S4 on a Kensa heat pump: P4 pressure sensor error (suction pipe, twin)
Short answer
On a Kensa heat pump, S4 means: P4 pressure sensor error (suction pipe, twin). The manual does not say whether the heat pump stops. An engineer is needed to fix the cause.
Reviewed 23 September 2026 · 2 sources
What it means
The manual says: P4 pressure sensor error (suction pipe, twin).
Part involved: P4 suction transducer.
When it shows: Error level per manual: Fault.
Likely causes:
- P4 sensor faulty or disconnected.
Is it safe?
| Does the heat pump stop? | Not stated |
|---|---|
| Engineer needed? | Yes |
The manual does not say whether the heat pump stops.
Resetting itself: unknown.
Manual reset: unknown.
What you can check
- Note the code shown on the controller/LED; check the heat pump isolator and consumer-unit breaker are on; check thermostat/timer settings.
What the engineer will check
- Follow Kensa fault table actions: P4 sensor faulty or disconnected.
Who to ask for: Refrigeration engineer (F-gas certified) / Kensa technical support.
Certification: F-gas Category I (refrigerant circuit work); MCS-certified GSHP installer.
What you might notice
Sources
- Q80 Series Heat Pump Operational Manual ↗ · Version 2 · page 25 · Reviewed 23 September 2026
- Shoebox Heat Pump Operational Manual (User Manual) ↗ · Version 8 · page 28 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026