Last week I ordered a 3 DVD (4 hour) program on off-grid PV installation and maintenance (I will be doing a review and recommendation soon) and one thing it reminded me of (although I already knew, but was sucessfully ignoring) is the need for disconnects and fuses between my PV array, charge controller, battery bank and inverter(s). What these do is not only allow me to isolate certain parts of the system, but it also provides a barrier of protection in the form of fuses that will blow in case of a large burst of current going through the system, stopping it before it gets anywhere else. So this morning, in 21 degree weather (wanted to do this while the panels were getting no power) I installed the first of my safety upgrades: a disconnect between the PV array and and charge controller.
Since I was mounting the disconnect to a 3.5″ surface I had two holes at the bottom of the box that are typically used for screws when mounting to the side of a house. Using those holes I ran the positive from one panel and the negative from the other (the other + and – I tied together to run the panels in series and double the voltage to my battery bank) through the holes like this
I think it looks great this way, though there is nothing to protect the wire insulation from rubbing against the metal so I will need to rig something up to give it more protection. Inside the box I customized it, taking out the ground bar since I am dealing with DC electricity and that gave me more room to run the thick panel wires to my line lugs. This line runs through two 35 amp fuses to get to the load lugs. I ran a piece of Romex through a piece of Carflex (that I had recycled from a job a while back) and after tying the Romex into the load lugs I ran it with two water tight connection to my battery box. Here is the inside of the disconnect
and here is how it connects to the battery box through the Carflex
and this is how it looks when it’s all closed up
OK, that’s that. Until next time…