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Navien NCB-240E Condensing Gas Combination Boiler (NCB)


  • Super condensing efficiency
  • Dual stainless steel heat exchangers
  • SCH40, 2″ PVC venting up to 60′
  • ½” Gas pipe up to 24′
  • Automatic water filling system
  • integrated controls

Ultra Condensing Efficiency

  • Navien’s Condensing Technology offers the high efficiency.
  • Money and energy savings over tank type water heaters 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

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

Where Technology Meets Ecology, Combination Boiler

  • The ideal solution for customers who need both domestic hot water and a space heating application.
  • Heats water when needed, making it environmentally sound as well as cost efficient.

Hydronic Heating Benefits

  • Clean: little chance to cause dust or lower humidity because there is no air movement.
  • Silent: offers silent heating because no blowers are needed for forced circulation.
  • Comfort: keeps floors warm but indoor air fresh, making people feel warm and comfortable.
  • Coverage: radiant heat makes heating from floor to ceiling possible.
  • Economical: radiant heat in the floors can transmit warmth throughout the house hours after turning off the heater.

Automatic Water Filling System

  • Automatically fills water into space heating pipes when the unit senses a water shortage.

Powerful Anti-Freeze Feature

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


  • Gas Input
    • Space Heating: 18,000–120,000 BTU/H
    • Domestic Hot Water: 18,000–199,900 BTU/H
  • AFUE: 95.0%
  • Flow Rate (DHW)
    • 77°F (43°C) Temp Rise: 4.5 GPM (17.0 L/m)
  • Dimensions: 17″(W) x 28″(H) x 12″(D)
  • Weight: 84 lbs (38kg)
  • Installation Type: Indoor wall-hung
  • Venting Type: Forced draft direct vent
  • Ignition: Electronic ignition
  • Water Pressure (Hydronic/DHW): 12–30 PSI /15–150 PSI
  • Natural Gas Supply Pressure (from source): 3.5″ –10.5″ WC
  • Propane Gas Supply Pressure (from source): 8.0″ –13.5″ WC
  • Natural Gas Manifold Pressure (min to max): -0.06″ WC / -1.20″ WC
  • Propane Gas Manifold Pressure (min to max): -0.03″ WC / -0.98″ WC
  • Minimum Flow Rate (DHW): 0.5 GPM (1.9 L/m)
  • Connection Sizes
    • Heating Supply/Return: 1″ NPT
    • DHW Inlet/Outlet: 3/4″ NPT
    • Gas Inlet: 3/4″ NPT
    • Auto Feeder: 1/2″ NPT
    • Condensate Outlet: 1/2″ NPT
  • Power Supply
    • Main Supply: 120V AC, 60Hz
    • Maximum Power Consumption: 200W (up to 2 amperes)
  • Materials
    • Casing: Cold rolled carbon steel
    • Heat Exchangers: Primary/secondary heat exchanger: stainless steel DHW heat exchanger: stainless steel
  • Venting
    • Exhaust: 2″ or 3″ PVC, CPVC, approved polypropylene 2″ or 3″ [special gas vent type BH (Class II, A/B/C)
    • Intake: 2″ or 3″ PVC, CPVC, polypropylene 2″ or 3″ specialty gas vent type BH (Class II, A/B/C)
    • Vent Clearances: 0″ to combustibles
  • Safety Devices
    • Flame rod, APS, gas valve operation detector, ignition operation detector, water temperature high limit switch, exhaust temperature high limit sensor