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  Tekmar tN4 Boiler Reset Module - One tN4, Boiler, DHW & Setpoint
Tekmar tN4 Boiler Reset Module - One tN4, Boiler, DHW & Setpoint
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Tekmar tN4 Boiler Reset Module - One tN4, Boiler, DHW & Setpoint

The Boiler Reset Module 420 is designed to operate all of the mechanical equipment in a hydronic heating system, except for zones, coordinating their operation through network communication. It can be used in applications ranging from a single zone of baseboard with an on/off boiler, to multiple radiant floor zones with a modulating/condensing boiler. This control regulates one space heating water temperature through Outdoor Temperature Reset and Indoor Temperature Feedback. It is capable of controlling a single on/off or modulating boiler, Domestic Hot Water, setpoint loads, and can expand up to 24 zones in total.


  • Automatic Boiler Differential
  • Boiler Protection
  • DHW Post Purge
  • DHW Priority (optional)
  • DHW control
  • Exercising
  • Indoor Temperature Feedback
  • One touch overrides (with optional User Switch)
  • Outdoor Temperature Reset
  • Powered pump outputs
  • Setpoint operation
  • Single on/off, or modulating boiler control
  • System Setback (with optional Timer)
  • System control for up to 24 zones
  • Warm Weather Shut Down
  • Zone Synchronization


Control Microprocessor control. This is not a safety (limit) control
Packaged weight 1.6 lb. (730 g)
Dimensions 3-5/8" H x 5-3/8" W x 9/16" D (92 x 137 x 14 mm)
Approvals CSA C US, meets Class B: ICES & FCC Part 15
Ambient conditions Indoor use only, 32 to 122°F (0 to 50°C), RH ≤80% to 88°F (31°C), down to 50% above 104°F (40°C), Altitude <6560 ft. (2000 m), Installation Category II, Pollution Degree
Power supply Provided by interconnected tekmarNet Zone Manager
Pump relays 115 V (ac) 5 A, 1/6 hp
Combined load 10 A max (for DHW and Primary Pump)
DHW zone valve 24 V (ac) 8 VA max
Modulation output 0-10 V (dc) minimum 2500 Ω
Boiler relay 115 V (ac) 5 A, 1/6 hp
Demands 20 to 260 V (ac) / 0.1 VA @ 24 V
Sensors NTC thermistor, 10 kΩ @ 77°F (25°C ±0.2°C) ß=3892
-Included Outdoor Sensor 070 and Universal Sensor 082
Warranty Limited 3 Year Warranty

Current Literature

Product Submittal

Jan 2011 - Present


Installation & Operation Manual

Aug 2007 - Present


Job Record

Aug 2009 - Present


Wiring Brochure

Mar 2009 - Present


Installing tN4 Reset Modules 420, 422 and 423 with Modulating Boilers

Mar 2011 - Present


RF Noise Interference

May 2009 - Present


Part Number: 420

2 +$439.52

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