Controller for HVAC
The Schneider TM172OBM28R is a Modicon M172 programmable controller purpose-built for HVAC control, packing 28 mixed I/O (8 digital inputs, 8 analog inputs, 8 digital outputs, 4 analog outputs) in a DIN-rail mount with IP20 protection. Rated supply voltage covers 24 V AC or 20–38 V DC, so it runs off the same rail the rest of the cabinet uses. The real-time clock drifts ≤30 s/month across its -20 to 65°C operating range — enough to timestamp trend data without a separate time sync.
I/O and Sensor Mix
The 8 analog inputs are configurable by pair for voltage (0–5 V, 0–10 V), current (0–20 mA, 4–20 mA), or resistance/temperature probes (NTC, PTC, Pt1000). That gives a single part number flexibility across a range of field sensors — one controller for a rooftop unit or a chiller. Analog outputs: two channels fixed at 0–10 V, plus two more configurable for 4–20 mA, 0–10 V, or PWM (2 kHz). Relay outputs cover SPDT and SPST on independent or shared commons, rated 3 A each. Digital inputs sink or source, 2.5 mA per channel at 24 V AC/DC — standard for HVAC I/O modules, no special sourcing needed.
Compliance package covers CSA, UL 60730, EN 60730, IEC 61000 series (EMC immunity), both EMC and LV directives. Pollution degree 2, overvoltage category II — clean enough for commercial buildings and light industrial HVAC. No direct pin-compatible alternative exists within the same family; the M172 line uses a fixed I/O mix per order code. If the BOM requires exactly 28 I/O, this controller is the target.