Conduit through attic vent

System
System Posts: 2,511 admin
in General Solar Power Topics #1
Does anybody know if there's a NEC problem with running wiring from the roof into the attic using an attic vent instead of using a roof jack? The wiring runs inside liquid tight flex, but I've never seen this done before.
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  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
    #2
    Re: Conduit through attic vent

    From my reading, the NEC does not specify what needs to be used for the penetration, only that all runs within the structure must be EMT
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  • Lefty Wright
    Lefty Wright Solar Expert Posts: 111 ✭✭
    #3
    Re: Conduit through attic vent
    Solar Guppy wrote: »
    only that all runs within the structure must be EMT

    I have read that in other threads on this site. But I have not been able to verify this.

    Up to the 2002 copy (my latest copy) there is no prohibition against running PVC (RNMC), flex (flexable metalic conduit) or liquidtite metallic conduit in a residential structure.

    Has the code changed?

    Anyone know a site that lets you read the latest NEC?
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  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
    #4
    Re: Conduit through attic vent

    NEC2005 was when EMT for solar wiring was allowed inside the structure, before that it was NOT allowed in the structure unless there was a over-current/disconnect before the penetration point.

    The point was NEC doesn't want a power source that can't be turned off running thru the structure unless its in EMT.
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  • Lefty Wright
    Lefty Wright Solar Expert Posts: 111 ✭✭
    #5
    Re: Conduit through attic vent
    Solar Guppy wrote: »
    NEC2005 was when EMT for solar wiring was allowed inside the structure, before that it was NOT allowed in the structure unless there was a over-current/disconnect before the penetration point.

    The point was NEC doesn't want a power source that can't be turned off running thru the structure unless its in EMT.

    Are you getting this from some building code other than the NEC?

    I have before me the 2002 code and there is no prohibition for using EMT in a stucture.

    IV. Wiring Methods
    690.31 Methods permitted.
    (A) Wiring Systems. All raceway and cable wiring methods included in this Code and other wiring systems and fittings specifically intended and identified for use on photovoltaic arrays shall be permitted.

    I think we are getting away from the code and into local lore when we say EMT is REQUIRED (or prohibited) in structures.
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  • halfcrazy
    halfcrazy Solar Expert Posts: 720 ✭✭✭
    #6
    Re: Conduit through attic vent

    um not positive where it is but you are 2 code books behind we are in the 2008 code now and it is in there. basically as SG stated they dont want unprotected conductors inside the dwelling unless they are in metal conduit
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  • sub3marathonman
    sub3marathonman Solar Expert Posts: 300 ✭✭✭
    #7
    Re: Conduit through attic vent

    In the 2005 NEC 690.31(E) it specifically says "they shall be contained in metallic raceways or enclosures from the point of penetration of the surface of the building or structure to the first readily accessible disconnecting means."

    But is Solar Guppy's statement about the PV disconnect before entering the house the key? If there is a PV disconnect can there be something besides EMT used inside?
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #8
    Re: Conduit through attic vent

    That would be the assumption...

    However, there are other limits (such as flexible conduit, PVC, commercial vs residential, local building codes, and such) that may prevent you from using these others in some instances.

    A talk with the local building department and/or local electrician may help.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • sub3marathonman
    sub3marathonman Solar Expert Posts: 300 ✭✭✭
    #9
    Re: Conduit through attic vent

    So does that mean that you could use PVC from the disconnect on the roof, through the roof and down to the charge controller / inverter?
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  • halfcrazy
    halfcrazy Solar Expert Posts: 720 ✭✭✭
    #10
    Re: Conduit through attic vent

    no the disconnect on the roof isn't "readily accessible".
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  • Lefty Wright
    Lefty Wright Solar Expert Posts: 111 ✭✭
    #11
    Re: Conduit through attic vent

    I'm not used to the code changing this fast.

    Now I'm looking for a big book store. Maybe the 2008 code is out.
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  • halfcrazy
    halfcrazy Solar Expert Posts: 720 ✭✭✭
    #12
    Re: Conduit through attic vent

    yes the 08 code book has been out for about a year any electrical supply house will have them
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  • Lefty Wright
    Lefty Wright Solar Expert Posts: 111 ✭✭
    #13
    Re: Conduit through attic vent

    Went to the book store. They want $130 for a copy of the 2008 NEC.

