Switch on Grid Export on Solar Inverter

[eddysacc]

This is my first post in the Solar Subforum so please be kind.

 

First of all thank you very much for sharing your stories and experiences about your Solar projects. It has really been a pleasure to read what you guys have been doing and it has been a motivation for me to try my own small Solar project.

 

I am currently runnung 8x450 W mono "sunpow" panels from lazada and a 6000Watt "Invt iMars MG6KTL-2M" inverter.

 

The panels got installed by a local Solar handyman on top of a pu enforced metalsheet roof. 

 

The Solar is running for 2 months now and the inverter is set to no grid export until now.

 

I assume from your posts that the 8 panels would able to generate 14 units/ day in average. We are using about 5 units from the Solar when the sun is shining and we are letting go 9 units every day.

 

I am thinking to partially feed the grid like some guys here gave advice.

 

But is there anything to be considered when switching on/off grid feed export in the inverter menu?

 

 

[Crossy]

Looks like a neat install ???? 

 

Do you have a link to the manual for your inverter, we need to see what it can do.

 

EDIT Also what kind of electricity meter do you have, spinning disc or electronic?

[eddysacc]

2 hours ago, Crossy said:

Looks like a neat install ???? 

 

Do you have a link to the manual for your inverter, we need to see what it can do.

 

EDIT Also what kind of electricity meter do you have, spinning disc or electronic?

Thanks Crossy. Its a neat install for thai standards you might mean.

 

There is a regular manual and a small manual for "setting up Export Limiting using a smart meter". (I haven't got a smart meter )

 

Ps:

 

The meter should be an ordinary style spinning disc type. Looks fine to me.

 

 

iMars-MG-Manual (1).pdf

[eddysacc]

This is the manual for the smart meter.

 

As mentioned I haven't got a smart meter installed. At least i speculate the small manual seems to a an export section in it. Not sure if it helps:

[Crossy]

This unit doesn't have a Current Transformer (CT) to sense the grid current, instead it uses an accessory they call a Smart Meter.

 

You will need one of these in order to control whether you export or not, hopefully your supplier will be able provide (and it won't be silly money - CTs are really cheap). 

 

EDIT Looks like a couple of k Baht  

http://www.ideasolarshop.com/product/348/smart-meter-กันย้อน-single-phase-invt

 

There's a bunch on Lazada too, some a bit cheaper.

 

Of course part of the Smart Meter is a CT ???? 

[eddysacc]

Thanks Crossy.

 

I was hoping to do the export meter DIY as wifey is strictly against anything that could be against the law. Actually If the solar guy comes to our house chances are high that she will find out what could mean lost trust in each other.

 

 

Would you say DIY is doable for somebody with rudimentary electrical skills and no skills in solar whatsoever?

 

[Crossy]

It shouldn't be rocket science.

 

Note that without the add-on you are probably exporting anyway as the inverter has no way of knowing where its generated energy is going.

 

The add-on allows you to STOP export (most important that the meter man doesn't see it going in reverse).

 

You can check easily by turning off all the loads in your house on a nice sunny day and observing the meter disk. If it goes in the opposite direction to the arrow then you are exporting.

[bluejets]

Another consideration, all_be_it at additional initial setup cost, is to run a storage type hot water system directly off your grid.

 

Isolate the circuit with a timer and relay say from 4 pm to 9am next day so unit only heats during daylight hours, hense using some of your valuable self generated energy and storing that energy in the form of hot water for night time use.  Works similar to a storage battery. Only downfall is when it is rainy weather and system uses grid power. There are ways to circumvent this also I might add.

[eddysacc]

10 hours ago, bluejets said:

Another consideration, all_be_it at additional initial setup cost, is to run a storage type hot water system directly off your grid.

 

Isolate the circuit with a timer and relay say from 4 pm to 9am next day so unit only heats during daylight hours, hense using some of your valuable self generated energy and storing that energy in the form of hot water for night time use.  Works similar to a storage battery. Only downfall is when it is rainy weather and system uses grid power. There are ways to circumvent this also I might add.

