June 28, 20197 yr Anyone seen something like this before? Burnt fuse holder and fuse on my income PV connection:
June 28, 20197 yr 16 minutes ago, Sethm said: Anyone seen something like this before? Maybe a lightning strike in you vicinity? Panels and the wiring still ok on the roof?
June 28, 20197 yr Author No lighting in JHb this afternoon. Discovered and in the progress of rewiring from the panels as i have added a panel and want to add another and realised the cable is too thin (4 o r6 mm currently and going to 16mm as its coming from the roof of a double story to the ground floor). My domestic called me to say she could smell burning so i got home as quick as i could. Electrician came by and suspects either there was a fault in the fuse holder or the cable got to hot at the connection and started melting the plastic. Anyone know if those fuse holders are DC rated? Cant find much online. But will be replacing both with 100% DC rated fuses next week.
June 28, 20197 yr 34 minutes ago, Sethm said: Burnt fuse holder and fuse on my income PV connection: Looks like a typical loose connection. Arc on DC even worse than ac, heating up everything and eventually melting it away. If the insulation of the wire is hard for the first 1 to 2 cm from the connection area, it indicates that it was happening over time. EDIT: Even the discoloration of the copper part in the picture points to overheating and again to a lose connection .
June 28, 20197 yr Author Just now, Jaco de Jongh said: Looks like a typical loose connection. Arc on DC even worse than ac, heating up everything and eventually melting it away. If the insulation of the wire is hard for the first 1 to 2 cm from the connection area, it indicates that it was happening over time. Ill take a look when i get home this afternoon.
June 28, 20197 yr 8 minutes ago, Sethm said: the cable is too thin (4 o r6 mm currently How many panels, size of panels and how were they connected? Distance from Panels to db? Will calculate if the wires are to thin, but to thin wires will show signs of overheating over almost the complete length of the cable as the complete cable heats up pretty evenly. That will be visible in the form of "bubbles" on the surface of the insulation. Just a suggestion. It seems like your AC and DC is in one DB. If its like that, Please rather Split them into different DB's. You dont want a sparky accidentally sending 220Vac back to your panels.
June 28, 20197 yr Author 2 minutes ago, Jaco de Jongh said: How many panels, size of panels and how were they connected? Distance from Panels to db? Will calculate if the wires are to thin, but to thin wires will show signs of overheating over almost the complete length of the cable as the complete cable heats up pretty evenly. That will be visible in the form of "bubbles" on the surface of the insulation. 4X 300W panels with a 8-10m run of cable. Controller has never shown more than 21 amps as its max.
June 28, 20197 yr 2 minutes ago, Sethm said: 4X 300W panels with a 8-10m run of cable. Controller has never shown more than 21 amps as its max. All in parallel, or series parallel combination? Looked at the picture again, even the discoloration of the copper part in the picture points to overheating and again to a lose connection .
June 28, 20197 yr Author 1 minute ago, Jaco de Jongh said: All in parallel, or series parallel combination? Looked at the picture again, even the discoloration of the copper part in the picture points to overheating and again to a lose connection . All in parallel (24V Axpert inverter wont allow my voltage to go anything in series)
June 28, 20197 yr 1 hour ago, Sethm said: 4X 300W panels with a 8-10m run Specs should be close to 36V (Vmpp) and 8.3A (Impp), with 4 in parallel its 33.2Amps at 36 volt (Worst case scenario) Using 4 mm wire over 10 meter will result in a volt drop of 3.79V (10.53%). In solar we aim for less than 3% and SANS regulation allows for 5% so 4mm wire would be to thin. Using 6 mm wire over 10 meter will result in a volt drop of 2.53V (7.02%) still to thin. Using 10 mm wire over 10 meter will result in a volt drop of 1.46V (4.06%) that is within SANS speck but not within general solar recommendation. Using 16mm wire over 10 meter will result in a volt drop of 0.927V (2.57%). This will be the best to use, but you can legally get away with 10mm. I think adding the 4th panel added just enough current to make the weak point show itself. DO you have a combiner box?
June 28, 20197 yr 1 hour ago, Sethm said: Anyone know if those fuse holders are DC rated? Cant find much online. But will be replacing both with 100% DC rated fuses next week. Those are not DC rated fuse holders and only rated for 32 amps, that is way to close to the max available current. You should also replace the fuse-holders with proper 1000volt DC rated fuse holders. You could get the Onesto DC fuse holders . I use them on most of my installations.
June 28, 20197 yr Author 8 minutes ago, Jaco de Jongh said: Those are not DC rated fuse holders and only rated for 32 amps, that is way to close to the max available current. You should also replace the fuse-holders with proper 1000volt DC rated fuse holders. You could get the Onesto DC fuse holders . I use them on most of my installations. If my controller is only set to 30 amps would the 32amp not be sufficient? These fuses above only go to 25amps, so would that not blow if i add an additional panel? Or should i just look at going to 48v system a bit earlier than planned?
June 28, 20197 yr 3 hours ago, Sethm said: These fuses above only go to 25amps, so would that not blow if i add an additional panel? The correct way in your case is to install a combiner box with a 2 x 10 amp fuse per string (1 on + and 1 on -) , A good addition will be a surge arrestor. Then on the combined wire close to your Inverter you can install one of these. (63Amp) 3 hours ago, Sethm said: Or should i just look at going to 48v system a bit earlier than planned? That is maybe not a bad idea at all. How many panels can you still add on your existing inverter, witch by the sound of it has got a PWM charge controller. With the bigger inverters, you can use higher voltage strings, bigger arrays, up to 30% production gain with MPPT, thinner wires, less fuses / inline protection components and less battery current and and and... And then most of all, if finances allows, you have the opportunity to go Blue..... (Victron!!)
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