LCD Room thermostat

The Z series is the digital room thermostat: an LCD display, capacitive keys and a programmed control sequence, in place of the dial and bimetal of a mechanical unit.

Adjustment range is 5 C to 35 C, indication range 0 C to 50 C, control accuracy plus or minus 1 C, rated output below 200 W and standby consumption below 2 W, on a 220 VAC plus or minus 10 per cent supply at 50/60 Hz. Five models (Z001 to Z005) cover different key layouts and functions.

The functions are the reason to choose a digital thermostat over a mechanical one: on/off switching, setpoint adjustment, room temperature measurement, temperature-limited switching (so the setpoint cannot be driven outside a band), timing, key lock, backlighting, and synchronous control of the valve and the fan. The last one matters on fan coils - the valve and fan are driven together so the coil does not run with no water flow, and the memory-on-power-down keeps the settings through a supply interruption without a battery.

Key lock is worth noting for commercial spaces: it stops a customer in a shop from changing the setpoint, which on a mechanical thermostat is impossible to prevent.

Installation: mount at about 1.5 m, on an internal wall, away from sunlight, draughts and the unit discharge, and keep the cable run from the fan coil separate from power cables where possible. Because these units switch 220 VAC directly, confirm the load is within the 200 W rating - a fan coil with a large motor needs a contactor, and a thermostat run beyond its rating fails in a way that looks like a control fault.