On a Webasto Thermo 300 water heater, is there an optional sensor that has a higher run temp shutdown? We have a fleet of city buses where the run temp sensor range 165-170F,an improvement would be 178-180F as the Webasto cycle of heating to restart is very high,because of doors opening,and trying to maintain temps with dpf/scr emission and our extremely cold climate Any help is appreciated. 300 series Webasto.

In the parts catalogue for this heater there is only the one sensor available, it typically switches at 78 - 85 Celsius = 172 - 185 F

On a Webasto Thermo 300 water heater this temperature sensor is planned to be fitted on the heater outflow. This is relevant because this temperature can be much higher than the coolant temperature circulating around the heat exchangers in your city bus, especially if there is a higher than expected resistance to flow in the coolant circuit. Could the flow rate in your cooling circuit have deteriorated? Many bus applications for example include a coolant water filter? Can you advise which model water circulation pump you have installed? A reduced flow rate within the heater exchanger could also explain your comment regarding, 'cycle of heating to restart very high' (also known as 'Hysteresis') - if the flow rate is impaired the heat will be slower to dissipate, hence a longer time before the heater switches back on. If you have any photos of  heater install or circulation pump please send to sales@butlertechnik.com