How to Install Suntouch WarmWire In-Floor Heating Part 1

One of the best upgrades for a bathroom or kitchen tile floor is the use of in-floor heating. There are several different products available to accomplish the coveted ‘warm tootsies when it is forty below’. One of the more popular products (around here, anyway) is the Suntouch WarmWire radiant in-floor heating. That’s just a really long term for wires that heat your floor (and warm your tootsies).

Now that I’ve used the word ‘tootsies’ twice in one paragraph I believe it’s time to move on.

As an ‘official’ reference the manufacturer’s installation guide can be found online in one of those fancy-ass pdf thingies HERE.  It contains all sorts of things that you need to be aware of before starting your installation. While this post will walk you through how I do it, your installation may differ in aspects of which you are unaware. You need to read through the manufacturers information as well before you actually install you WarmWire.

This is as close as I’ll ever get to an official disclaimer: Be aware that the methods I use will differ somewhat from the manufacturer’s instructions intended for the do-it-yourselfer. I am a professional tile guy (really – what are you laughing about?) I accept liability with everything I touch in a customer’s home and accept that risk with the methods I choose to utilize. Read the manufacturer’s instructions before installing your WarmWire!

This information focuses on the installation of the substrate below the WarmWire, the installation of the wire, and the installation of the Schluter Ditra membrane above the wire for the purpose of tile installation. The technical aspects of the electrical wiring are covered only briefly and in very basic terms. They are not meant to be a definitive guide to properly wiring the WarmWire underfloor heating element to your control box and power supply. READ THE MANUFACTURER’S INSTRUCTIONS REGARDING YOUR PARTICULAR CONTROL BOX! In English that means if your house blows up it isn’t my fault – I was all the way over here.

In your area it may be required to have an electrician wire your heating element. Check with your local building codes to make sure. If it’s required and you don’t do it you could be in heaps-o-trouble. Don’t mess with the city codes, they’re not very nice if you piss them off. Trust me on that.

Ass covering over – lets get on with it.

The WarmWire system consists of two basic elements – the wire and the control box. The control box is hard-wired to your house’s electrical system and the wire is attached to the control box. The wire is then routed down behind the wall and under your floor. After installed you can essentially control the temperature of your floor tile with the control box.

Before you begin you need to figure out how much WarmWire you need to purchase. The above referenced pdf contains a chart which will explain which wire you need based on the square footage of the floor in which it is being installed. There are three different spacings which can be used and utilize different wattage per square foot. That’s all just confusing crap so I’ll explain it like this: The closer you place your wire the warmer your floor will be – and the more power it will use to accomplish that. Easy enough, yes?

How long your wire needs to be depends on how much square footage you’re heating. The quick way I figure it out is the square footage of the room multiplied by 0.90 (because there is no need to heat along the walls, in closets, etc.) and multiply that by 4.7. That will give you the approximate length of the wire you need.

The wire is available in pre-measured lengths. It is not something you can just order to a specific length. It is a closed loop wire which means it is one complete unit and not a wire that can be cut to length. So you need to figure out the length and order the closest to that number.

The different spacings are 2, 2 1/2, and 3 inches. For the purpose of this post I will use the 2 1/2 inch setting as that will be the most commonly used – and because that’s what I have photos of.  You need to also purchase the wire straps which will attach the wire to the floor and hold it in place while you install your flooring above it. Do not use nails, screw, etc. – use the straps. They have pre-spaced clips to hold the wire in place correctly. And using any other method you risk damaging or severing the wire.

For this particular installation I chose to use 1/2″ Hardiebacker cement board on the floor with the heat wire installed to it. Above that I used Schluter Ditra membrane for the tile substrate. When using Ditra you want your heating element, whether it be the wire, a mat, or other type, beneath the Ditra – not between the Ditra and tile.

You can click on any of the badly taken photos for a full-size version.

