Replacement Ionization Electrode for Vitodens 200-W WB2 and WB2A Series Residential Wall-Mounted Gas-Fired Condensing Boilers. The Vitodens 200-W WB2 and WB2A boilers are designed to operate with natural gas and liquid propane gas (LPG). When ordering replacement parts, check with the manufacturer and provide the 16-digit boiler serial number or the 12-digit ASME/NB serial number to ensure a proper fit before purchasing.