The Honeywell ST9100S Single Channel Programmer is a Service Interval time controller with additional features to help landlords comply with the requirements of Regulation 36 of the gas regulations 1998. The ST9100S is a Service Interval time controller with additional features to help landlords comply with the requirements of Regulation 36 of the gas regulations 1998. The landlord, installer or service company can configure the Service Interval, the advance tenant notification period and how the controller will operate when the Service Interval has expired. The Honeywell ST9100S Service Interval Programme r is a 1 day timer with two on/off switchings times per day (which can be increased to 3). ST9100S can be used for combi boilers, heating zones or any application where small electric loads need switching. Honeywell ST9100S 24hr Single Channel Programmer With Service Reminder is a single channel timer, designed primarily for control of a single heating zone or combi boiler application. It is suitable for mains, low voltage, or potential-free switching of the heating load.