Via E-mail — I read with interest Mark Eatherton's article on Alternative Radiant Heating Solutions (January, p. 36) and was happy to see him take on this subject matter. It was more interesting in that we had a recent tech call from homeowner who just moved into a hydronically heated home that was being controlled with our floor heating thermostat and her floor wasn't rising over 60°F. We are concerned that as the market matures we will be seeing more of these tech calls. That being said it is important that all of us in the radiant heating business understand each other's products. I'd like to comment on some of the information in your article to help you educate your readers in future articles.
Mark is correct that sheetrock has to be moved to facilitate the install. Typically, for smaller areas, a single cable or mat with a thermostat are installed, and power is brought to the room. The power connections are made at the back of the thermostat and most floor heating thermostats switch a 15/16 amp load and contain a built-in GFCI for wet locations as is required by the national electric code. For larger areas a small relay panel can be installed near the main power distribution panel to switch the amp load. These thermostats also have a floor sensor that measures the floor temperature.
Depending upon the how thick the mortar bed and room insulation, the systems cycle differently and have varying start-up times, and operating costs associated with that.
Many people have the misconception of calling line voltage products high voltage. The proper terminology for 120 and 240 VAC is line voltage. High voltage refers to 600 VAC industrial power equipment such as high voltage power lines. Using 240 VAC typically allows the owner to cover twice the area size as a 120 VAC cable at the same amp load.
There are many meters available for electrical contractors to test electric resistance heating cables before the mortar is poured. We recommend that the installer use a megger to insure the correct performance including current, insulation, resistance, and voltage both before installing, after installing, and while the mortar is being poured.
One problem in the fast growing floor warming segment of the market is the do-it-yourselfer or tile contractor who doesn't understand the testing, can't afford the metering equipment, and uses only the continuity meter provided by the manufacturer. This occurs because the National Electrical Code requires the electrical contractor to make the power connections but not install the product from start to finish.
While. it's the owner who suffers if a cable is damaged during install, there are fault finders and other tools available to trace a circuit and locate the fault. Some of them work and some don't work so well. If the fault is located and that part of the flooring can be removed, the cable can be spliced and will continue to work as designed. It's not that the break is difficult to repair. It would be finding the exact location of the break that would be difficult. This is why the proper testing of the cable during the installation is very important and a layout of the cable installation should be left with the owner.
Free-form cables move around built-in fixtures much the same as hydronic tubing does and offer more flexibility than mats. The popular product today is dual conductor resistance heating cables. These cables have a single power connection and the lagging end may be placed anywhere in the floor.
The popular radiant heating mats can be cut and turned, (the matting material and not the cable), to fit the mat and cable into the space with some ability to move around the built-in fixtures.
If Mark or other contractors ever have any questions on electric radiant, snow melting, roof deicing, or heat tracing cables or controls, please give me a call or drop me an e-mail at 800/ 526-7887 or at [email protected]