Is a junction box required when connecting distant groups of panels wired in series?

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st4rgut
st4rgut Registered Users Posts: 36 ✭✭
edited November 2022 in PV Installers Forum - NEC, Wiring, Installation #1
Is it OK to skip the junction box when connecting groups of panels that are wired in series? For example I want to wire three groups of panels in String 1 below. Could I thread the wires through conduit to reach groups of panels on different roof faces and mount the conduit to the railing without a junction box?


I found an example of what I want to do on YouTube   (18:50). The conduit bridges the gap between the two groups of panels, and the conduit is affixed to the railing. I'd like to do this as well, but not sure if it's code compliant.
 
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  • littleharbor2
    littleharbor2 Solar Expert Posts: 2,044 ✭✭✭✭✭
    edited November 2022 #2
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    I see two problems here

    1, You have 13 panels in 3 different orientations in string one. You will get the lowest panels current output dictating all panels current down to the same level. Very poor design.

    2, String #2 has 10 panels. The voltage output from those 10 panels vs. the voltage from string #1 will be lower. When you combine the two strings the voltage of string 1 will be pulled down toward the lower voltage from string 2.

    As to your question, Yes you can skip the combiner box with only two strings due to the fact that you don't need to fuse each string in this case. All you need is a set of parallel connectors to combine the two strings 


    2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old  but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric,  460 Ah. 24 volt LiFePo4 battery bank. Plenty of Baja Sea of Cortez sunshine.

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  • st4rgut
    st4rgut Registered Users Posts: 36 ✭✭
    #3
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    Thank you. Actually I am using a solaredge optimizer for each panel so I'm allowed to mix different orientations in the same string.
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  • littleharbor2
    littleharbor2 Solar Expert Posts: 2,044 ✭✭✭✭✭
    edited December 2022 #4
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    That makes a big difference. Details matter when asking questions. So you have a Solar Edge inverter and are grid tied, correct? Does your inverter have multiple MPPT inputs?

    A junction box is for combining multiple strings in parallel. Looks like you are just trying to series connect panels in multiple locations with space in between. Extension cables, in conduit where needed should work.

    2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old  but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric,  460 Ah. 24 volt LiFePo4 battery bank. Plenty of Baja Sea of Cortez sunshine.

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  • Dave Angelini
    Dave Angelini Solar Expert Posts: 6,746 ✭✭✭✭✭✭
    #5
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    You really should ask the building department where you live. This should be inspected if you have Home Insurance.  

    Especially if on a roof !

    If this caused a fire, the Insurance company could deny the claim.
    "we go where power lines don't" Sierra Nevada mountain area
       htps://offgridsolar1.com/
    E-mail offgridsolar@sti.net

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  • st4rgut
    st4rgut Registered Users Posts: 36 ✭✭
    #6
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    yes, I am connecting two strings to a Solar Edge inverter that is grid tied. Thank you for the explanations.
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