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How a heated floor thermostat works
The sensor in the floor, protection against current leaks, settings and installation: what sets the thermostat of a heated floor apart.
In short
This guide covers the thermostat of an electric heated floor: what it measures, how it protects, and what installing it involves.
- According to the manufacturer Stelpro, only a thermostat with a floor sensor truly controls the floor temperature.
- According to the manufacturer, the heating cable requires permanent Class A (5 mA) GFCI protection, built into the thermostat or installed at the panel.
- Each enclosed room heated by the floor has its own thermostat.
- Floor heating connects to a circuit dedicated to heating.
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What the thermostat does
The thermostat of a heated floor switches the heating cable under the floor covering on and off, based on the temperature it measures.
According to the manufacturer Stelpro, only a thermostat with a floor sensor gets the most out of the system. An ambient air thermostat or a simple switch isn’t recommended: it can’t control the floor temperature, which will then always be either too cold or too warm.
In the 2018 edition of the Code, each enclosed room containing a heating appliance has its own temperature control device.
For a heated floor, the manufacturer says the same: each enclosed room has its thermostat; the cable can, however, extend into an adjacent room controlled by the same thermostat.
The floor sensor
The sensor goes in the floor, between two cable runs, at least 60 cm from the wall, where the temperature reflects that of the floor as a whole.
The manufacturer supplies two sensors, one with the cable and one with the thermostat, and recommends installing both in different spots: one serves as a backup if the other fails.
A sensor is checked by measuring its resistance, which varies with temperature according to a manufacturer’s table.
If a floor stops heating, the sensor is among the things that get checked: see our guide Heated floor not working.
GFCI protection
The manufacturer requires permanent Class A (5 mA) GFCI protection to protect the cable and the occupants in case of a fault.
This protection is either built into the thermostat or installed at the panel.
When a break in the cable’s insulation lets current leak, the GFCI trips, which shuts off the heated floor.
What a GFCI does in general is in our guide GFCI: what it protects, and where you need one.
A thermostat to connect?
Cable already laid? We do the hookup: circuit and thermostat. The price is in the written quote, at no charge.
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According to the cable manufacturer, ceramic, porcelain and stone are an ideal choice for a heated floor; other floor coverings may have a temperature limit set by their manufacturer.
In that case, the cable manufacturer recommends using the thermostat’s floor temperature limit feature.
The manufacturer prohibits laying a rug on a heated floor: the trapped heat can damage the rug, the floor covering or the cable. A bath mat is acceptable if it is taken off the floor after the bath. For the same reason, it asks not to place permanent furniture or large objects under which air does not flow freely.
Installation
Floor heating connects to a circuit dedicated to heating.
According to the Régie du bâtiment du Québec, a branch circuit that supplies a fixed heating appliance supplies no appliances other than heating appliances.
The thermostat is rated at least for the total of the appliances it controls (2018 edition). At Stelpro, one thermostat controls 15 A at most; beyond that, an expansion unit, a relay or another thermostat is added.
The manufacturer places it in an accessible spot in the room, at an appropriate height.
In a bathroom, the manual control of a heating appliance goes at least 1 m from the bathtub or shower. The 2018 edition allowed 500 mm, only if 1 m was impossible and if the control was protected by a Class A GFCI or supplied by a Class 2 circuit. The 2026 Code allows less than 1 m, inside the room but outside the perimeter of the bathtub or shower, under the same protection conditions.
According to the manufacturer, the electrical connections are made by a qualified electrician. In Québec, that’s work for an electrical contractor.
What we do
What we do for a heated floor, usually the hookup once the cable is laid, is on our electric floor heating page.
For baseboard heaters and their thermostats, see Baseboard heaters and thermostats.
Frequently asked questions
Can a baseboard thermostat control a heated floor?
The manufacturer Stelpro doesn’t recommend it: an ambient air thermostat can’t control the floor temperature. Only a thermostat with a floor sensor can.
Does the thermostat protect against current leaks?
It can: the Class A GFCI protection the manufacturer requires is either built into the thermostat or installed at the panel.
Do I need one thermostat per room?
Yes, each enclosed room heated by the floor has its own thermostat; the cable can extend into an adjacent room controlled by the same one.
What temperature should I set?
The manufacturer doesn’t give a single number: it points to the floor covering’s limits, and recommends the thermostat’s temperature limit feature for coverings other than ceramic, porcelain and stone.
Can I replace the thermostat myself?
No. According to the manufacturer, the connections are made by a qualified electrician, and in Québec, that’s work for an electrical contractor.
A heated floor to connect?
Cable already laid? We do the hookup of the circuit and the thermostat. The price is in the written quote, at no charge.
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Sources
Consulted on October 30, 2026.