This surface-mounted thermostat has been developed to be able to switch 2-wire boiler.  which is for upgrade for your old mechanical thermostat. Item No.: HT-16 Transmitter : 2*AAA battery Programmability: 7days programmable Temperature settings: 5°C ~ 35°C, 0.5°C increments Packing : Netural White Box, OEM acceptable Cetificate:CE, ROHS, RED