General Assist Technical Reference

Fan Speed Controller

Installation, wiring and Danfoss condenser fan control setup

For systems using a fan speed controller with a Danfoss 0-10 V condenser regulation signal

The Fan Speed Controller (FSC) modulates condenser fan operation in response to condenser pressure or a 0-10 V control signal. This provides variable fan speed for stable head pressure control, particularly during low ambient cooling operation.

Qualified personnel only: This procedure involves live electrical equipment and internal wiring. Isolate the unit before making or altering any connections and verify isolation before commencing work.

Components Mounting Wiring Danfoss Setup Verification Reference Images

1. Components involved

Fan Speed Controller Box - Lufrec / Danfoss interface.
Overload protection and contactor assembly.
Danfoss control module.
0-10 V control signal wiring.
Earthing bar.

2. Mounting location

Mount the Fan Speed Controller vertically to allow adequate heat dissipation.
Choose a location within the electrical panel or compressor compartment that remains accessible for service.
On single-stage systems, the recommended position is at the bottom of the electrical panel near the compressor.

3. Electrical wiring

3.1 Overload and contactor preparation

Isolate power to the unit.
Remove the existing wiring between the bottom of the overload and the top of the contactor.
These terminals become the connection points for the Fan Speed Controller wiring.

3.2 Wiring to the Fan Speed Controller

Circuit	Connection	Function
Line in	Bottom of overload to FSC L1, L2, L3	Supply to Fan Speed Controller
Line out	FSC T1, T2, T3 to bottom of contactor	Controlled output to condenser fans
Earth	Terminate earth conductors to the unit earth bar	Protective grounding

3.3 Speed control wiring

Two low-voltage control wires run between the Fan Speed Controller and Danfoss module.

Danfoss	Fan Speed Controller	Signal
A01	0.10V	0-10 V speed command
COM	0V	Control common

This allows the Danfoss controller to regulate condenser fan speed based on condensing pressure.

Polarity: Confirm A01 is connected to the FSC 0.10V terminal and COM is connected to 0V. Incorrect polarity may prevent correct speed control.

4. Danfoss parameter setup

Enter service password: 5653.
Navigate to Parameters > Condenser > Regulation.
Set Cond Setpoint in Cooling to 26.0 °C.
Confirm and save the setting.

This setting provides the control target used by the condenser fan modulation strategy during cooling operation.

5. Post-installation verification

Reapply power and confirm the Fan Speed Controller energises correctly.
Verify correct condenser fan rotation direction.
Observe fan speed modulation during operation. Fans should slow at low condensing pressure and increase as pressure rises.
Check that the controller housing remains cool and unobstructed.
Confirm there are no fault LEDs on the FSC or Danfoss module.

6. Safety and installation notes

Always isolate power before handling internal wiring.
Ensure all terminals are tightened to the manufacturer's specified torque.
Use only components suitable for the system and refrigerant application.
Maintain enclosure integrity and reseal cable entries with suitable cable glands after wiring.

7. Connection summary

Connection point	Terminal	Description
From overload	L1, L2, L3	Line input to Fan Speed Controller
To contactor	T1, T2, T3	Controlled line output from Fan Speed Controller
Earth	Earth bar	Protective ground
Control signal	0.10V ← A01 / 0V ← COM	Danfoss fan speed command

8. Functional outcome

Once correctly installed and configured:

The Fan Speed Controller varies condenser fan speed in proportion to the Danfoss 0-10 V command.
The control strategy maintains more stable condensing conditions as ambient temperature changes.
At lower condensing pressure the fan speed reduces; as condensing pressure rises, fan speed increases.