HTP · Boiler

TT Temperature blocking - thermostat (TT) demand

Normal status Elite EL

What the display is showing

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)

Good to know

Supply sensor reads higher than Central Heat setting minus Central Diff setting when the TT call arrives.

What to do

Compare the SUPPLY reading with CH set point minus the differential
Wait until the supply water drops below that value; the message clears by itself

Models that show this code

12 models in Elite EL

EL-110 LPEL-110 NEL-150 LPEL-150 NEL-220 LPEL-220 NEL-299 LPEL-299 NEL-399 LPEL-399 NEL-80 LPEL-80 N

Other codes on the same units

GAS VALVE ON / RUN Ignition then run status
LOCKOUT Lockout (display message)
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

Save it for the next call

Star this code in the HVACopedia app and keep the whole library on your phone for jobs with no signal.

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Source: Elite EL-80 N Installation Manual (LP-293), p. 66. Summarized in our own words; check the original manual for your model.

For licensed technicians. Gas, electrical and refrigerant work must be done by a qualified, licensed person. Shut off power and gas before servicing, never bypass a safety control, and follow the manufacturer’s manual for the exact model; it and local codes always take priority. HVACopedia is not affiliated with any manufacturer; brand and model names only identify the equipment.