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GaryM

I've had a quote for a 4kWp system to include 16 x LG2501C 250W panels but the quoted inverter is a Fronious IG35 Plus.
Would this be a good choice of inverter or would the Fronious IG TL 3.6 be a better choice?
 
Incidently, been to see a customer today who installed just before the 12th, its LG250's on a 3.6TL, its done 141 units and peaked at 2.8kwp - not bad for this time year i thought.
 
yeah LG panels have a positive power tolorance, look at this flash report i get each time we collect LG panels - "pmax" there all around 254w, its not much but its better in your pocket. and shows most LG250w are really LG254w!
 
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After questioning my potential installer over his reasons to choose a IG35 Plus over an IG TL 3.6 he said that due to my earthing arrangements being PME he would therefore have to supply and fit a type B 100mA RCD and also bond the array frame to an earth rod. Given that the total yield per annum between the two inverters it just wasn't worth opting for a transformerless inverter.

PV*SOL has 16 x LG250's with a IG35 Plus giving a total yield PA of 3565.5 and 3651 when using an IG TL 3.6 so a difference of 85.5kWh.
At 43.3p (hopefully!) that would amount to £37 PA and at 21p (worst case?) it would be £18 so not big numbers either way.
Seems a logical decision to me?
 
Hi,

I disagree with your installer (well thats what forums are for arent they?) The 35+ is not the best choice IMO, i attach PV Sol report showing its very close to its limits, and given that LG panels are actually more like 255W this only make the situation worse.

The 3.6TL has built in RMCU for the class B, and as for bonding yes that will need doing, albeit thats another debate and this has been covered many many times and with the onset of the 3rd edition looks unlikley to be done in the future.

VOC on a very cold bright winters morning is pushing very close to 600V and thats the limit the inverter can take, the inverter logs all this info and if ever you have a problem in the future and you need to claim on Fronius, they will look through the logs and pinpoint anything that is out of the inverters parameters and guess what? they will wriggle out of paying out.

Dont get me wrong it will work, but i think there is a better choice to be had ;-)
 

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It moniters DC fault current and in the event of detection it would shut down therefore preventing injection of DC into the AC.
 
Thanks very much. I would click the thanks button but I'm on my Blackberry and there doesn't seem to be one unlike the full web version.
 
Its all about costs really, you may pay more for the TL inverter as you were indicating and Dansk may be right in saying that he would recommend the higher costing unit. However 16 panels on a SMA 3300 installed just prior to the 12th December deadline has done 153kw (checked last night) so would that have been worth paying the extra several hundred pounds for a 4000TL inverter. Its hard to say.

Im not dis-agreeing with anyone, but there becomes a point in everyones quote where costs come into it, if your happy to pay the extra, then go for it, some people aren't so no 2 quoates are the same in that respect.
 
Thats why open discussion is healthy, were all here to learn.

My view on the 3300 is it will do well at this time of year, assuming when you say you have "16 panels" they are 250w panels, but you could lose out in the summer versus the bigger inverters. I read on here the other day in an ideal world you would have two inverters - a smaller one for the winter and a larger one for the summer, and the reason being inverters like to be worked hard at there upper limit, so in winter when its dull and the sun is low its ideal to have a smaller inverter on the end of a lot of panels, and in summer when the panels are beating out high output the smaller inverters are going to struggle to keep up - its like driving down the motorway in 4th.

Im not sure the price difference comes into much in the scheme of things when choosing between different models of inverters, and i feel design is more important - once someone has made up there minds to have solar its about getting the best out of the roof space for that given situation.
 
Thats why open discussion is healthy, were all here to learn.

My view on the 3300 is it will do well at this time of year, assuming when you say you have "16 panels" they are 250w panels, but you could lose out in the summer versus the bigger inverters. I read on here the other day in an ideal world you would have two inverters - a smaller one for the winter and a larger one for the summer, and the reason being inverters like to be worked hard at there upper limit, so in winter when its dull and the sun is low its ideal to have a smaller inverter on the end of a lot of panels, and in summer when the panels are beating out high output the smaller inverters are going to struggle to keep up - its like driving down the motorway in 4th.

Im not sure the price difference comes into much in the scheme of things when choosing between different models of inverters, and i feel design is more important - once someone has made up there minds to have solar its about getting the best out of the roof space for that given situation.

Yes - and if the panels aren't at an optimal facing (South) and an optimal angle to face the mid-summer, mid-day sun straight-on (about 25 degrees, if I remember correctly) then they won't ever reach maximum potential.
However, although South and about 25 degrees harvests the most in the middle of summer, it is by no means a good angle for other seasons due to the sun being lower in the sky and therefore no longer able to face the panels straight-on. For winter harvesting of sunlight, the optimal angle is quite steep.

Bearing in mind a combination of the direction in which the panels face, plus the angle at which they are mounted, plus the time of year, plus the capability of the inverter.

With East or West facing panel arrays, it should not be a problem to somewhat "oversize" the panel array because of the inability of the panels to ever work at more than about three-quarters maximum output.

I have 3.75kWp on a 3.6kW inverter, facing SouthEast at 40 degrees. If I could have made 4kWp fit nicely/look good on my roof, I would have preferred a 4kWp array and keep the same 3.6kW inverter because I doubt that my array can ever reach maximum potential.

Note that when I talk about maximum potential, we in the UK need to be realistic and appreciate that most of us have sub-optimal options for panel positioning, but we can still get a reasonable output.
 
I have 3.75kWp on a 3.6kW inverter, facing SouthEast at 40 degrees. If I could have made 4kWp fit nicely/look good on my roof, I would have preferred a 4kWp array and keep the same 3.6kW inverter because I doubt that my array can ever reach maximum potential.

Note that when I talk about maximum potential, we in the UK need to be realistic and appreciate that most of us have sub-optimal options for panel positioning, but we can still get a reasonable output.

How long have you had your system installed? At SE and 40 degrees, I'd say you will definitely hit maximum output.
 
Hi, Biggs

My system will see its first June peak sun this year.

However, I have a few friends/associaties with PV which I have used as a guesstimate for my system; a nearby friend has a 4kWp 16-panel Sanyo with SB4000TL with similar facing and pitch to mine and it managed to hit 99% output for only about an hour on only a handful of days last year.

In the sunny summer months, its average daily peak output (i.e. the hour around mid-day) was about 93.5%.
My 3.6kW inverter is 96% of my 3.75kWp array rating, while a 3.6kW inverter would be 90% of the rating of a 4.0kWp array.

With my panels being of a likely lower quality/performance than Sanyo (mine are Chinese-built; rather bulky and low-tech compared to Sanyo), I would be surprised if my panels can match the outputs of my friends system - especially once I get a few bird poo's on the panels!
 
With my panels being of a likely lower quality/performance than Sanyo (mine are Chinese-built; rather bulky and low-tech compared to Sanyo), I would be surprised if my panels can match the outputs of my friends system - especially once I get a few bird poo's on the panels!

I think you may be pleasantly surprised :)
 

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