Isc value too low

[jjnr78]

(Please be gentle, its only my second install)
I've just installed 10 RECs with an SB2500HF and i'm trying to commission for handover. I've measured the voltage of each panel, which was correct, and my Voc today was about 300V. However, I'm only measuring Isc of 0.4A. The install is a top row above dormers of 4 mods and a lower row of 6 mods. The inverter is not indicating any faults and after speaking with SMA they feel its the cloudy day and shading. The shading is across the bottom row and is being caused by the scaffolding which runs right across. Does this sound feasible? The inverter is consequently flashing green (lack of irradiance). It was solid green this morning and the chart is displaying a few bars. Whatsmore, and probably a red herring, I've just checked the elster generation meter and my colleague has wired it so that the light is solid red and therefore not wired correctly.
I'm concerned about the wiring now and there's v little sun out there (north M25) today. I wired from the inverter to the top row with the +ve (1m) and the bottom row -ve (c15m).
Will the sun brighten my day in many ways, or have I missed something??

Thanks

 

[SibertSolar]

I could be wrong but I think if you've got a horizontal shadow across the whole string, and your modules are mounted portrait (with typical cell topography/layout) then all the bypass diodes in each module will most likely be in operation and the MPPT value from the affected string is probably too low for the inverter. Just a thought. Hopefully someone else will "shed some light" on the matter..... ;-)

 

[JulianC]

What irradiance reading did you get when commissioning? This will give you a good indication of what Isc you should be getting. Had plenty of installations that only kicked out 0.4A - 0.5A on a dull day. If the inverter is not firing up due to low irradiance then the light will be on constantly on the gen meter - it's not necessarily wired up backwards.

 

[powervan]

it seems to be a dull month if u ask me!

 

[jjnr78]

Thanks Sibert. They're mounted landscape, but your comments make sense. I'll see if there are any changes tomorrow and then strike the scaffolding to (hopefully) see improvements...scaffolding cost 1500!!!

 

[jjnr78]

This project has been anything but dull for me!! i think i've lots a stone and half a head of hair!!

 

[Earthstore]

£1500, For scaffold, really.
Surly you bought it, not rented it for a couple of days at that price...

 

[powervan]

Lol everyone keeps saying to me blimey ur hair has nearly gone!!

 

[jjnr78]

"£1500, For scaffold, really.
Surly you bought it, not rented it for a couple of days at that price..."

Its platinum, heated, illuminated and plays music...at least that's what they told me. The it turned up cold, grey and huge! its a big scaffolding with different levels over a conservatory etc

 

[powervan]

1500 well must be a work of art! leave it up and santa can park on it!! save them bloody clay tilesbig fat bloater in red suit climbing up there!!

 

[bumcrack]

If you have 200 w/m2 or less, accurate calculations of Isc measured vs Isc STC is difficult.

Just get the thing generating something, get the application in and get back on a sunny day.

 

[powervan]

true as bruce used to say generation IS THE NAME OF THE GAME!! good game good game!!

 

[bumcrack]

also to say, if VocT is stacking up to the amount of modules x VocM, you can be happy enough you have continuity throughout...