164 on a NIBE heat pump: Low exhaust air temperature: See alarm 64 (exhaust air below 16 C)
Short answer
On a NIBE heat pump, 164 means: Low exhaust air temperature: See alarm 64 (exhaust air below 16 C). The heat pump keeps running.
Reviewed 23 September 2026 · 1 source
What it means
The manuals for this range word it in different ways:
- Low exhaust air temperature: See alarm 64 (exhaust air below 16 C).
- High pressure alarm: High pressure switch has triggered repeatedly.
Part involved: fans, air filters, air sensors; pressure switches/sensors, expansion valve.
When it shows: See alarm 64 (exhaust air below 16 C) High pressure switch has triggered repeatedly.
Is it safe?
| Does the heat pump stop? | No |
|---|---|
| Severity | Information only |
The heat pump keeps running.
Resetting itself: yes - Automatic reset when temperature exceeds 17 C.
Manual reset: Reset from the controller alarm menu ('reset alarm' / 'Reset alarm and try again'); alarm recurs if the cause remains.
What you can check
- Read the alarm text and the 'info/action' help on the controller display (VVM/SMO or S-series smartguide). NIBE's manuals let the homeowner select 'reset alarm' ('Reset alarm and try again' on S-series); if the lamp returns to normal the alarm has cleared. If it comes back, do not keep resetting: select 'aid mode' ('Auxiliary operation' on S-series) if offered, so any electric additional heat keeps heat/hot water going, and contact your installer. Check the exhaust air valves/grilles in the rooms are open and not blocked; check the filter reminder in the user manual maintenance section.
- Read the alarm text and the 'info/action' help on the controller display (VVM/SMO or S-series smartguide). NIBE's manuals let the homeowner select 'reset alarm' ('Reset alarm and try again' on S-series); if the lamp returns to normal the alarm has cleared. If it comes back, do not keep resetting: select 'aid mode' ('Auxiliary operation' on S-series) if offered, so any electric additional heat keeps heat/hot water going, and contact your installer. Air source systems: check the outdoor unit is clear of leaves/snow/ice. Read the heating system pressure gauge and note the reading for your installer.
What the engineer will check
- Check ventilation airflow, fans, filters, air sensors and condensate drainage/level monitor.
- Check heating medium flow, particle filter and circulation pump; check pressure switches/sensors, expansion valve, service valves and refrigerant charge (F-gas qualified).
Who to ask for: NIBE-trained heat pump installer (NIBE PRO / VIP); Heat pump engineer with F-gas qualification (NIBE-trained / NIBE PRO installer).
Certification: None specific beyond competent heat pump installer; electrical work to BS 7671; F-gas certification for refrigerant circuit work (plus flammable-refrigerant competence for R290/R32 models).
What you might notice
Sources
- ALARM LIST - NIBE products with Emmy display, Version 1747-1 (updated 2017-11-23) ↗ · 1747-1 · page 5 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026