Series N50 Low Water Cut-Offs are used on heating applications for low pressure, process, hot water heater boilers to protect them against emergency low water conditions. It has a float chamber that has 1 in. (25mm) NPT female top and bottom connections. Model N50S is for burner service with extra terminal for line voltage single pole, double throw service. Model N50D is for line voltage burner service and independent low (or high) voltage alarm, feed valve or pump starter.