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NTI Error Code Alert 99: CH max modulation rate was > absolute max rate (Boiler)

Updated · by Aurora Star Tech Inc.

NTI error code Alert 99 on a boiler means: CH max modulation rate was > absolute max rate. It is also called NTI diagnostic code Alert 99.

Low severityBoilerTrinity Tft

Homeowner? What NTI code Alert 99 means for you

Usually minor Your boiler is reporting: CH max modulation rate was > absolute max rate. This code is usually informational or minor. The safe checks below often clear it; call us if it keeps showing up.

Safe things you can check yourself

  • Check the thermostat: right mode (Heat or Cool), set a few degrees past room temperature, and fresh batteries if it uses them.
  • Make sure the unit has power: its on/off switch (often looks like a light switch near the unit) is ON and the breaker in the electrical panel is not tripped.
  • Look at the pressure gauge on the boiler. If it reads much lower than usual or near zero, or water is leaking, call a technician.
  • Outside, make sure the intake and exhaust pipes or vent cap are not blocked by snow, ice, leaves or a nest.
  • Check that the boiler gas valve is open (handle in line with the pipe).
  • Try one reset: turn the power off for 30 seconds, then back on. If the code comes back, stop resetting and call a technician.

Call (647) 657-2977Book a service call

Licensed technicians serving Vaughan, Toronto and the GTA.

What does NTI error code Alert 99 mean?

CH max modulation rate was > absolute max rate.

Applies to: Trinity Tft60, Tft85, Tft110, Tft154, Tft201, Tft285, Tft340, Tft399

Safety: Gas, electrical and refrigerant work must be done by a licensed technician. Turn off power and gas before servicing, never bypass a safety control, and always follow the manufacturer's manual for your exact model.

NTI models that use code Alert 99

Tft60Tft60Tft85Tft85Tft110Tft110Tft154Tft155Tft175Tft200Tft201Tft250Tft285Tft300Tft340Tft399Tft399

Other NTI Boiler codes

CodeMeaning
Alert 96Slow start was ended due to outlet sensor fault
Alert 97Slow start was end due to reference set point fault
Alert 97Slow start was end due to reference set point fault
Alert 98CH max modulation rate was invalid, % vs. RPM
Alert 98CH max modulation rate was invalid, % vs. RPM
Alert 99CH max modulation rate was > absolute max rate
Alert 100CH modulation range (max minus min) was too small (< 4% or 40 RPM)
Alert 100CH modulation range (max minus min) was too small (< 4% or 40 RPM)
Alert 101DHW max modulation rate was invalid, % vs. RPM
Alert 101DHW max modulation rate was invalid, % vs. RPM
Alert 102DHW max modulation rate was > absolute max rate
Alert 102DHW max modulation rate was > absolute max rate

All NTI Boiler error codes →

NTI code Alert 99: homeowner questions

What does NTI code Alert 99 mean?

CH max modulation rate was > absolute max rate. CH max modulation rate was > absolute max rate.

Is it safe to keep using my boiler with code Alert 99?

Usually yes. Code Alert 99 is normally minor, but if it keeps coming back have it checked.

Can I reset NTI code Alert 99 myself?

You can try one reset (power off for 30 seconds, then on). If NTI code Alert 99 comes back, the cause is still there and a licensed technician should check it.

Who can fix NTI code Alert 99 near me?

Aurora Star Tech Inc. repairs NTI boilers in Vaughan, Toronto and across the GTA. Call (647) 657-2977 or book a service call online.

Homeowner help: Boiler Not Heating: What to Check

Troubleshooting guides

Source: NTI Trinity Tft399 Installation and Operation Manual (2018-09-07), Sec. 16.0 Troubleshooting, Table 16-4. Written in our own words as a summary; always check the original manual.

General guidance for qualified technicians. The manufacturer's installation and service manual and local codes always take priority. Aurora Star Tech is not affiliated with, endorsed by or sponsored by any equipment manufacturer; brand and model names are used only to identify equipment and belong to their owners.

© 2026 Aurora Star Tech Inc. All rights reserved. This page may not be copied, republished or used to train other systems without written permission.

Emergency Boiler Repair

647-657-2977