strings with different number of modules going into an inverter

[SolarCity]

Back to the MET.

 

[Markc]

I heard something earlier which surprised me and I'm not sure it's correct. Someone has designed a system on house we have looked at where he has 12 panels on the main area of roof and then 4 panels on another section of roof in which the installer intends to install the 4 panels on a seperate string. Can this be possible? Surely we have two uneven strings which will require a dual MPP tracker but the voltage of the second string will be far below what is needed to fire the inverter and therefore effectively useless? Or will the inverter be fired by the 1st string and therefore allow the smaller string to operate?

I'm confused, as I'm sure you can see.

I recently tried to design a split west east system on 12 panels using a dual MPP tracker inverter but couldn't find one suitable for that few panels. (6 each) I would of thought 4 is way to low but I'm ready to be proved wrong. Were going twin inverter instead.

 

[mmccx]

Sma tl inverters don't require the type b rcd as it specifically states that the ac and dc are physically separate even tho there is no transformer. also the array frame must always be earthed if the inverter is tl

 

[dansk]

what reg number is that as i cant seem to find any refernce to bonding with certain inveters.

 

[SolarCity]

Sma tl inverters don't require the type b rcd as it specifically states that the ac and dc are physically separate even tho there is no transformer. also the array frame must always be earthed if the inverter is tl

Are you sure about that? I'm installing a system with a TL inverter and I'm going to be sticking a type b RCD on it. How do they physically seperate the AC and DC without a transformer?

 

[mmccx]

Read the sma tl installation manual and read bs 7671 the pv section 7 reg 712.411.3.2.1.2 page 200 and read the note underneath the reg

 

[JulianC]

Alternatively, read here:
http://www.electriciansforums.net/p...11-transformerless-inverters-type-b-rcds.html

 

[SolarCity]

Thanks fellas. Maybe I'll remember this time ;-)

 

[mmccx]

How much and where did u find the type b rcd?

 

[SolarCity]

I never got around to finding one. I suppose with more and more TL inverters coming out, there will either be loads on the market very soon or lots of TL inverters which use the SMA method.

Heres hoping.

 

[carolinebrett]

Hi, we have just had a system proposed for a dual aspect array with 2 strings of 6 and 10 panels (or possibly 7 and 9, if we can squeeze another in around our SolarTwin array!), and the installer/salesman suggested a SMA 3800 as the inverter. I challenged him on this, as i have gathered that only the SMA 4000TL has 2 MPP trackers, and he denied it was a problem. Do I take from this that he doesn't know what he is talking about? Our other potential system supplier suggested, for the same system, an Aurora 3.6 PowerOne, which I know can handle 2 unequal strings. What's your advice?

 

[SolarCity]

The installer that suggested an SMA 3800 doesn't know what he is doing. The Aurora Power One 3.6 is the answer.

 

[solarsavings]

T The Aurora Power One 3.6 is the answer.

And the question is "where to get one"

 

[mjanesuk]

This nearly answers one question I have been trying to get to the bottom of - two strings on a Power One 3.6.

But, the installer who is sorting out our system keeps saying there needs to be an even number of panels on each string, even though he is happy to have a Power One 3.6 and two unequal inputs of 10 and 6 (portrait and Landscape respectively) to solve the issue of partial shading on the lower string of 6.

My dilema now is that he can only get hold of Schuco 235 poly's or Schuco 190 mono's, both of which would be nearer to 4Kw if there were 17 or 21.

So any advice on the ability of the Power One 3.6 to accept 11 & 6 or 13 and 8, and is the mono/poly decision an important factor?

Cheers