Condensing Gas Boiler – NHB-55

Max Input : 55,000 BTU/H
Indoor Only
Residential / Commercial

  • Super condensing efficiency
  • Dual stainless steel heat exchangers
  • SCH40, 2” PVC venting up to 60’
  • ½” Gas pipe up to 24’
  • TDR up to 7:1
  • integrated controls


Ultra Condensing Efficiency

  • Navien’s Condensing Technology offers the high efficiency.
  • Money and energy savings over other boilers and traditional water heaters.

Two Stainless Steel Heat Exchangers

  • Provides longer life expectancy as they are highly resistant to corrosion and erosion compared to copper heat exchangers.
  • Reduces minerals deposits.

Low NOx Emissions (≤ 20ppm)

  • New metal fiber burner is designed to deliver a consistent air/gas mixture improving combustion efficiency.
  • Result in less acid rain and less green house effect.
  • Comply with SCAQMD 1146.2 strict NOx emissions standard.

2” PVC, CPVC, Polyprophylene Venting Up To 60’

  • 2” venting option allows for a flue to be pulled through the existing vent.
  • 3” vents can be used up to 150’ with standard 2” x 3” adapters.

Utilizes Existing 1/2″ Gas Line

  • The negative pressure gas valve and fan with dual venturi operation allows for better adaptability to low gas pressure applications.
  • Makes it possible for the NPE to be installed ½” gas lines up to 24’.

Field Convertible

  • NHB models allow for easy convertibility from NG to LP.

Hydronic Heating Benefits

  • Clean / Silent / Comfort / Economical

Powerful Anti-Freeze Feature

  • The Boiler's built-in Control System is designed to keep the unit's plumbing frost free in winter conditions.

TDR up to 7:1

  • Navien’s NHB series has a TDR up to 7:1 that helps eliminate short cycling


Data Field NHB-55
Dimensions 24in. (H) x 17in. (W) x 12in. (D)
Weight 73 lb (33 kg)
Installation Type Indoor Wall-Hung
Venting Type Forced Draft Direct Vent
Ignition Electronic Ignition
Natural Gas Supply Pressure (from source) 3.5 in.–10.5 in. WC
Propane Gas Supply Pressure (from source) 8.0 in.–13.5 in. WC
Natural Gas Manifold Pressure -0.03 in. WC
Propane Gas Manifold Pressure -0.03 in. WC
Gas Connection Size 3/4 in. NPT (female)
Power Supply Main Supply 120V AC, 60Hz
Maximum Power Consumption Less than 10A
Materials Casing Cold-rolled carbon steel
Heat Exchangers Primary and Secondary: Stainless Steel
Venting Exhaust 2 in. or 3 in. PVC, CPVC, approved polypropylene* 2 in. or 3 in. Special Gas Vent Type BH (Class III, A/B/C)
Intake 2 in. or 3 in. PVC, CPVC, polypropylene 2 in. or 3 in. Special Gas Vent Type BH (Class III, A/B/C)
Vent Clearance 0 in. to combustibles
Safety Devices Flame Rod, APS, Gas Valve Operation Detector, Ignition Operation Detector Water Temperature High Limit Switch, Exhaust Temperature High Limit Sensor

Spec Sheet