8 x 250w panels just fittled on sw roof only showing 300w output in sun .Poss causes?

kjo · Nov 28, 2011

Hi
Just had 8 x 250w panels installed on unshaded sw roof only showing 300w output in sun .Total 4kw after 3+ days incl. maybe 9hrs.bright sun. Not yet made final payment but electrician returning this wk, & scaffold coming down after which roof unreachable by ladder. Is this output "normal" ? Links between panels not secure ? Other causes ? How to check ? Or am I worrying about nothing ?

Incidentally I had another 250w panel installed in the only partly shaded area (to balance look)with separate lead coming to loft as yet unconnected.Could this at a later date be connected straight into existing Fronius IG invertor or would it need it's own micro invertor before feeding into FIT meter ?

Any help appreciated.

sharpener · Nov 28, 2011

Re: 8 x 250w panels just fittled on sw roof only showing 300w output in sun .Poss cau

Your installer should be able to give you estimated figures for the time of year but it doesn't sound at all right to me, Seniors will perhaps give you more details of what you can expect from 2kW on a SW roof in November. As you say DC wiring is the obvious thing to suspect but don't go prodding about as the voltages can be lethal even when the current is small.

Don't understand why the extra panel was left unconnected, you have paid for it and if it sees any sun at all it is potentially useful. Providing the panels have bypass diodes it can be wired in to the existing string(s) subject to the voltage limitations of the inverter, check with the manual or post exact details of panels and inverter here. You need to make sure it is on the paperwork as theoretically it would be problem to wire it in post Dec 12th (though in practice not easy to detect)

whinmoor · Nov 28, 2011

Re: 8 x 250w panels just fittled on sw roof only showing 300w output in sun .Poss cau

Please tell us your location, panel brand and roof pitch.

JohnBoyZ · Nov 28, 2011

Re: 8 x 250w panels just fittled on sw roof only showing 300w output in sun .Poss cau

300W in sun does sound a bit on the low side.
PV output is generally low at this time of year my 3.8KW system has only generated 6KWh over the last 3 days, (although it is partially shaded by trees at this time of year). if your interested you can see a graph of my output on the PVOutput website

CedarsPV 3.800kW

its a useful site for comparing systems, here is another graph for a 2.2KW system so similar to your 2KW

spikemooner 2.220kW

kjo · Nov 28, 2011

Re: 8 x 250w panels just fittled on sw roof only showing 300w output in sun .Poss cau

H
Thanks for speedy replies.
House is in Surrey. Roof pitch about 45% facing w/s .Panels are Sharp NU250. Invertor is Fronius IG
SAP projected annual kWh is 1461 for the 8 panels. ie av. 4kWh per day
No mention of bypass diodes by the installer though I did mention this & not specified in details of Quote accepted.

TedM · Nov 28, 2011

Re: 8 x 250w panels just fittled on sw roof only showing 300w output in sun .Poss cau

A 2kW system is going to produce a little less than 50kWh in November, so about 1.6kWh a day on average, assuming no shading issues.

SolarCity · Nov 28, 2011

Re: 8 x 250w panels just fittled on sw roof only showing 300w output in sun .Poss cau

I'd say that the figures sound about right for a 2kWp south west facing system.

The extra panel is a curious one. It may well have been the case that it would bring down the power of the rest of the system and so it was a good idea to leave it disconnected.

TrickyDicky101 · Nov 28, 2011

Re: 8 x 250w panels just fittled on sw roof only showing 300w output in sun .Poss cau

At 45º even on a SW roof I would expect better peak output than 300kW for 2 kW array. Steeper pitch is favourable at this time of year. Can you check on your inverter what your max voltage has been since the array was commissioned?

deeyup · Nov 28, 2011

Re: 8 x 250w panels just fittled on sw roof only showing 300w output in sun .Poss cau

Is the scaffold casting shadows over the array? That can have a major effect.

I think the fronius inverter only has one mpp tracker so if the ninth panel is connected
you won't see any benefit from it.

One of those photocopied sharps would have done the trick nicely.

sharpener · Nov 29, 2011

Re: 8 x 250w panels just fittled on sw roof only showing 300w output in sun .Poss cau

Don't follow your logic deeyup, the Sharp NU250 panel has 3 bypass diodes, so why not connect up the 9th? The OP has paid for it!

Voc is 37.9V so 9 panels on one string is well within the 500 Vmax and 400 Vmpp max of the IG20 (assuming that's what he has and it should help start-up as well.

series530 · Nov 29, 2011

Re: 8 x 250w panels just fittled on sw roof only showing 300w output in sun .Poss cau

We're in Surrey as well (west Surrey): we've managed 10KWh of generation over the past three days. The majority of that was on Sunday. Our system is 3.5KWp and we have micro inverters. Most scaffolding frames are erected with workforce safety in mind. Rails around the outside will almost certainly encroach upon your panels to some extent and will have a major effect upon harvest especially at this time of year. 4KWh doesn't seem artificially low because the irradiance is pretty poor at this time of year. It seems broadly in line with the figures that I have been getting taking into account the fact that we have micro inversion and you may be suffering from some shading due to the scaffolding.

You also need to bear in mind that virtually all properties have some degree of shading. It isn't necessarily in the form of a tree or a building. Telegraph poles, telegraph wires, clouds passing, gables, aerials, etc. all contribute to a reduction in harvesting which can be especially severe at this time of year.

I wouldn't get too concerned because it's a tall order to get decent harvesting at this time of year. Come the summer months you will see more harvest in a morning than you sometimes see in a winter week!

GreggElectrical · Nov 29, 2011

Re: 8 x 250w panels just fittled on sw roof only showing 300w output in sun .Poss cau

Doesn't sound too far out to me. Peak seems low but are you sure this is the highest it has ever been or just the highest you have seen?

jamescdrw · Nov 29, 2011

Re: 8 x 250w panels just fittled on sw roof only showing 300w output in sun .Poss cau

had the same problem found on the same panel was a rubbish connection on the mc4 plug on one of my pannels

pjcomp · Nov 30, 2011

Re: 8 x 250w panels just fittled on sw roof only showing 300w output in sun .Poss cau

The OP mentioned "average 4KWH a day" - it don't work like that. You may get that average over a year, but on any one day the generation will depend on too many variables to get a consistent day-on-day return.

PJ