Good Idea bluejets.

 

Now there is a hugh water tank outside with direct sun exposure all day round. That heats up the water house supply quite a bit.

 

I like to shower hot at 40°C yes. but Wifey and the small kids like it cold.

 

 

Another Idea would be a Life4Po battery.

 

How much capacity would be a fit for the 8x 450w panels?

 

Did you or crossy maybe come about a reasonable battery solution lately?

 

 

[eddysacc]

On 11/22/2022 at 4:16 PM, Crossy said:

It shouldn't be rocket science.

 

Note that without the add-on you are probably exporting anyway as the inverter has no way of knowing where its generated energy is going.

 

The add-on allows you to STOP export (most important that the meter man doesn't see it going in reverse).

 

You can check easily by turning off all the loads in your house on a nice sunny day and observing the meter disk. If it goes in the opposite direction to the arrow then you are exporting.

THANKS for sharing your thoughts crossy.

I am not exporting that is for sure.

All my considerations would be solved if the inverter would be exporting.

 

As you see its a bit rocket science, for me at least ????

[bluejets]

On 11/23/2022 at 7:14 PM, eddysacc said:

Another Idea would be a Life4Po battery

Costly and end up no advantage.

[Crossy]

On 11/23/2022 at 7:28 PM, eddysacc said:

I am not exporting that is for sure.

All my considerations would be solved if the inverter would be exporting.

 

Hmmmm. How do you know you are not exporting? (inverter settings mean nothing)

 

With a regular grid-tie inverter (which you appear to have from data provided) it will generate power to the limit of what's available from the panels. Once the local load is satisfied any spare energy is exported (this is controlled by physics, not by any inverter settings).

 

The inverter can limit or eliminate export by reducing its power output to match the local load. It can do this by either monitoring the local load OR by monitoring the grid energy. Your unit can monitor the grid energy using the add-on unit.

 

Have you tried killing the local load and watching the meter?

[Crossy]

9 hours ago, bluejets said:

Costly and end up no advantage.

 

Unless you want the UPS functionality provided by most if not all hybrid inverters, or you have an electronic meter that won't net-meter (there have been reports of electronic meters in Thailand actually charging for exported energy) and you want to store excess generation (there are of course other ways of using excess generation, such as hot water storage).

 

Costs are coming down and more second-life vehicle packs are coming on the market.

 

Our (well) used LiFePO₄ golf-cart cells keep our lights, TV, one A/C etc. on for 4-5 hours at night before the genset has to start, during the day the solar will happily supply our normal load and charge the batteries** with the grid off (we would normally be exporting if the grid was on).

 

** Assuming the weather plays ball, unlike the last 3-4 days ???? 

[eddysacc]

On 11/25/2022 at 5:06 AM, Crossy said:

 

Hmmmm. How do you know you are not exporting? (inverter settings mean nothing)

 

With a regular grid-tie inverter (which you appear to have from data provided) it will generate power to the limit of what's available from the panels. Once the local load is satisfied any spare energy is exported (this is controlled by physics, not by any inverter settings).

 

The inverter can limit or eliminate export by reducing its power output to match the local load. It can do this by either monitoring the local load OR by monitoring the grid energy. Your unit can monitor the grid energy using the add-on unit.

 

Have you tried killing the local load and watching the meter?

There is definitely no export to the grid.

 

There is a CT anti reflux installed. I guess its telling the inverter to limit down power generation to not exporting to the grid.

 

[Crossy]

Ah-ha, so you DO have a CT installed, I really wish you had said this a little earlier ????  

 

This is good because you should be able to control whether you export or not by turning the function on / off.

 

It might be as easy as simply unplugging the CT from the inverter (that's how I turn export on/off on our Sofar inverter).

 

Why not give it a try?

 

It's important to understand that a grid-tie inverter will, by default, send out as much power as is available from the panels, it doesn't care (or know) where it goes so any that's not used locally goes out to the grid.

