cable sizing / panel distance

New to renewable energy? Have questions? Here's a great place to ask them and view information about wind and solar power basics.

cable sizing / panel distance

Postby dinkum » Sun Jun 29, 2014 2:53 pm

hi all , it's time to move tracker [tilt frame atm] or risk death penalty by wife and cut a couple of trees down. think i will move panels...i'm thinking of having 4 strings of 3 panels in series. [1 trina 195w and 2 chinese 190w to each string ].paralleled to 20mm xlpe cable for a 50 m run to solar shed...... specs are
[vmp] [imp] [ocv]
trinas 37.1 5.25 45.6
chinese 37.1 5.11 45.3
about 111.3 5.11 136.2 for each string ..will this config be okay for classic 150 0r fm 80...my calculations for V drop are 1.7% for 20A/50 m run but wasnt sure whether to double distance for complete cable loop..all online calculators give wildly varying answers [thought EM would have a good one]...my sparky mate has surplus 20mm cable cheap which is why i picked this size..
1,,will he need to run an earth back to solar shed
2,,will each string need it's own c/b or just 1c/b and isolator for array and what types [everyone seems to have differing opinions on # poles etc,i'm confused ] ..maybe a member/installer is willing to sell me what i need..pm me
3,,can anyone recommend a solar installer around the n/e vic [wangaratta] area or someone thats willing to travel to this area to upgrade/cleanup my solar shed mess after years of add ons. by the way i'm a bit new to all these higher voltage strings etc , and my figures are probably way out..any input welcomed ...thanks... dennis...
dinkum
Solar Fanatic
Solar Fanatic
 
Posts: 42
Joined: Sun Oct 27, 2013 9:15 pm
Location: n/east victoria

Re: cable sizing / panel distance

Postby Tracker » Sun Jun 29, 2014 5:19 pm

..
Dennis.. just wondering just how the whole thing works.. and if there may be an alternative..

eg.. buy a separate small grid inverter, eg. PVE1200 and run AC back to the shed..

Anyway , perhaps start by saying what happens to the power.. Battery?? Grid Feed ??? Hybrid??
..
.
Retired Engineer and keen PV experimenter - Always ready to learn and share.
2 x CMS2000 (fan cooled) GCI and SE 170W panels
1.7kW First Solar/Outback Island circuit - Peak Replacement Power
Governments won't save the world :-) They will just TAX it :-(
Tracker
Solar Crusader
Solar Crusader
 
Posts: 5113
Joined: Wed Sep 23, 2009 5:54 am
Location: SYDNEY --- EA - Network, Retailer - EA

Re: cable sizing / panel distance

Postby dinkum » Sun Jun 29, 2014 7:07 pm

thanks tracker, i should of said it's to charge 24V batteries through mppt cc. i am totally off grid.i have toyed with the idea of building a new solar shed and just running ac mains to house but i still have a 24V freezer and about 800W of fixed panels on existing solar shed + wife does'nt want me to block any more of her view,so i thought it would be easier to move or build a new tracker.. as more or less stated.this is a bit of a learning curve for me,[they say ,,you can't teach an old dog new tricks] so i appreciate any help on cable sizes,fuses,c/b's etc....dennis
dinkum
Solar Fanatic
Solar Fanatic
 
Posts: 42
Joined: Sun Oct 27, 2013 9:15 pm
Location: n/east victoria

Re: cable sizing / panel distance

Postby Tracker » Sun Jun 29, 2014 7:21 pm

.
We are all learning.. there are only a few experts on off-grid..
The constant NEW call is AC coupling, and that is why I asked the question, wondering if AC coupling could be usefully..

The clear beauty of AC coupling is that the inverter will push whatever voltage it takes, to push the available power..

More detail please...
..
.
Retired Engineer and keen PV experimenter - Always ready to learn and share.
2 x CMS2000 (fan cooled) GCI and SE 170W panels
1.7kW First Solar/Outback Island circuit - Peak Replacement Power
Governments won't save the world :-) They will just TAX it :-(
Tracker
Solar Crusader
Solar Crusader
 
Posts: 5113
Joined: Wed Sep 23, 2009 5:54 am
Location: SYDNEY --- EA - Network, Retailer - EA

Re: cable sizing / panel distance

Postby dinkum » Sun Jun 29, 2014 8:41 pm

ac coupling ????g t how doe's this work,,,sound's expensive !,i have read nearly every post in solar basics and components and installation the last 6 months or so but haven;t taken much notice about ac coupling posts as i assumed you need grid connect power...
re ; more detail,,i'm not really sure what detail you need,,maybe i complicated or confused with first post. i just want to transmit solar power about 45 meters to charge 24V battery..dennis..
dinkum
Solar Fanatic
Solar Fanatic
 
Posts: 42
Joined: Sun Oct 27, 2013 9:15 pm
Location: n/east victoria

Re: cable sizing / panel distance

Postby Tracker » Mon Jun 30, 2014 3:15 pm

dinkum wrote:ac coupling ...... i just want to transmit solar power about 45 meters to charge 24V battery....


And what do the batteries do.. Do you have an Inverter ... WHAT make and model..

Describe all the components of what you have, otherwise folk are literally guessing and likely wasting time.

