipality sinking fast and having abandoned the previous prepaid meters for unknown Chinese "smart" ones that are even worse, this has me worried.
    If you have constant base loads connected to AC out 2 (eg. pool pump) of the victron you could possibly prevent this trip as this circuits could absorb the spike, i know it has been done with conlogs this way, but the ecolec is a nightmare device for solar - only other option is the mecer - not ideal in my opinion.

    You mentioned the chinese meters we have in VDBP, do you know if these also trip with solar systems?

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    Default Re: Preventing reverse current in domestic solar power installation?

    Quote Originally Posted by Bosvark_1000 View Post
    If you have constant base loads connected to AC out 2 (eg. pool pump) of the victron you could possibly prevent this trip as this circuits could absorb the spike, i know it has been done with conlogs this way, but the ecolec is a nightmare device for solar - only other option is the mecer - not ideal in my opinion.

    You mentioned the chinese meters we have in VDBP, do you know if these also trip with solar systems?
    Thanks Bosvark. I am in the process of moving some loads to AC2, should definitely help as there won't be such sudden load changes on the inverter, I believe. I specifically opted for Victron, I had a brand new sealed Mecer / Axpert, but it was the 24V 3kVA version and I sold it to partly fund the Victron.

    The damn Chinese meters in Vanderbijl are also a nightmare IMHO, I was involved in a fact-finding mission when the implementation was started. We met with BXC and some ex-ELM electrical specialists who were doing consulting work, things initially looked promising, but given the many reported failures, comms errors and gross mismanagement by ELM (and the contract breaches etc.), I am not so sure anymore. I will contact BXC and ask them.
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    Default Re: Preventing reverse current in domestic solar power installation?

    Quote Originally Posted by Paul Dold View Post
    This is common in most pre-paid meters.

    Only real solution as Fluffy says are reverse power tolerant meters. When last I looked these were expensive and clearly you would have to comply with municipal regulations.
    I'd be happy to buy one, but how to get the municipality to accept and register it?
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    Default Re: Preventing reverse current in domestic solar power installation?

    Quote Originally Posted by An3s View Post
    Thanks Bosvark. I am in the process of moving some loads to AC2, should definitely help as there won't be such sudden load changes on the inverter, I believe. I specifically opted for Victron, I had a brand new sealed Mecer / Axpert, but it was the 24V 3kVA version and I sold it to partly fund the Victron.

    The damn Chinese meters in Vanderbijl are also a nightmare IMHO, I was involved in a fact-finding mission when the implementation was started. We met with BXC and some ex-ELM electrical specialists who were doing consulting work, things initially looked promising, but given the many reported failures, comms errors and gross mismanagement by ELM (and the contract breaches etc.), I am not so sure anymore. I will contact BXC and ask them.
    Cool, let me know if you found something from BXC. I'm planning on doing a test with a small grid tie system with these chinese meters to see if they trip like the conlog/ecolec meters, just hoping emfuleni switches me back on if it does trip. Will keep you posted

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    Default Re: Preventing reverse current in domestic solar power installation?

    When you mention Chinese meters is it the Hexing which I see is used by some munics and they are flagged as good meters by people working with them.

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    Default Re: Preventing reverse current in domestic solar power installation?

    Quote Originally Posted by ekkekan View Post
    When you mention Chinese meters is it the Hexing which I see is used by some munics and they are flagged as good meters by people working with them.
    No not the hexing meters, i wish it was those as they do work with PV systems.

    Its these:

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