VRC700-HOT-WATER-TEMPERATURE-SENSOR-S1-NOT-CONNECTED on a Vaillant aroTHERM plus: Hot water temperature sensor S1 not connected
Short answer
On a Vaillant heat pump, VRC700-HOT-WATER-TEMPERATURE-SENSOR-S1-NOT-CONNECTED means: Hot water temperature sensor S1 not connected. The heat pump keeps running with some functions stopped. An engineer is needed to fix the cause.
Reviewed 23 September 2026 · 1 source
What it means
The manual says: Hot water temperature sensor S1 not connected.
Part involved: VRC 700 system control / VR 70 / VR 71 modules.
Likely causes:
- DHW temperature sensor S1 not connected to the VR 70.
Is it safe?
| Does the heat pump stop? | Partly |
|---|---|
| Severity | Warning |
| Engineer needed? | Yes |
The heat pump keeps running with some functions stopped.
Resetting itself: yes - clears when the connection/configuration is corrected.
Manual reset: not required.
What you can check
- Note the full code and text shown on the display (and the date/time it appeared). If the control display stays dark or will not respond, switch the heat generator's mains switch off and on again (VRC 700 instructions); otherwise contact your installer.
What the engineer will check
- Connect the DHW temperature sensor.
Who to ask for: Heat pump/controls installer familiar with Vaillant eBUS controls.
Certification: MCS installer certification; Vaillant product training recommended.
What you might notice
What owners and engineers report
12 owner and engineer reports mention this.
- Controller / thermostat problem on the aroTHERM plus (VWL ../6 A): 12 reports
Sources
- VRC 700 installation instructions ↗ · 0020262579_01 · page VRC 700 installation instructions 0020262579_01 p.35 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026