Heat pumps · Error codes · Danfoss
low-heat-cir-flowDanfoss · DHP-AQ
low-heat-cir-flow on a Danfoss DHP-AQ: The flow sensor has registered too low a flow
Short answer
On a Danfoss heat pump, low-heat-cir-flow means: The flow sensor has registered too low a flow. 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: The flow sensor has registered too low a flow.
Part involved: flow sensor.
Likely causes:
- Low heating-circuit flow (closed valves, blocked strainer, air, pump fault) - not separately tabulated.
Is it safe?
| Does the heat pump stop? | Yes |
|---|---|
| Engineer needed? | Yes |
The heat pump stops until the fault clears or is reset.
Manual reset: Set operating mode OFF then back to the desired mode.
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 circulation pump, strainer, valves, air; check flow sensor.
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