EVAPCO · Cooling tower
eco-Air controller with AC fan motors (adiabatic coolers, fluid coolers and refrigerant condensers) Modbus register map
Default configuration
- Protocol
- RS485
- Port
- 502
- Unit ID
- 1
- Addressing
- 1-based
- Byte order
- Big endian
- Word order
- High word first
- Baud rate
- 19200
- Parity
- Even
- Data bits
- 8
- Stop bits
- 1
This device has an RS-485 interface. Reach it through a Modbus RTU-to-TCP gateway, configured with the factory serial settings above.
Register map
| Address | Count | Name | Type | Unit | Scale | Access |
|---|---|---|---|---|---|---|
| 16384 | 2 | Setpoint #1 temperature Primary process temperature setpoint used when no alternate setpoint is active. | Float32 | - | 1 | RW |
| 16386 | 2 | Setpoint #2 temperature Alternate process temperature setpoint, activated by the scheduler, ambient temperature or a digital input. | Float32 | - | 1 | RW |
| 16388 | 1 | Maximum allowed fan speed Maximum allowable fan speed, 0 to 100 %. | Int16 | % | 1 | RW |
| 16389 | 1 | Quiet operation maximum fan speed Maximum allowable fan speed while quiet operation is active, 0 to 100 %. | Int16 | % | 1 | RW |
| 16390 | 1 | Energy savings fan speed Fan speed above which the pre-cooling system activates, 0 to 100 %. | Int16 | % | 1 | RW |
| 16391 | 1 | Minimum allowed fan speed Minimum allowable fan speed, 0 to 100 %. | Int16 | % | 1 | RW |
| 16393 | 2 | Proportional temperature regulation band Temperature band between minimum and maximum fan speed for proportional fan control, 0.0 to 30.0. | Float32 | - | 1 | RW |
| 16395 | 2 | PID controller gain Proportional gain constant of the PID fan-speed controller, 0.0 to 10.0. | Float32 | - | 1 | RW |
| 16397 | 1 | PID controller Ti term PID integral term, 0 to 999 s. | Int16 | s | 1 | RW |
| 16398 | 1 | PID controller Td term PID derivative term, 0 to 999 s. | Int16 | s | 1 | RW |
| 16399 | 2 | Setpoint #2 ambient temperature trigger Ambient temperature below which control switches to setpoint #2, -100.0 to 200.0. | Float32 | - | 1 | RW |
| 16401 | 2 | Setpoint #2 ambient trigger differential Temperature differential added to the setpoint #2 ambient trigger before control returns to setpoint #1, 0.0 to 20.0. | Float32 | - | 1 | RW |
| 16419 | 1 | Condenser refrigerant type 1=R22, 2=R134a, 3=R404A, 4=R407C, 5=R410A, 6=R407A, 7=R407F, 8=R290, 9=R507A, 10=R717 (NH3), 11=R723, 12=R1234ze, 13=R744 (CO2), 14=R448A, 15=R427A, 16=R450A, 17=R513A, 18=R449A, 19=R1234yf, 20=R454B, 21=R454C, 22=R455A, 23=R434A, 24=R422A, 25=R32, 26=R452B, 27=R452A, 28=Custom. | Int16 | - | 1 | RW |
| 16421 | 2 | Low temperature pre-cooling system lockout Minimum ambient temperature at which the pre-cooling system may operate, -9,999.0 to 9,999.0. | Float32 | - | 1 | RW |
| 16423 | 2 | Low temperature differential for pre-cooling lockout Ambient temperature offset added to the lockout temperature, 0.0 to 20.0. | Float32 | - | 1 | RW |
| 16425 | 1 | Stage #1 increase time setpoint Seconds the process temperature must stay above setpoint before stage 1 activates, 0 to 32,767. | Int16 | s | 1 | RW |
| 16426 | 1 | Stage #1 decrease time setpoint Seconds the process temperature must stay below setpoint before stage 1 deactivates, 0 to 32,767. | Int16 | s | 1 | RW |
| 16427 | 1 | Stage #2-4 increase time setpoint Seconds the process temperature must stay above setpoint before stages 2-4 activate, 0 to 32,767. | Int16 | s | 1 | RW |
| 16428 | 1 | Stage #2-4 decrease time setpoint Seconds the process temperature must stay below setpoint before stages 2-4 deactivate, 0 to 32,767. | Int16 | s | 1 | RW |
| 16429 | 2 | Stage #1 ambient temperature switch point Minimum ambient temperature above which stage 1 may operate, -999.9 to 999.9. | Float32 | - | 1 | RW |
| 16431 | 2 | Stage #2 ambient temperature switch point Minimum ambient temperature above which stage 2 may operate, -999.9 to 999.9. | Float32 | - | 1 | RW |
| 16433 | 2 | Stage #3 ambient temperature switch point Minimum ambient temperature above which stage 3 may operate, -999.9 to 999.9. | Float32 | - | 1 | RW |
| 16435 | 2 | Stage #4 ambient temperature switch point Minimum ambient temperature above which stage 4 may operate, -999.9 to 999.9. | Float32 | - | 1 | RW |
