SMA-7000 or SMA-8000?

bart

I'm building a new system using the SMA-7000US (240v) with 33 Yingli 230 w panels.

I want to add 3 additional panels (making it 36 panels total). Using Sunny Design application, it says this configuration would be acceptable (see image). However, when I went to order the additional 3 panels, the reseller says I would need to upgrade to SMA-8000.

I'm confused. I just want to verify with you this configuration. I assume he thinks that 36 panels will produce 8280 DC watts which would be too much for the the SMA-7000 and require an upgrade. However, it appears the calculator application is using the PTC rating of 206.6 watts at 36 panels would be 7439.6 watts, which would should be acceptable for the SMA-7000.

Am I correct?

Thanks, Bart

[IMG]http://icpage.com/solar/images/SMA 7000 with 3 x 12.jpg[/IMG]

mike95490

Re: SMA-7000 or SMA-8000?

That should work, dealer just wants a new car. Have you researched other inverters other than SMA (like Xantrex ?)

bart

Re: SMA-7000 or SMA-8000?

Great, Thanks...

So was I correct that Sunny Design App uses PTC rating or some other derated value?

Well, SMA-7000 has already arrived - next time

Bart

mike95490

Re: SMA-7000 or SMA-8000?

And most MPPT type systems, will gracefully throttle themselfs back, as they reach their programmed power limit, so you would just have wasted PV capacity, not BBQ inverter. They also throttle back when they get too hot, so watch the fans, as you will be at the upper limit, and the fans will likely run a lot, till the motor fails (they all will fail eventually)
With the PV's on a hot sunny roof, and less than optimum angle (except for about a month each year, when your roof is aimed just right) you won't exceed limits too often.