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Circumventing the COCT 3.5kVA limit


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If one has extra space in the DB, one can install an extra changeover switch so that the non-essential loads can be switched over to the Inverter Output.  You must then carefully manage the loads so t

But software limiting is allowed. When this limit is configured, the maximum power capacity of the Multi at the point of connection becomes 15A. The total capacity could be more (which is the point of

Out of curiousity...  the 25 % rule is for the breaker connecting your property to the grid?  In a complex, we have a 600A breaker - so I can merrily have 33 kilowatt of generation going on here?

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6 minutes ago, calypso said:

Too late to edit now. But IE: is it a once off inspection or annual etc. 

I doubt anyone would ever visit you again, unless the transformer on the street corner blew up and they're hunting for the cause.

If the option to override the current limit via a GX device is disabled, then you would need the (expensive) VE.Bus to USB cable in order to change the current limit. So your installer could make it hard for you to change the limit if he/she was so inclined.

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Well if its something like a Multiplus 2 3000w then you wont need any limits as it cant invert over the limit. Then just push more grid it to max out the 32A transfer switch. 

If a 5000w unit then yes you would need to put in the software limits. 

 

 

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5 hours ago, calypso said:

Well if its something like a Multiplus 2 3000w then you wont need any limits as it cant invert over the limit. Then just push more grid it to max out the 32A transfer switch. 

If a 5000w unit then yes you would need to put in the software limits. 

CoCT looks at the maximum current at the point of connection between the grid and the inverter, so even if you have a 3kW Multiplus you would still have to limit the AC transfer to 15A.

I strongly suspect that this interpretation is contrary to how they interpreted their own regulations previously, but this is the way things currently stand. There is no restriction on the amount of power you may generate for the loads connected to the inverter output, as long as you stay under the current limit between the grid and the inverter.

Edited by PierreJ
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11 hours ago, PierreJ said:

CoCT looks at the maximum current at the point of connection between the grid and the inverter, so even if you have a 3kW Multiplus you would still have to limit the AC transfer to 15A.

Again, I go back to basic principles. I was told this is about the pick-up. When you install the inverter, you should not make the situation WORSE than it is.

There are two kinds of pickup that needs to be considered (do tell me if I am missing something).

1. The first is the kind of pickup that happens when an embedded generator disconnects. In other words, this happens when there is a disturbance on the grid but it is not a full-blown outage. The embedded generators trip and all loads pile back onto the grid.

2. The second is the pickup that happens after an outage, when everyone's geyser and freezer turns on immediately.

Now let's consider the case of a 3kVA Multi that does not have its AC-in limited to 15A. This means that it can feed in 2400W into the grid, which means the maximum pickup in situation 1 above is 2.4kw. After an outage this inverter will wait 60 seconds, and then bring all the loads on the output back online. These loads cannot exceed 3kw... because the inverter would have been overloaded during the outage in that case. Requiring that these loads must be limited to 15A is impractical and adds nothing.

What does make things worse is if the inverter/charger immediately starts charging the batteries. Now it has to pick up the full 3kw load plus the charge power (35A times roughly 50, not even 2kw).

But what makes this really interesting, is that UPS setups are not required to register, not subject to these rules... and they are the ones most guilty of adding battery charging load to the grid.

So I'm really not sure about this overall 15A limit. Limiting the AC input on a 3kva is not necessary as far as I can see, since it is not making the pickup worse. With a 5kva it would be necessary, because you'd run into trouble with the first item above.

Edited by plonkster
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I think the municipality is opportunistic with their approach. They move the control to the home owner instead of being able to supply the maximum amperage we require - which is lot more than 15a. It will be utopia for them if they can reduce the home demand automatically to 15a max per connection. Just think, no more transformers tripping on overload.

When a stove, geyser and kettle are on simultaneously they far exceed the supposedly allowable 15 amps. And if the power trips you will hear the women complaining. My wife will definitely.

Something is wrong with their approach.

 

 

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28 minutes ago, plonkster said:

I was told this is about the pick-up.