Figure 1

Make sure your Hardiebacker, or whichever substrate you use beneath the wire, is installed correctly for a proper tile installation. This is imperative since it is the very base layer for your floor. If not done correctly you risk compromising the entire installation – pay attention, this gets expensive! Read How to Properly Install Backerboard for Floor Tile.  Check out that link – I’ll just sit back here and have a beer Pepsi while you do.

Allrighty! (I can’t believe I just typed that) The first thing to do (after properly installing your substrate – in this case hardiebacker – figure 1) is to install your straps. The metal straps made for WarmWire have tabs every inch. I’m certain you can figure out how to use them for whichever spacing you’ve chosen.

Figure 2

Figure 3

For this particular installation I’ve used every third tab in some areas and every other tab in others. I do this to make the floor warmer in certain areas (in front of the shower and tub) and less so in other areas. I do not know if this is standard practice or not – it is for me. If you are concerned about it please see the ‘disclaimer’ at the top.

The straps are placed on the floor and screwed down. (figures 2, 3)  Suntouch recommends using a spray adhesive to hold the straps in place until you get them screwed down – I do not do this.  I have no problem keeping them where they need to be without it and I do not like any foreign substances beneath my tile installations, especially one to which thinset may or may not adhere.

Tab Spacing

I place the straps every four feet to hold the wires in place. I find this gives me enough hold for what I need to do above the wire before the mortar is fully set. Once that happens they won’t go anywhere anyway. But you do need them to be held in place until that point. Don’t try to use a shortcut with this part, if you damage the wire you’ll need to 1. pay to replace it and 2. start over. Neither of which are my preferred method.

You may want to invest in the electronic box Suntouch makes called the ‘LoudMouth’. It is a small electronic box with a 9 volt battery which you hook the wire to when you start your installation. If you damage or sever the wire at any point the box will scream obscenities at you, call you names, light your dog on fire, or something that will let you know in no uncertain terms that you have screwed the pooch (hopefully not while it was on fire).

If you do damage the wire you can purchase the splice kit with which you can repair the damaged wire. I’ll cover that in another post – hopefully one nobody will need to read.

The end of the WarmWire which is attached to the control box is twice as thick as the heating part of the wire. You need to start your wire placement at the base of the wall beneath the control box. Unroll the WarmWire until you get to the smaller part of the wire – the heating element – and place that part of the wire at the base of your wall. In basic terms you do not want any of the thicker portion of the wire beneath your floor – only the thinner part.

Now the fun part. Starting at the point at the base of your wall start stringing the WarmWire back and forth across your floor utilizing the proper tab spacing for your wire distance. In the close-up photos I have it installed in every third tab. Place the wire beneath the correct tab and push it down to hold it in place. DO NOT use a hammer, screwdriver, or beer bottle Pepsi can to pound or push the tab down.

Figure 4

Figure 5

You want to start at one side of your room and end at the other. You NEVER want to cross the wires over one another. They need to remain a minimum distance of two inches apart at all points. Plan accordingly. This is why you want to get your layout figured before you start.

This is tedious but take your time and get it correct. It is imperative for proper performance of your WarmWire.

Figure 6

The end of the WarmWire is a bit thicker than the wire itself. I will usually take my knife or a screwdriver and cut a small groove into my backerboard or subflooring in which to place the end. Ideally you want the end of the wire to end up at a wall in which case you can simply tuck it between your backerboard and the wall footing (you left a gap there, right?) but sometimes you need to end it in front of your vanity or tub.

I do the same thing with the probe. There is also a temperature probe which must be placed beneath your tile to regulate the temperature. It is thicker than the wire itself also. You can simply cut a groove out of your subflooring in which to place it.

Figure 7

Once you are finished stringing the WarmWire over your floor you need to take care to not abuse it. You can walk on it but don’t dance on it, know what I mean? Take a break – you deserve it. When I sober up post the remainder we will cover how to install Schluter’s Ditra tile membrane over your Suntouch WarmWire for your tile installation.

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