    It's a nice book with color pictures and explanations of the code changes and intents. It's also way too big to fit into a tool box.

    The local library has a copy they will let me read but can't check out.

    Yes metal conduit is required before the disconnect.

    The disconnect must be outside or inside at the point of entry. The exception is if you are utility connected. I think that is the exception in 690.31(E)

    So: if you are not grid tied and roof mounted disconnects are not considered accessible how do you enter the building without dropping down the outside to near ground level?

    Or are roof mounted disconnects really OK?

    I know this has gotten away from the original post. I would think liquidtite would be considered metal conduit (as long as you are not running non-metalic liquidtite) and would be legal in the attic if you satisfy the requirements of 690.31(E).
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  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
    #14
    Re: Conduit through attic vent

    http://www.amazon.com/National-Electrical-Code-Protection-Association/dp/0877657904/ref=pd_bbs_sr_1?ie=UTF8&s=books&qid=1232293296&sr=8-1

    $67 on amazon
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  • halfcrazy
    halfcrazy Solar Expert Posts: 720 ✭✭✭
    #15
    Re: Conduit through attic vent

    Solar guppy are you saying we cant use RMC or IMC instead of EMT? i would think you could rigid is much heavier and better? i have not looked this up in the code but it really only allows emt? as an electrician i don't use emt i think it is cheesy with the set screw connectors and what not.
    There is no substitute for a good looking Rigid Metallic Conduit installation
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  • Lefty Wright
    Lefty Wright Solar Expert Posts: 111 ✭✭
    #16
    Re: Conduit through attic vent

    The NEC does not say EMT. It says metal conduit.

    That would mean EMT, IMC and RSC. Since flexable conduit and liquidtite are also metal I would think they too would be legal.

    That's what the 2008 code says, anyway.
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  • halfcrazy
    halfcrazy Solar Expert Posts: 720 ✭✭✭
    #17
    Re: Conduit through attic vent

    yes if it reads like the 05 code "my 08 code book is in my office" then it says metallic raceway so any metal conduit would suffice so flex would suffice as well provided its metallic. i will need to look thru my 08 book tomorrow but that's how the 05 read and i cant imagine NEC limiting us to just emt?
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #18
    Re: Conduit through attic vent

    Look up the limitations on running flexible metal conduit... I don't have a code book, but usually, the restrictions on length and mounting are fairly severe. Even two different electricians on the same job disagreed about flex...

    One installed 8' of it to save making a few bends around the water heater for my GT solar install. The second electrician did not even blink and pulled it out and put emt in its place.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • halfcrazy
    halfcrazy Solar Expert Posts: 720 ✭✭✭
    #19
    Re: Conduit through attic vent

    the limitations on length of flex has been discussed as well and i think they only apply to its ability to act as a ground we run flex all over above suspended cielings for lights etc.
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  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
    #20
    Re: Conduit through attic vent

    My apologies, I was going by memory from what I had to do for my install.

    My NEC2005 book, 690.31(e) lists the requirement for photovoltaic source as "metallic raceways or enclosures"

    Article 100 lists what is considered a raceway, which include:

    rigid metal conduit
    intermediate metal conduit
    flexible metal conduit
    electrical metal tubing

    So RMC, FMC, EMT would all be metal raceways

    Section 348 has all the rules for FMC, of which 348.12(3) list battery rooms as not permitted and it must be fastened every 4.5ft for support also fill factor appears to be much lower than EMT ( number of conductors allowed ).

    Personally, I have found installing EMT to be simple, much easier than working with flex so that's what I used and it meets code. I'm not a NEC expert, not much more than a novice and I know people spend a life time understanding all the in's and outs of the ever changing code.

    For more on this subject, one can search for "John Wiles" and his many writing on the subject of PV source circuits, he is the man behind most of the solar related code we try and understand
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  • sub3marathonman
    sub3marathonman Solar Expert Posts: 300 ✭✭✭
    #21
    Re: Conduit through attic vent

    I was wondering if you could run PVC for the wiring on the roof, or if that was too hot an environment for it. There seems to be a debate on that. I guess the NEC possibly allows it, although the actual temperature seems to be the real question.
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #22
    Re: Conduit through attic vent

    sidenote here on pvc. it occurred to me that last year my plumber made a comment about pvc (at least for plumbing) that it is not meant to be exposed to sunlight as it will breakdown if it's not furthered protected like with paint or something like that. i would think the pvc used for electrical may be the same as it is meant to be used indoors protected from the sun and the weather. i don't know if they make it differently than the plumbing type pvc, but i would be tempted to coat it with spray paint if outdoors.
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  • Ecnerwal
    Ecnerwal Solar Expert Posts: 101 ✭✭
    #23
    Re: Conduit through attic vent

    Most PVC electrical conduit specifically mentions being OK for sun (or UV) - right on the side of the conduit, in that long string of printing, which will also mention a temperature limit, IIRC (I'm a few miles from my pile of the stuff). Plumbing PVC does break down in the sun, so things like caps for cleanouts should always be under something, not out in the open.

    Temperature would be the bigger concern on the rooftop, IMO.

    Among other things, I use 1/2" PVC electrical for driveway markers (to tell where in this expanse of snow is the driveway, anyhow?), specifically because it does not turn to a crumbly mess in the sunshine, it's cheap, and it does not rot like wood does. I get about a half-dozen for the price of one fiberglass rod marker.
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #24
    Re: Conduit through attic vent

    ok, thanks for enlightening me as i don't use and have never used electrical pvc. as to the temps i can see questioning it as the wiring is often made to have a jacket capable of 90 degrees c and it would go along those lines that the pvc would have to have such a need too, but that inner insulation would not break down even if the pvc did so i don't know for sure.
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  • Ecnerwal
    Ecnerwal Solar Expert Posts: 101 ✭✭
    #25
    Re: Conduit through attic vent

    In reading though a document from Carlon (a, if not the, major maker of Rigid Nonmetallic Conduit, or RNC - what we peons call PVC conduit) it would appear that you can put 90C wire inside, but the exterior temp is supposed to be 50C max. When hot enough, it turns all bendy, and boiling water is certainly hot enough, having used boiling water to make a large sweep (for my water line, which is sleeved in RNC so it can be pulled out and replaced without digging out the slab floor and foundation, if needed.)

    It's a word doc, but I'm reading via google's HTML version of it. I don't like strange word docs...

    http://209.85.173.132/search?q=cache:cjML3TluA_oJ:www.carlon.com/FAQs/FAQ-RNC.doc+pvc+conduit+ratings&hl=en&ct=clnk&cd=3&gl=us

    They do specifically mention sunlight exposure and use on rooftops - though I'd suspect Florida rooftops (explicitly mentioned) probably exceed 50C at times.
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  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
    #26
    Re: Conduit through attic vent

    Our friendly NEC book lists

    362.12 Uses not permitted for ENT

    (3) Where subject to ambient temperatures in excess of 50C ( 122F) unless listed otherwise

    (7) In Exposed locations, except as permitted by 362.10(1)(5)(7)

    (9) Where exposed to direct rays of the sun, unless identified as sunlight resistant

    Pretty much rules out any roof application as ambient temperature at the roof surface easily exceeds this temperature in most climates
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  • Lefty Wright
    Lefty Wright Solar Expert Posts: 111 ✭✭
    #27
    Re: Conduit through attic vent

    RNC or rigid non-metalic conduit is ok for roof top installations if the conduit is stamped "sunlight resistant". All I've seen in the last 20 years is.

    It can be had in schedule 40 and also schedule 80.

    But ENT, or electrical non-metalic tubing is another animal. It is corrigated and usually blue in color. It would be a poor choice for exposed work.

    When doing underground conduit runs with sched.40 pvc I found that 1" and smaller sizes can be bent with a hickey or emt bender. This won't work well for exposed work because it has a memory and tries to straighten out.

    I have bent 4" pvc by slathering it up with PVC glue and setting it on fire. The ends have to be plugged so the pipe won't collapse when it gets hot.

    I try to do it so the charred side is down so the inspector doesn't get curious.

    Tell me if I misread this, but according to the 2008 code the PV output circuit must be in metal conduit before the first disconnect.

    But the disconnect must be on then outside of the structure or immediately inside.

    If the local authority says a roof top disconnect is inaccessable it would seem the only way to enter the building is by dropping down the exterior.

    The exception is if there is a utility connected inverter (grid tie?).

    This looks like an off grid installation could not enter the building through the roof no matter the type of conduit.
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  • halfcrazy
    halfcrazy Solar Expert Posts: 720 ✭✭✭
    #28
    Re: Conduit through attic vent

    i took it to say that any pv conductors from a grid interactive"grid tied" system inside a building have to be in metal. now the way i read the nec is any offgrid stuff can be in pvc or whatever it is just grid interactive systems
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  • Lefty Wright
    Lefty Wright Solar Expert Posts: 111 ✭✭
    #29
    Re: Conduit through attic vent

    Yes. But the requirement for a disconnect before source output circuits enter a structure (or immediately inside) in 690.14 (c) make me think it would be a rare installation that allows these conductors in a residential attic at all.

    Even the exception, 690.31(e), says that the conditions of 690.14 must be met.

    In a common residential structure I doubt that the conductors can be run through the attic unless the local authority says a roof top disconnect is readily accessible.

    From the 2008 code:
    690.14 (C) Means shall be provided to disconnect all conductors in a building or other structure from the PV system conductors.
    (1) Location. The PV disconnecting means shall be installed at a readily accessible location either on the outside of a building or structure or inside nearest the point of entrance of the system conductors.

    To answer the question that started this thread, unless you have a utility interactive inverter on the roof and need to run conduit (s) into the roof and come out again for DC and AC disconnects or your local authority decides roof top disconnects are readily accessible, you can not run your conductors through your attic, no matter the type of raceway.
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  • sub3marathonman
    sub3marathonman Solar Expert Posts: 300 ✭✭✭
    #30
    Re: Conduit through attic vent

    I've been doing a lot of research, and I've found that Solar Guppy's and niel's answers are always correct and helpful.

    You could possibly use PVC on the roof, with a large reservation though. The maximum temperature would be 122°F (50°C), and the PVC would have to be "sunlight resistant." I don't know many places where rooftop temperatures wouldn't rise to that temperature, especially since the NEC requires a temperature correction for conduit on the roof. Depending on the height above the roof, it could be as much as 60°F, which means your ambient temperature would have to be pretty much 60°F at most. If you went higher than ½" it would be 40°F, above 3.5" it would be 30°F, and above 12" it would be 25°F. So maybe somewhere it would be OK if it was raised high enough above the roof.

    I have found another website which stated that according to the NEC, the circuits must be in steel conduit. However, I think that as long as it is Rigid Metal Conduit it is OK, even if it is aluminum conduit.

    What I am still wondering though is the best method for getting the wiring through the roof. Can it be run completely in conduit, across the roof and down through the roof into the mechanical room or garage? Or does the conduit that goes across the roof end, and a very short run of unprotected wires to the conduit penetrating the roof? And what is the best way to seal the conduit that penetrates the roof? The OP was considering running it through an attic vent, would that be OK? The roofer I have was talking about a "gooseneck" but the electrician wants just conduit, so it is confusing.
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  • sub3marathonman
    sub3marathonman Solar Expert Posts: 300 ✭✭✭
    #31
    Re: Conduit through attic vent
    Lefty Wright wrote: »
    Yes. But the requirement for a disconnect before source output circuits enter a structure (or immediately inside) in 690.14 (c) make me think it would be a rare installation that allows these conductors in a residential attic at all.

    Even the exception, 690.31(e), says that the conditions of 690.14 must be met.

    In a common residential structure I doubt that the conductors can be run through the attic unless the local authority says a roof top disconnect is readily accessible.

    From the 2008 code:
    690.14 (C) Means shall be provided to disconnect all conductors in a building or other structure from the PV system conductors.
    (1) Location. The PV disconnecting means shall be installed at a readily accessible location either on the outside of a building or structure or inside nearest the point of entrance of the system conductors.

    To answer the question that started this thread, unless you have a utility interactive inverter on the roof and need to run conduit (s) into the roof and come out again for DC and AC disconnects or your local authority decides roof top disconnects are readily accessible, you can not run your conductors through your attic, no matter the type of raceway.

    It seems to me that they can be.

    "NEC 690.14(C)(1) Exception: Installations that comply with 690.31(E) shall be permitted to have the disconnecting means located remote from the point of entry of the system conductors."
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