Wednesday, April 23, 2014

Things Are Starting to Heat Up

Well technically they aren't quite yet but they soon will be. Back when we were discussing ideas for the bathroom remodel, my wife really wanted heated floors. I really didn't care either way but put it in the nice to have part of the list because I didn't think it would be within my technical range to do. Mostly this idea was because I thought it would have to be radiant water heated and I would have to put in some sort of manifold and temperature sensing device. However I started doing some research and found out that they sell kits that come with electric mats, a temperature sensor and a thermostat all bundled together.The mats can be cut (as long as you don't cut the heating element wire) and rearranged to fit various bathroom sizes and configurations and seemed really simple to install. They don't draw much electricity and with the thermostat only heat twice a day when we might be actually in the bathroom. The kicker was the kits were pretty darn cheap. Worst case if I really messed it up and it didn't work, I was only out about a hundred bucks. So I bought a kit.

So after completing the shower tiling, I unwrapped the package and installed it. The installation went smoothly and I was able to complete it in about three hours. The start of the mat is the one on the right and near the door. It has leads that are stuck down in a crack between the floor and the drywall and runs up into the hole you see in the upper right part of the picture down next to the floor. That hole will be covered up with the vanity after I get it built and installed. I fished the wires up to the thermostat base which you see mounted above the bank of electrical switches and outlet. I bought an remodel outlet box that clamps on the back side of the drywall and is made specifically for situations like these.

I think I ordered a nine foot mat and the bathroom is only five feet long (not counting the shower) so that I could bend the wire to fit around the vent opening in the lower left side of the picture and pretty much cover the area evenly. You aren't supposed to put the heating elements under any permanent fixtures like a vanity or toilet which is why there is nothing on the right side of the bathroom. To get everything to lay flat and stay where I wanted it, I used hot glue to tack everything in place.

To regulate the temperature so it gets warm when you want it too, doesn't run when we are not around and doesn't overheat, there needs to be a temperature sensor embedded along with the wires. That is the black wire you see kind of in the middle of the photo that ends in between a loop and runs out and into the hole in the wall up to the thermostat. I haven't plugged in the thermostat because the wires aren't supposed to run without mortar around them and I didn't want to have to figure out how to get the thermostat in vacation mode before things started melting.

The only problem I had was checking the resistance of the system before installing it and before I tile over it. You do this to verify that it is working before cutting it up to fit your area and again before you permanently tile over it. I checked the resistance on the mat before and after installation and it matched the range the manufacturer said it would. I DIDN'T check the resistance of the temperature probe before installing it because I didn't know I had to before I started hooking it up to the thermostat and saw a label wrapped around the wire. For some reason they didn't state that you were supposed to do this in the instruction manual. So when I discovered this omission, I got my multimeter and checked the resistance on the leads. Despite trying several times, I got only infinite resistance which means the thermister wasn't good. I was going to have to call it in, deal with customer service and get another one shipped to me which would be a week or two of delay.

I was actually on hold with their customer support due to 'heavy call volumes' when I decided I should gather all the information close to the phone so it would be handy. I peeled off the label from the wires telling me to check the resistance and the range along with the manual and box it came in when I read the label a second time. It said the resistance should be between 10k and 12k. Now the resistance in the floor mat had a range of 50 to 96 ohms so 10 to 12 ohms seems right in my brain for the thermister. But that k on the end is short for 10,000 to 12,000 ohms and I realized right then that my multimeter was set on the wrong scale to measure it. I quickly switched to a higher scale and my resistance was smack in the middle at 11,000 ohms. Before I could hang up, the service guy picked up and started asking questions. So I explained what I had just figured out and big him a good day.

So now everything is checked and working and ready for tiling. The wires were a lot thicker than what I had thought, probably around 1/8th of an inch so I have to account for that when tiling the left side versus the right side where there isn't a mat. I think what I am going to do so that I don't accidentally nick a wire is to fill the mesh and wires with mortar and use the wires to kind of screed it flat with a float. Then I will apply the mortar to the back of the tiles with a notched trowel and set in place. I think that will work better than trying to run a notched trowel over the wires and mesh and not nick anything.


Ron said...

I've seen those kits at Menards years ago, and I thought about it when I tiled our old bathroom, but didn't do it.

Ed said...

Ron - Since this bathroom was so small, I thought it the perfect test case to see how they worked. So far the warm tile certainly feels nice on the feet first thing in the morning!