Mitsubishi Ecodan fault 13

What it means

The space heating system fails to reach the set target temperature, with causes ranging from mode/schedule settings, sensor placement, heat pump faults, booster heater faults, heat emitter sizing, 3-way valve failure, battery issues, and mixing tank flow rate imbalance.

Likely causes

1. Prohibit, schedule timer or holiday mode selected
2. Battery power low (wireless control)
3. Temperature sensor located in a room with different temperature relative to rest of house
4. Heat pump not working
5. Booster heater cut-out tripped
6. Booster heater breaker (ECB1) tripped
7. Booster heater thermal cut-out tripped and cannot be reset using manual reset button
8. Incorrectly sized heat emitter
9. 3-way valve failure
10. Battery problem (wireless control only)
11. If a mixing tank is installed, flow rate between mixing tank and cylinder unit is less than that between mixing tank and local system
12. Immersion heater degradation causing earth leakage, triggering circuit breaker (heater always OFF)
13. Water circulation pump wear leading to pump failure

Where to start

1. Check settings and change as appropriate for prohibit/schedule/holiday mode
2. Check the battery power and replace if flat
3. Relocate the temperature sensor to a more suitable room if misplaced