Not required., Active/ passive cooling in 4-pipe system - ACS 45., Active/ passive cooling in 2-pipe system - HPAC 45., External electric additional heat elk - ELK 15., External electric additional heat elk - ELK 42., External electric additional heat elk - ELK 26., External electric additional heat elk - ELK 213., Extra shunt group - ECS 40/ ECS 41., Auxiliary relay HR 10., Communications module MODBUS 40., Assembly system FMS 40/42., Filling valve kit - BRINE 32., Current sensor - CMS 10-200., Accessory card - AXC 50., Buffer vessel UKV., Water heater/ accumulator tank., Hot water control - VST 11., Hot water control - VST 20.