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Navien NFC-175 Fire-tube Condensing Combination Water Heater-Boiler

Original price $4,600.00 - Original price $4,695.95
Original price
$4,600.00 - $4,695.95
Current price $4,600.00

Current stock level: In stock as of
Ship out time: Within 1 business day.
Delivery time: 1 to 5 business days to most addresses

Navien's NFC-175 fire tube combination of boiler and tankless water heater

The NFC-175 packs an amazing array of advanced efficiency tech and features in one unit. You get:

• Patented stainless steel fire tube ASME Certified heat exchanger
• TDR of 10:1 for both boiler and domestic water heating
• 3 zone control built-in for pumps
• 2" or 3" plastic venting allows for long, low-cost venting runs (up to 60' for 2" or 150' with 3" venting)
• Cascade up to 16 NPE series water heaters using Communication Cables #GXXX000546. (Cascading NFC units not possible.) Common Venting for up to 8 NPE series units (not NFC units).
• Advanced, user-friendly control panel on the unit front
• 5 control modes for external domestic recirculation (Always On, Scheduling, Intelligent, HotButton, Aquastat)
• AFUE efficiency rating of 95%
• 2019 Energy Star "Most Efficient" Certification

It's the ideal solution for people who need both a space heating application and a domestic hot water heater.


Benefits of Hydronic Heating

Allergy sufferers rejoice! With hydronics, there is no forced air through vents, and meaning no dust creating or dry air blowing around.
Silent: silent heating, and no air blower motors are used.
Comfort: Your feet and body feel warm and comfortable when the floor is warm and air is warmed by the warmth gently rising through the air.
Coverage: Get heat from the floor to the ceiling.
Economical: Radiant heat from the floor continues to send warmth throughout the house even hours after turning off the unit.

The NFC-175 can be used in all of these hydronic heating applications:

♥ Baseboard heating
♥ Radiators
♥ Radiant floor heating
♥ Air handler and fan coil


High turn down ratio reduces wasted energy and boiler cycling

→ The NFC's sophisticated gas flow control system provides a turn down ratio of 10:1 for heating and 10:1 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
→ Significant energy savings over traditional water heaters

Dual Stainless Steel Heat Exchangers
Plus, waterways are all stainless steel. Fittings and components are brass or polypropylene.

→ Longer life expectancy than copper heat exchangers. More resistant to corrosion.
→ Less mineral scaling and deposits

Low-nox-emissionsLow NOx Emissions

→ New metal fiber burner delivers a consistent gas/air mixture
→ Less greenhouse gas emissions and acid rain
→ SCAQMD 1146.2 compliant

2" PVC, CPVC, Polypropylene Venting

→ 2" vent allows you to install a flue through an existing vent
→ Schedule 40 2" venting up to 60 feet, but with no elbows
→ 3" vent can be used up to 150' on standard 2" x 3" adapters, but with no elbows

Uses Existing 1/2" Gas Line

→ Dual venturi fan and negative pressure gas valve for better adaptability with low gas pressure
→ Installation in 1/2" gas lines up to 24 feet

Field LP/NG Convertible

→ Allows easy conversion from/to natural gas and liquid propane. Important: Navien heaters are shipped ready for natural gas. For easy conversion to liquid propane, consult the Gas Conversion Guide.

Low gas pressure operation

→ Navien's innovative negative pressure gas valve ensures normal operation even with a low gas pressure of 3.5" of water column.

Automatic Water Filling System

→ Automatically fills the space heating pipes with water when the unit senses water shortage.

Internal Circulation Pump Included

→ Primary circulation pump and air vent for added value and convenience

Powerful Anti-Freeze Feature

→ Built-in Control System prevents the water inside unit from freezing in winter under most non-severe conditions.

Backlit LED Front Panel Command Center

→ Allows you to adjust the hot water temperature and boiler functions such as outdoor reset curve settings, pump operation, safety control with low water volume, indirect DHW priority, and unit output capacity.

• Easy setup
• Self-diagnostics
• User friendly interface
• Convertible display from °F (Fahrenheit) to °C (Celcius)
• Cascade operation status display
• Temperature and water flow rate indicator


→ ASME, AHRI, CSA. NSF/ANSI 372 for Low Lead (DHW only). SCAQMD Rule 1146.2 Type 1 which complies with 14 ng/J or 20 ppm NOx at 3% O2.

asme-logo NSF logo ahri-seal CSA-certified


NFC-175 (this page) NFC-200
Space Heating Specific Specs
Space Heating Gas Input, BTU per hour 18,000-175,000 18,000-199,900
Heating Capacity, MBH
(US DOE test procedures)
161,000 183,000

Net AHRI Rating, Water Heating, MBH
(based on piping and pickup allowance of 1.15)

140,000 159,000
AFUE (annual fuel utilization efficiency) 95%
Water pressure (hydronic) 12 to 80 PSI
Radiant heating Supply/Return Connection 1.25" NPT
More Specifications
Domestic Hot Water ("DHW") Gas Input, BTU per hour 18,000-199,900
Flow Rate that results in a 67°F water temperature increase 5.4 GPM (20.44 L/M)
Dimensions 17.3"(W) x 33.3"(H) x 17.3"(D)
(43.9cm (W) x 85.1cm (H) x 43.9cm (D)
Product Weight 145 lbs (65.8kg)
Weight with water 183 lbs (83kg)
Installation Type Interior Wall-Hung
Venting Type Forced Draft Direct Vent
Ignition Electronic Ignition
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) -0.05" WC to -0.47” WC
Propane Gas Manifold Pressure (min to max) -0.1" WC to -0.45" WC
Minimum Flow Rate (DHW) 0.5 GPM (1.9 L/M)
Maximum Flow Rate (DHW) 5.6 GPM
Radiant heating Supply/Return Connection 1.25" NPT
DHW Cold Water Inlet 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 less than 15 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
Safety Devices

Water Temperature High Limit Switch, Water Pressure Sensor, Ignition Operation Detector, Flame Rod, APS, Exhaust Temperature High Limit Sensor


Installation & Operation Manual

Gas Conversion Guide

Valuable Accessories Included FREE from GadgetsGo

Pressure relief valve for radiant heating
Outdoor temperature sensor & cable (part # 30012950A)
System temperature sensor (part # GXXX001769)
Air vent
Air vent bushing (1/4" to 1/2")
PRV-Air vent adapter (including a clip)
Condensate trap
2" Vent termination caps (x2)
2" in-wall flanges (x4) (part # 30010747A)
Wall mounting bracket
Tapping screws & anchors (x2)

FAQ (Frequently Asked Questions)

Q1: 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?
A1: Yes, the reason for using PVC versus metal is for energy efficiency. Navien recommends using PVC because the NFC 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).

Q2: Does the NFC-175 ship from the factory configured for natural gas or propane?
A2: It comes configured for natural gas with an easy conversion kit to liquid propane included. Instructions: Gas Conversion Guide.

Q3: Are there separate heat exchangers for domestic hot water and radiant heat zones? Which heat exchanger has priority?
A3: 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.

Q4: Can I use my existing, standard thermostat with this boiler? I have only one zone baseboard heaters. My thermostat has only 2 wires.
A4: Yes, many customers have used their existing 2-wire thermostat with new Navien NFC combi boilers. This is normal.

Q5: Can I use a glycol mix in the radiant loop with this combi-boiler? I believe the radiant loop and running water output are not mixed, but wanted to be sure.
A5: Correct, the radiant loop and domestic water heating output are completely isolated, and you can use a glycol mix in the hydronic radiant loop.

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: NFC175

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