Heater not heating at all
A heater (element, band, or bank) produces no heat — temperature won't rise, the process stays cold, despite the control calling for heat.
Safety first
Heater circuits run at full load current and elements get very hot in normal use. Prove dead and allow cooling before touching. A 'cold' heater may still be live.
Isolate, lock out / tag out, and prove dead before working unless a live test is specifically required, authorised, and carried out under proper supervision. Always follow local regulations, your site procedures, and the equipment manufacturer's documentation.
Full detail — causes, the why, and common mistakes.
Likely causes
Ranked from most to least likely.
- 1
Open (burnt-out) element
Most likelyThe element has gone open circuit and can no longer draw current or produce heat.
- 2
No switching — SSR/contactor not conducting
#2The switching device isn't passing power to the element even when heat is called.
- 3
Controller not calling for heat
#3The temperature controller isn't outputting a demand (wrong setpoint, sensor reading high, controller fault).
- 4
Blown fuse / lost supply to the heater
#4A blown heater fuse or open supply removes power to the element.
- 5
Over-temperature safety cut-out tripped
Least likelyA high-limit thermostat or cut-out has operated and is holding the heater off.
Reports are saved on this device to reflect what you actually find.
Testing sequence
Work through one test at a time. Expected reading and what each result means.
Confirm the controller is calling for heat (demand output active, setpoint above measured temperature).
Controller calling for heat.
Heat is being called — check switching and supply downstream.
No demand — check setpoint, temperature sensor reading, controller.
View all expected readings at once
Fault-finding flowchart
The same logic as a decision tree.
- 1start
Heater not heating
→ step 2 - 2decision
Is the controller calling for heat?
Yes→ step 3No→ step 4 - 3decision
Is the switching device passing voltage to the element?
Yes→ step 5No→ step 6 - 4result
No demand — check setpoint, sensor reading, controller.
- 5result
Power reaches a cold element — element is open; replace it.
- 6decision
Are fuses intact and the over-temp cut-out not tripped?
Yes→ step 7No→ step 8 - 7result
Switching device/drive at fault — check the SSR/contactor and its control.
- 8result
Blown fuse / tripped cut-out — find why, then restore.
Common mistakes apprentices make
- Assuming the element when the controller isn't even calling for heat.
- Not checking the SSR/contactor is actually conducting.
- Overlooking a tripped high-limit cut-out.
- Replacing the element without finding why a fuse blew or a cut-out tripped.
When to stop & escalate
A tripped over-temperature cut-out indicates a previous over-heat event — find the cause (failed control/SSR) before resetting. Repeated element failures suggest a control or rating issue to review.
If you're past your competence, authorisation, or the safe limits of the job — stop and hand it on. There's no fault worth getting hurt over.
Related faults
Heater bank drawing uneven current across phases
A multi-element heater bank pulls noticeably different current on each phase. Heating is uneven, output is low, or a phase reads much lower than the others.
Solid-state relay (SSR) stuck on — heat won't switch off
A heater (or other SSR-driven load) stays on even when the controller commands it off. Temperature overshoots, or the load runs continuously regardless of the control signal.
SSR not switching on (load won't energise)
A solid-state relay won't turn its load on even when commanded — the heater/load stays off because the SSR isn't conducting.
Learn the theory
How the gear and circuits behind this fault actually work.