 

The anti-reflux function (with the CT) actually limits what the inverter generates so that the grid energy is zero (or pretty close to it).

 

 

 

[eddysacc]

2 minutes ago, Crossy said:

Ah-ha, so you DO have a CT installed, I really wish you had said this a little earlier ????  

 

This is good because you should be able to control whether you export or not by turning the function on / off.

 

It might be as easy as simply unplugging the CT.

 

 

 

 

2 minutes ago, Crossy said:

Ah-ha, so you DO have a CT installed, I really wish you had said this a little earlier ????  

 

This is good because you should be able to control whether you export or not by turning the function on / off.

 

It might be as easy as simply unplugging the CT.

 

 

 

Crossy thanks to you.

 

So it would be okay to just plug out the cable from current transformer going in the inverter? Thats easy.

 

Does the inverter have to be turned off while doing that?

 

That would be an easy way. And there would be no need to reconfigure the inverter when the man from The PEA comes to check the meter reading.

 

Life can be so easy sometimes.

[Crossy]

Just pull the plug and see what happens, nothing will get damaged.

 

The worst that may happen is the inverter throw an error "CT disconnected" or something like, but I suspect it will just go to full chat.

 

I do see that our Sofar, won't go to full power if it's been limiting and has shut down one string, but we turn our CT on/off at midnight so everything is asleep anyway.

 

If you don't go to full power try turning the inverter off then on again with the CT disconnected.

[eddysacc]

Pulling the CT string brings the Solar output slowly down to 0w.

Why is it?

 

Restarting the inverter with pulled out cable results in the same. Going slowly to 0w.

 

Plugging in the CT cable brings the output back up to about 1000w solar production at this moment.

 

Am i missing something here?

Maybe the Invt inverter needs the cable to be plugged in?

[Crossy]

Sadly, it does look like the inverter manufacturer has pre-empted us ???? 

 

Can you disable the CT thingy or control the level of export via the inverter menu without adding that 2k bit of hardware?

 

Unfortunately, the manual isn't a lot of help without sitting in front of the inverter (our Sofar is just as bad).

 

It "might" be possible to simulate a CT connection that makes the inverter go to full power, but I think that's going to be beyond what we can do on an internet forum.

 

Does the inverter have a FaceBook group? There's often all sorts of handy hacks lurking in there ???? 

[eddysacc]

On 11/28/2022 at 4:50 PM, Crossy said:

Sadly, it does look like the inverter manufacturer has pre-empted us ???? 

 

Can you disable the CT thingy or control the level of export via the inverter menu without adding that 2k bit of hardware?

 

Unfortunately, the manual isn't a lot of help without sitting in front of the inverter (our Sofar is just as bad).

 

It "might" be possible to simulate a CT connection that makes the inverter go to full power, but I think that's going to be beyond what we can do on an internet forum.

 

Does the inverter have a FaceBook group? There's often all sorts of handy hacks lurking in there ???? 

It looks like it is working now.

The inverter did not like pulling the CT string while working on full load, though.

 

Strangely, pulling the CT string meant that the inverter did not come working again that day with the CT cable plugged out. I had to plug it in again.

 

But pulling the CT string out the next day while the inverter was sleeping worked fine and does so now.

 

Everything looks good now for a few days. The inverter is feeding back to the grid. The meter disc spinning backwards. Am me being a happy man observing it ????

 

Thanks Crossy for sharing your wisdom here.  ???? 

 

 

[Crossy]

3 minutes ago, eddysacc said:

But pulling the CT string out the next day while the inverter was sleeping worked fine and does so now.

 

Yeah, it's possible it checks for the presence of a CT when it wakes up, and just gets confused if things change when it's working, so any switching will need to be done at night.

 

Great that you have a solution ???? 

[MJCM]

1 hour ago, Crossy said:

Yeah, it's possible it checks for the presence of a CT when it wakes up, and just gets confused if things change when it's working, so any switching will need to be done at night

So what you are saying is that you can't switch off an inverter during the day, make some changes, start it up again and see if it works?

