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NTI Error Code Hold 49: 24VAC voltage low/high (Boiler)

Updated · by Aurora Star Tech Inc.

NTI error code Hold 49 on a boiler means: 24VAC voltage low/high. It is also called NTI diagnostic code Hold 49.

Medium severityBoilerAlso BoilerTrinity Tft

Homeowner? What NTI code Hold 49 means for you

Check, then call Your boiler is reporting: 24VAC voltage low/high. This is often caused by something simple. Try the safe checks below; if the code returns, book a service call before it turns into a no-heat or no-hot-water emergency.

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 Hold 49 mean?

24VAC voltage low/high.

Applies to: Trinity Tft60, Tft85, Tft110, Tft155, Tft175, Tft200, Tft250, Tft300, 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 Hold 49

Tft60Tft60Tft85Tft85Tft110Tft110Tft154Tft155Tft175Tft200Tft201Tft250Tft285Tft300Tft340Tft399Tft399

Other NTI Boiler codes

CodeMeaning
Hold 31Internal fault: SLO electronics unknown error
Hold 31Internal fault: SLO electronics unknown error
Hold 47Flame rod to ground leakage
Hold 47Flame rod to ground leakage
Hold 48Static flame (not flickering)
Hold 48Static flame (not flickering)
Hold 4924VAC voltage low/high
Hold 50Modulation fault
Hold 50Modulation fault
Hold 51Pump fault
Hold 51Pump fault
Hold 52Motor tachometer fault

All NTI Boiler error codes →

NTI code Hold 49: homeowner questions

What does NTI code Hold 49 mean?

24VAC voltage low/high. 24VAC voltage low/high.

Is it safe to keep using my boiler with code Hold 49?

It depends on the cause. This is often caused by something simple. Try the safe checks below; if the code returns, book a service call before it turns into a no-heat or no-hot-water emergency.

Can I reset NTI code Hold 49 myself?

You can try one reset (power off for 30 seconds, then on). If NTI code Hold 49 comes back, the cause is still there and a licensed technician should check it.

Who can fix NTI code Hold 49 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 Tft60-399 Installation and Operation Instructions (rev. 2012-04-09), Sec. 15.0 Troubleshooting, Table 15-3. 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