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.