CT Inaccuracies?

[radiomean]

I have a new Growatt system - SPH5000 +GBLI 6532, but the load is being reported inaccurately, and the battery is not supplying power overnight on a light load (200W or less). There is about 15 metres cat5 from the inverter to the CT - could the length be an issue?
Or could it be a poor installation of the CT in my consumer unit - pickup from other cables?

I am considering going to a meter - Eastron SDM230 modbus for better accuracy...
Thoughts appreciated?

 

[newbostonconst]

Need a shunt like the Victron BVM-700 models or their SmartShunt.

 

[SeaGal]

Need a shunt like the Victron BVM-700 models or their SmartShunt.

Err.. don't think that Victron Shunt would appreciate grid AC?

I would expect some inaccuracy from a CT clamp, but less than 50W or so, from experience. Try relocating the clamp position and make sure the connecting cable is not picking up too much interference, though, being twisted pairs should be OK. Not familiar with the Eastron SDM230, my Solis uses an Acrel CT clamp which seems accurate enough for the job.

 

[newbostonconst]

Err.. don't think that Victron Shunt would appreciate grid AC?

Doesn't say they are connected to grid.....and they are worried about having power over night thus battery capacity/usage is in question...

A shunt is a good diagnostic tool to verify battery is fully charged at the end of the day and the power being used over night and at any point in time.

What is your suggestion then?

 

[SeaGal]

Doesn't say they are connected to grid.....and they are worried about having power over night thus battery capacity/usage is in question...

A shunt is a good diagnostic tool to verify battery is fully charged at the end of the day and the power being used over night and at any point in time.

What is your suggestion then?

He refers to a CT clamp in his Consumer Unit - i.e. the house fusebox... which implies to me that it is the grid usage that is not being measured correctly, so the AC load is being supplied by the grid, rather than the from the batteries via the inverter. Apologies if I misunderstood.

 

[radiomean]

Hi, I think I have confused people. I think the battery is ok (if I use a substantial load like a cooker, kettle or immersion-heater, the appropriate power is taken from the battery). I just think the CT is reading wrong, or is receiving interference, which is causing energy to 'leak in' from the grid when it should not do so. I would appreciate advice about the proper location for the CT and reducing possible interference. Thanks!

 

[radiomean]

He refers to a CT clamp in his Consumer Unit - i.e. the house fusebox... which implies to me that it is the grid usage that is not being measured correctly, so the AC load is being supplied by the grid, rather than the from the batteries via the inverter. Apologies if I misunderstood

Hi SeaGal, you are exactly right and that is what I am worried about! My system is grid connected...

 

[SeaGal]

My 2p worth...

First, I'd see if you can re-locate the CT clamp outside of the CU - remembering that it must be around only one conductor not both live and neutral. Either wire would do, but you'd need to reverse the direction of the CT clamp if you put it on neutral.

Next.. is there any calibration possible on the GroWatt, or an ability to 'offset' the 200W inaccuracy via a sofware adjustment. You say "if I use a substantial load like a cooker, kettle or immersion-heater, the appropriate power is taken from the battery"... but does the battery deliver all the power or just all the power minus the 200W inaccuracy? Or don't you know? If you put the kettle on, does the utility meter stop showing any import? Just a few things to test to pinpoint the error.

Finally, if non of the above work and the Growatt supports interfacing with the Eastron SDM230 modbus meter, that sounds like a good option. Though it will mean you needing to tap into the meter tails, rather than using a non-invasive CT clamp (edited as CT clamp versions of eastron available).

HTH.

 

[radiomean]

My 2p worth...

First, I'd see if you can re-locate the CT clamp outside of the CU - remembering that it must be around only one conductor not both live and neutral. Either wire would do, but you'd need to reverse the direction of the CT clamp if you put it on neutral.

Next.. is there any calibration possible on the GroWatt, or an ability to 'offset' the 200W inaccuracy via a software adjustment. You say "if I use a substantial load like a cooker, kettle or immersion-heater, the appropriate power is taken from the battery"... but does the battery deliver all the power or just all the power minus the 200W inaccuracy? Or don't you know? If you put the kettle on, does the utility meter stop showing any import? Just a few things to test to pinpoint the error.

