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ErrBase

Noritz Code 20: Combustion Fan Motor Failure

Quick Answer

Noritz Code 20 means the combustion fan motor failed or could not reach the required speed. The fan is responsible for drawing in combustion air and pushing exhaust gases through the vent. Without it the unit will not ignite or will shut down immediately after ignition.

Noritz Code 20 means the combustion fan motor failed or could not reach the required speed. The fan is responsible for drawing in combustion air and pushing exhaust gases through the vent. Without it the unit will not ignite or will shut down immediately after ignition. The most common causes are motor bearing failure in older units, a foreign object blocking the fan wheel, or failure of the fan speed sensor. Code 20 almost always requires a professional technician because fan motor access involves disassembling the combustion chamber.

NoritzWaterheaterSeverity: highDifficulty: advanced82% DIY Success
Time to Fix
60–150 min
Difficulty
advanced
Parts Cost
$25 – $160
Tools Needed
Phillips screwdriver, Multimeter
Wrong code?

Not seeing 20 on your display?

Select what your appliance is actually doing and we'll take you to the right guide.

error code on display
HUB
combustion fault
90
error code on display
RESET

What Does the 20 Code Mean?

Combustion blower fan failed or cannot reach required speed. Professional repair typically needed for motor or fan speed sensor replacement.

Most Likely Causes

Based on aggregated repair data, here is the probability breakdown for this error code:

Fan motor bearing failure from age or moisture40%
Fan speed sensor failing to report correct RPM24%
Control board output circuit to fan motor failed22%
Foreign object or debris blocking the fan wheel14%

Symptoms You May Notice

  • Code 20 on controller display
  • Unit does not ignite and no fan noise is heard
  • Unusual grinding or squealing noise from unit before shutdown
  • Unit turns on briefly, fan starts, then Code 20 appears

Can you reset a Noritz waterheater to clear the 20 code?

Press the power button off, wait 30 seconds, then press on. If Code 20 appears again immediately or the fan still does not spin, a mechanical or electrical fault exists that a reset cannot clear. Schedule service.

Tools Required for Diagnosis

Phillips screwdriverMultimeterFlashlightCombustible gas detector

Diagnostic Checklist

Follow these steps in order. We start with the easiest external fixes before opening up the machine.

1

Listen when the unit starts up

Listen when the unit starts up. You should hear the fan motor spin up before ignition. If no fan noise is heard at all, the motor is not receiving power or has seized. If you hear the fan but it sounds rough or grinds, motor bearings are failing.

2

Inspect the exterior air intake termination for visible

3

With power off

4

With a technician

5

If the motor spins freely and the speed sensor is good

Replacement Parts

If your diagnostic testing proves the component has failed, you will need a replacement. We recommend OEM parts over aftermarket for water-handling components.

Part Name
Combustion Fan / Blower Assembly100073060 · $80–$160
Fan Speed Sensor (Tachometer)100073039 · $25–$55

Repair vs. Replace Calculator

Appliance Age (Years)7 Yrs
Labor Approach
Our Verdict
REPAIR
Estimated Cost: $93 (Parts) vs $1150 (New Machine)

Frequently Asked Questions

What does the combustion fan do in a Noritz tankless water heater?
The combustion fan (blower) serves two functions: it draws fresh air into the burner chamber for combustion, and it pushes exhaust gases out through the vent pipe. Without the fan, the unit cannot maintain safe combustion conditions and will not ignite or will immediately shut down.
How much does a Noritz fan motor replacement cost?
Expect to pay $200 to $450 for a fan motor replacement including labor. The fan assembly itself (OEM) is typically $80 to $160. Labor is 1 to 2 hours. If the control board is also found to be faulty, total repair cost can approach $600 to $800.
Can I replace the Noritz fan motor myself?
Fan motor replacement is rated advanced difficulty. It requires disassembling the combustion chamber, working near exhaust components, and correctly reassembling the sealed venting system. A gas pressure test is needed after reassembly. This repair is strongly recommended for a licensed plumber or Noritz service technician.
Why does Code 20 appear on a unit that is only 4 years old?
Premature fan motor failure is often linked to moisture intrusion, especially on outdoor-installed units or units in high-humidity environments. Insects building nests in the air intake can also cause the fan wheel to bind. Confirm the intake screen is in place and intact and that the unit has weatherproof installation.
Will a Noritz with Code 20 produce carbon monoxide?
A unit showing Code 20 shuts down immediately - it does not produce CO while shut down. However, do not attempt to bypass the fault or force the unit to run without a working fan. Running combustion without adequate airflow creates dangerous CO levels and will damage the heat exchanger.

Related Noritz Waterheater Error Codes

Code: HUBNoritz Tankless Water Heater Error Codes: Complete NR and NRCP Series GuideCode: 90Noritz Code 90: Combustion Abnormality or Exhaust RecirculationCode: RESETHow to Reset a Noritz Tankless Water Heater and Clear Error Codes

Models Known to Experience 20 Errors

This repair applies to most Noritz waterheaters with this error code. Common model numbers include:

NRCP199-DV, NRCP111-DV, NR98-DV, NR66-DV, NR711

Last verified for technical accuracy on March 14, 2026