E101 on a Samsung heat pump: Hydro Unit / Outdoor Unit communication connection error
Short answer
On a Samsung heat pump, E101 means: Hydro Unit / Outdoor Unit communication connection error. The heat pump stops until the fault clears or is reset. An engineer is needed to fix the cause. The wording differs by model range — each is shown below.
Reviewed 23 September 2026 · 2 sources
What it means
On the EHS Mono R290 (AE***CXYD*K and pump-integrated AE***CXYB*K)
The manual says: Hydro Unit / Outdoor Unit communication connection error.
Part involved: Hydro unit/control kit and outdoor PCB communication.
When it shows: Unit self-diagnosis: Hydro Unit / Outdoor Unit communication connection error.
Likely causes:
- Communication/addressing fault between hydro unit (control kit) and outdoor unit, or between outdoor PCBs: wiring fault, loose connector, incorrect setting, electrical interference or PCB failure.
- Engineer checks per Samsung service manual: Check the communication cable between the hydro unit/control kit and outdoor unit and the DC output voltage at the communication terminals.
On the EHS Mono R32 (AE***RXYD*G)
The manual says: CONTROL KIT / OUTDOOR UNIT wire connection error.
Part involved: Hydro unit/control kit and outdoor PCB communication.
When it shows: Unit self-diagnosis: CONTROL KIT / OUTDOOR UNIT wire connection error.
Likely causes:
- Communication/addressing fault between hydro unit (control kit) and outdoor unit, or between outdoor PCBs: wiring fault, loose connector, incorrect setting, electrical interference or PCB failure.
- Engineer checks per Samsung service manual: Check the communication cable between the hydro unit/control kit and outdoor unit and the DC output voltage at the communication terminals.
Is it safe?
| Does the heat pump stop? | Yes |
|---|---|
| Engineer needed? | Yes |
The heat pump stops until the fault clears or is reset.
Resetting itself: unknown.
Manual reset: unknown.
What you can check
- Note the full error code shown on the controller; check the heat pump breaker/isolator in the consumer unit is ON; then contact your installer or Samsung service; Samsung manuals do not describe a homeowner reset for this code.
What the engineer will check
- Check the communication cable between the hydro unit/control kit and outdoor unit and the DC output voltage at the communication terminals. Any work inside casings, on PCBs, wiring, sensors, pumps, valves or refrigerant is engineer-only.
Who to ask for: Heat pump engineer (Samsung-trained, controls/electrical).
Certification: Competent electrical worker (BS 7671) for work on live equipment.
What you might notice
What owners and engineers report
8 owner and engineer reports mention this.
- No heating on the EHS Mono R32 (AE***RXYD*G): 6 reports
- No hot water on the EHS Mono R32 (AE***RXYD*G): 1 report
- Heat pump will not start on the EHS Mono R32 (AE***RXYD*G): 1 report
Sources
- Air to Water Heat Pump User manual AE200DN**** / AE160DN**** / MIM-E03FN (2024 ClimateHub / control kit) DB68-12922A-05 ↗ · DB68-12922A-05 · page p.55 · Reviewed 23 September 2026
- EHS R-32 Mono Outdoor Unit Installation Manual (EU) DB68-08408A-07 ↗ · DB68-08408A-07 · page p.43 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026