Finally, if none of the above work and the Growatt supports interfacing with the Eastron SDM230 modbus meter, that sounds like a good option. Though it will mean you needing to tap into the meter tails, rather than using a non-invasive CT clamp.

HTH.

Many thanks. I can't check at the moment, but I plan to take the CT out of the consumer unit and put it in the meter box, which only contains the meter and the main service cutout. I think there is much less chance of picking up spurious signals there.

I have also been in touch with Growatt service in the UK, and a helpful chap there was able to remote login to my invertor when I told him the serial number. He said the CT data was 'not as expected' and that putting the CT on the live wire in the meter box was the best position - so that's what I will initially try... Thanks again.

 

[radiomean]

Hi there, I have moved the CT from the consumer unit to the external meter cabinet. I have also re-done the wire from the CT to the inverter. The installer did not use a twisted pair in the Cat5e - he used two separate pairs, which makes it more liable to interference. I soldered all the connections and I think my improvements have fixed the issue. All the readings now make sense and there is very little 'leak' in from the grid now.

It looks like I do not need to go to the hassle of putting a meter in the tails from the 'meter box'. Thanks!

I have just added a picture of my meter cabinet. The blue CT is the Growatt one that I moved, and the white one is for a solar iboost...

Cheers, Bill

 

[SeaGal]

Result!

 

[alan2404]

I have the same issue , newly installed growatt inverter and battery but now my smart meter is indicating approx 200w base load all day long that the solar or battery don't take up.

I was hoping we could tweek the setting to account for the Ct consumption errors.

 

[radiomean]

Quote 'newly installed growatt inverter and battery but now my smart meter is indicating approx 200w base load all day long that the solar or battery don't take up.'

Interesting - sorry you are having a similar issue to mine, and thanks for a reply.

I have a load of about 100-200 watts on my smart meter also, but I think it's when the system is running on battery (such as overnight). When the PV panels are supplying electricity in the day there is little or no 'leakage'...

a) Where is your CT installed and how long is the cable to the inverter? I have about 12 metres cable.

b) I now suspect it's the CT reading low (not detecting all the grid input) and the battery is thus supplying not enough power. I am going to thoroughly clean the CT contacts and (as far as I can) make sure it's working properly.

c) Also, I have ordered the Eastron SDM230 modbus meter and will consider having that put in the meter tails, for hopefully better accuracy.

Good luck!

 

[FVScimitar]

Quote 'newly installed growatt inverter and battery but now my smart meter is indicating approx 200w base load all day long that the solar or battery don't take up.'

Interesting - sorry you are having a similar issue to mine, and thanks for a reply.

I have a load of about 100-200 watts on my smart meter also, but I think it's when the system is running on battery (such as overnight). When the PV panels are supplying electricity in the day there is little or no 'leakage'...

a) Where is your CT installed and how long is the cable to the inverter? I have about 12 metres cable.

b) I now suspect it's the CT reading low (not detecting all the grid input) and the battery is thus supplying not enough power. I am going to thoroughly clean the CT contacts and (as far as I can) make sure it's working properly.

c) Also, I have ordered the Eastron SDM230 modbus meter and will consider having that put in the meter tails, for hopefully better accuracy.

Good luck!

How have you got on with this... have you installed a meter? If so where from

 

[radiomean]

Hi... I have installed the Eastron SDM 230 Modbus in my external meter cabinet, but have not yet fully connected it as it obviously needs connection in the tails, which means the main fuse must be disconnected.
I have tested it by powering it from an extension lead at 230V, and connected it to the CT1/Meter1 port on my SPH5000. Please see the attached photos - note on the SDM 230 the 'phone' icon is displayed, which means it's communicating correctly with the SPH5000 invertor. The connection to use on the invertor is the CT1/Meter1 port. (in the photo is it obviously not connected, and the CAN connection is to my battery)

Just waiting to get it connected in the tails now...

I am in the UK and I got the meter from eBay, but it is also available from - https://www.metermarket.co.uk/produ...ngle-phase-100a-direct-connected-energy-meter .

