Vaillant By-Pass 0020083526

The Vaillant by-pass, part number 0020083526, is a boiler component listed in the isolation valve category for Vaillant gas boilers. It sits in the heating circuit of ecoTEC PLUS VU appliances and regulates flow through the boiler as system demand falls. Its function is to maintain a minimum flow rate across the heat exchanger, protecting the appliance from overheating and excessive temperature rise.

• The boiler locks out or trips on an overheat fault, particularly as heating demand falls.
• Flow noise or system pressure changes noticeably as zone valves or TRVs close.
• Radiators heat unevenly and the boiler short-cycles.
• Scale, debris or mechanical damage is visible on the by-pass when the casing is opened.
• Water weeps from the by-pass body or its connections.

• Confirm your boiler model and GC number against the manufacturer's parts list.
• Check that part number 0020083526 matches the component removed from the appliance.
• Establish whether the by-pass is supplied as part of a larger assembly on your model before ordering it separately.
• Have the appliance's installation and servicing instructions to hand for reference.