3-4 strings on a SMA Sunnyboy 7000TL-22

[cromb]

I want to build a system with 26-27 panels using the Sunnyboy 7000TL-22. The most I can have on a string is 12 so I need to have 3 or 4 strings to make it work. I am thinking of doing 3 strings.

Do I need any more equipment like a combiner box to have more than 2 strings on that Sunnyboy model? Seems like I can have up to 4 strings without any extra parts. Is that correct or not?

[sensij]

The 7000TL-US-22 can accommodate 4 strings without extra parts if you put two strings on one MPPT input and two strings on the other. If all the panels are at the same orientation, you should be able to split up your system into three strings that satisfy the input specifications for each MPPT.

[cromb]

Thanks for the response. That is what I thought. They are all on the same section of my roof so I think I am good. I have an online retailer telling me that I either need a combiner box or I should do a microinverter or optimizer system. I don't understand how I can know more about this stuff than this person who sells the stuff. It blows my mind.

[bcroe]

Some inverters, like my Fronius, have a "built in" combiner for up to 6 strings. However this is only practical with the panels
close to the inverter, since each string must have its own feeds to the inverter. Bruce Roe

[silversaver]

With 26 to 27 panels on the same roof, all you need is 2 string (13 panel + 14 panels) feed into SMA 7000TL-US-22.

What panel are you using?

http://www.sunnydesignweb.com/sdweb/#/Home

easy tool

[cromb]

I was thinking of using the solarworld 280 watt with black trim. They all seem the same to me.

SMA has a tool that gives you a suggestion for the strings. It says to use either 3 or 4 strings wirh more than 24 panels. A max of 12 panels on a string.

[silversaver]

I was thinking of using the solarworld 280 watt with black trim. They all seem the same to me.

SMA has a tool that gives you a suggestion for the strings. It says to use either 3 or 4 strings wirh more than 24 panels. A max of 12 panels on a string.

I think you really need a professional to assist you. IMHO

Sunny Design Web is a web tool from SMA that is simple and straight forward.

[cromb]

What do I need a professional for?

[sensij]

What do I need a professional for?

Nothing, at least based on what you've written so far. The string sizing advice just posted above is not good... a 14 panel string can only tolerate temps down to -3 deg C before you'll exceed the Voc limit of your inverter. According to this map, there is no place in Utah with a min design temp of -3 deg or warmer. A 13 panel string could go down to -31 deg C, so with those SW280 panels that might be an option, but there is nothing wrong with the design you proposed.

[silversaver]

What do I need a professional for?

Where are your location? sensij has point on Voc. Depends on your location. If 14 panels were allow then you don't need a combiner box with 2 strings setting or settle with 26 panels. If you must choose 27 panels, then you can choose SMA 7000US with 3 strings of 9 panel with combiner box. Transformer inverter might last longer but with lower eff.

[sensij]

Where are your location? sensij has point on Voc. Depends on your location. If 14 panels were allow then you don't need a combiner box with 2 strings setting or settle with 26 panels. If you must choose 27 panels, then you can choose SMA 7000US with 3 strings of 9 panel with combiner box. Transformer inverter might last longer but with lower eff.

No, a combiner box is not needed for three strings on the SBxxxxTL-22-US series. Each MPPT input can be thought of as a separate circuit, with OCPD, so as long as you don't put more than two strings into a single tracker, the combiner isn't needed. Simple Y type MC4 connectors can put two strings in parallel if it saves on wiring costs (the conductors after the Y need to be bigger to carry the combined current).