The low flow alarm means that the heat pump does not detect the required water circulation.
Potential causes
Clogged filter, closed valves, air in the circuit, low circulator speed, or flow sensor failure.
What to check first
Actual flow rate, supply-return temperature difference, and filter condition.
Flow switch or flow sensor
An incorrect signal can trigger an alarm even when there is flow.
Correct troubleshooting
Do not bypass the flow protection. Determine if the problem is actual low flow or an incorrect reading.
