You always have losses. Nothing is as perfect as test conditions in a factory.

You will find that peek power is only around mid day, with a perfect angle to the sun (i.e. time of the year) and were the panels are very cool. 
In normal conditions your panels have heated up by mid day and you no longer can get the perfect watts out of them. So it is normal to over spec your panels a bit. I would say don't go over 20% more power and never more than the max voltage of your charge controller. Victron's MPPT calculator does not accept if you go more than 30% over your PV power, but you can still do less than that.

2 hours ago, Rclegg said:

 

That's correct. However, the Kings have a limitation of PV array size and max string size due to the MPP range (60VDC - 115VDC) vs the MKSII (120VDC - 450VDC) if I recall correctly. I decided to go with a bigger PV array size and output over the blending option and 0ms transfer - which is why I settled on the MKSII 

Unless I missed something, that's how I understand it.  

 

Thanks for the input, much appreciated! 
 

The PV array size for both are the same, i.e. 4000W. The King does have a smaller voltage range but that only influences your string setups. Trust me the blending option will become very relevant very quickly. With my previous inverter, if the panels are producing 3kW but the load is 3.1kW the whole load will be switched to Utility. With the King it will only supplement the 100W from battery or Utility pending settings. 

1 minute ago, Louisvdw said:

You always have losses. Nothing is as perfect as test conditions in a factory.

You will find that peek power is only around mid day, with a perfect angle to the sun (i.e. time of the year) and were the panels are very cool. 
In normal conditions your panels have heated up by mid day and you no longer can get the perfect watts out of them. So it is normal to over spec your panels a bit. I would say don't go over 20% more power and never more than the max voltage of your charge controller. Victron's MPPT calculator does not accept if you go more than 30% over your PV power, but you can still do less than that.

 

That makes sense. I was worried that on cold says there would be issues. Now you guys have me rethinking my panel sizing. The house load is not above 2.5Kw for more than a few seconds or minutes during the day. My calls say I should get 2.8KW of my panels at 65% efficiency. So far today my day time load has not exceeded that - its averaging 800w or so. So room let to charge the batteries too. 

Would going to bigger panels just be a waste in my case?

2 minutes ago, Plaashaas said:

The PV array size for both are the same, i.e. 4000W. The King does have a smaller voltage range but that only influences your string setups. Trust me the blending option will become very relevant very quickly. With my previous inverter, if the panels are producing 3kW but the load is 3.1kW the whole load will be switched to Utility. With the King it will only supplement the 100W from battery or Utility pending settings. 

 

According to the data sheet, the Kodak OCGX 5.48 has Max PV array power of 4500w Vs the Kings 4000w 

1 minute ago, Rclegg said:

Would going to bigger panels just be a waste in my case?

If you have space you can always add more later if you need to. It really depends on your scenario. Location, sun/shade, usage, devices in your home, etc. 

I my case I decided to start small, see how things are going and add more later when I know what impact my conditions has on the system. That is also why I went with a Multiplus based system as it gives me more flexibility to adjust. 

2 minutes ago, Louisvdw said:

If you have space you can always add more later if you need to. It really depends on your scenario. Location, sun/shade, usage, devices in your home, etc. 

I my case I decided to start small, see how things are going and add more later when I know what impact my conditions has on the system. That is also why I went with a Multiplus based system as it gives me more flexibility to adjust. 

 

Yeah that's a fair point. I could (And probably will) add more later if the need requires it. Will see how the 365W panels do first. I expect roughly 230w out of them at 65% 

Panels have 2 sets of values that are specified.

Standard Test Conditions (STC) is the wattage you buy the panel at (a 300W panel will supply 300W at these conditions). Measured in a factory at 1000W/m2 @ 25Deg C
Nominal Operating Cell Temperature (NOCT) is more what you can expect under normal conditions on your roof or in the field. Measured at 800W/m2 @ 20Deg C.

As an example one that I have the details close by, a 320W panel will have NOCT power rating of 237W and that is more what you can expect. Your 65% is close.

Well that confirms my experience to date

12 x 410w panels = 4920W

65% x 4910w = 3198W

At peak I get around 3.4KW but take into consideration that the roof angle is 30% and that my panels are split - 4 face NE for early morning generation and 8 faces NW for midday/afternoon generation. Currently I peak between 12:309 and 2:00pm

12 hours ago, Rclegg said:

Panels are going to be arranged in 4 strings of three.

The inverter can handle 450 VDC so make that 2 strings of 6. Furthermore if there is place on your roof you can go 7s as well. Inverter will clip a little but you will have more power earlier and longer. Furthermore: batteries. Lots of them!

Edited July 31, 20206 yr by RikH

I'm sorry, didn't read the entire thread before I posted above. It is already discussed and I would like to add some basic PV knowledge. The max. PV power is the maximum power that the inverter can draw from the panels. So if your panels CAN produce more than that, they just won't because the inverter cannot take more out of them. Compare that to a 2 kW heater that you simply plug in the wall, the inverter powering the outlet can make 5 kW max so will your heater blow up due to too much power? No it will not. It'll take just the 2 kW. So does the inverter work as well, it cannot take more out of the panels than it can use, even if the panels are able to produce more. This phenomenon is called clipping. So you cannot take the max PV power in account as you do with the max voltage. Don't go above that voltage and calculate what the voltage will be on the coldest day you can expect on the location. For the max power you connect I think what is said already 20 to 30% is ok. No need for more, clipping will take the most of the profit.

Edited July 31, 20206 yr by RikH