Diogram for 10 panels.

[Gavin A]

polarity protection merely means that it won't work the wrong way round, so it still matters.

 

[valet]

What is the best way to test panels before installation on the roof. Iam planning to use multimeter with test cables for MC3 connectors on the ends. Any suggestions, precautions I should take? On Panasonic 250w

 

[Worcester]

You can test the panels indiviually using an inexpensive meter so lang as it can take 10 amps and 50 V DC.
You do two tests
1) Voc = Volts OPen Circuit, i.e. just measure the voltage across the panel - depending upon the light conditions and so long as you line the panel up to the sun, you should get a reading similar to that on the Panel Specification Sheet.
2) Isc = Current Short Circuit, and yes we do mean short circuit make sure you put it thoruigh the 10 Amp shunt on the multimeter and join the ends together. ! DON't Us this to do the string test though, you'll blow it up! The current is HIGHLY dependant upon the light/sun's output though so don't worry if this is way off, a bright sunny day with the panel at the correct angle is the only time you'll get the Isc quoted on the Spec sheet and you'll need an Irradiance meter to check it anyway.

You may find it worthwhile to get a push switch rated at 10 Amps and put it in the circuit that way you wont be pulling apart a 'live circuit'

http://www.electriciansforums.net/a...-testing-does-everyone-really-do-dscf2621.jpg

When you've installed the string you should also do a Voc and Isc on the whole string - unless you've got a DC clamp meter don't do the Isc test, (7 or 8 amps at 300 or so volts..) also make sure your voltmeter is rated to 10 x Voc - and that is the reading you should be looking for. Be VERY careful with the DC cables after the panels are connected in a string you are working with very high DC voltages. You can get big sparks and bangs from shorted DC cables - just remember you can melt a screwdriver across a car battery and that's only 12V!!

 

[valet]

Thank you for that respect to all.

That the multimeter I am going to use, do you think ist ok for the test?
Just going to attach MC3 connectors on the end.

AC VOLTAGE

• Measurement Range 200V-600V
• ±1.2% ± 10 digits
• Overload Protection: 600VDC or rms

DC CURRENT

• Measurement Range DC 2000-10A
• ±1% of rdg ± 2 digits
• Overload Protection: F 200mA/250V fuse (10A range unfused)

Purchased on ebay:
DIGITAL LCD MULTIMETER VOLTMETER AMMETER BUZZER AC DC METER OHM CIRCUIT TESTER | eBay

 

[valet]

Thanx for that do I have to do isc test a bit concern to short panels.

 

[solarfred]

Hi every one,

Wondering is anyone can help me with regard to this diagram please see picture attached.

How that looking to you, can I connect 10 X 250w panels in one array on one string this way?

Thank you View attachment 15892

If you wire it up by connecting "alternate" panels then you end up with both ends at the same point only one panel away from each other. If the leads are long enough they should reach across to do this thus no long "end".

 

[valet]

Thank for advice. I don't get "alternate" could you please if it's not too much to ask draw little diagram?
Thank you

 

[solarfred]

Diagram sent.

 

[valet]

Hello guys. Just a question about how to test panels with clamp meter sorry to sound confused dc volts and short circuit. Just purchased new clamp meter but my new meter got settings 40A and 400A. And if any one knows if its possible to test panes dc volts with clamp meter? Or I have to get MC3 leeds.

 

[Worcester]

You can so long as it is a DC Clamp meter. In fact to test the completed strings you'll need a DC clamp meter, else you'll likely fry it.

 

[valet]

But what if my clamp meter have 40A setting on it. Do I need to buy diferent clamp meter would reed 7A?
Would my clamp meter manage to reed 7A on each panel if setting on meter 40A? What's min Isc A clamp meter could reed ? Also I still need MC3 adapters leeds to check Voc on Panasonic panels?

 

[valet]

Hi thank you for all your help grate to have this forum.

Have a look at my two diagrams please. Which you think will perform better on ten Sanyo panels on three split roof spaces on one string?

 

[Gavin A]

just wire the things up will you it's been 4 days, this is getting painful to watch.

oh an I vote for option 2, as it's complex enough trying to work out the wiring across 3 roofs without trying to also do some bizarre doubling back through the array arrangement that I'd imagine would make the installation process a nightmare, and fault finding nie on impossible for whichever poor sod has to come and work out where the earth leakage is coming from several years down the line.

 

[SolarCity]

Valet, have you not already had these panels installed?

I go for option two. For reasons that Gavin states and because I can't fathom what on Earth is going on with option 1.

Don't panic. Get them connected up and they'll do their job. If you take any longer over this then you'll find your neighbours all have domestic rooftop fusion power generators and you'll end up with the equivalent of a Sanyo Brahman bull on your roof.

 

[valet]

This is a second project house exactly the same.
Thanx boys for that. Some one suggested me an option one to alternate panels. Also option one have shorter cable on last panel on the third roof. On option two it seems to be too long going allway around. I rather be careful then sorry and get best performance from this project that's all. Sorry if it's painful.