Heat pumps · Error codes · Danfoss
20Danfoss · DHP-AT
20 on a Danfoss DHP-AT: Air temperature sensor (T1) failure
Short answer
On a Danfoss heat pump, 20 means: Air temperature sensor (T1) failure. 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: Air temperature sensor (T1) failure.
Part involved: Air temperature sensor (T1) failure.
Is it safe?
| Does the heat pump stop? | Partly |
|---|---|
| Severity | Fault — clears by itself when the condition goes |
| Engineer needed? | Yes |
The heat pump keeps running with some functions stopped.
What you can check
- Note the 2-digit code. Check the outdoor unit is not blocked by snow, ice, leaves or debris and that airflow around it is clear. If the code persists, call an engineer.
What the engineer will check
- Measure sensor/cable resistance or check the indicated circuit; consult VMGFI302 section 4.4 check and safety functions.
Who to ask for: heat pump engineer.
What you might notice
Sources
- Installation Guide DHP-AT - Installation and service manual (VMGFI302 / AN089486453198) ↗ · VMGFI302 · page p.32 (section 10.1.1); safety functions pp.16-17 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026