Heat pumps · Error codes · Grant
PP6Grant · Aerona (1st generation)
PP6 on a Grant Aerona: Discharge gas overheat protection
Short answer
On a Grant heat pump, PP6 means: Discharge gas overheat protection. The heat pump stops until the fault clears or is reset. An engineer is needed to fix the cause.
Reviewed 23 September 2026 · 1 source
What it means
The manual says: Discharge gas overheat protection.
Part involved: compressor discharge.
When it shows: Shown on the ATC controller display.
Likely causes:
- Return water temperature too high causing compressor discharge gas to be too high.
- Insufficient refrigerant to compressor causing discharge gas to be too hot.
Is it safe?
| Does the heat pump stop? | Yes |
|---|---|
| Engineer needed? | Yes |
The heat pump stops until the fault clears or is reset.
Resetting itself: Not stated.
Manual reset: Not stated.
What you can check
- Note the exact code shown on the controller display and tell your installer or Grant-trained engineer.
- Check the heat pump isolator switch and the consumer-unit breaker/RCD for the heat pump are ON (do not repeatedly reset a tripping breaker).
What the engineer will check
- Check return water temperature / flow and ATC parameter 1 (max return water temp 47C).
- Check refrigerant charge for leaks (F-gas engineer).
Who to ask for: Heat pump engineer.
Certification: F-gas certified refrigeration engineer (refrigerant circuit work).
What you might notice
Sources
- Grant Aerona Air Source Heat Pump - Air to Water Heat Pump Range - Installation & User Instructions (DOC.87) ↗ · Rev.05 · page 37 (PDF p41); s13.5-13.6 p36 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026