Start here — before replacing any parts
If the heater cuts out hot, stop repeated restart attempts until fuel, air-path and protective shutdown conditions are known.
Hcalory has published conflicting E-code descriptions across heater and controller editions. These pages are research drafts until the TB2S controller-code table is confirmed.
Manual scope: Combustion/exhaust safety; no DIY component bypasses
Do these checks in order
Follow the steps below and keep a record of what changes after each one. Stop when an actual cause is confirmed.
Allow the programmed cool-down to finish; never block the exhaust or cover the air intake. If anyone experiences headache, dizziness or a CO alarm sounds, turn off if safe and move to fresh air immediately.
Once cool, inspect the installation for blocked warm-air outlets, crushed intake ducts, restricted combustion exhaust, and nearby combustible material—without opening the burner.
Check the supply voltage, fuel level and any specific alarm indication against the exact controller manual; do not assume every auto-stop means overtemperature.
Remove only a verified external obstruction consistent with the original installation instructions; otherwise obtain a technician’s assessment of the fan, sensor and combustion system.
If the problem is gone
An obvious outlet restriction is corrected and an authorized single test cycle runs normally: continue monitoring and keep clearances.
If the problem is still there
Shutdown repeats or any fume/CO concern exists: do not continue use, bypass a thermal cutoff or modify the burner.
Which cause matches your result?
Use these more specific checks only when the earlier steps point to that possibility.
01An over-temperature shutdown may be in progress
Watch for the normal cooling cycle; check whether the installation and intake/exhaust environment are unobstructed.
Keep the required power available for the approved cooldown. Never bypass thermal protection.
02It overheats again
Do not assume any one internal part is at fault.
Stop using the heater and request an installation and combustion-system safety inspection.
How can I tell it is actually fixed?
One correctly vented supervised cycle must reach normal heat, sustain output and complete its automatic cool-down.
Before buying a replacement part
Any overtemperature protection/CO accessory variant must be identified from the actual TB2S model.
Where this guidance comes from
Primary reference: View the manufacturer or manual reference ↗
Applicability: Combustion/exhaust safety; no DIY component bypasses. Source evidence: Symptoms in research; specific root cause not established.
The instructions are original English troubleshooting explanations derived from the listed technical facts; they are not a verbatim service manual. Do not apply them to an unverified revision.
Important limitation: This is a safety-first symptom diagnosis, not proof of a specific failed sensor.
Editorial hold: The exact fault-code meaning, controller edition, part specification or root cause remains incompletely verified. This page is NOT approved for public indexing as a confirmed repair procedure.