Heat pumps · Error codes · Thermia
low-heat-cir-flowThermia · Atec
low-heat-cir-flow on a Thermia Atec: The flow sensor has registered too low a flow
Short answer
On a Thermia 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. (causes from the equivalent Danfoss DHP-AQ service instructions VMGFJ202).
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. Acknowledge once (operating mode OFF then back); if it remains, contact a service technician (user manual 086L0130 p.25).
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 Atec (VIIFM102) - silo.tips copy ↗ · VIIFM102 · page p.10 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026