Bosch Therm 520HN Tankless Hot Water Heater – No longer available

Certified by OTL US

Certified for use in all provinces and states in North America.

NOTE: Due to a change in CSA Regulations regarding minimum thermal efficiency, Bosch On-Demand Water Heaters are no longer available.


  • 1371

The Therm 520 HN incorporates an evolutionary hydro-power ignition system which allows this tankless water heater to work without a standing pilot, grid connection or battery! A small turbine inside the water heater uses the energy from the flowing water to ignite the burner. The modulating gas valve then maintains a constant temperature at varying flow rates. This innovative technology, patented by Bosch, makes this an ideal product for installations without access to electricity or regions prone to inclement weather and power outages.


  • Patented Hydro-power ignition requires no electricity
  • 80% thermal efficiency
  • 117,000 BTU maximum input
  • 5.3 gallons per minute capacity at 35F degree rise
  • Endless hot water for up to 2 applications at a time
  • Minimum activation flow rate of 0.5 gallons per minute
  • High to low temperature control
  • Vents with galvanized B vent – natural draft
  • Built for durability and serviceability with 15-year warranty and 20+ year life expectancy
  • Available in NG and LP models

    15 year
    limited warranty on heat exchanger.
    2 year warranty on all other parts.We service and provide replacement parts.


Therm 520 HNSpecifications
Max Input (BTU)117,000
Min Input (BTU)30,735
Capacity at 35°F Rise (gpm)5.2
Capacity at 55°F Rise (gpm)3.4
Intelligent CascadingNo
Min Flow Rate0.6 gpm
Temp Range (°F)n/a
Temp Stability (°F)n/a
Default Temp (°F)n/a
Energy Factor0.78
Thermal Efficiency80%
Installation OptionsIndoor
Dimensions (w x h x d)18½” x 36¾” x 10½”
Weight (lbs.)35
Inlet Connection½” NPT
Outlet Connection½” NPT
Gas Connection¾” NPT
Max Water Pressure150 psi
Min Water Pressure40 psi
Min LP Presure11″ WC
Condensing Heat Exchangern/a
Venting OptionsGalvanized B-Vent
Vent Maximun Runn/a
Energy Star RatedNo

Bosch Therm Tankless Water Heaters Brochure


Bosch Therm520HN Manual

Bosch Therm 520HN Replacement Parts 

We do not sell the venting required for these units but they are available at:

7959 Enterprise St, Burnaby, BC V5A 1V5
(604) 420-4323

Installation Guide for B-Venting