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Andybear

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Joined: 26/07/2009
Location: Australia
Posts: 6

Posted: 05:42am 09 Oct 2009

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Hi all,

Herewith a bit of a ramble. Earlier in the year, I had six 165w panels installed by a large well known company. With intention of getting the system expanded later in the year, I asked for a larger inverter to be installed so that I could use a total of 12 panels. To be fair, the inverter that they installed was the next size up, a Fronius 15IG.

My query is, and by my rough calculations 12 panels could develop near 2Kw, which seems to be a lot more than the 15IG seems likely to be able to bear. Would the inverter just convert the extra input to heat, and throw it off? Would the inverter more likely say "Goodbye forever"?

I could "bite the bullet" and upgrade to a Fronius IG20, or tone it down, and just get 3 perhaps four extra panels.

A bit more ramble here. I'm pretty sure the IG15 would never exceed its rated output, and I don't have a problem with it sitting on 1.5Kw, I just dont want to fry it. I dont suppose there is much of a market for second hand inverters!

Cheers all Andybear

When in trouble delegate. When in doubt mumble

micke
Newbie

Joined: 25/10/2008
Location: Australia
Posts: 15

Posted: 08:19pm 10 Oct 2009

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Hi Andybear

The IG15 inverter has a recommended maximum array power of 2000 Watts (nominal 1630W). Although it has a maximum AC Power output of 1500 Watts (nominal 1300W).

If you installed another 6 panels you would have 1980 Watts of array power and when you factor in losses I believe the inverter would be under rated by about 5 to 10%. When the inverters have too much DC power they shift the maximium power point and run at a lower efficiency to protect themselves and in effect waste the power.

In my opinion adding another 4 165 Watt panels of the same type to end up with one string of 10 panels would make a good fit for IG15 inverter.

The money that you save on not purchasing the extra two panels could probably be better spent increasing energy efficiency in the home, like lighting, appliances, insulation, painting roof white and Solar HWS.

Thanks Mick

Andybear

Newbie

Joined: 26/07/2009
Location: Australia
Posts: 6

Posted: 10:51pm 10 Oct 2009

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Thanks Mick,

Your recommendation taken on board.

Just as a "by the way guess what" Kind of comment. When the solar panels were installed, they put them on the Southern side of the roof, to avoid a small amount of shading by a neighbours tree. I thought they would rack them so as to face the right way, but no, they are facing South, but at least there is very little roof pitch, but I feel they have stolen about 12 degrees worth of best angle from me.

Ill go for the 4 panels, but will insist that they go on the proper side of the roof, the shading only really affects the proposed area for 2 months of the year, and then only for an hour a day.

Possibly worthwhile getting them to re rack the panels already in place, as well as the new ones

Thanks again

Edited by Andybear 2009-10-12

When in trouble delegate. When in doubt mumble

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