E425 on a Samsung heat pump: Outdoor Reverse Phase or Missing Phase Detect Error
Short answer
On a Samsung heat pump, E425 means: Outdoor Reverse Phase or Missing Phase Detect 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 · 3 sources
What it means
On the EHS Mono R290 (AE***CXYD*K and pump-integrated AE***CXYB*K)
The manual says: Outdoor Reverse Phase or Missing Phase Detect Error.
Part involved: 3-phase power supply.
When it shows: Unit self-diagnosis: Outdoor Reverse Phase or Missing Phase Detect Error.
Likely causes:
- 3-phase supply wiring fault: phase reversal or missing phase (3-phase models only).
- Engineer checks per Samsung service manual: Check 3-phase power supply wiring R, S, T, N at the outdoor unit (phase reversal/missing phase).
On the EHS Mono R32 (AE***RXYD*G)
The manual says: Power source line missing error (only for 3-phase model).
Part involved: 3-phase power supply.
When it shows: Unit self-diagnosis: Power source line missing error (only for 3-phase model).
Likely causes:
- 3-phase supply wiring fault: phase reversal or missing phase (3-phase models only).
- Engineer checks per Samsung service manual: Check 3-phase power supply wiring R, S, T, N at the outdoor unit (phase reversal/missing phase).
On the EHS Split Generation 4 (AEX/AEN, 2014)
The manual says: Miss wiring error at 3Phase power source line (Only 3Phase Model).
Part involved: 3-phase power supply.
When it shows: Unit self-diagnosis: Miss wiring error at 3Phase power source line (Only 3Phase Model).
Likely causes:
- 3-phase supply wiring fault: phase reversal or missing phase (3-phase models only).
- Engineer checks per Samsung service manual: Check 3-phase power supply wiring R, S, T, N at the outdoor unit (phase reversal/missing phase).
Is it safe?
Switch the heat pump off at its isolator and call an engineer.
| Does the heat pump stop? | Yes |
|---|---|
| Severity | Fault — clears by itself when the condition goes |
| Engineer needed? | Yes |
The heat pump stops until the fault clears or is reset.
Resetting itself: yes - Samsung SM lists product operation as "restart operation".
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 3-phase power supply wiring R, S, T, N at the outdoor unit (phase reversal/missing phase). Any work inside casings, on PCBs, wiring, sensors, pumps, valves or refrigerant is engineer-only.
Who to ask for: Heat pump engineer / electrician (3-phase).
Certification: Competent electrical worker (BS 7671).
What you might notice
What owners and engineers report
1 owner and engineer report mentions this.
- Heat pump will not start on the EHS Mono R32 (AE***RXYD*G): 1 report
Sources
- EHS R290 Mono Outdoor Unit Installation Manual AE***CXYD** (EU) DB68-12496A-03 ↗ · DB68-12496A-03 · page p.24 · 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
- Samsung Eco Heating System Service Manual - Outdoor Unit AEX060-160ED*HA / Hydro Unit AEN080/160YD*HA (file RC160MHXGA_SM_E_34513A(1)) ↗ · 34513A(1) · page ManualsLib viewer p.52 (printed p.51) · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026