tdc4266 Posted September 19, 2012 Share Posted September 19, 2012 Hello again It has been a while but we have just received our sp kit . All seems ok and fairly straight forward. However (there is always one).There was no fuse or holder included in the kit. The instructions say a fuse is needed between control box and battery. The fuse needs to be Be 1.5 to 2 times the rated amp of the control box. The box is rated at 20amps. I guess that means A 60amp fuse. This seems a a big fuse. I am looking for clarification that I am not missing some thing. About northern Germany we have not been here long and busy with the house.Will Get back to you. Thanks Eg. Tried to send this earlier dont think it worked. Link to comment Share on other sites More sharing options...
Keithl Posted September 19, 2012 Share Posted September 19, 2012 Tim, 1.5 times 20 is 30 Amps or 2 times is 40 Amps, NOT 60 Amps. Keith. Link to comment Share on other sites More sharing options...
Brambles Posted September 20, 2012 Share Posted September 20, 2012 I would use a 10 or 15 amp fuse. Panel is rated at 5.5 Amps so 10 amp fuse would offer max protection. Link to comment Share on other sites More sharing options...
lennyhb Posted September 20, 2012 Share Posted September 20, 2012 I agree with Jon if it's an 80W panel 10Amp will be more than adequate. The fuse must be of a lower rating than the cable it is supplying to prevent risk of fire under fault conditions. Link to comment Share on other sites More sharing options...
tdc4266 Posted September 20, 2012 Author Share Posted September 20, 2012 Thanks for the info must have had a brain blockage with the mathmatics! The panel is a 100W. The The controller is rated at 20A. The instructions say....... WE STRONGLY RECOMMEND CONNECTING A FUSE IN SERIES WITH THE BATTERY TO AVOID SHORT CIRCUIT. THE FUSE RATING SHOULD BE 1.5 TO 2 TIMES CONTROLLER RATED CURRENT. This would seem to indicate a 40A fuse (thanks Keith). Again am I missing something. Thanks tdc4266 Link to comment Share on other sites More sharing options...
Robinhood Posted September 20, 2012 Share Posted September 20, 2012 tdc4266 - 2012-09-20 11:35 AM Thanks for the info must have had a brain blockage with the mathmatics! The panel is a 100W. The The controller is rated at 20A. The instructions say....... WE STRONGLY RECOMMEND CONNECTING A FUSE IN SERIES WITH THE BATTERY TO AVOID SHORT CIRCUIT. THE FUSE RATING SHOULD BE 1.5 TO 2 TIMES CONTROLLER RATED CURRENT. This would seem to indicate a 40A fuse (thanks Keith). Again am I missing something. Thanks tdc4266 The controller may be rated at 20A, but this is the maximum it can cope with. The 100W solar panel you are connecting is likely to max out at something over 6A, and the controller can't generate additional amps itself. So, if that is the only panel you are connecting, then the suggested 10A fuse should be quite adequate (15A at maximum). If you were to connect more solar panels, to drive up the potential output from the controller, then upping the provision to, say, 30A would be appropriate (but that would require something in the region of two additional panels of the same, 100W, spec). Link to comment Share on other sites More sharing options...
Brambles Posted September 20, 2012 Share Posted September 20, 2012 Don't forget the current handling of the cable used..if it is 4mm cross section then its max current at 50 degrees C is around 30 Amps, so allowing for the fact a fuse may not blow until 1.5 times its rating then max fuse size is 20 Amps for the cable you have been supplied. You could get away with saying 42 amps at 30 degreesC and then 28amps would be max fuse size so you could pushe it to 30amp fuse, but 40 amp fuse with 4mm cable...No way. Fit a 10 Amp fuse and if you ever fit an extra panel change it to 15 amp fuse or 20 amp fuse maximum. Yes you are missing something... whoever wrote the instructions is looking only at the controller and not the cable used or the actual current it will be used for. If you want to fit a 30 amp fuse, then you would have to uprate your cable to the controller to 1.5 x 30 amps which would mean using 6mm cross section cable. I would then suggest a second fuse of 10 Amps between the controller and the panel, which is not a bad idea to do anyway. Jon. Link to comment Share on other sites More sharing options...
tdc4266 Posted September 20, 2012 Author Share Posted September 20, 2012 Thanks for the quick replies. I now understand what is being said and will fit a 10A fuse. Thanks again. Link to comment Share on other sites More sharing options...
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