tekmar 518 radiant thermostat fits one-stage hydronic heating, including in-floor radiant. It states room, floor, and outdoor sensing from the auxiliary input, with auto heating cycle and pulse width modulation — short on/off pulses that hold temperature steadier than simple on/off.
120V system wiring is not needed; low-voltage sensor wire links the included slab sensor 079 for floor protection and overheating control. Room-by-room use suits heat-only zones, with direct drop-in replacement for tekmar 507 and 508 in minutes and optional adaptor plate 012 for single-gang boxes.
518 Thermostat – Highlights
Pulse width modulation
Meters heat in short pulses for stable radiant floor comfort.
Slab sensor 079 included
Measures floor temperature to protect floors from overheating.
Freeze protection
Maintains minimum heat to guard pipes and slab in cold spells.
Drop-in for 507 / 508
Replaces those models without rewiring, saving install time.
Backlit display
Large readout with simple up/down buttons for daily changes.
518 Thermostat – Specifications
Use: Indoor use only, up to 90% RH non-condensing
Sensor: NTC thermistor 10k at 77°F (25°C), Beta 3892; includes slab sensor 079
Dimensions: 3-11/16 x 3 x 15/16 in (94 x 76 x 24 mm)
Sensor input: Floor, room, or outdoor auxiliary sensor, auto-detect
Sensor range: -60 to 255°F (-51 to 125°C)
Control method: Pulse width modulation with auto heating cycle
Replacement for: tekmar 507, 508, 509
Thermostat range: 32 to 122°F (0 to 50°C)
Sensor dimensions: 3/8 in OD x 3/4 in (9.5 OD x 19 mm)
System compatibility: One-stage heating or cooling, radiant floor hydronic
