Sunny Boy 7000 - TL or non TL?

Craigaz

Hi gang,
I'm a noob so please be gentle. I have pretty much settled on this inverter but I'm not sure which is the better option, transformerless or the standard model. Cost difference is minimal so put that aside, which one would you choose and why?

Thanks in advance for your help, I really appreciate it.

BTW - It will be powered by 30 Canadian Solar CS6P-250M panels in sunny Arizona @ 18 degrees elevation, due south with no shading.

BB.

Re: Sunny Boy 7000 - TL or non TL?

I am not sure which "would be better"...

However, you should check with your local building department/utility to see if the "new" transformer-less design is acceptable (I don't know, but anything new can have drawbacks when dealing with building inspectors/utilities).

-Bill

solarix

Re: Sunny Boy 7000 - TL or non TL?

If I was you, I would put in two of the smaller new TL Sunnyboys. Yes it will cost a little more, and you'll have the extra expense of an AC combiner, but these 3,4,5kW Sunnyboys have the new emergency power feature. In an outage, you will have two outlets to switch over your important loads to -you'll be off-grid with no batteries! (when the sun is up) Plus these TL inverters have dual inputs - making your array more shade tolerant if that is a problem. Unfortunately, SMA is only doing this in the smaller models. Hopefully, the 6 and 7kW sizes are going to be upgraded before long. With 2 small inverters - each having dual inputs, you will have 4 individually optimized strings. 30 modules total would be two strings of 7 and two of 8. (might be able to do strings as short as 6 on these inverters - check the SMA.com string sizer).

jaggedben

Re: Sunny Boy 7000 - TL or non TL?

The determining factor will be minimum input voltage. SMA's higher power transformerless design requires a higher input voltage, so whether it works depends on your string configuration. With 30 panels I gather you'll have 3 strings of 10 panels. That's going to be too low an input voltage for the TL, especially at Arizona temps. Strangely enough, it seems to me that in many places in the US SMA's 6000W and higher TL will only work and be allowed with strings of 13 panels, not any other number. Places without temps below 20F or so can do 14 panels. (All this depends slightly on panel specs, but applies to your 60cell 250W panels.)


Anyway, go to SMA's sunny design page and see if your configuration works in their opinion:
http://www.sunnydesignweb.com/sdweb/SunnyDesign/Home

You can also put in your panels, and choose "Design Suggestions" and see what SMA options you have.

The 5000TL and lower power SMA inverters do not have the high input power requirement, and they also have 2 MPPT inputs for greater flexibility. So you could go with Solarix suggestion and choose a 4000TL plus a 3000TL. But you'd have some more expense in BOS.

All else being equal, I'd go with a TL because they are more efficient, and because ungrounded systems are safer in my opinion. But with a 7.5kW system, all else is not equal. You have to weight the advantages/disadvantages of one vs multiple inverters.

ggunn

Re: Sunny Boy 7000 - TL or non TL?

jaggedben wrote: »

The determining factor will be minimum input voltage. SMA's higher power transformerless design requires a higher input voltage, so whether it works depends on your string configuration. .

True, the minimum voltage is higher, but the maximum voltage stays the same, so you have a narrower operating window. The MPPT window for the regular 7000 is 250-480V, while the MPPT window for the 7000TL is either 300-480V or 345-480V, depending on whether your AC line voltage is 208 or 240V. This makes it harder to design into systems for places with wide temperature swings.