LC on a Grant heat pump: Anti Legionella Function Not completed
Short answer
On a Grant heat pump, LC means: Anti Legionella Function Not completed. The heat pump keeps running. An engineer is needed to fix the cause.
Reviewed 23 September 2026 · 2 sources
What it means
The manual says: Anti Legionella Function Not completed.
Part involved: anti-legionella (DHW pasteurisation) cycle.
When it shows: Chofu footnote (*3): alarm resets automatically when the anti-legionella function has completed.
Likely causes:
- DHW used during anti-legionella cycle.
- Clogged water pump and/or water circuit.
- Heat source setting failure.
Is it safe?
| Does the heat pump stop? | No |
|---|---|
| Severity | Fault — clears by itself when the condition goes |
| Engineer needed? | Yes |
The heat pump keeps running.
Resetting itself: Yes (Chofu 'Auto').
Manual reset: Engineer: press - and + on the master remote controller for 3 s, or Reset SW on PCB(Terminal).
What you can check
- Note the exact code shown on the controller display and tell your installer or Grant-trained engineer.
- Grant advises homeowners NOT to reset Aerona3 fault codes themselves - leave the reset to the engineer.
- Check the controller/thermostat and timer settings are as normal.
What the engineer will check
- Check if DHW was used during anti-legionella; restart and avoid heavy DHW use during the cycle.
- Check the pump and water circuit; clean filter.
- Check parameters and heat source; correct settings or replace heat source.
Who to ask for: Grant-trained heat pump engineer.
What you might notice
What owners and engineers report
1 owner and engineer report mentions this.
- Hot water not hot enough on the Aerona³ R32: 1 report
Sources
- Chofu Service Manual AEYC-0643XU-CH / 1043XU-CH / 1242XU-CH / 1643XU-CH (RA-98(5)) - Air to Water Heat Pump, Monobloc DC Inverter ↗ · RA-98(5) · page 31 · Reviewed 23 September 2026
- Chofu AEYC-0639U-CH / AEYC-1039U-CH / AEYC-1639U-CH Installation and Instruction Manual (R410A) ↗ · Chofu AEYC-0639U/1039U/1639U-CH Installation and Instruction Manual (ManualsLib-derived copy) · page 146 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026