Edit - when you connect the Eastron to the Invertor, you need to change a menu item from CT to meter to get it to work...

 

[FVScimitar]

Great just had last November 2022 solac x1 ac 3.6kw inverter and two solax batteries 11.6kw
working which is lovely and saving hopefully on electric bill....

Just found the forum, and a thread came up like yours on CT clamps, I thought I had Eastron SDM 230 meter, which there is in the
mini CU with seperate tails from the henley block for my battery system.... there is Eastron but the cable is NOT connected... only CT clamp
next to Grid Live in Meter cabinet (UK), will look at the manuals and Eastron sheet about the connections... which the Installer did.

On solax ac inverter only one connection for either Meter or CT.... mine is CT .....
Yes have tried the Meter and change inverter setting to Meter and check export control is 0...
when reconnecting power to the inverter and goes through its cycle to operate.. it states Meter Fault....
could be how the Eastron SDM 230 Meter is wired using the 4 connections/ports in the mini CU.
Mine is V2 on the box the meter came out of.

No Telephone icon on my Eastron.... probably as cable to inverter is not connected.

 

[radiomean]

Hi, several thougts...

a) My install (see the top of this thread) had the CT initially in my consumer unit, but it was hideously inaccurate so I moved it to my external meter box, where it still it - and it is performing within tolerance, according to Growatt (it 'leaks' up to 100 plus watts in per hour - but with current electricity costs, that is still up to one pound a day, so it is well worth spending £40 on a meter to sort it...)

b) As you see from my photo, the connection to the invertor is labelled Meter/CT so I expect there will be a setting to change on the invertor to accomodate the meter, as opposed to the CT. Oh, you say you've found that. Maybe you need to change baud rate or something else on the meter...
My meter is also a V2.

c) Could you post a picture of your setup with the meter? Did you power up the meter when you tried it?! I assume so...

d) I've got 6.5 kW battery, considering another 5 kW battery but waiting until more sunlight!

e) I assume you've found (or have) the Solax manual for the connections for the Meter (I found it on the Solax site - is this the right one?

X1-Boost G3 Series Installation Guide-20220929-EN )​

Cheers...

 

[FVScimitar]

Baud rate and address 1 on solax and eastron meter match...

Yes have checked the manuals for the solax x1 AC 3.6kw battery inverter... my solar is on Solax X1 Boost 3.6kw

My battery system 11.6kw has been great since middle of november 2022 when installed... previously just the
solar and iboost+ made a great difference for electric and hot water in 2021 which made me investigate the cost of
battery system... glad I did with what has happend in 2022 energy crisis happening.... It did take 6 months of waiting from
ordering with ITS in stockport to finally get my batteries and get prior approval from DNO on G99 Fast Track to install
as my previous solar array system is G98 with SEG with Octopus on their Octopus Go for my EV, but well worth the wait now...
considering what has happened. Really glad I made the choice, decision then in late April 2022.

i also made some comments in this thread...

Growatt SPH and Power import control from grid

dont give up, get your self a meter and dump the rubbish ct clamp, the amazon link above the the correct one, works great and its only £50/$55 ish. Good hardware bad support.... just use the community for help, not their support line :) Should have mentioned the make and model of the smart...

diysolarforum.com

 

[FVScimitar]

Will try to get some pictures on iphone

 

[FVScimitar]

Did some changes to the Solax X1 AC 3.6kW inverter which is using CT clamp in Main electric cabinet with the DNO meter and 100A fuse.

On the iphone Solax App in settings changed/checked the Advanced settings>CT Enabled which is correct and never changed

Meter/CT ID > 1 correct and never changed

Meter/CT 1 > Direction> Negative changed from the installer from the Default of Positive.
(Curious as to what this would do no harm in trying, if importing 3000w then return setting.)
I can check the wattage from the iboost+ setup with the iBoost Buddy monitor located in
hallway of the house... to see import or export readings.

CT lamp is Eastron 16mm with white and black/white wires with Accurracy 0.5% for monitoring.

