Navien NCB-240E Condensing Combination Water Heater/Boiler
Updated and improved NCB-E series combination boiler: Where Technology Meets Ecology
Heats water only when needed, making it environmentally sound and cost efficient.
Benefits of Hydronic Heating
→ Clean and comfortable: no air movement means low likelihood for creating dust or excessively dry air.
High turn down ratio reduces wasted energy and boiler cycling
→ The NCB's sophisticated gas flow control system provides a turn down ratio of 6:1 for heating and 11:1 for DHW. This reduces energy waste and excessive boiler cycling and enhances temperature control for domestic hot water use.
Ultra Condensing Efficiency
→ Navien's condensing technology allows high efficiency heating
Dual Stainless Steel Heat Exchangers
|Space Heating Specific Specs|
|Space Heating Gas Input, MBH||12,000-60,000||14,000-80,000||18,000-100,000||18,000-120,000|
|Heating Capacity, MBH
(US DOE test procedures)
Net AHRI Rating, Water, MBH
|AFUE (annual fuel utilization efficiency)||95%|
|Water pressure (hydronic)||12 to 30 PSI|
|Heating Supply/Return Connection||1" NPT|
|Domestic Hot Water ("DHW") Gas Input||12,000-120,000 BTU/H||14,000-150,000 BTU/H||18,000-180,000 BTU/H||18,000-199,900 BTU/H|
|Flow Rate that results in a 77°F (43°C) water temperature increase||2.6 GPM (9.8 L/m)||3.4 GPM (12.9 L/m)||4.0 GPM (15.1 L/m)||4.5 GPM (17.0 L/m)|
|Dimensions||17"(W) x 28"(H) x 12"(D)|
|Product Weight||66 lbs (30kg)||74 lbs (34kg)||84 lbs (38kg)||84 lbs (38kg)|
|Installation Type||Interior Wall-Hung|
|Venting Type||Forced Draft Direct Vent|
|Water Pressure (DHW)||15-150 PSI|
|Natural Gas Supply Pressure (from source)||3.5"-10.5" WC|
|Propane Gas Supply Pressure (from source)||8.0" to 13.5" WC|
|Natural Gas Manifold Pressure (min to max)||-0.08" WC to -0.34” WC||-0.07" WC to -0.66” WC||-0.05" WC to -0.36" WC||-0.06" WC to -1.2" WC|
|Propane Gas Manifold Pressure (min to max)||-0.08" WC to -0.30" WC||-0.06" WC to -0.62" WC||-0.1" WC to -0.66" WC||-0.03" WC to -0.98" WC|
|Minimum Flow Rate (DHW)||0.5 GPM (1.9 L/m)|
|DHW Inlet/Outlet Connection||3/4" NPT|
|Gas Inlet Connection||3/4" NPT|
|Auto Feeder Connection||1/2" NPT|
|Condensate Outlet Connection||1/2" NPT|
|Main Power Supply||120V AC, 60Hz|
|Maximum Power Consumption||200W (up to 2 amps)|
|Casing||Cold Rolled Carbon Steel|
|Heat Exchangers||Stainless Steel Primary, Secondary, and DHW Heat Exchanger|
|Exhaust Venting||2” or 3" PVC, CPVC, Polypropylene 2” or 3" Special Gas Vent Type BH (Class II, A/B/C)|
|Intake Venting||2” or 3" PVC, CPVC, Polypropylene 2” or 3" Special Gas Vent Type BH (Class II, A/B/C)|
|Vent Clearances||no required clearance distance to combustibles|
Water Temperature High Limit Switch, Ignition Operation Detector,
Installation & Operation Manual
User's Information Manual
Quick Installation Manual
Wall Mounting Bracket
Tapping Screws & Anchors
LP or NG Conversion Kit
2" Vent Termination Caps
2" Wall Flanges
Pressure Relief Valve for Heating
Spare Parts (fuse, etc.)
FAQ (Frequently Asked Questions)
Q1: What is the difference between the NCB-240 and the NCB-240E?
A1: The NCB-240E has five differences: It has an added integrated air vent on top of the internal circulator to purge air from the boiler system, a pressure release valve ("PRV") on the top of the unit, a Grundfos recirc pump, a quieter fan, and a more appealing, beveled design on the front cover.
Q2: I would like to buy this Navien heater to replace another water heater that uses metal vent pipe. I read the manual that describes various PVC products to use for venting. The manual does not state that metal should not be used. Are there any performance issues if I use my metal exhaust vent pipe and not the PVC type pipe?
A2: Yes, the reason for using PVC versus metal is for energy efficiency. Navien recommends using PVC because the NPE and NR heaters are condensing type heaters. Using PVC provides the maximum condensing function. The Navien heaters will run more efficiently with PVC.
Yes, you could use your metal venting instead of PVC; the heater will still work safely. Alternatively, you could install the PVC inside the metal venting, using the metal venting as a chase (like a conduit).
Q3: Does the NCB-240E ship from the factory configured for natural gas or propane?
A3: It comes configured for natural gas with an easy conversion kit to liquid propane included. Instructions: Gas Conversion Guide.
Q4: Are there separate heat exchangers for domestic hot water and radiant heat zones? Which heat exchanger has priority?
A4: The primary heat exchanger is used for heat (boiler function). The separate flat-plate heat exchanger is for DHW. The DHW function does have priority over heat in the combi units.
Installation Help and Recommendations
We recommend that you have a professional tankless water heater installer review the above recommendations. Improper installation may cause loss of life and/or property. Need an installer? Get 4 FREE Tankless Water Heater Installation Estimates Now. It's Quick and Easy!
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Alternate model number spelling: NCB240E
The NAVIEN and KD NAVIEN, and ComfortFlow trademarks are the property of Navien America, Inc. and/or KyungDong Navien.