Heat pumps · Error codes · Danfoss
high-return-line-tempDanfoss · DHP-AQ
high-return-line-temp on a Danfoss DHP-AQ: Return line temperature too high
Short answer
On a Danfoss heat pump, high-return-line-temp means: Return line temperature too high. The heat pump keeps running with some functions stopped. An engineer is needed to fix the cause.
Reviewed 23 September 2026 · 1 source
What it means
The manual says: Return line temperature too high.
Part involved: return line temperature.
Likely causes:
- Return temperature above limit (causes not tabulated).
Is it safe?
| Does the heat pump stop? | Partly |
|---|---|
| Severity | Fault — clears by itself when the condition goes |
| Engineer needed? | Yes |
The heat pump keeps running with some functions stopped.
Resetting itself: Yes, when the condition clears (inferred).
What you can check
- Note the exact alarm text. Check the heating-system pressure gauge is in the range given in the user guide (Thermia/Danfoss: 1-1.5 bar when cold) - do not top up yourself unless you have been shown how; check radiator/underfloor valves and room thermostats are open. The manual allows acknowledging by setting operating mode OFF then back once; if the alarm returns, call an engineer.
What the engineer will check
- Check heat curve, hot water settings, emitter flow/bypass.
Who to ask for: heat pump engineer.
What you might notice
Sources
- Service Instructions DHP-AQ (VMGFJ202) ↗ · VMGFJ202 · page p.10 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026