low generation

[tombennetts]

Hi guys, i have just installed my first pv system for a company that has just been set up (used for mcs accreditation all passed fine) The problem is the system is only generating 800watts an hour on a very nice sunny day. Its a 3.8 ish system with fronius ilgt3.6 inverter. The panels are 17 x 230 watt upsolar panels. The connectors on the panels werent compatible with the standard mc4 connectors so i chopped them off the panel yesterday and changed them so we now have better connections, the weather was awful yesterday so dont yet know if its made any difference. Anyone got any other ideas as to what it could be? shading is not an issue, the roof is south west facing with 35 degree incline, down in cornwall so it should be producing far more than this!
Thanks
Tom

 

[SolarCity]

What kind of figures did you get with your tests? Presumably this system is on one string?

 

[tombennetts]

hi, yes its on one string. Do you mean voltages? cant remember exactly now but it was around about 600volts from the panels, which i thought sounded about right.

 

[SolarCity]

What about the short circuit current and the irradiance?

 

[tombennetts]

waiting for my dc clamp meter so i can do the short circuit current, we didnt do irradiance tests but surely just down to the fact that its south west facing, 35 degree pitch and no shading it should be producing a hell of a lot more than it is?

 

[SolarCity]

You say that it's producing 800 watts per hour. What is it producing per day?

 

[tombennetts]

on the best day its produced 10 units, whereas a neighbour who has a similar installation did 17 on the same day!

 

[SolarCity]

Hmm, really difficult one. First thing I'd do is get an irradiance meter and a DC clamp meter and go and do some tests. This should give you a bit more of an idea what the problem might be. To be honest, you're going to need to do them anyway when you send the DC test forms off to the DNO.

Your voltage seems ok.

The problem may be with your connectors. The UpSolar 230w panels use MC4 connectors, is this what you used?

 

[tombennetts]

Hi, sorry internet has been down last couple of days. The panels came with rubber mc4 connectors that screwed together, but the mc4 connectors they supplied us to joint the cable were the plastic type that clip together with 2 'prongs'. I have changed the connectors on the panes on the end of the string for the same plastic ones now.
to do the short circuit current can i literally plug the string in end to end and put the clamp meter round it? does that not cause a problem with arcing when i disconnect?
thanks
tom

 

[Worcester]

Our crews use a simple test box with a DC isolator and probe leads with MC4's on so we can do Voc and Isc quickly on every panel before it goes on the roof, as well as once strung :

Sounds to me like your rubber MC4's that 'screw' together were MC3's ...

 

[MorganPVI]

Hi guys, i have just installed my first pv system for a company that has just been set up (used for mcs accreditation all passed fine)

I'm intrigued by this company - do you work for them or just use them for the MCS accreditation?

Upsolar are supplied with MC4 - one is a prongy one like you describe, the rubbery ones are MC3 like Worcs said. You may have a dodgy connector or perhaps you've strung 8 panels and the rest are disconnected.

 

[tombennetts]

I initially thought they were mc3's but i got some mc3's from the wholesaler to make the leads up with those and they were far smaller than what we had on the panels. Think i might have to make myself up one of those!

 

[Worcester]

Got a photo?

 

[tombennetts]

not at the moment, will take one when i go back there to have another crack. The company set up and i subcontract commissioning the electrical side of things.

 

[Graeme Harrold]

I find it quite strange that you do not already have the test kit and are unsure about arcing, connector types and overall testing. How can the panels be installed an commissioned if the testing has not been done fully or correctly? This is probably the reason you are having problems now.

Best thing is to unplug the dc at the inverter an test Voc, then short, go outside and test Isc while noting panel temp and irradiance. From this you can compare your results against that of the manufacturers data sheet at STC according to the panels on the string.

 

[solgen]

At risk of rubbing salt into your wounds. If you have changed the connectors that were supplied with the panels you may have invalidated their warranty.Hope this isn't the case for you?

 

[tombennetts]

the Voc has been tested and all results met the panel specs, my clamp meter decided to stop working the day we started working on the system and haven only just had a chance to get a new one! About changing the connectors, we tried contacting segen (who supplied the system initially) about compatible connectors but they didn't seem to know anything about them. Will be back there on friday to try to get the problem sorted once and for all.
I do know about the different types of connectors but the types supplied by segen to fit with the panels just didn't fit. The rubber ones on the panels did not connect with the 'fork' types supplied seperately. This is why i assumed they were mc3's which it turned out they were not.

 

[MorganPVI]

Segen have some kind of a T connector for upsolar panels on their site, no picture though.

So whats this MCS company you mentioned earlier?