Over panelling Victron 150/100

[SoakedUp]

I currently have a 3s2p with 6 320 panels fed into a Victron 150/100 on a 12v system.

Panel VOC is 40.1v
Panel ISC is 10.36a

My array is currently at 120.3v and 20.72a. I’m using 10awg cable to feed into the SCC. The panels are flat mounted on top of a shipping container. As of right now, being close to the winter solstice, I’m only able to pull in about 1000w. I’d like to be able to max out the full 100a output of the SCC (1450w).

So I’m thinking about adding another 3 panels to make a 3s3p array. I will have to then fuse my panels which I’m fine with, but I will be over 30a Isc which means I would need to switch to 8awg feed into the SCC which is a bit more of a pain. I’ve only ever seen the SCC pull about 13a from the array and that was at about 1300w. So if the SCC pulls its max 1450w will I ever get close to 30a? Can I fuse the panels with 30a inline fuses and keep the 10awg PV cable? I can’t see ever pulling more than 20-25a out of the array.

 

[FilterGuy]

If you want to remain within the NEC code. No, you can't. However, the math may be different than you think.

The proper size of the wire from the combiner box to the SCC should be sized for 1.55 X Isc. For 3 strings that is 10.36 x 3 x 1.55 = 48.2A.

Fusing & Wire Sizing guidelines for solar panels

To get the paper, click on the orange'' button at the top of the screen. This resource is intended to help the user understand when they need to add Over Current Protection Devices (OCPDs - Fuses or Breakers) to the solar panel array and what...

diysolarforum.com

But I suspect that is not the answer you were hoping for. Could you get away with the 10AWG and 3 strings? Probably. You would definitely want to fuse the strings. If you are using solar cable wire on the run to the SCC, it is usually a 90C rated wire so it is not a problem till you get to 40A (following the NEC ampacity chart). On the other hand, if the wire is running in the sun along the metal roof, there is derating that needs to be considered. I guess you could put a 35A fuse on the 90C rated wire and see if it holds. If it does, you are ok. If it ever blows.... you should probably bite the bullet and run a new pair of wires.

 

[SoakedUp]

If you want to remain within the NEC code. No, you can't. However, the math may be different than you think.

The proper size of the wire from the combiner box to the SCC should be sized for 1.55 X Isc. For 3 strings that is 10.36 x 3 x 1.55 = 48.2A.

Fusing & Wire Sizing guidelines for solar panels

To get the paper, click on the orange'' button at the top of the screen. This resource is intended to help the user understand when they need to add Over Current Protection Devices (OCPDs - Fuses or Breakers) to the solar panel array and what...

diysolarforum.com

But I suspect that is not the answer you were hoping for. Could you get away with the 10AWG and 3 strings? Probably. You would definitely want to fuse the strings. If you are using solar cable wire on the run to the SCC, it is usually a 90C rated wire so it is not a problem till you get to 40A (following the NEC ampacity chart). On the other hand, if the wire is running in the sun along the metal roof, there is derating that needs to be considered. I guess you could put a 35A fuse on the 90C rated wire and see if it holds. If it does, you are ok. If it ever blows.... you should probably bite the bullet and run a new pair of wires.

Thanks for the reply. It is PV 90C rated wire and the wire is tucked under the panels, 100% shaded and off the metal container. I’m off grid so no inspections but I would like to be safe. My other option was to pick up a 250/100 SCC with their new discounted price and 4 more panels and do two strings of 5 panels instead.

 

[rodrick]

Thanks for the reply. It is PV 90C rated wire and the wire is tucked under the panels, 100% shaded and off the metal container. I’m off grid so no inspections but I would like to be safe. My other option was to pick up a 250/100 SCC with their new discounted price and 4 more panels and do two strings of 5 panels instead.

If you are off grid you might just get another 150/100 and build a 2nd system like the first for some redundancy that way you will never be totally down if something happens

 

[Jack Rabbit Off Grid]

If you are off grid you might just get another 150/100 and build a 2nd system like the first for some redundancy that way you will never be totally down if something happens

I am currently doing exactly this. I purchased all of the exact parts as my original purchase. Panels, charge controller and inverter. I’m in the planning stage now of where and how I plan to mount the spare panel array. Of course the second charge controller will be mounted by its older brother and the spare inverter will be left in its box.