circuit breaker size !

[Pyana1]

panel isc is 8.64 do i simply multiply that by 125% ?
in addition, the panel reads "Maximum Series Fuse Rating" at: 10A .
is that what i should aim for? i was thinking about a 15A circuit breaker !

[Mike90250]

use the same size as the suggested fuse, a 10A breaker. Be sure it is rated for DC and you wire the line & load sides properly

[inetdog]

use the same size as the suggested fuse, a 10A breaker. Be sure it is rated for DC and you wire the line & load sides properly

If the project will be inspected, an inspector would be justified under the NEC to reject the installation because you used a breaker where the panel instructions called for a fuse.
The same issue comes up with motorized appliances where the manufacturer may specify a maximum OCPD (OverCurrent Protection Device) or may specify maximum fuse size.

You could very well find that your inspector does not care, but may want to confirm the DC rating of the breaker.

[Amy@altE]

The Max series fuse is a rating on the label, not the instruction. I have designed thousands of systems that have been inspected, they have never ever had a problem using a breaker instead of a fuse.

The OCPD coming from the solar panel must be multiplied by 1.25 twice, once for over irradience and once for 3 hour continuous use, so 1.56. So that circuit with 8.64 Isc should require 15A. I'm very curious why it is labeled for 10A. That's not even big enough for a single 1.25. Is it a cheap panel or a quality brand name?

[Pyana1]

The Max series fuse is a rating on the label, not the instruction. I have designed thousands of systems that have been inspected, they have never ever had a problem using a breaker instead of a fuse.

The OCPD coming from the solar panel must be multiplied by 1.25 twice, once for over irradience and once for 3 hour continuous use, so 1.56. So that circuit with 8.64 Isc should require 15A. I'm very curious why it is labeled for 10A. That's not even big enough for a single 1.25. Is it a cheap panel or a quality brand name?

they're Sonali solar poly; not really a big name here in the states but pretty descent in the Middle East ; i gotta 'em here in Miami Florida at Sunelec, about 20 minutes from where i am at.

Amy, do you strongly suggest that I spit all 4 panels each receiving its own 15A circuit breaker or can I leave them already tied in parallel 34 ISC *1.25 *1.25 = 60 amp breaker ; and simply use a 60 amp beaker i just need a quick disconnect.

[inetdog]

they're Sonali solar poly; not really a big name here in the states but pretty descent in the Middle East ; i gotta 'em here in Miami Florida at Sunelec, about 20 minutes from where i am at.

Amy, do you strongly suggest that I spit all 4 panels each receiving its own 15A circuit breaker or can I leave them already tied in parallel 34 ISC *1.25 *1.25 = 60 amp breaker ; and simply use a 60 amp beaker i just need a quick disconnect.

Any time you have three or more panels or strings of panels in parallel each one needs its own fuse or breaker. And that overcurrent protection must be no larger than 10A.

the panel reads "Maximum Series Fuse Rating" at: 10A .

That is in the National Electrical Code, not just good advice.

Also, however, the fuse needs to be at least 8.64 x 1.25 (~13). And the wire needs to be rated for 13.3 x 1.25, 16.74A as well under recent NEC versions.
You are between a rock and a hard place because the maximum series fuse spec on the label is smaller than the NEC mandated OCPD.

For four strings the total amperage is 67A, so you need larger wire than that as well as a larger breaker. And unless you are on the 2014 NEC you have to consider the sum of your individual breakers (basically 20A each) when calculating the 120% rule where the backfeed enters your wiring system.

[SunEagle]

The Max series fuse is a rating on the label, not the instruction. I have designed thousands of systems that have been inspected, they have never ever had a problem using a breaker instead of a fuse.

The OCPD coming from the solar panel must be multiplied by 1.25 twice, once for over irradience and once for 3 hour continuous use, so 1.56. So that circuit with 8.64 Isc should require 15A. I'm very curious why it is labeled for 10A. That's not even big enough for a single 1.25. Is it a cheap panel or a quality brand name?

Amy

I believe that second 1.25 multiplier is to determine the Conductor Ampacity (NEC article 690.8(B) not the fuse. So the fuse would be 1.25 x the Isc rating and the wire capacity would be 1.25 x (1.25 x Isc).

So technically 1.25 x 8.64a = 10.8amp fuse. Maybe the manufacturere felt the 10 amp fuse met that value since there are no 10.8amp or even 11amp fuses.