#91 on an Ochsner OTS touch controller alarm platform: Minimum flow rate, heat sink system - troubleshooting: Water pressure too low, circulation pump faulty, valve closed/air in system, check hydraulics, check selected pump speeds, filter (strainer) clogged
Short answer
On an Ochsner heat pump, #91 means: Minimum flow rate, heat sink system - troubleshooting: Water pressure too low, circulation pump faulty, valve closed/air in system, check hydraulics, check selected pump speeds, filter (strainer) clogged. The manual does not say whether the heat pump stops. An engineer is needed to fix the cause.
Reviewed 23 September 2026 · 1 source
What it means
The manual says: Minimum flow rate, heat sink system - troubleshooting: Water pressure too low, circulation pump faulty, valve closed/air in system, check hydraulics, check selected pump speeds, filter (strainer) clogged.
Part involved: Minimum flow rate, heat sink system.
Likely causes:
- Water pressure too low.
- circulation pump faulty.
- valve closed/air in system.
- filter (strainer) clogged.
Is it safe?
| Does the heat pump stop? | Not stated |
|---|---|
| Engineer needed? | Yes |
The manual does not say whether the heat pump stops.
Manual reset: Faults are acknowledged via the controller Alarms menu (manual section 22.2).
What you can check
- Note the alarm number and text shown under Menu > Alarms and contact your system installer or OCHSNER customer service.
- Check the heating system pressure gauge reading and tell the installer the value.
What the engineer will check
- Water pressure too low, circulation pump faulty, valve closed/air in system, check hydraulics, check selected pump speeds, filter (strainer) clogged.
Who to ask for: heating installer (OCHSNER system partner).
What you might notice
Sources
- OCHSNER AIR HAWK 208 Operating manual (valid from app V03.03.xxx), incl. OTS fault messages ↗ · EN13 (BA_982010) · page 48 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026