Tech Talk – March 2017

Using the NTCA Reference Manual to prevent or solve radiant heat issues

By Lesley Goddin 

Radiant heat and electric floor warming is one of the fastest growing sectors in the tile industry. In fact, in our TECH and TRENDS issues, it’s one of the biggest section – with more products being introduced that take advantage of NEST or smart phone technology to monitor and operate automated temperature controls, or new mat-and-cable configurations that speed installation while offering a more custom layout and guarding against cracking at the same time.

Electric floor warming systems seem to get simple to install all the time – a far cry from the days of cumbersome hydronic pipe systems. These simple, easy mat-and-cable systems make installation fast and relatively easy.

That being said, there are cautions when installing radiant heat systems that are best heeded to ensure a flawless project. The 2016/2017 NTCA Reference Manual examines Radiant Heat Issue for Tile & Stone Installations in chapter 6: Specialized Installation Procedures, page 134. Presented in a Problem/Cause/Cure format and compiled from decades of field experience, the recommendations in the NTCA Reference Manual help installers prevent problems in the field and give guidelines on managing them if they do occur.

For instance, a few of the scenarios include:

Problem: Excessive tile lippage

Cause: Lack of mortar of self leveling underlayment cement used to encapsulate the radiant heat system

Cure: Securely attach the radiant heat system so it stays flat on floor and cover the system with sufficient mortar or self leveling underlayment cement. 3/4” of dry pack of 3/8” SLU over the system.

Problem: Grout or mortar system is very powdery or weak.

Cause: Provided the grout and mortar system was properly mixed and installed, the main cause would be running the radiant heat system before the cement based products are allowed to cure: a minimum of seven days.  Excessive moisture exposure from below or above may impact mortars or SLUs.

Cure: Make sure all parties involved with the radiant heat system know the system cannot be put in service until the installation products are allowed to cure.

Problem: The thermostat overheats or even melts when the radiant heat system is turned on.

Cause: Damage of this type generally is caused by overloading the circuit, trying to heat too much floor area on one thermostat or running a 120v thermostat on a 240v circuit.

Cure: Make sure the radiant heat system is matched in terms of voltage and sized correctly to the circuit capacity and thermostat. It also could indicate the wire nuts are not sufficiently tightened. Make

sure a licensed electrician makes the final connection.

Problem: The radiant heat system doesn’t warm up.

Cause: The main reason for this is a broken or severed heating element.

Cure: Take care to protect the heating system during installation. This problem will require splicing/repairing the heating element.

Problem: The radiant heat system doesn’t provide evenly spread or consistent warmth.

Cause: The main reason for this is varying or wrong spacing of cables or tubes. Follow manufacturer’s recommendations. Lack of insulation under the heat system may also cause heat-loss or heat-sink in areas of the subfloor. Proper insulation underlayment should be designed by the architect.

Cure: Re-design floor and heat system installation including insulating tile underlayment. This cure will require splicing/repairing the heating element. In case of heat loss due to lack of insulation under the heat system, the application must be redesigned.

The NTCA Reference Manual provides more recommendations for successful radiant heat installations – and successful installations for a range of situations and products. To obtain your copy, visit the Industry Technical Manuals section under the NTCA Store link on the NTCA website,, or enter into your browser.

The SunTouch SunStat® Connect Programmable Touch Screen w/ Wi-Fi / Model# 500875  lets you control floor heating remotely, using a mobile app or via the web. Adjust floor heating settings any time from anywhere. Additional features let the system compensate for weather changes to save on energy

The OJ Microline® touchscreen thermostats can be used with any electric floor heating system to provide intelligent, intuitive, programmable and adaptive control. WLAN connectivity allows homeowners to remote control their heating system via an app from anywhere at all.


















Schluter’s DITRA-HEAT-TB, now DITRA-HEAT-DUO, reduces sound transmission in multi-story residential buildings, while warming the floor and supporting the covering to ensure a lasting installation.  It also offers faster warm-up times.

Nuheat electric radiant floor heating systems offers a variety of solutions from pre-built custom mats, off-the-shelf standard sizes, cable for on-site modifications fitting perfectly into uncoupling membrane. The Nuheat line of Next Generation Thermostats includes the industry’s first WiFi-enabled thermostat that Works with Nest, taking comfort and energy savings to the next level by working together to automatically adjust to your schedule, sensing and reacting to your ever changing lifestyle.



















RPM Mats, “the original” heat wire installation mat system, can be used to replace anti-fracture membranes and are designed to ease the installation process for all brands of electric in-floor heat wire with wire spacing at any 1/2″ increments. Made in the USA of recycled materials.

The Warmup 4iE® thermostat finds the smart way to heat your home more efficiently. Two options are offered, with and without WiFi. The 4iE can be installed like a traditional underfloor heating thermostat or 3-wire thermostat for central heating. The WiFi is simple and intuitive to set up. Free installer training classes, and a selection of decorator faceplates available.






Providing consistent comfort and control for many years, the Warm Tiles® New FGS (programmable) & FG (non-programmable) model thermostats offer state-of-the-art temperature control, and easy programming functionality.A sensor embedded in the mortar below the finished floors monitors the actual floor temperature to obtain optimal comfort levels.

The WarmlyYours TempZone™ Heating Cable (Twin) warms any room with an ultra-low EMF. The twin conductor has a 15’ cold lead and is available in two voltage options and a range of lengths. It can also be paired with the Prodeso Cable Installation Membrane, an uncoupling and crack isolation membrane with rounded square-shaped reliefs,  that offers versatile layout options and waterproofing.