Snow Melting & Deicing Cable System Installation In Concrete

Today we are working on a concrete installation job with radiant snowmelt heating tables to be installed. With me today is Tom Fitzgerald from Able Concrete. Hi Tom!

Thank you so much for coming out. We are going to be talking about some of the things that you need to look out for and some of the things that you need to take care of while you are planning to do your concrete install and then we will also be showing you putting the concrete in and all the electrical that has to go along with it, laying the cables out that sort of stuff. All right Tom, can you tell us about the job in a whole as what is going to be happening this week here at the house?

Sure. We are going to be removing the existing patio, installing a radiant heat system to melt snow and make the patio available for year round use, installing a new decorative concrete patio, and then installing a hot tub on a portion of the patio.

All right, well, we are here on day two and can see that we have got all the old concrete, all the reinforcement, all that stuff has been taken away and they have brought fresh new gravel in here to get a nice level feel. Well, what we are going to be doing today is putting down the installation and reinforcement metal to install the wiring.

Tom and I are taking a look at the roll here of the heating wire and we are looking at the mesh that the wire is attached to. What would you say, Tom, that you need to do as a concrete contractor to work with something like this?

Well, the mesh has a relatively small opening, so we are going to change our typical concrete mix to use a smaller aggregate, about a three-quarter inch minus aggregate, so we know it will travel through the mesh and make it down to the bottom portion of the slab.

All right, what we have done is we have flipped the mat over the rollover and there is a couple of things on here, I would like to bring up. The first thing you want to do is make sure they are the correct voltage and there will be voltage sticker on the mat itself to let you know 240 or 120, whichever one it is. Also, on the mat, there is going to be a couple of labels on the mat that are telling you what the ohms values are, what the cable lengths are, that sort of stuff.

That information you do not want to bury in the concrete. You want to take them off and give them to the homeowner, so that they can complete the warranty card and turn that in. We know that the mesh really does not provide a lot of reinforcements. Well, what does that mean for you as a concrete contractor?

We will install a bit more rigid steel reinforcement. In this case will use a six gauge wire mesh to support this system and reinforce the concrete.

Now, we can take a look at the setup here. We can see that we have reinforcement bars installed. The reinforcement bars are sitting on concrete blocks. The concrete blocks are on top of an insulating layer. The concrete blocks are under the reinforcement bars to keep them propped up into the middle of the pour. When we pour the concrete, we do not want the cables to go all the way to the ground. We want them to be in the middle of the slab. So, we pour the concrete, the concrete goes through, and the cables stay right in the middle of the slab.

All right, before you do anything with the electric mats, what you want to do is, is you want to make sure that you test them. So, what we have here is, is we have a mega ohmmeter and this mega ohmmeter should be used now to make sure that the mats are good and the mega ohmmeter should be used constantly while the concrete is being poured over the mats to make sure that the mats are not being damaged by any of the tools or people using the tools while the concrete is going down.

So, what I am going to do now is we need to test these to see if we have any connectivity between the cores and the ground. You want to make sure you have no connectivity between either core or ground to make sure that your mat is good. So, what I am going to do is I am going to attach the ground here to the ground wire, then I am going to take the probe here and attach it to the black wire and I have set it for 500 volts and I am going to hit ‘Measure.’

What I am getting is an OF, which means overflow, which is exactly what you want to get. It means it is infinity. The two wires do not see each other in the mat. What I am going to do now is I am going to go along the other conductor, the red one and make sure I get the same reading. I am getting overflow on here, which means I have infinity between the red core and the ground. When you are doing this test, this test is, as I said, 500 volts; so you need to be careful.

The last thing you want to do is grab any of these wires right now because there is a chance of you getting shocked. So, what I am going to do now is, I am going to test to make sure I have the correct ohms across the two conductors. So, I move the ground over to one of the conductors, move the red over here, and I press ‘Test,’ and I write the number down on the warranty card.