Dixell/Copeland F11

What does Dixell/Copeland F11 mean?

On the Dixell IC100CX iChill controller, DF11 is the combined defrost start setpoint used when Pb4 (condenser probe 4) is configured as CF07 = 5. The controller monitors Pb3 falling below DF03 to start the DF10 interval countdown. When DF10 expires, the system checks Pb4 against DF11 — if Pb4 is below DF11, defrost starts; if not, the unit stays in heat pump mode until Pb4 drops below DF11.

Symptoms

• Defrost does not start despite DF10 expiring (Pb4 has not yet fallen below DF11 setpoint).
• Defrost triggers only after combined conditions of DF10 elapsed and Pb4 below DF11 are both met.
• DF11 functionality only active when CF07 = 5 and CF06 = 1 or 2.

Common causes

• DF11 set too low — system requires Pb4 to drop to very cold temperatures before combined defrost triggers.
• CF07 not set to 5, so the combined defrost logic and DF11 are not active.
• Pb4 probe fault causing incorrect reading that prevents the DF11 condition from being met.
• Actual outdoor conditions not cold enough to satisfy both DF10 and DF11 simultaneously.

Diagnostic steps

1. 01

   Verify CF07 = 5 configuration

   Access the CF sub-menu on the IC100CX. Confirm CF07 = 5 to enable combined defrost mode using Pb4. If CF07 is set differently, DF11 is not used.

2. 02

   Verify CF06 setting

   DF11 combined logic also requires CF06 = 1 or 2 (Pb3 configured appropriately). Confirm the probe assignment is correct for the system wiring.

3. 03

   Check DF11 setpoint value

   Access the DF sub-menu and confirm DF11 is set to a temperature or pressure that represents a genuine icing condition on the Pb4 probe. Adjust to match system field conditions.

4. 04

   Verify Pb4 probe reading

   View the Pb4 reading on the IC100CX display. Compare to an independent measurement at the Pb4 sensor location. A faulty probe causes the combined defrost condition to never be satisfied.

5. 05

   Review DF12 (combined defrost end setpoint)

   DF12 sets the Pb4 temperature above which the combined defrost cycle stops. Confirm DF12 is set correctly to terminate the defrost once the coil is sufficiently clear of ice.

When to call a professional

Combined defrost configuration using Pb3 and Pb4 requires careful commissioning to match the heat pump system design and outdoor coil thermal characteristics. A licensed HVAC/R technician familiar with the Dixell IC100CX combined defrost feature should configure DF11 and DF12 during initial system setup and seasonal calibration.