Grant Plate Heat Exchanger MPCBS21/A

The Grant MPCBS21/A is a plate heat exchanger used in Grant combi boilers, where it transfers heat between the primary circuit and the domestic hot water supply. It is the component that separates the boiler water from the mains water passing through the appliance. The part is listed for the Grant Combi 70 MKII, Combi 90 MKII and Combi Outdoor 90 MKII ranges.

• Domestic hot water temperature fluctuating or running cold while the heating circuit works normally
• Reduced hot water flow rate through the boiler, often linked to scale or debris blocking the plate passages
• Water weeping from the plate stack or from the connections at the heat exchanger
• Pressure rising on the heating circuit when the hot water is drawn, indicating transfer between the two circuits
• Repeated lockouts or overheat faults on the hot water side of the appliance

• Confirm the boiler model against the fit list above, as the part is listed for specific Grant Combi MKII variants
• Check the part number on the existing component or in the manufacturer's parts list before ordering
• Inspect the surrounding pipework and seals for scale or debris that may have contributed to the failure
• Verify whether the alternative part numbers listed apply to your appliance