Solar design input for the States

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Solar design input for the States

Postby Watchdog » Thu Jun 19, 2014 11:57 am

Hello from Texas,

The more I read, the more I learn that I don't know a lot about solar setups. The installers I am shopping around here in San Antonio are like car salesmen (and I used to be one too) :D

I just want an efficient grid tied system for my home.

I like the Sunny Boy inverters from what I've read. And I have been offered two types of panels.

In the States, the best exposure is on the South side of a roof. The array I want (6 - 6.5 kW) would have panels on the South and East side of my roof. Now comes the tricky part...

The panels I have narrowed it down to are similar I believe. They are the Canadian Solar CS6P-250P and the Phono Solar - PS250P-20/U (Black/Black). In both systems, there will be 24 panels for a 6kW system or 26 for a 6.5kW system.

I am trying to decide what are the choices I have in an SMA inverter. My home will have an South and East array system. One set on the a South slope and the other on an East slope of the home. The West side is too small.

I have heard that if there are two different orientation of panels (South and East), that the panels have to be the same amount on each side (12 on the South and 12 on the East - total of 24 panels). If they are uneven, the inverter will be "unbalanced". Is this true? Again, I am getting two different answers from the companies I am talking to. One company says it's okay to put 11 panels on the South and 13 on the East side with the SMA SB6000TL-US-12 (240v) inverter. The other company says it has to be even set of panels on each side.

The SMA inverters they suggested were the SMA SB6000TL-US-22 and the SMA SB6000TL-US-12 (240v). I was leaning toward the SMA SB6000TL-US-12 (240v) but there is so much I don't understand which can affect production like...

how two arrays tie in and if they need to be "balanced",

if MPPT has anything to do it; does series or parallel have anything to do with my type of grid tied system

if I should take into account the start up voltage difference

I did a comparison of the inverters on a web page that gave me this...

I would appreciate any help you solar wizards can give me ;)
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Re: Solar design input for the States

Postby davidg » Fri Jun 20, 2014 5:18 pm

Watchdog wrote:SMA SB6000TL-US-12 (240v) but there is so much I don't understand which can affect production like...

If it is a dual MPPT SMA Sunnyboy the number of panels can be uneven no problem, provided the voltage windows and power ratings per MPPT are also adhered to, having said that SMA invteres can be be over-driven in terms of watt ratings as log as the Voltage rating is not exceeded, they will cope with that fine,

Don't know about the US, but in Aus it does not void warranty to overdrive the MPPT channels, over peak voltage will void warranty though.

It is only when you have a single MPPT or one of the cheap brands of inverters that panels typically need to be matched per MPPT, they don't cope well with different voltages on each MPPT, I cant tell you why but some of them in the instructions make pretty clear not to do it.

Check the US SMA website for detailed specifications.
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