A lot has been posted about this but I am confused on one issue:

To protect the grid one must not tie an inverter with a maximum  output of more than  3.5 KW.

But there are inverters on the approved list with far higher outputs - Goodwe is one at 4.6KW.

Can someone please clarify?

Edited April 3, 20197 yr by Mistral

The short version, if your home is on a 60A breaker, 3.5kW max. On an 80A breaker, 4.5kW max.

Thanks . So  What does it cost to upgrade from 60A  to 80A?

 

Very confusing!

COCT's limits are based on potential feed-in. Even if your grid-tied inverter has a limiter it may feed in maximum power for a brief period on a big load dump on your side.

This seems directly based on a document done several years ago where great fear has been expressed on what happens if there is too much PV power connected to the supply for your area. This is an attempt to limit the possible issues if every second house starts to put PV on their roofs and feeds in.

Of course it is based on the idea that the distribution network is an unmovable monster and cannot change to accommodate this. Of course this is wrong as has been shown in many other countries. The meltdown does not happen and excess peak power can be put to good use - here in Cape Town in particular - we have many hundreds of megawatts of solar batteries in the form of our two pump storage stations. Imagine we would use excessive PV power to pump water into these schemes rather than use coal for that ?

But that is far in the future - it will take a really long time before enough PV is installed on private homes and commercial PV farms to get to such a scenario. Right now the limits are, if anything, overprotective. But COCT takes this as being the law so that's just it - you have to live with it.

Thanks!

So what precisely in plain non-tech English is the existing regulation so we can all comply.

We all want to install legal systems!

22 minutes ago, Mistral said:

So what precisely in plain non-tech English is the existing regulation so we can all comply.

We have discussed this to death on the other threads and I have posted emails I have sent to the DA.

The bottom line: If you:
1) have the CoC in hand for the install,
2) have the engineering sign off report in hand,
3) having used a inverter on the list,
4) with max 3.5kw capabilities on a 63amp breaker, (or bigger if you have the breaker in place)
The curve ball comes in with a hybrid inverter re. the batteries:
5) you need a "separate suitably interlocked change-over switch" .

I quote the reply from the engineer I used, a reply which I forwarded to CoCT, DA etc:

A switch that in consultation with an suitable qualified registered engineer turns out to be technically impossible to meet, to name a three reasons:

• the technology does not exist,
• those that do exist are not certified under the right codes,
• inverters as a rule cannot communicate at all with external disconnect switches.

On some inverters you can limit how much is fed back to the grid so you can still benefit from the bigger inverter and more panels 

Just now, SilverNodashi said:

On some inverters you can limit how much is fed back to the grid so you can still benefit from the bigger inverter and more panels 

Technically that does not comply unless you can prove a hard limit. A hard limit is on that acts instantaneously or is dictated by the maximum power the inverter can produce. Note that this is peak power. The typical grid limiters (internal or external) use regulation to limit the power. This is not instantaneous and can take anywhere from just a few cycles to a few seconds. The assumption is that during the start of this period you are feeding in your peak maximum power briefly if the following condition is met: Your inverter is working at 100% of peak capacity supplying your loads and then you trip all of your loads. At that point in time your inverter feeds all of its power into the grid. Your limiter reacts and regulates the inverter to zero feed in within a few seconds. 

Yes, who cares ? The assumption is that every second house in your street has PV and you all do a maximum load dump at the same time. What does the grid look like at that point in time ? Not very pretty. Those still connected may experience a brief surge causing potential damage. Yes - this is highly unlikely, I know.

COCT is allowed to make exceptions to the inverter size on your connection. That does not mean they have to. 

Nevertheless - it appears they will accept soft limits (i.e. limits set in the inverter setup) - depending on how the South Easter blows on the day of application.

6 minutes ago, The Bulldog said:

Technically that does not comply unless you can prove a hard limit. A hard limit is on that acts instantaneously or is dictated by the maximum power the inverter can produce. Note that this is peak power. The typical grid limiters (internal or external) use regulation to limit the power. This is not instantaneous and can take anywhere from just a few cycles to a few seconds. The assumption is that during the start of this period you are feeding in your peak maximum power briefly if the following condition is met: Your inverter is working at 100% of peak capacity supplying your loads and then you trip all of your loads. At that point in time your inverter feeds all of its power into the grid. Your limiter reacts and regulates the inverter to zero feed in within a few seconds. 

Yes, who cares ? The assumption is that every second house in your street has PV and you all do a maximum load dump at the same time. What does the grid look like at that point in time ? Not very pretty. Those still connected may experience a brief surge causing potential damage. Yes - this is highly unlikely, I know.

COCT is allowed to make exceptions to the inverter size on your connection. That does not mean they have to. 

Nevertheless - it appears they will accept soft limits (i.e. limits set in the inverter setup) - depending on how the South Easter blows on the day of application.

I didn't see anything in their documentation that defines this very clearly. The way I understand it is that the soft limits won't feed back more to the grid than what is set. I get what you're saying though, but it's rather tricky, or vague, speaking to suppliers and trying to fit it all into the regulations. I have been assured though that the soft limits are acceptable. 

1 minute ago, SilverNodashi said:

I have been assured though that the soft limits are acceptable

@SilverNodashi this is a very important statement you make. We are in discussions with the CoCT how to handle the > 3.5kW dilemma preventing a lot of systems at the moment from successfully achieving SSEG connection. Can you please advice who made this statement. It would be of great help to us. 

3 minutes ago, Fuenkli said:

@SilverNodashi this is a very important statement you make. We are in discussions with the CoCT how to handle the > 3.5kW dilemma preventing a lot of systems at the moment from successfully achieving SSEG connection. Can you please advice who made this statement. It would be of great help to us. 

Let me clarify, this was from a supplier. I am not in CT and don't know anyone there to confirm this. And I think this is why the CoCT list of approved inverters have the bigger units listed. 

 

This is still new to everyone, so I think there is still a lot of miscommunication and misunderstanding about it all. 

 

As a side note: Ask 3 different electricians to sign off a COC for an inverter installation. One will tell you that you absolutely have to have a seperate DB. The next will tell you it's not necessary as long as the DB is split and labeled properly (which is acceptable according SANS) and the third one will tell you an inverter with solar panels cannot get a COC. 

Edited April 4, 20197 yr by SilverNodashi

So in this example - what figure do CocT use?

I've seen it says KVA not W so

the model number eg 3000VA or 5000VA

or the cont output power 3000VA or 5000VA

or the max apparent feed in power  2500VA or 4000VA

That refers to regulated power. Peak feed in can be anything up to the stated 9000W. The inverter is simply connected to the grid and the transfer relay is closed. The inverter does not know which way the power is going and does not care. It is the input current measurement that is used to regulate the current exported. That is not instantaneous.

But - regardless of that - if you are on a 60A single phase connection you are snookered. Unless COCT gives you permission they will currently fail your application.

The only real statements of value in the SSEG guideline are these:

** Generation Capacity refers to the total output capacity of the generator. For PV systems in particular, this refers to the maximum output of the inverter as limited either by hardware, or by software settings. The system designer/installer will provide guidance here. 

*** kVA and kW ratings for SSEGs are similar in most cases and can be used interchangeably for estimation purposes.