| 16438 | 1 | Stage #1 minimum run time Minimum time stage 1 stays active before it may turn off, 0 to 32,767 s. | Int16 | s | 1 | RW |
| 16439 | 1 | Stage #2 minimum run time Minimum time stage 2 stays active before it may turn off, 0 to 32,767 s. | Int16 | s | 1 | RW |
| 16440 | 1 | Stage #3 minimum run time Minimum time stage 3 stays active before it may turn off, 0 to 32,767 s. | Int16 | s | 1 | RW |
| 16441 | 1 | Stage #4 minimum run time Minimum time stage 4 stays active before it may turn off, 0 to 32,767 s. | Int16 | s | 1 | RW |
| 16443 | 1 | Pre-cooling flush period Minutes the flushing routine runs, 0 to 9,999. | Int16 | min | 1 | RW |
| 16444 | 1 | Pre-cooling drying period Minutes the pre-cooling pads are dried after a flush, 0 to 9,999. | Int16 | min | 1 | RW |
| 16445 | 2 | Pre-cooling flush fan speed Fan speed used during a flushing cycle, 0.0 to 100.0 %. | Float32 | % | 1 | RW |
| 16448 | 1 | Source for fan speed control 1 = analog input, 2 = communication (see register 409158). | Int16 | - | 1 | RW |
| 16449 | 2 | Signal failure ambient trigger When fan-speed control comes from the analog input, decides whether a signal failure falls back to the high or low default fan speed, -100.0 to 200.0. | Float32 | - | 1 | RW |
| 16451 | 1 | Signal failure high default fan speed Fan speed used when the analog input is lost and the ambient temperature is above the trigger, 0 to 100 %. | Int16 | % | 1 | RW |
| 16452 | 1 | Signal failure low default fan speed Fan speed used when the analog input is lost and the ambient temperature is below the trigger, 0 to 100 %. | Int16 | % | 1 | RW |
| 8961 | 1 | Actual unit state 1 = unit on and operational, 2 = off by alarm, 4 = off via BMS, 6 = off via digital input, 7 = switched off locally, 8 = manual fan-speed mode. | Int16 | - | 1 | R |
| 8962 | 2 | Process temperature Outlet temperature of the process fluid; on condenser applications a saturated value calculated from the condensing pressure. | Float32 | - | 1 | R |
| 8964 | 2 | Ambient temperature Temperature read by the ambient sensor. | Float32 | - | 1 | R |
| 8966 | 1 | Reference fan speed Fan speed the controller is requesting, 0 to 100 %. | Int16 | % | 1 | R |
| 8967 | 2 | Current active temperature setpoint Setpoint the eco-Air unit is currently maintaining. | Float32 | - | 1 | R |
| 8969 | 2 | Inlet pressure Inlet pressure from the pressure-sensor input. | Float32 | psig/bar | 1 | R |
| 9158 | 1 | Remote fan speed reference (communication) Fan speed reference when remote fan speed is enabled and the source is communications; value is x10, 1000 = 100.0 %. | Int16 | % | 0.1 | RW |
| 9159 | 2 | Remote fan speed reference (analog input) Fan speed reference derived from the analog input, 0.0 to 100.0 %. | Float32 | % | 1 | R |
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Related guides
Notes
Source: EVAPCO "Controller User's Manual - Addendum, Communications Guide AC Motor Edition", COMM24AC-E_1025, October 2025 (https://www.evapco.eu/sites/evapco.eu/files/2025-12/EVAPCO%20eco-Air%20Communications%20Guide%20AC%20Motor%20COMM24AC-E_1025.pdf), with the factory communication defaults from the "EVAPCO Controller User's Manual" dated 5/10/2022, Table 23 (https://www.evapco.com/sites/evapco.com/files/2022-05/Controller%20Users%20Manual_edited_5_10_22.pdf): Modbus RTU, node address 1, 19200 bps, even parity, 1 stop bit, 8 data bits (Modbus RTU). The guide publishes holding registers as six-digit 4xxxxx references (e.g. 416384), i.e. a 4 followed by the five-digit one-based register number, so this file stores the register number (16384) and declares one_based addressing. Rows ending in ',nn' in the source are single bits inside a holding register and are not modelled. 32-bit runtime counters are also left out because the document does not state their word order. The source's Units column renders as '0°' for temperature rows without saying °C or °F, so those rows carry no units and use whatever temperature scale the controller is configured for; fan speeds and percentages are %. Values are transmitted in engineering units, with the one documented exception of register 409158, which is x10.