Navien Error Code △T High – No. of Times: EMS Data counter 10 (Boiler)

Updated October 16, 2026 · by Aurora Star Tech Inc.

Navien error code △T High - No. of Times on a boiler means: EMS Data counter 10. It is also called Navien diagnostic code △T High - No. of Times.

Low severityBoilerNavien NHB-H

Homeowner? What Navien code △T High - No. of Times means for you

Usually minor Your boiler is reporting: EMS Data counter 10. 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) 657-2977 Book a service call

Licensed technicians serving Vaughan, Toronto and the GTA.

What does Navien error code △T High - No. of Times mean?

History counter: number of times combustion stopped because of the supply/return temperature difference. Read-only information in the EMS Data list (item 10).

Applies to: NHB-055H, NHB-080H, NHB-110H, NHB-150H

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.

Navien models that use code △T High - No. of Times

NHB-055H NHB-080H NHB-110H NHB-150H

Other Navien Boiler codes

Code	Meaning
Tank Sensor Temp	Status Information item 13 - Tank Sensor Temp
Water Press	Status Information item 14 - Water Press
Zone2 Pump Status	Input/Output Status item 7 - Zone2 Pump Status
Zone V/V 1 Status	Input/Output Status item 9 - Zone V/V 1 Status
Zone V/V 2 Status	Input/Output Status item 10 - Zone V/V 2 Status
Zone V/V 3 Status	Input/Output Status item 11 - Zone V/V 3 Status
△T Limit - No. of Times	EMS Data counter 8

All Navien Boiler error codes →

Navien code △T High - No. of Times: homeowner questions

What does Navien code △T High - No. of Times mean?

EMS Data counter 10. History counter: number of times combustion stopped because of the supply/return temperature difference. Read-only information in the EMS Data list (item 10).

Is it safe to keep using my boiler with code △T High - No. of Times?

Usually yes. Code △T High - No. of Times is normally minor, but if it keeps coming back have it checked.

Can I reset Navien code △T High - No. of Times myself?

You can try one reset (power off for 30 seconds, then on). If Navien code △T High - No. of Times comes back, the cause is still there and a licensed technician should check it.

Who can fix Navien code △T High - No. of Times near me?

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

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Source: Navien NHB-H Installation and Operation Manual, 11.11, p.108-109. 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.