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openspaceman wrote: ↑Sun Nov 20, 2022 9:37 pm

Countrypaul wrote: ↑Sun Nov 20, 2022 12:54 pm I too have been looking at the Victron for our next step.

As I understand it, you could feed the output of your inverter after your TGM into the Victron and it would not affect you FITS - please check this though (I want confirmation for one thing )

This is showing that arrangement witout the TGM: https://www.victronenergy.com/live/ac_coupling:start

Yes this looks okay, with the meter after the inverter and before the load and Victron.

It would then sit in the place of the Growatt and hopefully run the growatt battery.

Is the DNO likely to accept its ability to limit export to 3.68kW if I add the new panels's 1.8kW? or must I still just couple the panels to the battery via the mppt charger? i.e. does this victron accept input from a string of PV, as I see it will accept the generator?

Also the Victron info says the PV power must not exceed the 5kVA it can cope with. Now as my panels are at right angles to each other they will never sum to 1.8+4=5.8kW but technically this exceeds the 5kVA.

BTW two of us (combined age 130year) managed to haul up and fix the first of the panels in the afternoon and, subject to weather, will get the next two up tomorrow.

I have found a new electrician who underwent the MCS assessment last week and fingers crossed he will be able to make the connection after Xmas.

Are you sure the 5kW referred to is the power in from PV and not the power the inverter is asked to deliver? It is very common for there to be PV panels that could deliver more than the inverter as the inverter will normally only draw to its specified level.

I am never sure of anything about this technology as I am relatively naive but this quote

"2. The Factor 1.0 rule

The max PV power must be equal or less than the VA rating of the inverter/charger"

Is what worried me in the blurb but as I cannot see both panels exceeding 5kVA I;m not worried and of course in high summer I can switch the smaller string off.

It's been normal to fit more panels to an inverter than it's rated output power for a long time, and causes no harm as long as the inverter MPPT input voltage and current limits are not exceeded. For example, we have 25 panels, rated at 250W each, but which in reality can output a bit more than the nominal 6.25kWp total, at times when the panels are cold and the sun is bright and lined up well with respect to the array. The inverter we have is an Aurora 6kW unit, rated to output 6kW.

The inverter has two MPPTs, each rated to accept up to 4kWp, so the inverter input can be up to 8kWp in total, although the output is limited to about 6kW. As long as the total current and voltage PV panel input limits are respected there is usually no issue with fitting more panels than the inverter output rating, in fact it's often useful to do this, as it can increase the overall net energy output over the course of each day. The inverter may turn on earlier in the day and turn off later, extending the time that it delivers useful power.

openspaceman wrote: ↑Mon Nov 21, 2022 12:03 pm I am never sure of anything about this technology as I am relatively naive but this quote

"2. The Factor 1.0 rule

The max PV power must be equal or less than the VA rating of the inverter/charger"

Is what worried me in the blurb but as I cannot see both panels exceeding 5kVA I;m not worried and of course in high summer I can switch the smaller string off.

There is a lot of nonsense written on this topic!

Rule 1: The string voltage must never exceed the maximum string voltage. (In fact you need a 10% cushion because panels can exceed their rated Vsc in very cold /bright conditions).

Rule 2: You can have as high a string current as you like but the inverter will never pull more than its max value.

The Victron Factor 1.0 rule applies the the power of a PV inverter connected to the AC output of the Victron inverter. You can connect as many PV panels as you want to your PV inverter provided you don't exceed the max O/C voltage, but the output power of the PV inverter must be no more than the power of the Victron inverter. There is a full explanation here:

https://www.victronenergy.com/live/ac_c ... ar%20power.

I have copied it below:

""2.1 Rule definition
In both grid-connected and off-grid systems with PV inverters installed on the output of a Multi, Inverter or Quattro, there is a maximum of PV power that can be installed. This limit is called the factor 1.0 rule: 3.000 VA Multi >= 3.000 Wp installed solar power. So for a 8.000 VA Quattro the maximum is 8.000 Wp, for two paralleled 8000 VA Quattros the maximum is 16.000 Wp, etc.

