MTC5 is a compact controller for heating, ventilation, air-conditioning and refrigeration systems (HVAC/R). Control is based on chains of conditions configured through predefined logic rules. Intended for OEM manufacturers and installers.
Instead of classic programming, the behavior of the system is defined by selecting and arranging predefined functional conditions. Control is built from a set of logic operators, math blocks and timers/counters.
The input data can be the value of a measured temperature, a process variable or another system state. Based on these, logical processing is performed that controls the output elements – relay outputs and analog 0-10V / PWM control signals.
The device uses logic based on chains of conditions, in which the operation of a single output is controlled by individual chains of conditions/events. For each output the system provides four independent parallel chains of conditions, where each chain is a sequence of up to five conditions. When all conditions within a given chain are met, the corresponding output (relay) is activated.
The controller supports two fully independent configurations – for heating and for cooling – with manual, automatic switching or locking. Parameterization, monitoring and service functions are performed over Wi-Fi, via a mobile application for the end user and installer software for Windows.
Main functions:
| Power supply | 230 V ±10% / 50 Hz, ≈ 3 VA | Mounting | On DIN rail 35 mm; for embedding |
| Operating conditions | −5…+40 °C, RH 80% | Dimensions | 68×85×58 mm |
| Storage and transport | −20…+60 °C | Protection rating | IP20 |
| Temperature inputs | 4 pcs. | Outputs | 4 pcs. relay |
| Digital inputs | 2 pcs. | R1…R4 | 220 V, 5 A and 180 W/AC3 (motor) |
| Analog outputs | 2 pcs. 0-10V (PWM 1 kHz), 0.5% | Interface | WiFi / ModBus RTU |
| Sensors | NTC10K/20K, Pt1000, KTY81-110 | Measurement | −20…+150 °C; accuracy ±0.5 °C |
Instead of classic programming, the behavior of the system is defined by selecting and arranging predefined functional conditions. The input data can be a measured temperature, a process variable or another system state; based on these, logical processing is performed that controls the relay outputs and the analog 0-10V / PWM signals.
The heart of the controller is the relay logic. Each physical relay (RA…RD) and each internal (MEM) relay (MA…MD) is controlled by its own grid (table) of comparison cells. The logic runs cyclically — the whole set of conditions is recomputed many times per second, so the outputs track the sensors, digital inputs, timers and clock in real time.
Each cell holds one condition of the form Tx (sign) Ty:
The cell is evaluated every cycle and yields TRUE or FALSE. When Ty is a relay state, a mode or RUN, the left side and the sign take on a special meaning — e.g. for a relay state „>" means "the relay is OFF" and „<" means "the relay is ON".
The cells are arranged in rows of 5 columns:
The tables of the physical relays (RA…RD) have 4 rows × 5 columns — up to 4 independent conditions for turning on the output. The tables of the internal (MEM) relays (MA…MD) have 2 rows × 5 columns. An unused column is filled with the setpoint TRUE (so it does not block the row), while FALSE temporarily disables a whole row without deleting it.
The logic of each relay can be represented as an electrical contact (ladder) diagram: each cell is a contact, the five cells in a row are 5 series-connected contacts (logical AND), and the up-to-4 rows are parallel branches (logical OR). A cell with the setpoint TRUE is a permanently closed contact, while FALSE is a permanent break of the whole row.
For chatter-free switching the composite setpoints T+dT+dTHist are used — the turn-on and turn-off limits are offset from one another by the hysteresis band (dT.HIST), so the relay does not switch frequently around the threshold value.
In OFF mode all relays are off by default. A row can drive an output in OFF only if it contains a RUN ALWAYS or RUN @OFF cell or a MODES==… condition — so e.g. frost protection keeps working even when the controller is otherwise off.
Through the relay-state setpoints (Relay1…4, MEMRelay1…4) one output can depend on another — building interlocks, mutual exclusion and priorities between channels. The internal (MEM) relays (MA…MD) are program flags that do not directly control an output but serve to extend the logic chains. The MERGE option directly combines (logical OR) a physical relay with the MEM relay of the same name.
Example: turning on a circulation pump (Relay 1) when there is a sufficient difference between the collector (T1) and the tank (T2), without overheating — Row 1: „T1 > T2+dT2+dTHist2" AND „T2 < T.Max2" AND TRUE AND TRUE AND TRUE. The relay turns off when the difference drops, thanks to hysteresis, and is blocked when T.Max2 is reached.
| dT1…dT4 | Offset to the respective sensor; forms the value T+dT (range −20…+20 °C) |
| dT1.HIST…dT4.HIST | Hysteresis band for the respective object (−5…+5 °C) |
| T1.Good…T4.Good | Desired target temperature for object 1…4 |
| T1.Min…T4.Min | Minimum temperature for object 1…4 |
| T1.Max…T4.Max | Maximum temperature for object 1…4 |
| T.Deice1, T.Deice2 | Limit temperatures for defrosting/de-icing |
| ThdTimer1…ThdTimer4 | Thresholds for timers 1…4 |
| Timer1_Max…Timer4_Max | Period (maximum value) of the timers |
| Math1Const…Math3Const | Constants for the math channels |
| Schedule1_ON/OFF, Schedule2_ON/OFF | Start and end of time schedules 1 and 2 |
| AnOut1QLo/QHi, AnOut2QLo/QHi | Minimum/maximum of the PWM output (%) |
| AnOut1RefLo/RefHi, AnOut2RefLo/RefHi | Limits of the input quantity for the conversion |
| SensorType | Selection of temperature sensor type |
Three math channels compute a result of the form "result = Tx ± Ty" from any two inputs and store it as a sensor value (e.g. difference T1−T2, error signal setpoint−sensor, time-compensated setpoint). The result can be used by the logic, as a temperature limit, as a timer threshold or as an input quantity for an analog output.
The controller has four independent timers (Timer1…Timer4) driven by a common driver — each channel can do everything. The timers provide on/off delays, minimum run time, protection against frequent switching, periodic events, a slow PWM/ramp generator and a watchdog. Each timer is configured with four settings:
The timer output is read in the operands via the setpoint Timer? vs. ThdTimer — a cell triggers when the counter is above (or below) its threshold. The timer value can also be fed to an analog output for a smooth ramp over time.
The two analog outputs (AnOut1, AnOut2) are 0-10V or PWM 1 kHz with a range of 0…200 steps (resolution 0.5%) and control modulating valves, mixing dampers and speed control. Each output is recomputed once per second along the chain: Tx (±) Ty → data → controller → range scaling → limiting and forced control → AnOut%.
The controller stores two full configurations — a heating set and a cooling set — for both the logic program and the parameters; the mode (season) selects which one is active. Switching can be manual (from the keypad), hard-locked to a single mode, controlled by an internal MEM relay or by a digital input.
A real-time clock with two on/off schedules (Schedule1, Schedule2) and a day-skip option. Day/night mode, scheduled boosts (e.g. anti-legionella), a fixed and a user-selectable time zone (HH:MM – hh:mm) are supported, as well as a "vacation" function with a calendar to disable the time zones until a given date.
A single MTC5 controller can implement many schemes by configuring the logic, parameters, math, timers and analog outputs. Examples: