Using 7.5kw of panels on a metal roof with this inverter

The project will have 24 panels, 315w Warree mono.  They will be mounted on a metal R-panel roof. 
The inverter is an: SMA SB7.0-1SP-US-41, a transformerless design.

Is this a good match? 
How do the panels have to be mounted to be ungrounded as required?

Thank you for your help.




Bill

Comments

  • mike95490mike95490 Solar Expert Posts: 8,961 ✭✭✭✭✭
    I think in any case, the panel frames have to be grounded.   The - or+  cables may not have a grounding requirement.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • BB.BB. Super Moderators, Administrators Posts: 30,939 admin
    As Mike says (and as I understand)...
     
    The "ungrounded part" is referencing the + and - power cables from the array... You just wire up in series/parallel (as required) and run the wires directly to the GT inverter's input.

    The panel frames and racking need to be grounded as normal (following code with something like a continuous run of 6 AWG cable from each frame, and ground the mounting frame work (per code, per installation manual for panels and frame). Down (typically) to a ground rod at the base of the frame/outside of wall (if roof mounted)--The ground rod beneath the array is usually a very good idea for lightning prone areas (you don't want to bring lightning into your home/home grounding system). Otherwise ground to your your home ground rod/cold water pipe (if you have two or more ground rods, run ground to nearest ground rod, and tie each "remote" ground rod with 6 AWG back to the main home ground rod/cold water pipe connection--This is to provide a safety ground for AC utility power, and your DC solar panel power--If shorts to ground ever occur).

    Surge suppressors can be a big help for Lightning prone areas too (see GT inverter manual for their recommendations/requirements).

    A "metal" siding building--The metal siding is not allowed (or a very good) as a safety ground (very thin, lightning and shorts to power sources can easily blow holes in the "tin". And metal siding to siding connections are not "electrical" electrical connections.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
Sign In or Register to comment.