All the regulations to limit the inverters to 3.5kW yet if I dont have solar and want to install a second 4kW geyser there is nothing stopping me.

Now the grid has to pick up my 4kW geyser plus whatever else I have running which can go up to 13.8kW on a 60A breaker.

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So long story short. CoCT being an unnecessary pain in the ass. Noone really wants to feedback to the grid anyways as there is no payback. 

Question is if inspections are constant or once off, just to allow one to use the full transfer capacity of the inverter to make things more livable. I don't think this is being malicious either,  if it really was a big issue the other municipalities would have also instituted such restrictions. 

 

 

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1 hour ago, calypso said:

I don't think this is being malicious either,

Me neither. I've seen some of the things customers get up to though. I've seen a 45kw single phase installation. Well, not in person, but someone required support. When I asked why on earth they did that, the response was "the customer has a big house". Yes, I understand that... but you guys do realise that at such power levels you should at the very least go 3-phase? Aaah, but you see, the house has an existing single-phase supply and they did not want to modify that...

So I can easily see some customer adding 10kw of self-generation, and then BECAUSE of that extra capacity he adds appliances... and now he expects the grid to pick it all up. Sure, you could argue that the average guy is not going to do that, but people who write regulations try to be very thorough 🙂

But i any case, if this 15A limit is really in both directions, well then the AC-input limit feature of these inverters fits like a glove. For people who want to oversize, it does the trick perfectly. The only downside is that you must have a large enough battery to carry the bits over 3kw. Which again, to my mind, is not going to be much. You're not going to put those large loads on the output anyway. 15A really should be enough for the plugs/lights of most 3-5 bedroom single-phase houses.

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2 hours ago, plonkster said:

These loads cannot exceed 3kw... because the inverter would have been overloaded during the outage in that case. Requiring that these loads must be limited to 15A is impractical and adds nothing.

If the 3kVA multiplus trips while transferring 32A then the transformer on the street corner would see a 32A load change. If one inverter trips it would just be noise, but if all the inverters in the neighbourhood trip in unison (which is not inconceivable) it could be a significant event.

I'm not defending it, just stating what I believe the rationale behind it is.

 

Quote

But what makes this really interesting, is that UPS setups are not required to register, not subject to these rules... and they are the ones most guilty of adding battery charging load to the grid.

According to an e-mail exchange I had with CoCT the same limit applies to a UPS system - you may not draw more than 15A to charge batteries:

"Any inverter used as a UPS must adhere to SANS 62040 for UPS systems. Also note: That the maximum battery charger power drawn from the utility (kVA) shall not exceed the Maximum Total Generation Capacity limit as listed in the City of Cape Town's 'Requirements for small scale embedded generation in the City of Cape Town's 'Requirements for small scale embedded generation, Table 1')"

Edited by PierreJ
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7 minutes ago, PierreJ said:

If the 3kVA multiplus trips while transferring 32A then the transformer on the street corner would see a 32A load change. If one inverter trips it would just be noise, but if all the inverters in the neighbourhood trip in unison (which is not inconceivable) it could be a significant event.

If a Multiplus trips due to a grid event, it takes the loads with it. The input is disconnected and the loads are not transferred to the grid, they remain connected to- and powered by the inverter.

Practically, this is what will happen. If the Multiplus is transferring 32A at that point in time (max transfer switch capacity) and an event on the grid causes it to disconnect, the 32A load on the output will immediately overload it and cause it to shut down completely.

The maximum feedin just prior to the disconnection was 2.4kw. If you have a load greater than 2.4kw on the output, the grid saw none of that, and there would be zero pickup. The maximum pickup is 2.4kw, and this happens if you have zero load on the output.

Edit: Aaah I see, you mean the sudden release of 32A that is no longer consumed could be equally problematic? Yes, that could be the case. Reverse pickup... the grid has to absorb the sudden extra supply, voltage goes up, etc.

Edited by plonkster
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9 minutes ago, plonkster said:

Me neither. I've seen some of the things customers get up to though. I've seen a 45kw single phase installation. Well, not in person, but someone required support. When I asked why on earth they did that, the response was "the customer has a big house". Yes, I understand that... but you guys do realise that at such power levels you should at the very least go 3-phase? Aaah, but you see, the house has an existing single-phase supply and they did not want to modify that...