[Crossy]

2 minutes ago, MJCM said:

So what you are saying is that you can't switch of an inverter, make some changes, start it up again and see if it works?

 

Generally, turning off completely would make it start from scratch, so you "should" be able to do that.

 

But you would have to ensure it was completely "off", so no grid, no solar and then have a coffee to ensure everything was discharged.

[Muhendis]

1 hour ago, Crossy said:

 

Generally, turning off completely would make it start from scratch, so you "should" be able to do that.

 

But you would have to ensure it was completely "off", so no grid, no solar and then have a coffee to ensure everything was discharged.

So making physical changes requires a complete reboot.

Sounds pretty normal to me otherwise how can the software know if something has been deliberately changed or if there is a malfunction for example?

[MJCM]

13 hours ago, Muhendis said:

So making physical changes requires a complete reboot.

Sounds pretty normal to me otherwise how can the software know if something has been deliberately changed or if there is a malfunction for example?

I agree, but I was confused by this remark

 

15 hours ago, Crossy said:

so any switching will need to be done at night.

And I sincerely doubt that I can get my installer to come over at night

[Crossy]

51 minutes ago, MJCM said:

I agree, but I was confused by this remark

 

16 hours ago, Crossy said:

so any switching will need to be done at night.

And I sincerely doubt that I can get my installer to come over at night

 

I'm not sure which part is confusing you.

 

If you are going to be turning export on/off by disconnecting the CT you need to do it when the inverter is sleeping, i.e. at night.

 

Unless, of course, you intend re-booting the beast each time.

[MJCM]

5 minutes ago, Crossy said:

 

I'm not sure which part is confusing you.

 

If you are going to be turning export on/off by disconnecting the CT you need to do it when the inverter is sleeping, i.e. at night.

 

Unless, of course, you intend re-booting the beast each time.

Maybe using confused was the wrong word.

 

But I now fully understand what you mean by it. Because at night the Panels don't generate and thus easier to disconnect things and also the Inverter is already in Standby mode.

[Muhendis]

3 minutes ago, MJCM said:

Maybe using confused was the wrong word.

 

But I now fully understand what you mean by it. Because at night the Panels don't generate and thus easier to disconnect things and also the Inverter is already in Standby mode.

If the inverter has batteries then it will still be running without solar input. The grid is not connected in these circumstances so disconnecting the CT should not be noticed by the inverter. But that would depend on whether or not the CT is monitored for any reason.

[eddysacc]

Thanks everybody for the value added.

[007 RED]

On 11/28/2022 at 3:00 PM, Crossy said:

Just pull the plug and see what happens, nothing will get damaged.

 

The worst that may happen is the inverter throw an error "CT disconnected" or something like, but I suspect it will just go to full chat.

 

I do see that our Sofar, won't go to full power if it's been limiting and has shut down one string, but we turn our CT on/off at midnight so everything is asleep anyway.

 

If you don't go to full power try turning the inverter off then on again with the CT disconnected.

Today was meter reading day (16/12/22), so my small scale system has been in NO EXPORT mode since yesterday just in case the meter reader came early.

 

The meter reader arrived at 14:10pm, so a few minutes after his departure I flicked the NO EXPORT switch back into EXPORT mode and looked at the meter.  The disc was merrily spinning backwards again.

 

As shown in the screen shot below from the system's monitoring facility, the inverter appears to have picked up that the CT was disconnected at approximately 14:15pm and thus allowed power to feedback into the grid.   FYI... I switched on one of our AC units for approximately 10 minutes at around 14:30pm and the graph below doesn't show any consumption spike which I would have expected if the system was in NO EXPORT mode.  This confirms that the inverter was not getting any consumption feedback information via the CT.

 

Tomorrow I will do a reverse test e.g. allow the system to operate in the EXPORT mode in the morning and then throw the switch to NO EXPORT in the afternoon and see what happens.  Hopefully no magic smoke ????.   I will report back.