Single Range Thermostats Single Range Thermostats The Eaton SRT Thermostats (Also called Hydraulic) were designed for use in conventional ovens. The SRT employs a double pole single throw switch actuated by the hydraulic temperature sensitive bulb. Shaft rotation is clockwise to increase temperature. The SRT thermostat does not have a positive "Off" position. At the lowest setting, 150OF, it is in a "warm" position. The oven is turned on and off by a separate switch. The length of the capillary tube between 30" and 80". The operating temperature rating of the sensing bulb is 550OF (288OC) due to the type of hydraulic oil used.