Solar --Wire and Battery Fuse Size Confusion- How Big?
Can somebody please explain the math on this? I get really confused.
Previously, I have seen how you have to allow 1.25 oversizing for the wires from the panel, the controller, and the wires from controller to battery, but then the battery fuse size was to be even more oversized, so that fuse itself would be operating at no more than 80% of its rating. (When the 1.25 oversized stuff was running "filled up" to the 1.25 amount)
But then some blurbs on this warned against "counting the 1.25 twice", which made no sense concerning the battery fuse or CB (at least to me :( )
Now , reading the manual for my new Canadian Solar panel, it says,
" A module's Voc and Isc at STC should be multiplied by 1.25 when determining component voltage ratings, conductor ampacities, overcurrent device ratings, and the size of controls connected to the PV output." AND THEN, it says, "An additional 1.25 multiplier for a short-circuit current (for a total of 1.56), for sizing conductors and fuses MAY be applicable, as described in section 690-8 of US NEC."
(stresses mine)
So I need more coffee maybe, but where did that 1.56 come from doing two 1.25s ? And what is the difference between an "overcurrent device" as in the first list, and a "fuse" in the second part?
And-- does the second part's "conductors" for the 1.56 mean the same wires as in the first part's 1.25 "conductor ampacities"?
So if you did want to follow the US NEC (whether or not it applies to you--being not in the USA or because you are doing an RV not a house perhaps) what exactly do you do picking wire size and battery fuse size wrt panel Voc and Isc?
Does the solar controller size stay at 1.25 since it is not mentioned in the 1.56 part?
Thanks!
Previously, I have seen how you have to allow 1.25 oversizing for the wires from the panel, the controller, and the wires from controller to battery, but then the battery fuse size was to be even more oversized, so that fuse itself would be operating at no more than 80% of its rating. (When the 1.25 oversized stuff was running "filled up" to the 1.25 amount)
But then some blurbs on this warned against "counting the 1.25 twice", which made no sense concerning the battery fuse or CB (at least to me :( )
Now , reading the manual for my new Canadian Solar panel, it says,
" A module's Voc and Isc at STC should be multiplied by 1.25 when determining component voltage ratings, conductor ampacities, overcurrent device ratings, and the size of controls connected to the PV output." AND THEN, it says, "An additional 1.25 multiplier for a short-circuit current (for a total of 1.56), for sizing conductors and fuses MAY be applicable, as described in section 690-8 of US NEC."
(stresses mine)
So I need more coffee maybe, but where did that 1.56 come from doing two 1.25s ? And what is the difference between an "overcurrent device" as in the first list, and a "fuse" in the second part?
And-- does the second part's "conductors" for the 1.56 mean the same wires as in the first part's 1.25 "conductor ampacities"?
So if you did want to follow the US NEC (whether or not it applies to you--being not in the USA or because you are doing an RV not a house perhaps) what exactly do you do picking wire size and battery fuse size wrt panel Voc and Isc?
Does the solar controller size stay at 1.25 since it is not mentioned in the 1.56 part?
Thanks!
