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ErrBase

Noritz Code 29: Heat Exchanger High Limit Exceeded

Quick Answer

Noritz Code 29 means the heat exchanger exceeded its safe temperature limit. This is a recoverable fault - the unit shut down but no components are consumed. The most common cause is scale buildup on the interior heat exchanger walls that reduces the efficiency of heat transfer from the burner to the water.

Noritz Code 29 means the heat exchanger exceeded its safe temperature limit. This is a recoverable fault - the unit shut down but no components are consumed. The most common cause is scale buildup on the interior heat exchanger walls that reduces the efficiency of heat transfer from the burner to the water. The water does not absorb enough heat, so the metal overheats instead. Low water flow rate through the unit has the same effect. On condensing NRCP models, a blocked condensate trap can also reduce flow enough to trigger Code 29. Address Code 29 promptly - repeated trips lead to Code 14 (thermal fuse blown).

NoritzWaterheaterSeverity: highDifficulty: intermediate80% DIY Success
Time to Fix
45–180 min
Difficulty
intermediate
Parts Cost
$5 – $45
Tools Needed
Phillips screwdriver, Multimeter
Wrong code?

Not seeing 29 on your display?

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

error code on display
HUB
thermal fuse blown
14
condensate drainage issue
CONDENSATE-DRAIN
error code on display
RESET

What Does the 29 Code Mean?

Heat exchanger overtemp fault. Recoverable, but repeated trips lead to Code 14 (blown thermal fuse). Descaling and flow rate check required.

Most Likely Causes

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

Scale buildup on heat exchanger walls restricting water-side heat transfer40%
Water flow rate too low through the unit24%
NTC temperature sensor reading high (false positive)22%
Blocked condensate trap on NRCP condensing models14%

Symptoms You May Notice

  • Code 29 on controller display
  • Unit shuts off after several minutes of operation
  • Hot water stops mid-shower or mid-use
  • Code 29 recurring multiple times per day

Can you reset a Noritz waterheater to clear the 29 code?

Press the power button off, wait 30 seconds, then press on. Allow the unit to cool for 5 to 10 minutes before restarting if it has been tripping repeatedly. Code 29 will clear with a reset, but the underlying cause must be fixed or the code will return.

Tools Required for Diagnosis

Phillips screwdriverMultimeterSubmersible pump (descaling)5-gallon bucketBucket and timer (flow rate test)

Diagnostic Checklist

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

1

Perform one soft reset (power off 30 seconds, power on)

Perform one soft reset (power off 30 seconds, power on). Check if Code 29 returns within the first 5 minutes of operation with a fully open fixture.

2

Check water flow rate through the unit

3

On NRCP condensing models, inspect the condensate trap

4

Check the unit's maintenance history

5

If Code 29 continues after descaling

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
NTC Temperature Sensor100163938 · $20–$45
Condensate Trap100062581 · $15–$40
Inlet Filter Screen100113571 · $5–$15

Repair vs. Replace Calculator

Appliance Age (Years)7 Yrs
Labor Approach
Our Verdict
REPAIR
Estimated Cost: $25 (Parts) vs $1150 (New Machine)

Frequently Asked Questions

What is the Code 29 temperature threshold on a Noritz?
Noritz Code 29 trips when the heat exchanger outlet temperature exceeds approximately 160 to 180 degrees F (71 to 82 degrees C), depending on the model and software version. The exact threshold is calibrated to the unit's safe operating range.
Can I keep resetting Code 29 until I get a technician?
You can reset it once and use the unit conservatively at reduced temperature settings to minimize heat exchanger stress. Do not repeatedly force resets while running the unit at full demand. Each overtemp event degrades the thermal fuse. If the code trips more than twice in a day, stop using the unit.
How is Noritz Code 29 different from Code 14?
Code 29 is a recoverable shutdown - the heat exchanger got too hot and the unit shut off, but no components were permanently damaged. Code 14 means the one-time thermal fuse physically opened. Code 29 is the warning. Code 14 is the consequence of ignoring Code 29.
How often should I descale to prevent Code 29?
In areas with water hardness above 11 GPG (grains per gallon), annual descaling is recommended. Below 7 GPG, every 2 to 3 years is typical. You can confirm water hardness with a $10 test strip kit from a hardware store or by contacting your water utility.
Can a clogged condensate trap cause Code 29 on a Noritz NRCP?
Yes, on condensing NRCP models. The condensate trap is part of the heat exchanger drainage circuit. When it blocks, condensate backs up into the lower heat exchanger section, restricting water flow through that section and causing localized overheating. Clearing the trap resolves Code 29 in this scenario without requiring descaling.

Related Noritz Waterheater Error Codes

Code: HUBNoritz Tankless Water Heater Error Codes: Complete NR and NRCP Series GuideCode: 14Noritz Code 14: Thermal Fuse Blown - Overheating FaultCode: CONDENSATE-DRAINNoritz Tankless Water Heater Condensate Drain: Blockage Codes and FixesCode: RESETHow to Reset a Noritz Tankless Water Heater and Clear Error Codes

Models Known to Experience 29 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