2.2 Example and background
To understand the background, consider the following situation: the PV inverter is at full power, supplying a big load. The Multi is in inverter mode. Then, suddenly and at once, this load is switched off. At that moment the PV inverter will continue operating at full power until the AC frequency has been increased. Increasing this frequency will take a very short time, but during that time all power will be directed into the batteries as there is no other place for it to go. This causes the following:

When batteries are (nearly) full, the battery voltage will spike, possibly causing the Multi to switch off in DC over-voltage alarm.
The same spike will cause the AC output voltage of the Multi to spike, as these two are directly related, and when the spike on the battery voltage is high and fast enough, the Multi can never regulate its PWMs down fast enough to prevent the spike on AC. This spike can damage the PV inverter, the Multi and also any connected loads and other equipment.
Another problem is that the Multi starts charge current protection.
In the best case it might switch the grid inverter off immediately by setting the AC frequency to the disconnect frequency as configured in the assistant.
It is no problem to overpower the grid inverter by installing more solar panels. Some people do this to increase the generated solar power in winter time or rainy weather. Refer to the PV Inverter datasheet to maximum allowed installed PV power. Two times the inverter nameplate rating or even more is not uncommon!""

My own SMA system specifies a max of 12kWp of PV on a single phase in order for the power limitation to meet the 5 second response time of the G100 export limitation device.

marshman wrote: ↑Mon Nov 21, 2022 12:50 pm The Victron Factor 1.0 rule applies the the power of a PV inverter connected to the AC output of the Victron inverter. You can connect as many PV panels as you want to your PV inverter provided you don't exceed the max O/C voltage, but the output power of the PV inverter must be no more than the power of the Victron inverter.

This.

sharpener wrote: ↑Mon Nov 21, 2022 4:07 pm

marshman wrote: ↑Mon Nov 21, 2022 12:50 pm The Victron Factor 1.0 rule applies the the power of a PV inverter connected to the AC output of the Victron inverter. You can connect as many PV panels as you want to your PV inverter provided you don't exceed the max O/C voltage, but the output power of the PV inverter must be no more than the power of the Victron inverter.

This.

Just for clarification, I have a 5000VA Multiplus II and a grid tied 3.68KW PV system, I intend to add about 5 KW of panels to the system via MPPTs entirely on the DC side direct into the batteries.
Is this OK ?

newtoallthis wrote: ↑Mon Nov 21, 2022 6:14 pm
Just for clarification, I have a 5000VA Multiplus II and a grid tied 3.68KW PV system, I intend to add about 5 KW of panels to the system via MPPTs entirely on the DC side direct into the batteries.
Is this OK ?

I hope so! I am just about to do the same (but only 3.2kW in my case). But IIRC the Multi can shut down the MPPTs quicker than it can the grid tied inverter so the 1:1 rule is not applicable. The other benefit is that one does not need to involve the DNO again.

The other consideration is whether the Multi can use all the output (it can only charge at 3.5kW in aggregate, for which it will need ~4kW before losses) and whether the battery can accept it - but I think your four Pylons will be OK there.

sharpener wrote: ↑Mon Nov 21, 2022 6:32 pm

newtoallthis wrote: ↑Mon Nov 21, 2022 6:14 pm
Just for clarification, I have a 5000VA Multiplus II and a grid tied 3.68KW PV system, I intend to add about 5 KW of panels to the system via MPPTs entirely on the DC side direct into the batteries.
Is this OK ?

I hope so! I am just about to do the same (but only 3.2kW in my case). But IIRC the Multi can shut down the MPPTs quicker than it can the grid tied inverter so the 1:1 rule is not applicable. The other benefit is that one does not need to involve the DNO again.

The other consideration is whether the Multi can use all the output (it can only charge at 3.5kW in aggregate, for which it will need ~4kW before losses) and whether the battery can accept it - but I think your four Pylons will be OK there.

Thanks for that, my existing panels are on 35 degree roof facing south which is great for summer production but not so good in winter, around 1 KW of my new capacity will be on the same roof, but the other 4 ish KW will be ground mounted at about 85 degrees optimised for winter production.

Do we have any expterise in home made ground mounts for quite vertical systems ? any advice would be appreciated.