The Belimo VRP-M VAV system is a ready-to-connect, adaptive digital PID VAV controller designed for pressure-independent variable air volume (VAV) and constant air volume (CAV) systems. It is particularly well-suited for applications requiring controlled extraction of contaminated or slightly aggressive air in closed rooms, such as laboratory workplaces, chemical and pharmaceutical plants, hospital buildings, digesters, and other industrial settings. The system comprises the VRP-M controller, static differential pressure sensors (VFP-...), and Belimo VAV damper actuators (NM...-ST or NMQB24-SRV-ST), forming a cohesive control solution.

Function Description:

The core function of the VRP-M VAV system is to precisely control volumetric airflow. It achieves this by converting the pressure differential measured by the static pressure sensor into a volumetric flow signal. This signal serves as the actual value (x) for the adaptive PID-VAV controller. The controller then compares this actual value with a user-defined setpoint (w) and adjusts the connected damper actuator accordingly to minimize any system deviation.

The system supports both VAV and CAV operating modes. In VAV mode, the volumetric flow is specified by a modulating reference signal, typically supplied by a DDC controller, room temperature controller, EIB Konnex, or LONWORKS® system. The Vmin and Vmax settings define the operating range, with Vmax representing the upper limit (30-100% of Vnom) and Vmin representing the lower limit (0-100% of Vnom). In CAV mode, the system operates with predefined steps, offering options like CLOSED, Vmin, Vmid, Vmax, and OPEN. The VRP-M controller can be integrated into an MP system via its MP-Bus connection, allowing for digital control signals from a higher-level bus master.

A key feature is the "Creep flow limitation," which suppresses differential pressure signals in the zero region (1-6 Pa) to prevent undefined actuator movements. This ensures stable operation, especially at very low flow rates. Additionally, the "Unit manufacturer's minimum setting limit" addresses challenges with oversized VAV units at low differential pressures, allowing for a minimum volumetric flow setting to avoid functional restrictions.

The system also incorporates override functions for special applications, such as CLOSED or OPEN, which can be triggered by control inputs. In bus operation, the VRP-M receives its reference signal from the higher-level control system and adjusts the volumetric flow to the selected value within the Vmin...Vmax range. The system saves the last setpoint received from the bus master, ensuring that operation continues with this setpoint even if the MP network fails. Upon power failure, the VRP-M starts with its MP initial status (setpoint 0%, corresponding to Vmin setting).

Usage Features:

The VRP-M VAV system is designed for ease of use and integration. It is a ready-to-connect solution, meaning components are optimally matched and pre-configured by the unit manufacturer (OEM) according to system requirements. This simplifies installation and commissioning.

The VRP-M-Tool is a crucial diagnostic and service tool that allows for direct adjustment of operating data, such as Vmin, Vmid, Vmax settings, and reference signals (mode setting – voltage range). This tool can be connected directly to the VRP-M VAV controller's diagnostics socket or via a terminal in the control cabinet.

The pressure sensors (VFP-...) are robust, designed for static differential pressure measurement in air ducts, and are suitable for contaminated or slightly aggressive air. They feature a wear-free, inductive measurement method and temperature compensation to minimize drift, ensuring maintenance-free operation. The sensors are calibrated at the factory in a vertical position but can be readjusted on-site if mounted in another position.

The damper actuators (NM...-ST and NMQB24-SRV-ST) offer simple direct mounting on the damper spindle with a universal spindle clamp and an anti-rotation strap. They include a self-resetting pushbutton for manual override, which also triggers a synchronization process for position calculation, preventing deviations. The angle of rotation is adjustable and adapts to the available setting range of the damper, with mechanical end stops protecting the actuator and damper mechanisms. The fast-running NMQB24-SRV-ST actuator performs a synchronization after power-on or manual disengagement, moving to the CLOSED position before returning to its nominal position.

The MP-Bus functionality allows for the integration of up to eight Belimo MP devices (VRP-M, VAV-Compact, damper actuators, valves) into various systems, including DDC controllers with integrated MP-Bus protocol, EIB Konnex, and LONWORKS® systems. Addressing MP devices is straightforward, either by serial number or by acknowledging the selected address via a pushbutton on the VRP-M.

Maintenance Features:

The VRP-M VAV system is designed for maintenance-free operation. The pressure sensors, with their wear-free inductive measurement method and temperature compensation, require no routine maintenance. Similarly, the damper actuators are overload-proof, do not require limit switches, and automatically stop at the end position, reducing the need for adjustments or repairs.

The VRP-M-Tool facilitates diagnostics and service work, allowing technicians to check electrical connections, zero offset of the pressure sensor, damper mobility, supply pressure, Vmin/Vmax settings, and control signal settings. This tool simplifies troubleshooting and ensures optimal system performance without requiring complex manual interventions. The ability to adjust operating data directly on the system with the VRP-M-Tool means that fine-tuning and recalibration can be performed efficiently, minimizing downtime.

Replacement devices, if needed, are pre-parameterized by the OEM according to the installed system, ensuring seamless integration and continued maintenance-free operation. The system's robust design and self-monitoring capabilities contribute to its high functional reliability and reduced maintenance requirements over its lifespan.

Belimo VRP-M - Page 27

Table of Contents