#Distech
VIM CAD HR BASIC (EVOD controller): Modbus link for ECLYPSE
An EC-gfxProgram program that integrates a VIM CAD HR BASIC heat-recovery AHU with the EVOD controller, constant airflow and electric heater version: occupancy schedule, forced airflow, supply setpoint, alarms decoded bit by bit and loss-of-communication detection.
- date
- 30 October 2026
- tested with
- EC-gfxProgram 7.10 · ECLYPSE ECY-3x0 (IP2) · VIM CAD HR BASIC, EVOD controller, CAV, electric heater
- license
- MIT
- tags
- #modbus,#ahu,#heat-recovery,#vim,#eclypse,#ec-gfxprogram,#schedule
What it does
The program controls and supervises a VIM CAD HR BASIC AHU fitted with the EVOD controller, the one with the communicating touch remote. It is written for a constant airflow (CAV) unit with an electric post-heater. The register table comes from VIM manual NT-509003, and it is detailed in the VIM CAD HR BASIC (EVOD controller) entry of the Modbus catalogue.
Watch out: recent CAD HR BASIC units with the EVCO controller (EPJcolor colour remote) have a completely different table, and this program won’t work on them. Their entry is here.
The pages
The page and point names are in French, as in the program.
- CTTA_Modbus: how the link works (addressing, timeout, what is read and what isn’t).
- CTTA_Mesures: outdoor, return, exhaust and supply temperatures, measured fan speeds and airflows, electric heater output, run-hour counter, setpoint read-back.
- CTTA_Etats_Alarmes: the status and alarm words (registers 5, 86, 90 and 97) decoded bit by bit into BVs, loss of communication and a general fault.
- CTTA_Commandes: schedule and run mode, season and bypass, forced airflow, supply setpoint.
- CTTA_Planning: the BACnet weekly schedule, with sample time slots to adapt.
Objects: 26 Modbus points, 20 AVs, 39 BVs, 3 MSVs, 62 trend logs and one schedule.
The commands
- Occupancy schedule: Confort (comfort) = AHU running; Réduit (reduced), Congés (holidays) and Hors gel (frost protection) = stopped.
- Run mode (MSV): 1 Auto (follows the schedule), 2 Forced on, 3 Forced off. Stopping uses bits 5 (fans) and 6 (post-heating) of register 20: the program writes season + bypass + 32 + 64.
- Season and bypass: bits 0-1 and 2-3 of register 20.
- Forced airflow: register 51, in m³/h (500 by default). 65534 = AHU time schedule, 65535 = auto.
- Supply setpoint for the electric heater: register 52, 5 to 30 °C, 0 = off.
Commissioning
- The
CTTAModbus device is set to slave 1, with no IP. For RTU, wire the bus to the RS485 option of the EVOD remote: 9600 baud, 8 bits, even parity, 1 stop bit. For TCP, enter the AHU’s IP (192.168.1.243 out of the factory) and port 502. - The addresses entered in the program are the manual’s register numbers minus 1: outdoor temperature, register 81 in the manual, is read at address 80.
- Also set the schedule on the AHU’s remote: it takes over if the BMS drops out.
The timeout, left on on purpose
The AHU keeps its factory timeout (10 s). Writes to registers 20, 51 and 52 are a temporary override: the AHU does not store them. The program reads the outdoor temperature every 2 s to keep the link alive. If communication drops, the AHU forgets the writes after 10 s and goes back to its own schedule: that is the fallback mode.
CTTA_Defaut_Com goes to 1 when the Modbus status stays non-zero (No error) for 30 s. The measurements then stay frozen at the last read.
Not included
The water coil, COP pressures, pre-heating, forced fan speeds (register 54), units 2 to 4, and the password-protected settings 8502 to 8559. For a water-coil or constant-pressure AHU, the program has to be extended.