What size screw for fronius ig plus v 3.0

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quique
quique Solar Expert Posts: 259 ✭✭
in Solar Beginners Corner #1
I'm installing my inverter bracket on a wall following the manual. It reads that I should use 1/4" or 5/16" screws that hold 31lbs.

The thing is it doesn't specify the length. How should I determine that?
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
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    Re: What size screw for fronius ig plus v 3.0
    quique wrote: »
    I'm installing my inverter bracket on a wall following the manual. It reads that I should use 1/4" or 5/16" screws that hold 31lbs.

    The thing is it doesn't specify the length. How should I determine that?

    What are you screwing/bolting it to?
    Rule-of-thumb for screws is 3X as long as that is being supported. But of course there has to be enough material to take the thread length.
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  • quique
    quique Solar Expert Posts: 259 ✭✭
    #3
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    Re: What size screw for fronius ig plus v 3.0

    Solid concrete wall.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
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    Re: What size screw for fronius ig plus v 3.0
    quique wrote: »
    Solid concrete wall.

    Oh what fun!
    In that case you will need to drill holes in it and epoxy in anchor sleeves to take the bolts. Or use Dynabolt anchors like these: http://www.homedepot.ca/webapp/wcs/stores/servlet/SearchView?catalogId=10051&storeId=10051&langId=-15&N=0&Ntt=concrete+anchor+sleeve&Nty=1&D=concrete+anchor+sleeve&Ntx=mode+matchallpartial&Dx=mode+matchallpartial&s=true

    That's one of the things about fastener types; what you put it in to makes as much difference as what it is holding up.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,447 admin
    #5
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    Re: What size screw for fronius ig plus v 3.0

    Note that you probably do not want to rely on epoxy bolts in constant tension (load pulling bolts out of hole). As long as the load is in "shear" (load pulling sideways to hole), you should be OK.

    Big Dig     ceiling collapse - Wikipedia
    The collapse of the ceiling structure began with the simultaneous creep-type failure of several anchors embedded in epoxy in the tunnel's roof slab. Each of the panel's intersecting connection points consist of several individual bolts anchored into the roof slab concrete. The failure of a group of anchors set off a chain reaction which caused other adjacent connection groups to creep then fail, sending 12 tons of concrete to the roadway below.
    Numerous problems with this same system of bolts and epoxy in the Ted Williams Tunnel had been previously revealed in a 1998 (Massachusetts) Office of the Inspector General report. Not only were the bolts too short, but the epoxy used to glue the bolts into the concrete was not up to standard.[1] The state Turnpike Authority and the Federal Highway Administration, citing the ongoing criminal investigation, refused requests received after the accident to release documents relating to the work conducted along the Seaport connector, including:[

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
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    Re: What size screw for fronius ig plus v 3.0

    Yup. In fact any such fastening (including screw into wood) has much more 'holding power' against perpendicular loads that linear ones. In other words in a wall it will hold against force pulling down much better than against force pulling out.

    Hopefully no one will be trying to pull your inverter off the wall and you'll have to worry about keeping it from dropping to the floor (darn gravity). :p
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  • peakbagger
    peakbagger Solar Expert Posts: 341 ✭✭✭
    #7
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    Re: What size screw for fronius ig plus v 3.0

    I attached the same size unit to a concrete wall with some spacers between the wall and the baseplate. I drill a couple of inches in the wall with a hammer drill and then mix up some epoxy with some thickener and put it on a piece of threaded rod and slide it in the hole. Once the epoxy sets, I set the inverter on the studs and put nylon insert locking nuts on the studs and just barely snug them up against the baseplate. Using nylock nuts keeps the nuts from loosening and there is far less tensile load applied than with conventional nuts. Fronius cant recommend a specific fastener as they don't know the conditions or makeup of the wall, if it rotten concrete or damaged drywall it will require a lot more anchoring than if its mounted a concrete wall or piece of plywood.
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  • jcheil
    jcheil Solar Expert Posts: 722 ✭✭✭
    #8
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    Re: What size screw for fronius ig plus v 3.0

    Tapcons have never failed me and are used extensively here in Florida for hurricaine strap connections from roof trusses to concrete walls. If they can support a minimum 120mph uplift force, I would think they would hold your panel on the wall :)
    Off-Grid in Central Florida since 2005, Full-Time since June 2014 | 12 X Sovello 205w panels, 9 X ToPoint 220w panels, 36x ToPoint 225w panels (12,525 watts total) | Custom built single-axis ground mounts | Complete FP2 Outback System: 3 x FM80, 2 x VFX3648, X240 Transformer, FLEXnet-DC, Mate-3, Hub-10, FW500 AC/DC | 24 x Trojan L16RE-B Batteries 1110ah @ 48v | Honda EU7000is Generator and a pile of "other" Generators | Home-Made PVC solar hot water collector | Custom data logging software http://www.somewhatcrookedcamp.com/monitormate.html
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  • peakbagger
    peakbagger Solar Expert Posts: 341 ✭✭✭
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    Re: What size screw for fronius ig plus v 3.0

    Minor rant - I hate tapcons. Once they go in they rarely come out without shearing off at the head. I have had them fail to catch. They are a PITA for something that might need to be removed but most electricians use them and let the next person deal with the aggravation. I ma much happy with threaded studs set in Epoxy but its a bit slower. If the equipment ever needs to be moved they make it easy - End rant
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
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    Re: What size screw for fronius ig plus v 3.0
    peakbagger wrote: »
    Minor rant - I hate tapcons. Once they go in they rarely come out without shearing off at the head. I have had them fail to catch. They are a PITA for something that might need to be removed but most electricians use them and let the next person deal with the aggravation. I ma much happy with threaded studs set in Epoxy but its a bit slower. If the equipment ever needs to be moved they make it easy - End rant

    Fail to catch: yep, seen that.
    Heads sheer off: usually means they've been over-tightened.

    One of the most difficult parts of mounting a big, heavy inverter to concrete is getting the holes lined up. Sometimes it is desirable to mount some PT wood to the concrete and then lag the inverter to that.
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  • jcheil
    jcheil Solar Expert Posts: 722 ✭✭✭
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    Re: What size screw for fronius ig plus v 3.0
    Cariboocoot wrote: »
    Fail to catch: yep, seen that.
    Heads sheer off: usually means they've been over-tightened.

    One of the most difficult parts of mounting a big, heavy inverter to concrete is getting the holes lined up. Sometimes it is desirable to mount some PT wood to the concrete and then lag the inverter to that.

    The most important thing about tapcons, which very few people do, is to be sure to blow out the hole you drilled with a can of air (or other source). The concrete dust in the hole prevents the tapcon from seating completely in the hole leaving too much of the bolt exposed which allows the head to strip off easily. If you clean out the hole completely you will never strip off a head (unless you over do it).

    And I agree the plywood to the wall is the best option and exactly how I did mine.
    Off-Grid in Central Florida since 2005, Full-Time since June 2014 | 12 X Sovello 205w panels, 9 X ToPoint 220w panels, 36x ToPoint 225w panels (12,525 watts total) | Custom built single-axis ground mounts | Complete FP2 Outback System: 3 x FM80, 2 x VFX3648, X240 Transformer, FLEXnet-DC, Mate-3, Hub-10, FW500 AC/DC | 24 x Trojan L16RE-B Batteries 1110ah @ 48v | Honda EU7000is Generator and a pile of "other" Generators | Home-Made PVC solar hot water collector | Custom data logging software http://www.somewhatcrookedcamp.com/monitormate.html
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