Before the Change of settings above, I was drawing 200w baseload and was always showing on Octopus iphone App, with Live Tab for date, and the Day for live data usage... as I have connected up previously Octopus Home Mini....
The live data was always showing a Positve number ie 75w to 150w which is grid import
as new to battery storage never realised the data...

checked with iphone Apps Octopus Watch and Octopus Compare using Octopus API data credentials....
which give daily usage in kWh, 30min time periods for the 24 hours and the price compared with the other Octopus tariffs from the settings.
I am on Octopus Go and could see the data for the octopus flexible tariff versus the Octopus Go.... was making savings...

Now with the above change, Octopus Live is showing constantly a Negative number ie -30w - -125w readings constant export
but it is not really export.

So todays reading on the apps show a big reduction in the Daily price Price which is fantastic now...

Not really worried now that the Eastron SDM 230 meter is not connected to the solax x1 AC 3.6kw inverter via the RJ45 cable as it is not connected.
Before paying for 11.6kw battery usage from £2.05 to £2.50 for battery consumption and a daily import of 2.4kw from the base load, without the EV charger being used.

Now the Price is saying £1.47 for about the same usage without the constant daily import of 2.4kw base load.

Bill for last month with full use of batteries was £70.10 down from £120 with out batteries.

next month's bill will be very interesting to see, all in all the batteries are doing a great job, now without consuming import of the 200w base load.

This might help someone with Solax connected inverter with CT clamp by Eastron... not all CT's are equal.

 

[radiomean]

SEG with Octopus on their Octopus Go for my EV, but well worth the wait now...
considering what has happened. Really glad I made the choice, decision then in late April 2022.

Hello again... Just popped in to say I have today changed over to Octopus, (currently away for a few days) but when I get back I am ready to do the setup to go onto Intelligent Octopus tariff. Suggest you investigate it as it's 6 hours at 10p overnight (up from 4 hours on the Go tariff). I think I said I also have an EV...

Will have a look at your answers shortly. Still have to get my Eastron SDM230 wired in fully, and am investigating a 'Chinese' sourced battery as my 6.5 kW does not quite last overnight. Considering a 3 kW rack mounted unit, which at around £850 is dirt cheap and the supplier claims it works with Growatt... Battery is - https://www.aliexpress.com/item/1005004004392051.html

 

[FVScimitar]

Update on last month the setting for the Solax CT clamp have not changed, Grid Off Peak usage 350 kWh and 14.5 kWh for Peak usage so well pleased.

Electric Bill of £46.48 with Standing daily charge of £14.66 included
So we’ll pleased

 

[MACNETWORK]

I think one of the problems with Growatt and the CT is that Growatt supply a plastic coupler to extend the cable - this leaves the shield on the CT end un-earthed - it needs a shielded coupler. And of course the installer coiled the excess cable up in the meter cabinet next to the power cables. Notice how the cable supplied with the CT clamp is very neatly looped and not coiled - it's important.
Also, I see someone used Wago connectors - these are specifically not recommended in the CT datasheet.

 

[FVScimitar]

After reviewing the amount of batter kWh per day to prevent Grid Import; my Live Data from Octopus Home Mini was reporting fluctuating negative -80 to -150 hour per day to prevent Grid Import from my battery storage of SolX 11.6kW minus 10% so 10.2 kW of usable energy, so my daily export for battery was about 2.4kW considering a lack of sun for this March,

I looked at the how the the CT cable was arranged from inverter to Main Meter Box located on outside wall, RJ 45 was unshielded cable and ran along the new Tails to the Mini CU that the installer put in for solar and battery systems.

Purchased a 5m Shielded cable STP, drilled a new hole in brickwork away from the Tails from Henley Block, connected up to the CT using inline wago connectors and guess what the negative - 100 to - -150 W Battery consumption to prevent Grid import reduce the number to under -50w which is probably less than 0.8 kWh so less than 1kW export daily compared to the usual 2.4kW daily as Octopus app now reads so know doubt save battery export plus less Off-Peak battery charging from now on.

 

[nathanharryuk]

Hi all, with regards to the meter and pigtails needing to be done by an electrician because of the main fuse, is it possible to flick the main breaker in the CU and add it to that breaker itself? Meaning when flicking the breaker back on the meter should come on and should give the same reading as if it was connected to the pigtails? Hope that made sense!