S.276 on a Glow-worm GeniaAir: Wait. per.: Underfl. surf.-mnt thermostat blocks the unit Contact S20 is open at the heat pump's main PCB. Incorrect limit thermostat setting. Flow temperature sensor (heat pump, gas-fired boiler, system sensor) measures values that deviate downwards. Adjust the maximum flow temperature for the direct heating …
Short answer
On a Glow-worm heat pump, S.276 means: Wait. per.: Underfl. surf.-mnt thermostat blocks the unit Contact S20 is open at the heat pump's main PCB. Incorrect limit thermostat setting. Flow temperature sensor (heat pump, gas-fired boiler, system sensor) measures values that deviate downwards. Adjust the maximum flow temperature for the direct heating …. The heat pump keeps running with some functions stopped.
Reviewed 23 September 2026 · 1 source
What it means
The manual says: Wait. per.: Underfl. surf.-mnt thermostat blocks the unit Contact S20 is open at the heat pump's main PCB. Incorrect limit thermostat setting. Flow temperature sensor (heat pump, gas-fired boiler, system sensor) measures values that deviate downwards. Adjust the maximum flow temperature for the direct heating ….
Part involved: Heat pump control (status/Live Monitor).
When it shows: Wait. per.: Underfl. surf.-mnt thermostat blocks the unit Contact S20 is open at the heat pump's main PCB. Incorrect limit thermostat setting. Flow temperature sensor (heat pump, gas-fired boiler, system sensor) measures values that deviate downwards. Adjust the maximum flow temperature for the direct heating ….
Likely causes:
- Operating status reported by the heat pump control (not a fault in itself).
Is it safe?
| Does the heat pump stop? | Partly |
|---|---|
| Severity | Information only |
| Engineer needed? | No |
The heat pump keeps running with some functions stopped.
Resetting itself: yes - status changes automatically with operating state.
Manual reset: not applicable.
What you can check
- Operating status only - no action needed. If heating or hot water is not being delivered for a long period, note the status code and tell your installer.
What the engineer will check
- None required unless heating/hot water is not delivered; then review status history, settings and application limits.
Who to ask for: Vaillant-trained heat pump installer/engineer (MCS-certified installer).
Certification: MCS installer certification; Vaillant product training recommended.
Sources
- GeniaAir Appliance Interface installation and maintenance instructions ↗ · 8000043014_01 · page HPIM 7 8000043014_01 p.28 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026