The Carel PCO3NL0BS0 is a pCO³ series programmable controller (specifically a Medium or Large variant in the pCO3 family). It is an older-generation microprocessor-based controller designed for HVAC/R applications, including chillers, heat pumps, compressor packs, air handling units, fan coils, and refrigeration systems. Key Specifications • Power Supply: 24 V AC (±15%), 50/60 Hz. Maximum power consumption: ~40 VA / 15 W (as labeled on the unit in your image). • Processor: 32-bit microprocessor for improved calculation speed and performance compared to earlier pCO² models. • I/O Configuration (typical for pCO3 Medium/Large): • Digital Inputs (DI): Up to 14–18 (voltage-free or 24 V AC/DC, with some fast inputs possible). • Analogue Inputs (AI): Up to 8–10, highly configurable via software (NTC/PTC/PT1000 probes, 0-1V, 0-5V, 0-10V, 0-20mA/4-20mA, ratiometric pressure sensors). • Analogue Outputs (AO): Up to 4–6 (0-10 V or PWM for modulating valves, fans, inverters). • Digital Outputs (DO): Up to 13–18 (relays: SPST/SPDT, some models support SSR for frequent switching). • Display & Interface: The image shows a built-in or attached service card with a small LCD screen (alphanumeric or basic graphic) and 6-button keypad (alarm bell, Prg, Esc, up/down arrows, left arrow for navigation). It supports external terminals like pGD0 semi-graphic displays or 4x20 character LCDs. Connectivity: • 3 serial ports standard: pLAN (for local terminals), plus FieldBus and BMS ports (configurable for Carel proprietary protocol, Modbus, or optional cards for BACnet, LonWorks, KNX, RS485, etc.). • Optional plug-in serial cards (the “serial card” section in your photo). • Programming via Carel EasyTools software or hardware key (programming key). • Mounting: DIN rail, modular design with separate field card (main I/O terminals J1–J3/J24 for power, sensors, actuators) and serial card (J4/J5 for communication). • Other Features: Real-time clock (RTC), alarm logging, multi-language support, compatibility with electronic expansion valve drivers (external EVD), time-band scheduling, and pump/compressor rotation logic. • Status: This model is obsolete/discontinued with no direct official replacements listed by Carel in many catalogs. Migration to pCO5+ (or newer c.pCO) is common, as pCO5+ offers pin-to-pin compatibility in many cases, more memory, faster processing, universal I/O channels, and better connectivity (including USB and optional built-in EVD drivers with Ultracap for power-fail safety). The photo you shared matches the typical pCO3 layout (service card on top with LCD/buttons, field card below with terminals labeled J1 power/GND, J24 for probes/power, J2/J3 for inputs/outputs, and serial area J4/J5). Note that the image was previously associated with a pCO5+ description, but the hardware appearance is very similar across the pCO family due to modular design. Primary Uses • HVAC/R Control: Common in chiller/heat pump management (compressor staging, defrost, condenser/evaporator fan control, water temperature regulation), compressor racks/packs (suction/condensing pressure control, up to multiple compressors and fans), and air conditioning units. • Custom OEM Applications: Programmable for specific logic like proportional/integral control, set-point compensation based on outdoor temperature, alarm handling, pump rotation, and integration with BMS/supervisors. • Networked Systems: Works in pLAN networks for multiple units or with BMS for building-level monitoring. Typical application software examples include modular chiller programs, compressor pack management, or area controllers for hydronic systems.
