Connecting PV Modules to Inverter

I am new to the postings and am looking for information on wiring my solar panels to the inverter. I am installing 18 175 watt panels in three portrait arrays. These are on a west facing roof tilted 30 degrees toward south. I will be making two strings of nine panels and running these to a Xantrex inverter. The panels have MC connectors, but I will need to run an extension cable from one array to the next about seven feet away. What should I use for this stretch? I will then need to do the same thing from my middle array to my last array. Both strings will then need to run about forty feet to the inverter. What type of wire should I use to go from arrays to inverter? I also should connect grounding wire from each array to the ground copper post. Which wire should be used for this?

Comments

  • crewzer
    crewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    Re: Connecting PV Modules to Inverter

    Jonathan,

    I split your post off as a topic of its own. This will hopefully make it easier for the members to focus on your specific request.

    Regards,
    Jim / crewzer
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Connecting PV Modules to Inverter

    i thought you did that jim as one minute while i was posting it was there and next it was gone.

    jonathon,
    i am confused as to how you have your pvs. are they facing west with and upward tilt or what. describe this better so we are sure of the arrangement there. i am very surprized though that you would buy without knowing how everything was going to be done. i can't recommend cutting the mc connections as i've heard this void many pv warrantees so you will have to get extensions with mc connections on them. once you are ready to make a run for going to the controller this can be done from a combiner box. you will run each string into this box and no mc connections will be in this box. if the location is accessable it's possible to fuse each string as well and have a disconnecting switch there otherwise you may need to adapt each string with its own seperate run to a more convenient spot to have the fuses and disconnect.
    as to the wire you use that depends on the pv system voltage you are using with those pvs. higher pv system voltages can present lower losses and thusly allow smaller wires to be used in the system. i can't seem to find the thread on the subject for you to make your own calculations as we have a calculator available for use with an excel program or any clone of excel, but if you give me the details of each strings voltage and current and the wire run distance involved to the combiner and then the distance from the combiner to the controller(not the inverter as it has to be regulated) i could give you a rough idea of the wire gages you'll need.
    for ground wires go wire #6 or thicker. you could daisy chain each string of pvs and have seperate runs to the same 8ft ground rod. if seperate rods are used they must be tied together underground with the same or better thickness of wire used in the ground wires from the pvs, but it must be solid wire underground. try to go as straight from the pvs to ground as you can without sharp bends.
  • RCinFLA
    RCinFLA Solar Expert Posts: 1,484 ✭✭✭✭
    Re: Connecting PV Modules to Inverter

    What type of Xantrex inverter do you have?
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Connecting PV Modules to Inverter

    yes i can appreciate you trying to save some $. i still am confused though as to how you got pvs to face south when mounted on a west facing roof? i do hope they are aimed properly for your location and i'll assume that they are.
    i also hope you understand about the mc connections. if you can get more wires with the connections on both ends, you can cut the wire in 2 so that you can plug into the pvs and then wire the other end as you need to for your interconnections or what have you. it is expensive doing it that way because for every wire you buy it will connect to 2 pvs. that's 9 wires to be bought that will be cut into 2 leaving an mc connector on 1 end and the bare wire on the other.
  • halfcrazy
    halfcrazy Solar Expert Posts: 720 ✭✭✭
    Re: Connecting PV Modules to Inverter

    if this is a xnatrex gt inverter it has the combiner in side the inverter so if it is and i am following this right you have 3 arrays and you need to pick up half of the middle array for each of the 2 strings. so you would need to buy a 6 mc connector extensions 2 to get each outer array to the middle and then one to cut in half to tie each of the 2 strings into the wire in conduit going to the inverter. so bascally you will connect each outer array in series so you will end up with a + and a - mc connector that you will add extensions to to get to the middle array where you will connect half of it in series also and connect the - of this array to the + of the outer array leaving you with a + and a - mc connector this is where you would take the 3rd extension cable and cut it in half and use it to tie this string to the inverter. then repeat on the second string.