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A HIGH LIMIT thermostat should be fitted to the gravity flow pipe close to the boiler and set at 90°C. This
should override any pump control, switching the pump on and dissipating any excess heat around the radiator
circuit.
To prevent boiler corrosion due to condensation it is necessary to maintain the return water temperature
above 45°C. This can be achieved by the use of a LOW LIMIT thermostat on the return pipe from the hot water
cylinder, close to the boiler. The thermostat should make on temperature rise, preventing the circulating
pump from operating until the gravity circuit is up to temperature.
A corrosion inhibitor should be added to the system to ensure satisfactory performance and long system life.
Wiring Diagram for general guidance only
All electrical work must be carried out by a competent electrician in accordance with the rules in force and the
instructions provided by the circulating pump and heating controls manufacturer.