So I can easily see some customer adding 10kw of self-generation, and then BECAUSE of that extra capacity he adds appliances... and now he expects the grid to pick it all up. Sure, you could argue that the average guy is not going to do that, but people who write regulations try to be very thorough 🙂

But i any case, if this 15A limit is really in both directions, well then the AC-input limit feature of these inverters fits like a glove. For people who want to oversize, it does the trick perfectly. The only downside is that you must have a large enough battery to carry the bits over 3kw. Which again, to my mind, is not going to be much. You're not going to put those large loads on the output anyway. 15A really should be enough for the plugs/lights of most 3-5 bedroom single-phase houses.

15A is plenty for all the critical loads. Just need the additional AC in to supply all the non critical loads on AC-2 out. 

And yes, you could just connect the non critical loads directly to the grid, but then you lose solar covering them when the sun is shining.

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5 hours ago, calypso said:

15A is plenty for all the critical loads. Just need the additional AC in to supply all the non critical loads on AC-2 out. 

That's unfortunately not supported. The easiest solution is simply to not use AC-out-2. Install a grid meter. Put the non-essential loads directly on the grid.

Now you can theoretically use 2 x 5kVA in parallel (cause they have NRS097), set the AC input limit to 15A, and it will feed 3.5kW to loads on the input side (when required), or up to 8kW of combined loads (3.5kW which can be on the input side).

The grid will never see more than 15A imported or exported. It's as if the other 4.5kW isn't there.

But... your inverter and battery had better be able to carry anything above 3.5kw... cause that's the only help it's allowed to get from the grid.

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23 hours ago, plonkster said:

That's unfortunately not supported. The easiest solution is simply to not use AC-out-2. Install a grid meter. Put the non-essential loads directly on the grid.

Now you can theoretically use 2 x 5kVA in parallel (cause they have NRS097), set the AC input limit to 15A, and it will feed 3.5kW to loads on the input side (when required), or up to 8kW of combined loads (3.5kW which can be on the input side).

The grid will never see more than 15A imported or exported. It's as if the other 4.5kW isn't there.

But... your inverter and battery had better be able to carry anything above 3.5kw... cause that's the only help it's allowed to get from the grid.

Not supported by the Victron or CoCT?

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40 minutes ago, calypso said:

Not supported by the Victron or CoCT?

The Victron unit cannot exempt AC-out-2 from the input limit. The current limit is applied on the input of the Multi, and since both outputs are downstream of that, the maximum "help" the loads on both outputs can get from the grid would be 15A or around 3.5kw. So in this application the usual trick of putting non-essential loads on AC-out-2 would be a mistake. Put them directly on the grid and use a grid-meter. The Multi will then know how much loads there are on the input side (because the meter tells it), and it will feed that much into the grid to compensate for those loads... except the pickup of those loads are limited to 15A, which is what you want.

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HI All

As a user for some time now I share my experience on the 15Amp limit and how to manage it. I have two Axperts (2x5kVA), 6000W PV and 12kWh storage.

It is deemed as a UPS with solar charging. Not a SSEG connected to the grid.

I post these four diagrams for use to users that want to install more than 3500 watt of solar panels and have battery storage. In my case I utilize shore power (municipal power) for between 3.6% and 12% of the time per month over a 12 month period. There are many days (even weeks) when I do not connect back to shore power at all, but I need shore power when cloudy days persist for many days at a time and battery drops to below +-20%. August is the worst. Connecting back to shore power usually happens between the hours of midnight and say 09h00 at the latest the following day. In August it is longer, but it is only for that month.Solar block diagram 1-4.pdfThe purpose of my system is to be independent of municipal power as far as possible, and If the basic service fee increases to such an extent, then I will go completely off grid and operate a remote start generator for the 3,6% to 12% of the time.

