Through my personal experience in installing floor warming cable, I have come up with a few tips and tricks that I thought might be helpful to share.
Tip #1
It is important to follow the instructions in the installation manual, do all your preparation and tests. Doing so can eliminate a lot of issues, so please heed this advice! I also recommend you (or your installer) view the floor warming installation video before proceeding.
Tip #2
The first thing I found in placing the spacing strip is that as it is in a 25’ roll, it does not lay flat. If you bend the strip at the joints between the raised tabs until the plastic goes frosty in appearance, it will lay flat for you. This is especially important if you have to glue the strip down instead of stapling.
Tip #3
My home is slab on grade and we installed floor warming directly on the concrete. We tried a few different approaches as an experiment, but we found that PL400 construction adhesive worked best for us on concrete. Make sure the concrete is clean! We simply ran a bead of PL400 on the back of the spacing strip and placed boxes of tiles and bags of mortar on the spacing strip to weigh it down. We found that we had to wait a minimum of 20 hours for the adhesive to set firmly enough. If the adhesive is not set fully and you start running your cable, as soon as you put tension on the cable, the strip will want to shift on you. You don’t want that to happen.
Of course, if you’re installing on a wood sub-floor, stapling the spacing strip down is the easiest and fastest route to take.
Tip #4
My next tip has to do with returning the end lead to the electrical box. How do you run the cable to get it back to the box and not cross the wires? I cut a two-inch section of the spacing strip and run it around the perimeter of the room where the cable needs to return and put the slot in the opposite direction. Since you step the main strip in a few inches from the wall, this space is already there, so you are not compromising your heated floor space.
Tip #5
How do you maintain the cable’s spacing on a long run? Well, firstly I try to lay the cable in the shortest direction if at all possible. If the location of the control makes this tricky, then I find it helpful put an extra spacing strip across the middle of the room. Not only does this help you maintain the spacing as you are installing, it also helps to keep the cable from floating up when you cover it with self-leveling cement.
Tip #6
Okay, now we’re to the point where you’re ready to run the cable. Before you do, inspect the electrical box location (where the leads and sensor will be fished up through the wall). You may need to enlarge the opening above the sill plate, unless the plate has been pre-notched. Just make sure not to cut higher than the baseboard trim will cover. You will also want to inspect the fish line to make sure it is free-floating not stapled into place. You really don’t want to find this is the case as you are fishing the leads and sensor up the wall as you could damage the cable. Note that in some jurisdictions, it’s permissible to run the cold leads in the wall cavity without the need for conduit. Other jurisdictions require that the cold leads be run in conduit. Check your local codes for what is applicable for you.
Tip #7
Ready to lay down the cable? Make sure to do an ohm reading on the cable as the installation guide describes before you start laying the cable on the floor. I cannot stress this enough: make sure you have the right model, both for square footage and for voltage. Many times I get calls about a cable not heating up, yet everything tests fine, only to find out they did not supply the correct voltage. Did you know that if you install a 240 volt model and give it 120 volt power supply, you do not get 1/2 of the wattage? You get 1/4! So an FW23-240 that will give you 280 watts at 240 volts, will only give you 70 watts at 120 volt.
Tip #8
If at all possible, have a second person available to help. If you take a large, long screwdriver and place it through the middle of the spool it will unspool evenly and save your fingers. The second person is handy at this point just to walk back and forth while you make the turns of the cable around the tabs of the spacing strip. Using the chart given for model spacing, run your wire. As an example, if you have 19 square feet of available space and are using an FW12-240, your spacing will vary from 2-3 inches. There is a colored tape about halfway on the cable to help you gauge when you may need to change your spacing.
Tip #9
Now, your cable is all out on the floor and you are ready to pull the leads and sensor up the wall or through the conduit to your Floor Warming Control. I find it easier to pull them all at once by using electrical tape to tape the leads and sensor to the fish wire (if you’re not pulling through conduit). If using conduit, you’ll have to do this for each conduit, but the principle is the same. Make sure the wires are not crossed, but laid flat together. It helps to tape down several inches of the wires. The extra fish wire can be left in the wall for future use if necessary.
Tip #10
Once the cold leads have been fished into your electrical box, now is the time to again test the cable and braid as described in the installation instructions. You want to discover any damage done to the cable during installationbefore you cover it with self-leveling compound and tile. It takes only a few seconds to do, but it can save you a lot of grief in the long run.
Tip #11
Cover the floor warming cable with cardboard or a similar material to protect the cable until you’re ready to cover it with self-leveling compound and tile. Even though the cable is quite hardy, it’s not impervious to damage. When I installed our floor warming cable in the kitchen, it was the chief traffic area for all the contractors coming in and out of the house during construction. Hard-soled boots, dragging in stones and sharp pebbles could have damaged the cable but since it was covered, I had no issues.
Tip #12
S.I.D. SmartRooms Installation Detector is a great way to monitor the health of the cable when pouring self-leveling compound, installing tile and grout. It will issue a warning should the cable be damaged and you’ll know instantly about it. Odds are really good, too, that you’ll know exactly where the damage is thanks to the instant feedback. You’ll know were to fix it before it’s covered up.
Tip #13
When installing the tile, grout lines should be cleaned as you go along (this is recommended industry practice, by the way) instead of waiting for it to harden and cure. However, if you find that you need to clean out grout lines after the tile adhesive has hardened, do not use a metal knife, scraper or equivalent as the floor warming cable may be accidentally damaged. Using a stiff plastic knife or scraper will remove the unwanted adhesive but is far less likely to damage the cable.
Tip #14
Enjoy your new toasty-warm floor for years to come! Congratulations!
