HTP Error Code TT: Temperature blocking – thermostat (TT) demand (Boiler)
HTP error code TT on a boiler means: Temperature blocking - thermostat (TT) demand. It is also called HTP diagnostic code TT.
Homeowner? What HTP code TT means for you
Check, then call Your boiler is reporting: Temperature blocking - thermostat (TT) demand. 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 HTP error code TT mean?
Thermostat call is present and the pump runs, but the supply water is too hot for the boiler to ignite.
Applies to: EL-80, EL-110, EL-150, EL-220, EL-299, EL-399 (N/LP)
Common causes of HTP code TT
- Supply sensor reads higher than Central Heat setting minus Central Diff setting when the TT call arrives.
HTP models that use code TT
EL-80 LPEL-80 NEL-110 LPEL-110 NEL-150 LPEL-150 NEL-220 LPEL-220 NEL-299 LPEL-299 NEL-399 LPEL-399 N
Other HTP Boiler codes
| Code | Meaning |
|---|---|
| LOU | 24 volt supply low |
| MAINTENANCE REQUIRED | Service reminder |
| PP | Control programmed |
| PRO | Low water pressure |
| SERVICE PUMP CH / DH / SH | Pump service mode |
| SERVICE RUN | Test mode running |
HTP code TT: homeowner questions
What does HTP code TT mean?
Temperature blocking - thermostat (TT) demand. Thermostat call is present and the pump runs, but the supply water is too hot for the boiler to ignite.
Is it safe to keep using my boiler with code TT?
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 HTP code TT myself?
You can try one reset (power off for 30 seconds, then on). If HTP code TT comes back, the cause is still there and a licensed technician should check it.
Who can fix HTP code TT near me?
Aurora Star Tech Inc. repairs HTP 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
- Condensing/corrosion of conventional boiler All brands · Boiler
- No heat or some zones cold All brands · Boiler
- Noise All brands · Boiler
- Poor heat / circulation All brands · Boiler
- Relief valve weeps every cycle / pressure climbs All brands · Boiler
- Short cycling / wasted fuel All brands · Boiler
- Symptoms of air in system All brands · Boiler
- Uneven heating All brands · Boiler
- Won't fire All brands · Boiler
- Boiler overheating lockout (F00, F05, F06) HTP · Boiler
- Cascade set-up HTP · Boiler
- Check thermostat circuit for stray voltage HTP · Boiler
- False flame signal with burner off (F11) HTP · Boiler
- Fan speed error (F13) HTP · Boiler
- Flame drops out while running (F10) HTP · Boiler
- Lockout on ignition (F09, no flame) HTP · Boiler
- Menu access codes HTP · Boiler
- Pump service mode to purge air HTP · Boiler
- Read fault history HTP · Boiler
- Reset a lockout HTP · Boiler
- Reset the maintenance reminder HTP · Boiler
- Start-up combustion and gas checks HTP · Boiler
- Test mode (fixed-fire, gas pressure and combustion) HTP · Boiler
- Thermostat calling but boiler not firing HTP · Boiler
Source: Elite EL-80 N Installation Manual (LP-293), p. 66. 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.