E556 on a Samsung heat pump: Capacity mismatching between indoor and outdoor
Short answer
On a Samsung heat pump, E556 means: Capacity mismatching between indoor and outdoor. The heat pump stops until the fault clears or is reset. An engineer is needed to fix the cause.
Reviewed 23 September 2026 · 1 source
What it means
The manual says: Capacity mismatching between indoor and outdoor.
Part involved: Hydro unit/control kit and outdoor PCB communication.
When it shows: Unit self-diagnosis: Capacity mismatching between indoor and outdoor.
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: EEPROM data wrong: exchange EEPROM or main PBA (per Samsung SM).
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
- EEPROM data wrong: exchange EEPROM or main PBA (per Samsung SM). 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
Sources
- Samsung EHS TDM Plus Service Manual Code AC-07002A_0 (Feb 2017) ↗ · AC-07002A_0 · page p.89 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026