Adjusting lockshield valves to balance radiators
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Balancing radiators ensures equal heat distribution around the system. Start by opening all lockshield valves fully — remove the plastic cap and turn anti-clockwise until fully open.
Turn the heating on from cold. Note which radiators heat up fastest — these are the ones closest to the boiler and will need their lockshield valves partially closed.
Your target is for the temperature difference between the flow pipe (into the radiator) and return pipe (out of the radiator) to be approximately 12°C on every radiator. This is called the delta-T.
Starting with the radiator that heats up fastest, partially close the lockshield valve — typically a half to one full turn from fully open — until you achieve the correct delta-T reading.
Work through all radiators, making small adjustments until all radiators reach similar temperatures at similar times. This process takes patience — allow 20–30 minutes between adjustments.
Note the number of turns each lockshield valve needed so you can restore settings if a valve is disturbed during maintenance.
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