conecting panels series parallel

[robroofer]

shello everyone,

im starting a pv course tuesday and was wondering about a few things.

the mounting of panels isnt much concern as im a roofer by trade the boss wants me on the course , there will be a electrician with us during the installs but i wanted to go on the course aswell as my boss.

this forum is great and I've learnt so much.

one thing is connecting the panels together, ive been reading up on series and parallel connections but a bit clueless on it all.

if you have say 3 panels or 15 panels does it make a difference connecting them up or do you put them all in series?. do they go through this at the course as i assume just sparky's go on this course and know already.


regards
Rob

 

[moggy1968]

Basically if you connect the panels in series, the voltages are added together and the current stays the same. If you connect them in parallel the voltage stays the same and the currents are added together. because of the problems of voltage drop it is usually to connect in series to gain a high voltage so the effect of voltage drop becomes less significant. on larger arrays though this may produce more volts than is desirable (beyond the range of the inverter for example) so on a 16 panel instal for example you might connect 2 strings of 8. the voltage of 8 panels is added together whilst the current of the 2 strings is added together, this would give the same watts as if you just connected 16 panels in series.

also current is more susceptable to shading. on panels connected in series if one panel is shaded it will drop the current, and therefore the power, of the whole string (bypass diodes etc excepted) so if you had a 16 panel array where half the panels were susceptable to shade for part of the day if you connect those as a string in parallel with the unshaded ones you will reduce the effect of the shade on the whole array.

hope that helps

 

[platty1005]

Here is any easy way of trying to understand series and parallel using house bricks imagine the length is voltage and height is current
Take ten bricks each 20cm long and 7cm high now lay the bricks on the floor end to end you add together the 20cm's to get 200 cm The height is just 7cm
This is like wiring the panels in series 10 panels of say 20 Volts and 7 Amps
Wired in series add the volts = 10 x 20 = 200V but the current is just 7amps similar to the height of the bricks
The simple output power is 200 x 7 = 1400W

Now stand the bricks on top of each other length 20cm but the height is 10 x 7 = 70cm
Same for Panels 10 panels connected in parallel volts only 20Volts but current is 70 amps The simple output power is now 20 x 70 = 1400W
Now lay 2 rows of 5 bricks length on top of each other to look like a wall of 2 rows high this gives a length of = 5 x 20 = 100cm height but 2 rows high = 2 x 7 = 14cm
2 rows or strings of panels of 5 are connected in series then the 2 strings of 5 are connected in parallel is like the 2 rows of bricks length = voltage = 5 x 20 V = 100V
But current is like height so 2 strings = 2 x 7 amp = 14 amp
Output power is now 100 x 14 = 1400W
The 2 strings are a combination of 2 x 5 in series then the 2 strings are connected in parallel (like 2 rows of 5 bricks)
PV design as you will learn on the course is the best selection of panel, inverter and string combination to give the best solution for any particular installation
Hope this helps !!

 

[robroofer]

thanks guys , im going on a electrical course soon so the other guy has gone on the PV course was looking forward to it but need more electrical guidance.

i think ive got it from above, so you connect live of one panel to negative to the next and so on until you have two cables left in the roof space.

looking at the site test-meter.co.uk i see you then make off your ends , i assume thats what you'll do for the last two cables?. these go to a DC isolator then to the inverter?.

also if i have a live and negative cable left in the roof space i will put a negative end and plug into the live and same for the negative, so what end is live and what is negative negative.

sorry to sound so stupid

Rob

 

[SolarCity]

Just be very careful. You could end up with a dangerously high voltage on the end of those panels and it can very easily kill.

Don't worry. You don't sound stupid! But I would strongly advise that you don't do anything more than plug the panels together. If you start going down the road of making ends off then you are very much entering electrician's territory and if you don't know what you're doing then you could kill yourself, someone else or create a fire risk.

 

[robroofer]

lol, its ok i wont be doing anything on my own, i just wanted the simple questions out of the way, im reading the DTI guide as i type, i was drawing the circuit onm paper and it seemed to me that you would make a negative end off but its the live from the DC isolator and a positive end is neutral just sounds strange.

 

[SolarCity]

You're right. And I've had sparkys on site with me that have put the wrong ends on (and I'm one of them!)

 

[grandfortune]

easy done:yes: