Anybody out there have experience wiring a greenhouse? I've been asked to wire one that is in the shape of a geo-desic dome, and I'm trying to figure out what to use for raceway. Because of the dome-shape, flexibility would be a real help so I'm thinking of using seal-tight (LiquidtightFlexibleNonmetallic Conduit). I can't see any code problems as long as I secure it at the proper distances.
I have not done any dome work- this sounds like an interesting challenge!
A geodesic dome is actually an assembly of pentagons and hexagons, with triangles filling each "major" shape. Rather than a smooth curve, there is a slight angle at each junction. Unlike a conventional building, the shape itself is what gives it its' strength, rather than specific structural members. The effect of this is that the only place you can safely place an anchor is dead center where the major shapes come together.
With that in mind, it seems that you'ld either have to run romex, zig-zagging along the frames....or build some sort of trellis to support your stuff. An arched "ladder" made from strut comes to mind. Or, you could be conventional, and "build a box" within the dome, so you can run your pipe in the usual manner.
Reno - I was thinking no romex because of the moisture factor. Also, not sure what you mean by "build a box". Do you mean create a structure within the structure? Don't think that would work: the triangles of this dome are translucent pieces made specifically for that filtered sunlight effect; don't want to block them in any way. The structure connecting each triangle to the next is 2x4 wood, with the 2" face being the surface I could strap to. Not too concerned about that. Just wondering if sealtight seems like a reasonable way to go and, if so, how to go about strapping with the 1/4" spacing required by 300.6(c). Thanks.
Re: Greenhouse wiring#97891 04/13/0607:15 AM04/13/0607:15 AM
LFNC-B is a non-metallic conduit, so why do you need to keep it 1/4" off the beam? I always thought "sealtite" was LFMC, and since that has metal would have to be off the surface. LFNC is cheaper, non metallic, and easier to work with.
Will you have any issues protecting the conduit from physical damage? You could also use UF cable. It should have the same physical damage constraints and plastic conduit and may be easier to protect because its much flatter.
Mark Kent, WA
Re: Greenhouse wiring#97893 04/13/0611:28 AM04/13/0611:28 AM
Good question, Markp, about the 1/4" airspace for LFNC. I quess when I read 300.6(c), it's not clear to me that they are referring to just metallic materials: "...the entire wiring system, where installed exposed, including...all conduits and cable, shall be mounted so that there is at least 1/4" airspace...." That sounds to like even UF cable would require the airspace. You think maybe I'm misinterpreting?
As for the possibility of using UF, I would love to go that simple route, but I'm afraid "subject to damage" might be an issue in this greenhouse. It's a very dynamic space, with an upper deck and waterfalls, etc., plus constant digging and planting. Not your ordinary retail greenhouse, but more of a personal botanical garden.
RNC is probably the best way to go, though "easy to bend" doesn't exactly fit my experience. I haven't yet wanted to shell out the bigbucks for a heating blanket and so have made do thus far with a heat gun: SLOW!!!
Half inch RNC is pretty bendy stuff. As long as the dome has a reasonable raduis you should be fine. I userd 3/4" RNC for the bows in my boat lift cover. That has a pretty good bend in it too. I think the 300.6 exception should ease your concerns about the 1/4"
Exception: Nonmetallic raceways, boxes, and fittings shall be permitted to be installed without the airspace on a concrete, masonry, tile, or similar surface.