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Install your own under-floor loose wire
This article courtesy
Here is an
overview on how to install your own under-floor
loose wire radiant
heating system. This type of heating system is a great supplement to
your whole-house heating system. Or do you have a "cold room"... a space
that never seems to warm up enough? Or do you want to install tile on
your kitchen or bath floor but are concerned that it will be cold in the
winter? An under-floor system can keep these areas warmer at a lower
cost and greater comfort than any other type of heating unit!
1) Take measurements
and plan wiring locations carefully
Any type of installation requires figuring out exactly how much material you
will need to do the job. It is no different with an under-floor heating
project. As noted in the diagram below, you will first need to measure the
area you want to heat, excluding any furniture or fittings so that you
purchase the right amount of product for your project.
It is important to avoid placing the radiant heating wire underneath areas where you plan to
install fixed furniture, such as cabinets. You can place the heating wire close
to toe kicks or the shower/tub enclosure, but leave a little room around toilet
drains (so it isn't underneath the toilet) and walls are needed.
2) Decide where to install your thermostat...
The thermostat is the "heart" of your radiant heating system, controlling the
power to the heating wires and also regulating the temperature of the floor.
All wiring for your radiant heating system either runs to it or from it. Most people will install their thermostat near the entryway of the room they
are heating, near the light switches. However, anywhere you install it is
fine as long as the area is dry and unobstructed.
In some cases, the
location may need to be based on the layout of your home and the location of the
main circuit board. Consult an electrician if you need assistance with the
specifics. Of course, any electrician would be glad to do the final wiring
for your project! (If you're interested in seeing what a state-of-the-art floor heating
thermostat looks like, Warmup offers an excitingnew energy efficient, programmable floor heating thermostat called the 3IE.
See pictures below.)
Floor heating thermostats usually require a double-gang box with two
conduits down to the floor level... one for the heating wire and one for the
3) Insulate your floor beneath the heating wires for
We recommend using our
insulation boards when installing over concrete slabs. Warmup Insulation
Boards will save you money when used in conjunction with underfloor heating by
acting as a very efficient thermal barrier. They reflects the heat upwards into
the floor tile instead of allowing heat to warm up the concrete slab below. By
using Warmup Insulation Boards you will find that after switching on your
heating, your floor tiles will warm up in about 10-15 minutes. Without
insulation boards it could take anything from 2-3 hours, or more.
When installing insulation boards, determine how many you need based on the
measurements of the area you are heating. Each board is 2' x 4' x 1/4" and can
easily be cut with a utility knife to allow for placement in every nook &
cranny. You will apply a construction adhesive to the subfloor and place your
boards on top. Over plywood sub-floors, you will add provided screws every 8 to
12 inches for added bonding. Due to the thinness of our boards, you can have
the benefits of insulation without interfering with your design plans!
4) Testing makes perfect... be sure your wires are not
damaged before, during or after installation!
You should get a multimeter or ohmmeter to test the resistance of the wires.
This should be done before, during and after you lay down your wires, prior to
installing the actual flooring. The reading you should get for each type of
wire system (120V or 240V) is provided in the included installation manual.
These testing meters are about $20 at your hardware store or available from
5) Laying down the wire...
Start at the thermostat and route the power cable or "lead wire" into
the conduit. From here, lay down your heating wire in loops at 2", 3" or 4"
spacing with the provided tape.
1) For MORE HEAT or to compensate for a cold subfloor, use
a 2-inch spacing between wires, giving you the highest heat production.
2) At 4" spacing, you will have less output, but it is the
recommended spacing over Warmup Insulation Boards as you do not lose heat
downwards and therefore require less wire for great results.
When ordering your loose wire system, review the manufacturer charts which
will give you the square footage you can achieve at various spacing. Advanced
users even alternate the spacing within a same room, with more heat at the
vanity, and less heat in the walking closet for example.
Here are some pictures of a typical installation pattern. Note that the
wire is held in place with tape (supplied by the manufacturer), not staples or
other mechanical fasteners that may can cause shorts and/or damage the wires.
The first graphic shows the layout with small pieces of tape holding the wires
in place. The second graphic (below) shows the entire length of wire being
affixed to the floor with tape. This is important so the wires do not
become displaced with applying the thinset over the top.
Warmup's wires are only 1/8" thick, and do not raise your floor levels by
more than 3/16" when coated with self-leveler or thinset.. the minimum recommended thickness of thinset. As thin as they are, Warmup's wires
provide the fastest heat up times in the industry and are made with advanced,
commercial grade polymers that have the strength and durability to last longer
than traditional PVC wires. Note: Warmup wires can be applied with cable straps or
"clips", but often only require the provided tape, in order to maintain the
floor profile as low as possible.
Installing the floor probe...
The purpose of the floor probe is to monitor the temperature of the floor.
Remember that the thermostat reads the air temperature, not the floor
temperature. There may be a circumstance where the room may become warm
(such as a sunny day) but you still want the floor to stay warm. The floor
probe allows some control over the floor temperature independent or in concert
with the thermostat.
Install the floor probe or "sensor wire" by routing it into the second
conduit to the thermostat box. Lay the sensing tip of the probe into the heated
area. Make sure not to overlap or cross over any heating wires, and keep it
centered between the nearest wires for accurate readings.
Depending on the thickness of the probe, you may want to chisel a channel
into the floor (or insulated panel) so it lays beneath the level of the heating
wires. It should be taped in place, as were the wires.
Protect the wire with a thinset mortar coating...
Using a flat trowel, cover your wiring system completely with either a floor
leveler or a modified thinset. In this example the contractor is using a
polymer-modified thinset mortar. (We often use MAPEI FLEX or CBP Versabond for
our installations.) You can reduce that layer to a strict minimum,
but it will provide for an easier tile job. In any event, you must always make
sure that the wires are completely imbedded in these compounds so as not to be
exposed to the air and over-heat. Do not attempt to set tile into this
After it has cured (a few hours to overnight
depending on thickness and the manufacturer's suggestions), start laying down the tiles or other
flooring) as normal.
Important: Do not activate your radiant
floor heating system until the cementitious materials are fully cured. This
will be determined by your floor installer or by reading the manufacturer's
instructions. As a rule of thumb, we recommend 3 to 7 days wait time.
Watch this instructional video!
Here is a video of an actual installation job in a small bathroom with Regis and Mike of Warmup.
This will give you a realistic view of the taping of the wire and the coating
with a floor leveling compound.
We have a helpful
FAQ page on our website that will answer additional questions you might
have. Once you visit, you will also be able to view all of our product
offerings along with installation pics and helpful step by step videos. Our
experienced staff at Warmup is always on hand to answer your radiant floor
heating questions. You can visit us at
www.warmup.com and fill out a no obligation "quick quote" to see how we can
help, or just give us a call toll-free at 1-888-927-6333.
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