Jacques1s Posted August 19, 2020 Posted August 19, 2020 Hi – I have a Kodak 5kw ( Axpert ) inverter. I have 2 strings of 5 JA Solar 390w Panels. Each sting has a 6mm cable to 32amp fuse. All is working just great. I now would like to add a second Inverter in parallel and add another identical PV. The PV is on a very high roof and getting the 2 cable stings up in Runking is a huge mission. I am now thinking of combining the existing 2 strings and parallel them on the roof so I can use the other cable for the new PV. I think the cable 6mm is good at 24M. The question I have is, do I need to put inline fuses on the roof or can I just combine 2 stings ( Parallel ) and will the 32A fuse be adequate? Panel is IMPP 9,7A VOC 49,35. Quote
0 Jaco P Bloem Posted August 19, 2020 Posted August 19, 2020 Hi Jaques A single 6mm sq cable (pair) is sufficient for the 2 strings in parallel as the source is 2 x 9.7A, so less than 20Amp. Even a 4mm is enough but yes the losses are less in the larger diameter and the given distance. In my installation I've connected the parallel strings on the roof without fuses using a connector box (self made, but I see you do get the MC4 type PV parallel connectors). It then passes through a single fuse and 30Amp Isolator switch before it goes into the Inverter. The 32amp fuse is sufficient, as stated the current will be below 20amp and less. (I do run 2 Inverters in parallel, with 2 different PV sets) I had both fuses and isolators, so I installed them but in my mind, the fuse will never blow : if you spec the fuse correctly for the load (the current draw into the inverter) in this case 20amp, then the current in the PV cable will/can not exceed that, as the source (PV) cannot give more. The 9.7A in the spec sheet is the short circuit (fault) current and the two strings in parallel gives 19.4amp. So effectively you cannot short-circuit the cable at any point before or after the fuse to blow it, as the max current is lower than the fuse rating. The only possibility for the fuse to blow is if the fuse is a poor design or rated lower than source (PV) capability and perhaps lightning - but if a lightning surge blow a fuse, chances are there is damage all over. You may consider Surge Protection on the 2 PV inputs on the Inverters - this is more sensible to me. (surge arresters of higher than 246.75V in your case) But what you have in mind will work, you have enough cable capacity for 2 PV sets already Kind Regards Jaco P Quote
0 Jacques1s Posted August 20, 2020 Author Posted August 20, 2020 Thanks Jaco. will install next week. Happy days - glad I don't need to run more cable to the riif. Quote
Question
Jacques1s
Hi – I have a Kodak 5kw ( Axpert ) inverter. I have 2 strings of 5 JA Solar 390w Panels.
Each sting has a 6mm cable to 32amp fuse. All is working just great. I now would like to add a second
Inverter in parallel and add another identical PV. The PV is on a very high roof and getting the 2 cable stings up in
Runking is a huge mission. I am now thinking of combining the existing 2 strings and parallel them on the roof so I can
use the other cable for the new PV. I think the cable 6mm is good at 24M. The question I have is, do I need to put inline fuses
on the roof or can I just combine 2 stings ( Parallel ) and will the 32A fuse be adequate?
Panel is IMPP 9,7A VOC 49,35.
2 answers to this question
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.