Boiler room and HVAC automation with PLC
Boiler rooms and HVAC systems are the second most common automation target after pump stations. The PLC controls burners, circulation pumps, three-way valves, fans — all with PID temperature and pressure control.
A typical 2-3 boiler room needs 30-60 I/O and 4-8 analog channels. We have built dozens using Siemens S7-1200 and Delta DVP.
PLC tasks
- PID temperature control with weather compensation
- Boiler cascade management
- Burner sequencing and flame monitoring
- Circulation pump rotation
- Three-way valve control (0-10 V)
- Heat metering via Modbus
Sensors
| Parameter | Sensor | Output | Module |
|---|---|---|---|
| Supply temperature | Pt100 | Resistance | RTD |
| Pressure | Pressure sensor | 4-20 mA | AI |
| Flame | Ionization | Discrete | DI |
| Gas detection | Gas analyzer | 4-20 mA | AI |
HVAC
- Supply fan via VFD
- Dampers with actuators
- Water heater — three-way valve + PID
- Heat recovery unit
- Filter — differential pressure sensor
PLC selection
- Budget: Delta DVP-SA2 + modules — from $400
- Standard: Siemens S7-1214C + modules — from $800
FAQ
Which PLC for a gas boiler room?
Siemens S7-1200 or Delta DVP-SA2. Gas boilers need dedicated burner controllers (Honeywell, Siemens).
Safety controller needed?
For industrial gas boilers — yes. For small installations — standard protections suffice.
Weather-compensated control?
Outdoor temperature sensor → heating curve → PID on valve.
Analog channels for HVAC?
3-4 AI + 2-3 AO = 5-7 channels for a typical AHU.
Remote control?
Via Ethernet or GSM to HMI or S7-1200 web server.
Summary
Siemens S7-1200 — standard. Delta DVP-SA2 — budget option.
