ct clamps too close together?

[UKMeterman]

You didn't mention the I boost, lets get one inverter working first!

 

[sean_ork]

Given that the installer appears to have been unable to install the CTs correctly, I very much doubt that they'll have been able to configure those inverters in cascade configuration (If indeed that's even possible with those inverters)

Given the usual SEG limit, did you receive permission to connect that capacity by your DNO, and did they ask to witness test the means of export limitation ?

You might want to start looking for a proven competent installer to have a look over that install.

 

[davesparks]

If each inverter is separately measuring the current to limit itself to 4kW then they will surely all be fighting against each other.

Each inverter would be measuring the combined output of all three inverters but trying to regulate that output as though it is the only inverter on the system.

 

[Gary K]

What are you doing with the rest of the power produced?
Are you heating a swimming pool or do you have another way to absorb the additional power if and when you can control the export to 4KW?

 

[jouleflow]

We have no gas so our electricity usage is high. We do have a pool heater & the iboost use a lot of the power. I try to use enough so the ct's don't limit the inverters. I don't think the concept is correct & maybe one large inverter with one ct should have been the way to go. I can understand the inverters fighting against each other & they are certainly not intelligently linked.

Regarding the dno accepting the install, I left this to the installer & I believe that the ct clamps have to be hard wired to the inverters, which they are, so they are reasonably tamperproof ?

I have been considering asking one of the trade organisations to look over the system. Is this a good idea.

 

[sean_ork]

Good luck getting anyone in a suit looking at it.

Do you get any errors displayed when they fault ?

 

[jouleflow]

The problem is that when it trips, it is in the main house but the inverters are in an outbuilding & often when I get to the inverters they are functioning again. So I haven't see any particular messages but the alarm light has been on occasionally.

Can I assume the trade organisations aren't be too bothered to check on their members work.

 

[sean_ork]

What actually "trips" ?

If you turn two of the inverters off will the remaining one function without issue ?

 

[jouleflow]

We have a split cu in the house & the rcd to on one side trips. None of the mcb's trip. This main cu controls the house plus feeds, one cable to the outbuilding via a 32A mcb. The outbuilding has the inverters which feed back to a garage style cu in the house that has a 100A main switch plus a 63A mcb. From this the + & - cables feed into two henley blocks below the meter.

I haven't tried switching off individual inverters, I am not confident that I could do everything in the correct order or know how to interpret the results.

I did consider disconnecting one of the ct clamps so only two would fight it out, This would give a theoretical maximum feedback of 5kW with the disconnected one running at 100% & the other two turned off by their ct signals. I'm sure this is not the done thing but just something to consider.

The rcd was off this morning, I assume this was due to the inverters start up load.

The rcd that controls the inverter side of the main cu is 80A and 30ms & seems to be the most sensitive part of the whole system. Due to the high startup demands, could this be changed for an 80A 100ms rcd?

 

[sean_ork]

If each inverter has it's own individual AC isolator just turn two off, removing CTs will not do anything helpful.

Has this system ever worked for any extended period of time without faulting ?

 

[Wilko]

Hi - Some invertor manufacturers advise using 100mA RCD on them. If you've the details we might be able to check. Also please confirm if you mean 30mA where you've said 30ms in #24 .
Changing the consumer unit RCD from 30mA to 100mA may not be possible here as the 30mA RCD may still be required for the other circuits.

 

[jouleflow]

If each inverter has it's own individual AC isolator just turn two off, removing CTs will not do anything helpful.

Has this system ever worked for any extended period of time without faulting ?

I will try that when I get home. Is it ac off first then dc off? to turn on is it ac on then dc on?

 

[jouleflow]

Hi - Some invertor manufacturers advise using 100mA RCD on them. If you've the details we might be able to check. Also please confirm if you mean 30mA where you've said 30ms in #24 .
Changing the consumer unit RCD from 30mA to 100mA may not be possible here as the 30mA RCD may still be required for the other circuits.

Sorry I meant mA. The feed from the inverters goes via the garage unit to the Henley blocks so dosen't go through the cu where the rcd trips. I believe the inverters use power from the grid to start up and although this does not go through the rcd could the brief startup cause an imbalance & still trip the rcd?

The inverter is a Solis 4G 5kW single phase.

 

[Wilko]

Hi - thanks - do you know the installation earthing type and any test results?
Ok, what is attached to the RCD that trips?

 

[jouleflow]

Hi - thanks - do you know the installation earthing type and any test results?
Ok, what is attached to the RCD that trips?

The incoming cable was increased to 135mm sq and I think is called tt. It was supposed to increase the available power and the main fuse was increased to 80A. This was also supposed to help with earthing. We are on the end of a line. There are a couple of earth rods that were put in to help years ago, should these be removed now so we just use the grid earth. I believe our earth is atached to the neutral anyway. They tested the ohms to see if the main fuse could be increased and the reading was ok to do so. It was 60A.

Attached to the rcd that trips? I am at work at the moment & I will post when I get home.

To try to solve the initial issues when the solar was installed was that it was originally connected to an existing new upstairs cu in the outbuilding. This cu was designed to have the lights - ring main etc of the upstairs part of the outbuilding. This cu had it's own armoured cable back to the house cu & the downstairs also had it's own cu that also had it's own armoured cable back to the house cu. To try to solve the issue all the upstairs cables were routed downstairs leaving the upstairs cu empty & purely for the solar input.