sunny boy inverter?

[inetdog]

inetdog-"strings are the same length", maybe my definition of string is wrong, but i will have 7 panels that are at 1 position, and 6 at close to but different angle, no shading issues at peak time, but all 13 will be in series creating around 450 peak volts.

Having panels at significantly different angles (either elevation or azimuth) in series in the same string is likely to reduce the available power from the string. This is the sort of situation where either two strings to two MPPT inputs or optimizers on all panels would be considered the proper choice.

The rule of thumb that differences of 5% of less in Vmp (for parallel panels) or Imp (for series panels) when adding a single panel are not likely to cause significant production loss does not apply as strongly when you are talking about two substrings of approximately equal size combined in series.

Are you talking about different azimuth (facing direction) or elevation (roof angle) differences between the two groups of panels? How many degrees in either case?

[mudhole]

inetdog-"strings are the same length", maybe my definition of string is wrong, but i will have 7 panels that are at 1 position, and 6 at close to but different angle, no shading issues at peak time, but all 13 will be in series creating around 450 peak volts.

[inetdog]

My system has a DC to AC ratio of 1.5 to 1 so it is overclocked to the max. Make sure you don't exceed the manufacturers recomendations. Every manufacturer is different.
I think azimuth differences would affect the strings enough where I have seen installations that use different MPPT channels. I honestly don't know the answer about tilt and I don't think PV Watts gets that granular. It is a matter of differences in the relationship of voltage and current that may be affected by tilt. If you have panel level MPPT it would not make a difference.

An experimental paper by SMA shows that as long as the strings are the same length and neither of them have partial shade during their peak production hours there is no need to have separate MPPT channels. The less insolated string will produce less current at its MPP voltage then the higher insolated string, but the VMP values will be close enough that any power loss will be in the low single digits percentage.

[Ampster]

the highest reading i have got so far is 4.3kw, I bought 18 but due to logistics i only installed 15- 275 watt panels, so obviously the 275 watt is not the max out put of them if i got 4.3kw. what i want to do is buy 3 more panels (same ones), which would give me 6 more to install. my inverter is 5.0Kw rated, so i guess i am overclocking it by about 15% from which i read is very doable.

anyway, i have several options for installing them, it makes it a lot easier if i just tie into the string on the roof rather than running two new pv wires all the way to the inverter (i do have another mppt slot i could use), however if i do , the new 6 panels will be tilted differently...how much will that adversely affect the string?

My system has a DC to AC ratio of 1.5 to 1 so it is overclocked to the max. Make sure you don't exceed the manufacturers recomendations. Every manufacturer is different.
I think azimuth differences would affect the strings enough where I have seen installations that use different MPPT channels. I honestly don't know the answer about tilt and I don't think PV Watts gets that granular. It is a matter of differences in the relationship of voltage and current that may be affected by tilt. If you have panel level MPPT it would not make a difference.

[mudhole]

the highest reading i have got so far is 4.3kw, I bought 18 but due to logistics i only installed 15- 275 watt panels, so obviously the 275 watt is not the max out put of them if i got 4.3kw. what i want to do is buy 3 more panels (same ones), which would give me 6 more to install. my inverter is 5.0Kw rated, so i guess i am overclocking it by about 15% from which i read is very doable.

anyway, i have several options for installing them, it makes it a lot easier if i just tie into the string on the roof rather than running two new pv wires all the way to the inverter (i do have another mppt slot i could use), however if i do , the new 6 panels will be tilted differently...how much will that adversely affect the string?

[mudhole]

the power company checked it out and changed out the meter, i commissioned the inverter and it is currently up and working!!!!!!!!!!!!!, thanks for ALL the help on this project. I just need to figure out how to hook it up to my phone or computer, and what the purpose of having it hooked to a computer does for me??

[Ampster]

well it passed the electrical inspection!!!!, power company coming out shortly!! thanks for all the help so far!!

Great news. Keep us informed about how your system performs.

[mudhole]

well it passed the electrical inspection!!!!, power company coming out shortly!! thanks for all the help so far!!

[mudhole]

i have the sunny boy 5.0 -41, i am confused with the installation book, is the multi function relay necessary to compete the install?

[Ampster]

ok, so no ground rod at the panels, just run them via the ground through the inverter to the panel.

Yes, but pay attention to the wire gauge requirement. If I recall, many jurisdictions require at least 8 AWG. Any splices need to be crimped so they are more permanent.

[mudhole]

ok, so no ground rod at the panels, just run them via the ground through the inverter to the panel.

[Ampster]

1. The house ground presumably connects to your earth ground at the main panel. You can have multiple devices or wires connected to your earth ground but not multiple earth grounds

2. There is no need to switch the neutral. The neutral is never switched in 120 volt circumstances and the same logic applies. If you saw switchgear with three legs, it was probably for three phase motors.

[mudhole]

nevermind number 2, i went and purchased the correct one.

to clarify my question number 1 the instructions from sma, it says to ground the AC out on a lug and the rails/panels to a lug on the inverter as well, do i also run a special ground rod for all the equipment?

[mudhole]

1. my sunnyboy inverter diagram for split 240 shows only ground coming via home panel (house ground), i thought i read somewhere where you dont want your equipment on separate earth grounds?

2. my disconnect does not have a neutral ground lug, do i need to get another type disconnect with L1, L2 , N and ground?

[Ampster]

is there any disadvantage to running 1 mppt input at around 300v dc in and the other feed around 180 v dc in? (the dc input range for the inverter is 125-550v per mmpt input)

........ do most people cover up the solar panels as you plug them in? i read that somewhere, but all the videos just show people plugging them in as they go...

I don't know the specifics of your inverter. My inverter has two inputs but actually only one MPPT channel so in my case it would not make any difference. My inverter has a much higher minimum voltage than yours. Did you decide on that configuration using your inverters string sizing tool?

The following is not based on any in depth knowledge of an actual MPPT curve but I would prefer to have one string running at a higher voltage than two strings at lower voltages. That is assuming that there is a safe margin at the top so on a clear sunny day at low temperatures the max voltage will not be exceeded. The only other reason some people have two strings on separate channels is if they have different orientations. In that case the MPPT curves would be different for each string depending on the time of day.

As far as plugging them in, I just make sure the breaker is off so there is no load to create a spark and damage the contacts.