The Arthur Grillo ALC230A is a compact, wall‑mounted room temperature and CO₂ controller. Designed for demand‑controlled ventilation (DCV) and VAV applications, it combines an NTC temperature sensor, an NDIR CO₂ sensor, and a PI controller in a single IP30‑rated polycarbonate housing. The unit outputs a 0‑10 V DC signal based on the larger of the temperature or CO₂ demand, directly controlling an EC fan, damper actuator, or air handling unit without requiring a separate DDC controller. It is suitable for independent rooms such as offices, classrooms, and meeting spaces where individual climate control is required.

How It Works

• Dual Sensor Input, One Output: The controller continuously measures room temperature (NTC) and CO₂ concentration (NDIR). An internal PI algorithm calculates the required ventilation rate for each variable independently. The output signal is the maximum of the temperature and CO₂ demand—if the room is at the correct temperature but CO₂ is elevated, the ventilator runs. If CO₂ is low but the room is too warm, the ventilator runs. This ensures comfort and air quality are both maintained.
• Fixed PI Tuning for Easy Setup: For each SW1 position (0–5), the P‑band and I‑time are pre‑defined. This eliminates the guesswork of manual PID tuning: the technician selects a room‑appropriate setting based on thermal inertia—small offices use a smaller P‑band, while larger or high‑inertia rooms use a wider P‑band to prevent oscillation.
• Automatic Heating/Cooling Changeover: A jumper (JP1) selects the output polarity: closed 1‑2 for heating applications, closed 2‑3 for cooling. This single setting determines whether the 0‑10 V signal increases when the room is cooler than the setpoint (heating) or warmer (cooling).

Adjustable Parameters

• Temperature Setpoint (R23): A potentiometer directly adjusts the room temperature target between 5 °C and 30 °C.
• Temperature Proportional Band (SW1): The proportional band controls how much the temperature must deviate from the setpoint before the output reaches 100 %. Setting range: 0.5–8.0 °C. A narrow band (e.g., 0.5 °C) produces a strong response to small deviations; a wide band (e.g., 8.0 °C) provides gentler, more stable control.
• CO₂ Setpoint (SW3): Adjustable between 350 ppm and 1500 ppm. Typical settings aim around 800–1000 ppm for offices to balance air quality and energy consumption.
• CO₂ Proportional Band (SW2): The proportional band for CO₂ control, adjustable between 10 ppm and 1000 ppm.
• Fan Speed Limitation: R28 sets the minimum fan speed (0–30 %), R29 sets the maximum (30–100 %). This prevents uncomfortable drafts and reduces energy consumption during low‑demand periods.

Connectivity and Installation

• 0‑10 V Output (Max. 1 mA): The universal output connects to standard 0‑10 V inputs on EC fans, damper actuators, and frequency converters. The signal reflects the greater of temperature or CO₂ demand, providing seamless integration with existing HVAC actuators.
• Wall‑Flush Mounting: The enclosure is designed for direct wall mounting without a spacer. The installer should place the device approximately 1.6 m above floor level in a location with unobstructed air circulation and avoid direct sunlight or draughts. A switch or circuit breaker for disconnection from the mains supply must be installed within easy reach.

Applications

• Demand‑controlled ventilation (DCV) for individual offices, classrooms, and meeting rooms
• VAV damper control with integrated CO₂ monitoring
• EC fan speed control in residential and commercial ventilation systems
• Retrofit projects where a standalone, non‑networked room climate controller is required