What are the specs for a breaker needed between the solar panels and inverter?

[Buttercup]

Hi,

I have a 24v off-grid system, with three panels in parallel (each panel is 450 watts). I've just replaced two 12v 150AH gel batteries in series, with one 24v LifePO4 100ah battery.

The inverter is a 3KW 24v MPPT 50A/100V VPM hybrid from WCC Solar in Spain: Hybrid inverter 3KW 24v MPPT 50A/100V VPM

Which breaker is needed between the solar panels and inverter?

The breaker that's being used (here's a photo of the specs:
https://www.dropbox.com/t/Fr9mNyTYVutNeOlw ) is heating up...

Each solar panel's VOC is: 41.25V, Short circuit current: 13.62A, max series fuse rating 20A.

Thanks

[sdold]

Hi Buttercup and welcome to the forum, hopefully you can get some assistance. Here's the breaker in case others don't want to deal with Dropbox:

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[littleharbor2]

That breaker is not rated for DC voltage very likely your problem. You need DC rated breakers to be safe

[Buttercup]

Thank you both for your help, it's appreciated.

[Shafferdr]

littleharbor2 has the main point. A breaker marked only with an AC rating is not rated to interrupt DC. A DC arc has no zero crossing to put it out, so on DC an AC breaker can run hot and fail to clear a fault.
The 2023 NEC states the same principle in 110.9. Equipment that interrupts current "shall have an interrupting rating at nominal circuit voltage at least equal to the current that must be interrupted." For your array, the nominal circuit is DC at up to about 41 V open circuit. More in cold weather, since Voc rises as the temperature drops. So you need a breaker with a DC voltage rating on its label, and that rating should be well above that figure.
A second issue comes from wiring three panels in parallel. Each panel lists a 20 A maximum series fuse rating. If one panel or its wiring faults, the other two can feed current backward into it: 2 × 13.62 A is about 27 A, which is more than that panel's 20 A limit. That's why parallel strings normally get a fuse or DC breaker per panel, sized at or below the 20 A rating. A single breaker after the combiner doesn't do it.
The total current is also close to your breaker. Three panels at 13.62 A short-circuit current is about 41 A. Check that the breaker's DC ampere rating suits that, and check the inverter manual's maximum PV input current. The 50 A in its name is usually the charge current to the battery, not the PV input.
Finally, check that the terminal screws are torqued. A loose connection carrying 30 to 40 A of DC will also heat a breaker.

[sdold]

Shafferdr: I like your videos, just finished the one about neutral and ground bars on subpanels and keeping the grounding conductor from "moonlighting as a current-carrying conductor" Welcome to the forum.