AC Coupling does assume that you have an existing system that can be used to provide the synchronizing power.. naturally, the issue with AC Coupling, is that you generally need to be able to USE all that power, being generated..
..
.
Retired Engineer and keen PV experimenter - Always ready to learn and share.
2 x CMS2000 (fan cooled) GCI and SE 170W panels
1.7kW First Solar/Outback Island circuit - Peak Replacement Power
Governments won't save the world :-) They will just TAX it :-(
Tracker
Solar Crusader
Solar Crusader
 
Posts: 5113
Joined: Wed Sep 23, 2009 5:54 am
Location: SYDNEY --- EA - Network, Retailer - EA

Re: cable sizing / panel distance

Postby dinkum » Mon Jun 30, 2014 8:13 pm

i have a selectronics sa32 inverter, 2,PL40 c/cs ,1700 ah c/100 bats,,1 fixed 800W array,, 1 tilt frame with 1500W panels which i plan on moving / upgrading..i also have a small 12V system which runs few lights,radio, and most importantly,,a 70L engel beer fridge....i did have a more detailed description typed up then dragged a smilie down and all this computer jargon came up so i clicked on preview,and asks me to login again ,then the whole post is gone...anyway thanks again for replying , and i appreciate your suggestions and anyone elses....how doe's this ac coupling work,,do u use my inverter to run gridtie inverter to produce 240V ac power to run back to my solar shed ? ..thanks...dennis..
dinkum
Solar Fanatic
Solar Fanatic
 
Posts: 42
Joined: Sun Oct 27, 2013 9:15 pm
Location: n/east victoria

Re: cable sizing / panel distance

Postby offgridQLD » Wed Jul 02, 2014 10:35 am

Yes you need to double all distances when doing the cable calculations.

130v will work on a classic 150 but you do loose some efficiency going to high from your charge voltages considering your system is 24v. Controller runs hotter. It's a compromise between efficiency loss in the charge controller and efficiency loss in the cable.

I just did a 20m run (40m return length) from my shed to the power room (4200w pv on the shed at just over 100v) I went with 50mm2 cable from the shed to the power room and 6mm2 from the shed wall junction up to each 3s string, 7 stings in total. (distance from the shed wall to each string from 12 - 15m-( 22 - 30 return).

If your getting some one to do it they should know what you need to set it up and be able to do all the cable calcs for you and correct breakers and earthing .

Kurt
offgridQLD
Solar Crusader
Solar Crusader
 
Posts: 2117
Joined: Thu Jan 26, 2012 11:50 am
Location: South Australia, Fleurieu Peninsula

Re: cable sizing / panel distance

Postby dinkum » Thu Jul 03, 2014 9:34 pm

thank's kurt, for your reply..when i did'nt get a lot response i looked back through my posts i guess it looks like,
"oh yeah,he's made up the sparky mate bit,,quiz us a bit,,and do it himself " i should of said, a neighbour who doe's electrical contract work at my workplace,,some of it heavy duty stuff and he has grid connect solar ,he said 25mm would be ample,i did'nt discuss any other details , just assuming he knows what he;s doing and could do my job.. i thought i'd do a bit of research so i would be armed with a bit more knowledge when i do get back to him and ask about more details on isolators,c/b s ,costs ,, in saying all this,i have no problem playing with 24V but HV dc is over my head.hopefully this will be my last major upgrade ,except for some real batteries down the track..my aim is to get my solar system,cleaned up,legal, and safe...my questions are: is a general electrician qualified to wire up panels,or does he need accreditation [disregarding any solar rebates]
do you think [he's cheap 25mm cable will suffice] or maybe 2 pairs of 25mm and run 2 strings on each pair ..i am not worried about a bit of loss as panels are cheap.[my first 80W panel cost me $ 800.oo, 2 full weeks wages] ...all the solar installers in town are not interested in grid free work...or work on existing installations..tracker talked about ac coupling, but sounds complicated.. the reason i'm still asking about cable size is because , if it suits, i can by it now for the right price ,for who ever does the job...i welcome all suggestions...thanks...dennis
dinkum
Solar Fanatic
Solar Fanatic
 
Posts: 42
Joined: Sun Oct 27, 2013 9:15 pm
Location: n/east victoria

Re: cable sizing / panel distance

Postby offgridQLD » Thu Jul 03, 2014 10:27 pm

Dennis,
Ac coupling requires a inverter / charger that is designed to take advantage of AC coupling and has the features to controller and distribute the power from a AC charge controller feeding into it. Typical it's the newer top of the line inverter chargers that offer this feature. It's something to consider if starting out fresh or upgrading to a high spec inverter/ charger like the selectronic SP pro along few others but most likely by the sound of it wont apply to your system as it stands.

Considering you have a 24v system I would do some research into comparing the efficiency losses with MPPT in the charge controller converting a high voltage string back down to 24v and the losses in your cable run from PV to charge controller. Copper is expensive now days but perhaps like you say two runs of 25mm might be a good idea. Just mention it top your installer.

I am not a installer or electrician . I live off grid and do all my own extra low voltage work.

Though I recommend you arm your self with as much info and advice as you can. Even if your not doing the work your self. I'm sure it helps you ending up with the best outcome if your somewhat informed.

Some of the on line cable calculators do take the return run into consideration (though it's usually clear as the losses are double)

What do you call a good price for 25mm2 ? Just had to ask to see if its worth working around.

Kurt
offgridQLD
Solar Crusader
Solar Crusader
 
Posts: 2117
Joined: Thu Jan 26, 2012 11:50 am
Location: South Australia, Fleurieu Peninsula

Next

Return to Q&A - wind and solar power basics

Who is online

Users browsing this forum: No registered users and 4 guests

new solar power specials