Using a floor sensor is usually considered the most precise way to control an in-floor hydronic heating system. Surface temperatures above about 87°F can make floors uncomfortably hot to walk on. Wood flooring in particular can be damaged by excessively hot floor temperatures. Although the limit depends on the recommendations of flooring manufacturers, surface temperatures generally should not exceed 82°F to 85°F with wood floors. Floor sensors control surface temperatures while also preventing rooms with multiple heat sources from overheating and making the floor more comfortable for small children or pets.
Especially when tubing is installed in a slab, rooms can take a long time to heat up and cool down. This means that the rooms may overheat when a standard thermostat is installed (although some thermostats offer features designed to combat this, including Uponor WT1 and Nest models). It also means that programmability does not normally benefit in-floor systems.
A temperature controller such as part A419GBF-1C can be used to control systems based solely on floor temperature. It may take a little experimenting to figure out which floor temperatures are ideal for comfort in the room, and not having a wall thermostat could take some getting used to. Tekmar makes some thermostats (e.g. part 519) with floor sensor options. They operate just like standard thermostats, but you can also set high and low limits for the floor temperature. These limits take precedence over the ambient temperature settings on the thermostats.
When dealing with in-floor electric heating cables, thermostats with floor sensors and GFCI protection are normally required.
