ECN Forum Forums Code Related Discussion NEC & other Code issues Greenhouse wiring

Hey Greg- I just checked the UL White Book and it says RNMC is not Listed for boat lift covers and you'll need "Special Permission" signed by at least 5 inspectors and you and I know that those 5 inspectors will need some "encouragement" and a boat ride before they sign off on "special permission"

I have already taken 3 inspectors for that boat ride and provided some 12 oz ecouragement but if you think we need one more come on down.

Greg - 300.6 exception doesn't mention wood. The 2x4s between triangles is what I would be strapping to. Back to you.(pin-pong anyone?)

It is clear the wood is what you should be worried about. If it is treated it shouldn't rot. The RNC will be fine.

You really need to back up and read the scope of 300.6 before we start nitpicking the language. Lets start over.

It doesn't even sound like we care what 300.6 says if we use a plastic wiring method

I have used the Carlon clamps for years and they do a good job of raising the RNC just a little off the surface and at the same time allow it to slide with expansion and contraction better than an ordinary 2 hole strap. Would be my choice here. http://www.carlon.com/Brochures/2B10-Straps_Clamps.pdf

I have wired over 5 acres of production greenhouse. In Ohio where I did it, it was agricultural and not subject to inspection.
The inspector didn't even want to discuss methods.
I have seen RNC used and it turns into a terrible mess in a few years. The temperature swings make it expand and contract until it pops out of straps and busts fittings. If the greenhouse is unused and the heating and ventilating systems are shut down an 80 degree swing is easily possible.
Also the condensaion that occurs will fill any watertight raceway until the devices are swimming.
The best job I feel is done with EMT and set screw fitting to let the moisture out.
I have run EMT following the curved portions of the structures pretty sucessfully. Try using small bends at intervals and minis as straps.
Any tie wraps or T-stat/Low voltage wiring needs to be UV resistant or it will be toast in a couple years.
If it is a commercial operation the oxidation from the pesticides and fertilizers also will hasten the degradation.

Good Luck

Wet location, aluminum MC?

added;
Drip loop so you enter the bottom of all boxes

[This message has been edited by gfretwell (edited 04-15-2006).]

More great ideas and input. Thanks to everyone. Keep those cards nd letters coming!