Heat pumps · Error codes · Ideal Heating
26Ideal Heating · Logic Air
26 on an Ideal Heating Logic Air: Header Thermistor Fault (used for Cascade Systems)
Short answer
On an Ideal Heating heat pump, 26 means: Header Thermistor Fault (used for Cascade Systems). 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: Header Thermistor Fault (used for Cascade Systems).
Part involved: header thermistor.
Likely causes:
- Header thermistor wiring loose; thermistor out of tolerance; RVS21 PCB fault.
Is it safe?
| Does the heat pump stop? | Not stated |
|---|---|
| Engineer needed? | Yes |
The manual does not say whether the heat pump stops.
What you can check
- Note the code or fault message shown on the controller/Halo and when it appeared; check the heat pump's isolator and consumer-unit breaker are on.
What the engineer will check
- Check header thermistor wiring at both ends; measure resistance per manual; replace thermistor or RVS21 PCB.
Who to ask for: Heat pump / heating controls engineer.
Sources
- Logic Air Monobloc Heat Pump System - Installation & Maintenance (UIN 241428 A03) ↗ · UIN 241428 A03 · page 76 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026