Why a heating system is balanced and an ordered way to set the lockshield valves for even heat.
Without balancing, the radiators nearest the pump grab most of the flow and the far ones stay cool. Balancing shares the water out so the whole system heats evenly, and it is done at the lockshield valves. In principle:
- Make sure the system is clean and free of air first, because sludge or air will upset any balance you set.
- Identify the two valves on each radiator: the lockshield, capped, valve is the balancing valve, and the other valve is the wheelhead or thermostatic valve that turns the radiator on and off or controls its temperature.
- Open everything up to start: all radiator valves fully open, so you can see the natural imbalance.
- Bring the system up to temperature and let the flow settle.
- Measure the temperature drop across each radiator, comparing the flow side with the return side, since a radiator giving up heat properly shows a sensible drop between the two.
- Adjust the lockshield valves so each radiator shows a similar temperature drop: throttle back the greedy radiators near the pump so more flow reaches the far ones.
- Work round the system more than once, since adjusting one radiator affects the others, until the drops are reasonably even.
A balanced system heats evenly and helps the boiler and controls work as intended. Use the temperature drop and method appropriate to the system and follow the current guidance and the manufacturer instructions.