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Forum Index : Solar : solar cable size for 48 volt
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| brucedownunder2 Guru  Joined: 14/09/2005 Location: AustraliaPosts: 1548 |
I'm a bit old and confused , have done many "look-ups" ,but not much in the way of cable sizes . My intended system is this 1Kw of panels + 1.5 Kw of panels =these two banks will be seperate ,but similar in positioning . question , what size cable from the panels factory tails to the controller ,either for each bank of panels or combined close in a junction box up near the panels. This is an off - grid stand alone system ,into a 48 volt battery bank ,approx 700 Ah @48 nom. cable run would be approx 12 Mtrs to the controller/regulator. I have 4mm tinned, 6 mm copper, 10mm copper, 25mm copper -all copper is bare ,not tinned. Thanks bruce Bushboy |
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Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
According to this calculator you will need 16mm square wire if you combine at the panels. 2x(1x2c) 16 mm2 Cu/PVC/SWA PVC (70 °C, thermoplastic) - armoured, Two Core Copper SWA Details 48 V, d.c. , circuit length 12 m, total cable length 24 m Load current: 50 A , protective device rating: 100 A , power loss 37 W Cable impedance: 0.00735 Ω Voltage drop: 0.73 V (1.53%) - required ≤3% Fault level: source = 10 kA , destination = 2.9 kA Derating factors: - Ground temperature °C [30]: derating = 0.89 - Number of ducts [2]: derating = 0.9 - Buried Circuits Adjustment [1]: derating = 0.9 - Depth of laying, m [0.9]: derating = 0.98 - Thermal resistivity, K.m/W [1.2]: derating = 1.13 There are only 10 types of people in the world: those who understand binary, and those who don't. |
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| brucedownunder2 Guru Joined: 14/09/2005 Location: AustraliaPosts: 1548 |
Thanks Mad. 50Amps x 48volts =2400 watts . IKw +1.5Kw =2.5Kw max output , so 16mm square for both arrays combined at the combiner junction box adjacent to the panels ,would be sufficient cable size from there ,down to the regulator/controller .? How ,s this add up ,mad? Thanks, Bruce Bushboy |
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| Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
What does not add up? 50A won't be your maximum anyway, you will get maximum power at around 59 volts and your current will be around 42 Amps. There are only 10 types of people in the world: those who understand binary, and those who don't. |
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| brucedownunder2 Guru Joined: 14/09/2005 Location: AustraliaPosts: 1548 |
Oh ,its ok ,,just confirming that what ,s calculated is for both the arrays, thats good . I,d never question your calculations, very thankful for your assistance.. I have some 10mm figure 8 from data rack work years ago ,its double insulated ,but not tinned . you reckon I could get away with using this on each array back to the combiner ,then some 16mm building wire down to under the house into the regulator ,with short flexible tails,?? so, I'd have 2x runs,,say 5 mtrs., of figure8 from my panels to the combiner from each array . then single ,1 x run ,16mm ,rigid building wire single insulated ,around another 8 mtrs. to under the bearers/floor/balcony to under the house regulator/controller. (50 amp,48 volt model). or do you reckon ,run seperate figure 8 runs,all the way for both arrays,- just for flexibility/testing /trouble shooting later on ,hopefully not necessary. a bit long winded, sorry for the drama Bruce Bushboy |
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| Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
10mm for each array is going to be heaps, I would not worry about being tinned unless in a marine environment. There are only 10 types of people in the world: those who understand binary, and those who don't. |
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| brucedownunder2 Guru Joined: 14/09/2005 Location: AustraliaPosts: 1548 |
thanks Mad. have a roll ,part roll, of that red/blue figure 8 big stuff .. I'll use that with bootlace terminals. Thanks for the help Bruce Bushboy |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
That will work fine. Should drop about one volt flat out or very roughly 2% loss. Cheers, Tony. |
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| brucedownunder2 Guru Joined: 14/09/2005 Location: AustraliaPosts: 1548 |
Thanks Tony , Wealth of knowledge ,as usual. This site has to be the best solar ,wind, construction site that I've come across. My rambling on about the 16mm building wire ,UNDER THE HOUSE ALONG THE BEARERS, was suggested because 1. , I have it in red and black 2., it,s protected from sunlight ,so maybe ok within the rules ,except it,s not tinned and it,s semi-rigid single insulated. That was my idea of using it . I'd of course, use crimps and heat shrink at the terminations. I'm also thinking of using a seperate controller/regulator for each array ,,just for the sake of sharing the load from the arrays, plus redundancy in case one carks it ?. looks like another day in paradise up here Gold Coast hinterland. Stay safe, guys, Bruce Bushboy |
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yahoo2 Guru Joined: 05/04/2011 Location: AustraliaPosts: 1166 |
the tinned thing is to stop water getting into the cable on the roof and traveling down inside the cable, laying in the cable and helping the DC potential to corrode the copper away. It can also syphon out of the cable into the junction box and reek havoc. If the insulation splits or is nibbled by a parrot or the crimped end is exposed at a point where water can capillary inside then gravity and syphon down its a problem, if that cant happen it's all good. I used a lot of thick untinned cable back in the BP solar days and never had a problem. You would have to make a judgment about the local rules. I'm confused, no wait... maybe I'm not... |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
If you are worried about UV damage, electrocution, water ingress, attacks by critters, or various acts of God, you can always run your wiring through plastic electrical conduit. Its not that expensive and gives the installation a professional look. Cheers, Tony. |
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renewableMark Guru Joined: 09/12/2017 Location: AustraliaPosts: 1678 |
Bruce, down here in Vic the regs say to use double insulated solar cable to the inverter/controller. As soon as it leaves the panels it must be in some UV stable conduit. Not sure on your regs up there. When I wired up my 4500w east array they were 3 in series 90 odd volt max amps, they got solar cable all the way to the junction box without a join all the way next to controller. The west array is two in series, for the Mad PWM controller, they have the same solar cable all the way to their junction box. It appears the preference is to use double insulated solar cable from the panels without a connection all the way to the controller/inverter. It does mean if you are trying to keep it extra low voltage (under 120v oc) then you have lots of cables going to the controller, but that's the trade off. Other solution is to pay a sparky to wire up for higher voltages and use controllers/inverters that are suitable. If you have an android phone you can download a app called electrodroid that will measure volt drop etc. Plenty other calculators on the net. Cheers Caveman Mark Off grid eastern Melb |
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