This part of ISO 12176 specifies the main performance requirements for electrofusion control units for use with PE electrofusion fittings, conforming to ISO 8085-3, for gas distribution systems. The control units are divided into two input voltage classes: SVLV [safety, very low voltage (0 V to 50 V)] and LV [low voltage (50 V to 240 V)]. This part of ISO 12176 is applicable to electrofusion control units designed for use in the construction of joints between polyethylene (PE) pipes and fittings conforming to ISO standards for gas distribution systems, where the normal operating temperature of the control unit is in the range of – 10 °C to + 40 °C. If temperatures outside this range are expected, suitable operating limits will have to be agreed between manufacturer and purchaser. This part of ISO 12176 is applicable to control units with current or voltage control for fitting systems based on standard resistance wire heating technology.