The mechanical room thermostat is an economical and simple to use room thermostat. Simply turn the mechanical control dial to your desired temperature to control your room temperature. This unit also produces an audible “click” when you turn the dial past the current temperature so you know when the system is being turned ON or OFF. The mechanical two wire thermostat is very easy to install And, by having volt free contacts, is suitable for systems with either a combination or normal boiler. If you have a three wire installation, simply cut back and make safe the neutral, and this two wire thermostat will give you years of faithful service.