Driveway Snow Melt System Questions

[mkgrady]

I am getting ready to install a snow melt system in a new concrete driveway. Total load is 27.5KW and will cover 550 square feet. The system is made by Danfoss and I am using mats and two ground sensors that will tell the controller when to turn on/off. I looked over att. 426. I'm in the 2011 version.

The old driveway is being removed and dropped an inch or so for a layer of 1 inch insulation boards. The mats will lay on top of the insulation and about four inches of concrete will be poured over the mats.

426.22,b tells me that because the cold leads are not shielded they must be in a raceway. They list GRC, emt, IMC and others. Is PVC or Liquid Tight an other? Seems to be but they did not list it. And can the raceway be within the concrete pour? Or does it need to be buried 18 inches deep. That would make my job much more difficult.

426.20,e tells me not to bridge expansion joints. I assume that means the little groves the cement gets or does it mean something else? The exception is that if provisions are made for expansion it is OK to cross a joint. How can provisions be made to cross an expansion joint when its all in concrete?

This is my first time doing snow melt. Any additional advice is welcome. Thanks

 

[ceb58]

Do not see why you cannot use PVC look at art. 352. Then look at table 300.5 note 2 This is from 2008.
I think the expansion joint they are referring to is a thin strip of metal that is stood on end every 10 ft or so as an expansion joint. You could not take the mat over or under such a joint. Most concrete contractors now dont use this any more. They come back the next day and cut a 1/2'' deep slot across the concrete for expansion.

 

[mkgrady]

Do not see why you cannot use PVC look at art. 352. Then look at table 300.5 note 2 This is from 2008.
I think the expansion joint they are referring to is a thin strip of metal that is stood on end every 10 ft or so as an expansion joint. You could not take the mat over or under such a joint. Most concrete contractors now dont use this any more. They come back the next day and cut a 1/2'' deep slot across the concrete for expansion.

Thanks. It still makes me wonder if the slot cut in the concrete is the types of expansion joint they are saying not to bridge with the mat.

 

[ceb58]

Thanks. It still makes me wonder if the slot cut in the concrete is the types of expansion joint they are saying not to bridge with the mat.

I do not think so. As I said some times they use a thin strip of metal as the joint or a treated 1x4. You could not bring the mat over the top (bridge) of the metal or wood because the top is flush with the slab.

 

[tkb]

The saw cut groves are not expansion joints, they are control joints.
They are cut to control the cracking of the concrete into the groves and not onto the flat surfaces.

An expansion joint would have a rubber or fiber material between slabs.