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Circumventing the COCT 3.5kVA limit


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22 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. 

If you're able to shift your heavy loads to the sunshine hours (like I am) it would be slightly more efficient to have one Multiplus together with a Fronius AC coupled inverter on the output of the Multiplus. The total capital outlay would be about the same, but there's one less DC - DC conversion.

I submitted my application to CoCT last week and I'm now waiting for approval. I went for a 5kVA Multiplus, SmartSolar battery charger on 8 x 400W panels, and a Fronius Primo on another set of 8 x 400W panels. During daytime the Fronius will carry most of the load while the SmartSolar charges the batteries. During the evening the Multiplus will carry the loads from the batteries.

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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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3 minutes ago, PierreJ said:

If you're able to shift your heavy loads to the sunshine hours (like I am) it would be slightly more efficient to have one Multiplus together with a Fronius AC coupled inverter on the output of the Multiplus. The total capital outlay would be about the same, but there's one less DC - DC conversion.

One problem for Fronius is that they don't have NRS097-2017 certification, so since Feb this year... CoCT dropped them from the list. Which is a shame, as they make some of the most high-end stuff on the market, have excellent support, and their equipment very likely comply already and it's just a matter of getting the paperwork...

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Just now, plonkster said:

One problem for Fronius is that they don't have NRS097-2017 certification, so since Feb this year... CoCT dropped them from the list. Which is a shame, as they make some of the most high-end stuff on the market, have excellent support, and their equipment very likely comply already and it's just a matter of getting the paperwork...

Surely that is only an issue if it is connected directly to the grid? In my case the Primo is on the output of the Multiplus, so CoCT should approve my application right? The Multiplus will limit the current to 15A and also prevent feed-in, so as far as I can see all their major concerns are covered.

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2 hours ago, PierreJ said:

Surely that is only an issue if it is connected directly to the grid? In my case the Primo is on the output of the Multiplus, so CoCT should approve my application right? The Multiplus will limit the current to 15A and also prevent feed-in, so as far as I can see all their major concerns are covered.

Nope. Talk to @The Bulldog who has been through this. They completely ignore the Multi, it is considered a UPS and not part of the SSEG installation. The Fronius is the conversion interface and must comply. They don't care that it is on the output, and frankly they are right: When the Multi connects to the grid, the backfeed relay closes and the Fronius is for all practical purposes connected directly to the grid.

Also, the Multi cannot prevent feeding in beyond 15A in all conditions. When the batteries are full, and the pv inverter feeds in more than the configured limit, the Multi goes into passthru and simply passes the current. It can't do anything else. Sure, you can use the limiter function in the GX device (which, btw just got an overhaul in v2.60... you must check it out!), but this limits feedback at the point of connection (the grid meter) and the whole pick-up issue becomes applicable again.

This trick of using the Multi with an AC input limit really only works with DC-coupled PV. For AC-coupled PV, you'd still be limited to 3.5kw, even if the Fronius is on the output of the Multi.

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3 hours ago, plonkster said:

Nope. Talk to @The Bulldog who has been through this. They completely ignore the Multi, it is considered a UPS and not part of the SSEG installation. The Fronius is the conversion interface and must comply.

Well, that just threw a spanner in the works. It makes perfect sense of course, but I was foolishly assuming the CoCT wouldn't look that far.

I've already paid the deposit on the Multiplus and SmartSolar, and I was about to pay the deposit on the Fronius. Thanks for the warning - you've saved me some money. If we both survive this virus thing and we cross paths in the future, remind me to buy you a beer :).

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5 hours ago, plonkster said:

One problem for Fronius is that they don't have NRS097-2017 certification, so since Feb this year... CoCT dropped them from the list. Which is a shame, as they make some of the most high-end stuff on the market, have excellent support, and their equipment very likely comply already and it's just a matter of getting the paperwork...

I've noticed this on the specifications page for the Fronius Primo:

Fronius Primo 5.0-1, Fronius Primo 6.0-1 and Fronius Primo 8.2-1 are not fully compliant with VDE AR N 4105.

I'm not familiar with the German standards, but perhaps that's also why it also does not have NRS0970-2017 certification?

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13 minutes ago, PierreJ said:

I'm not familiar with the German standards, but perhaps that's also why it also does not have NRS0970-2017 certification?

Could be. Usually, if it has VDE AR N 4105, then the other grid standards are just a hop, skip and a jump away.

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  • 4 months later...

So I chatted to one of the bigger solar installers in CT today. According to them, you can put a 5kw grid tie inverter on a 60A residencial circuit in CT, just as long as you never put more than 3500w of panels on your roof. That way, the inverter can never invert more than 3500w. Sure the batteries can further contribute to it, but the batteries will never give anything back to the grid so thats fine. 

Im not sure if this is correct, but it is what I was told, and they would get it signed off + engineering papers ETC. 

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3 hours ago, calypso said:

Im not sure if this is correct, but it is what I was told, and they would get it signed off + engineering papers ETC. 

I sometimes wonder if they wrote the rules with an SMA system as the reference (everything AC-coupled, separate battery storage). Because we're told the limit is due to the pickup. If I have a 5kVA Multiplus installed, it can push 4kW into the grid to offset loads. If it trips, the pickup is 4kW...

But let sleeping dogs lie I say 🙂

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On 2020/07/29 at 3:59 PM, calypso said:

According to them, you can put a 5kw grid tie inverter on a 60A residencial circuit in CT, just as long as you never put more than 3500w of panels on your roof

i can confirm that. They have signed off my system. You can even have more that 3.5kW of panels on the roof if you can proof that (because of all the losses) the inverter output is not exceeding 3.5kW. I have 4.4kW on the roof 🙂. As @plonkstersays lets sleeping dogs lie regarding the pickup concern if you have a hybrid inverter with batteries 🤣.

Edited by Fuenkli
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16 hours ago, Fuenkli said:

i can confirm that. They have signed off my system. You can even have more that 3.5kW of panels on the roof if you can proof that (because of all the losses) the inverter output is not exceeding 3.5kW. I have 4.4kW on the roof 🙂. As @plonkstersays lets sleeping dogs lie regarding the pickup concern if you have a hybrid inverter with batteries 🤣.

What inverter do you have?

 

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