E403 on a Samsung heat pump: Protect for Freezing Control Error
Short answer
On a Samsung heat pump, E403 means: Protect for Freezing Control 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 · 4 sources
What it means
On the EHS Mono R290 (AE***CXYD*K and pump-integrated AE***CXYB*K)
The manual says: Protect for Freezing Control Error.
Part involved: Plate heat exchanger / water circuit freeze protection.
When it shows: Unit self-diagnosis: Protect for Freezing Control Error.
Likely causes:
- Freeze protection of plate heat exchanger/water circuit triggered: low water flow, low water temperature, refrigerant cycle issue.
- Engineer checks per Samsung service manual: Check refrigerant cycle status; plate heat exchanger/condenser freezing; check water flow rate.
On the EHS Mono R32 (AE***RXYD*G)
The manual says: Detection of OUTDOOR UNIT compressor freezing (During cooling operation).
Part involved: Plate heat exchanger / water circuit freeze protection.
When it shows: Unit self-diagnosis: Detection of OUTDOOR UNIT compressor freezing (During cooling operation).
Likely causes:
- Freeze protection of plate heat exchanger/water circuit triggered: low water flow, low water temperature, refrigerant cycle issue.
- Engineer checks per Samsung service manual: Check refrigerant cycle status; plate heat exchanger/condenser freezing; check water flow rate.
On the EHS Split Generation 4 (AEX/AEN, 2014)
The manual says: Detection of Outdoor Freezing when Comp. Stop.
Part involved: Plate heat exchanger / water circuit freeze protection.
When it shows: Unit self-diagnosis: Detection of Outdoor Freezing when Comp. Stop.
Likely causes:
- Freeze protection of plate heat exchanger/water circuit triggered: low water flow, low water temperature, refrigerant cycle issue.
- Engineer checks per Samsung service manual: Check refrigerant cycle status; plate heat exchanger/condenser freezing; check water flow rate.
On the EHS Split R32 (AE***RXED*G)
The manual says: Detection of freezing (During cooling operation).
Part involved: Plate heat exchanger / water circuit freeze protection.
When it shows: Unit self-diagnosis: Detection of freezing (During cooling operation).
Likely causes:
- Freeze protection of plate heat exchanger/water circuit triggered: low water flow, low water temperature, refrigerant cycle issue.
- Engineer checks per Samsung service manual: Check refrigerant cycle status; plate heat exchanger/condenser freezing; check water flow rate.
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; check the heating system pressure gauge reading (typically 1-2 bar when cold; do not top up unless you have been shown how); check the outdoor unit is not blocked by leaves, debris or snow and air can flow freely; then contact your installer or Samsung service; Samsung manuals do not describe a homeowner reset for this code.
What the engineer will check
On the EHS Mono R290 (AE***CXYD*K and pump-integrated AE***CXYB*K)
- Check refrigerant cycle status; plate heat exchanger/condenser freezing; check water flow rate. Any work inside casings, on PCBs, wiring, sensors, pumps, valves or refrigerant is engineer-only.
Who to ask for: Heat pump engineer (hydraulics and refrigeration); R290 (A3 flammable refrigerant) competence.
Certification: F-gas certification if refrigerant circuit work is needed; R290/flammable refrigerant handling training (e.g. hydrocarbon refrigerant course).
On the EHS Mono R32 (AE***RXYD*G)
- Check refrigerant cycle status; plate heat exchanger/condenser freezing; check water flow rate. Any work inside casings, on PCBs, wiring, sensors, pumps, valves or refrigerant is engineer-only.
Who to ask for: Heat pump engineer (hydraulics and refrigeration).
Certification: F-gas certification if refrigerant circuit work is needed.
On the EHS Split Generation 4 (AEX/AEN, 2014)
- Check refrigerant cycle status; plate heat exchanger/condenser freezing; check water flow rate. Any work inside casings, on PCBs, wiring, sensors, pumps, valves or refrigerant is engineer-only.
Who to ask for: Heat pump engineer (hydraulics and refrigeration).
Certification: F-gas certification if refrigerant circuit work is needed.
On the EHS Split R32 (AE***RXED*G)
- Check refrigerant cycle status; plate heat exchanger/condenser freezing; check water flow rate. Any work inside casings, on PCBs, wiring, sensors, pumps, valves or refrigerant is engineer-only.
Who to ask for: Heat pump engineer (hydraulics and refrigeration).
Certification: F-gas certification if refrigerant circuit work is needed.
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
- Keeps stopping / cutting out on the EHS Mono R32 (AE***RXYD*G): 2 reports
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
- EHS R-32 Split Outdoor Unit Installation Manual (EU) DB68-08407A-06 ↗ · DB68-08407A-06 · page p.50 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026