In diagram 4 you have the best of both worlds. A Bypass switch, is very useful when things go wrong, but so is a suitable change over contactor that is operated by the software on the inverter. Diag 1 and 3 are similar but in diag 3 the bypass can handle more than the 15A as is currently allowed. In any case manage your loads via software or timers. Use the washing machine, tumble dryer and dishwasher when the sun shines.

Any comments or questions will be welcome.Solar block diagram 1-4.pdf

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41 minutes ago, HennieW said:

HI All

As a user for some time now I share my experience on the 15Amp limit and how to manage it. I have two Axperts (2x5kVA), 6000W PV and 12kWh storage.

It is deemed as a UPS with solar charging. Not a SSEG connected to the grid.

Do I understand this correct:
To circumvent (or rather comply to) the 3.5kW requirement of COCT you simply install a 15A breaker?  (15A x 230V = 3.45kW)

Then it is up to you to manage the 3.5kW draw from the grid. Hardware or software management however you want to do it.  The 15A breaker is a fail safe from COCT view that you will not draw more than that.

 

If this satisfies COCT it kinda makes sense to me. Adding an inverter but limiting the draw to 15A.  It is like saying yes you can add another geyser to your home but as long as it is below 3.5kW if you have a 60A breaker, nevermind if it is on or off or you feed it power mostly from somewhere else.

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53 minutes ago, HennieW said:

It is deemed as a UPS with solar charging. Not a SSEG connected to the grid.

Like what you are saying that an off grid inverter is a UPS with solar charging and not a SSEG (it does not push power back to the grid)

 

Supplying a Hybrid inverter with a 15A breaker should also work then.  You will just have to balance the loads on grid side vs off grid that you don't try to feed more than 15A to the grid connected loads or do some form of load management.  For me it would be easy. Put everything on the backup side and only the geyser and oven on the grid side but use a load control so that the geyser switch off when the oven is in use.

 

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HI Piet

 

You are correct in what you are posting.

The Inverter must conform to the SANS code for a UPS system. Look up the SANS code for inverters and your electrician must also sign it off as such. Then also the UPS maximum charging current  from the municipal grid (draw and push through to the load) must be limited to 25% of the main breaker (60A) size. It must be a hard limit. i.e Breaker of size 15A. is preferable. The software limit can be easily changed and is not recommended. However during sunny, sunshine days you may push to the load as much as needed from the sun and battery, but not draw from the grid more than 15A. Usually the load is drawn from the sun and batteries at the same time or from the battery only or from the sun only. It is the SBU setting  (Solar battery and then utility), but in utility mode up to max 15A.

I feel very sorry for the municipal guys that need to manage their grid as the grid was not designed for load shedding. Full stop. Look closely at this photo of the supply voltage quality the first couple of minutes after load shedding. It is terrible and will cause failure. That is why I recommend you place all your sensitive equipment on the UPS.

The 25% load limit is placed there because the grid cannot handle more than that AT THE SAME TIME.  After load shedding this is what happens to the grid voltage. You are warned.1878975401_Loadsheddingnonsens.thumb.jpg.2b49146f1a612f2babeab83f69561f61.jpg

 

 

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18 hours ago, calypso said:

So realistic outcome. Install the 1 x Multiplus 3000 as per CoCT spec, get it approved and CoC. Soon as that's done, install another, run them in parallel and remove the limits. 

... Your post makes me think of this humourous car-repair video I watctched recently where this guy is up in the woods repairing his old beater, and he needs to remove the AC evaporator. Now of course the AC system hasn't worked properly in years... but there is still some gas in the system, and it being Freon and all... he announces on the video that he just needs to go to the shop and fetch the AC machine. The video comes back, clearly still the same day with the sun in the same place, and he says he's taken the machine back already cause he's short of space... and continues.

Now everyone who watched that video KNOWS he just vented that thing into the atmosphere... but there is no evidence 🙂

 

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Well this isnt releasing Freon into the air. This is just allowing use of the transfer switch, just like i can happily use the whole 60A now, but I dont. Noone needs to be charging batteries at max amps so the grid isnt gonna slammed. Allowing people to move more freely in this direction will mean that more people take on solar and such and at the end of the day the impact on the grid will be lower. 

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