Copyright 2018, Michael Bryant
Balancing a heating system...
I get asked about this surprisingly often. There is much confusion about this apparently mysterious thing heating engineers do called 'balancing'.
Many people don't realise a radiator has a valve on both ends (the blank cap at the opposite end of the radiator to the normal on/off valve also has a valve underneath it), and those who do, sometimes don't realise it has two completely separate functions...
1) To allow the radiator to be isolated and removed from the heating system without turning off and draining the whole system.
2) To partially close and restrict the flow of hot water through the radiators closest to the pump in order to divert it to the more distant radiators.
When the lockshield valve (the plumber's name for the valve with the blank cap) has been adjusted as in 2), the system is said to have been balanced. So balancing is quite a simple concept really. When a perfectly balanced system is turned on, all the radiators will warm up equally quickly, rather than some sooner at the expense of others., but of course there is no such thing as a perfectly balanced system in real life.
Balancing is actually a very hit-and-miss affair. A quick, rough, intuitive balance (if any balancing at all) is all that's done when a heating engineer commissions a new system, and this is usually perfectly adequate. He'll fully close then open half a turn the lockshield valves on any radiators very close to the pump, then perhaps half close those a bit further out, and leave fully open all the more distant radiators. Upstairs radiators usually need to be closed more than downstairs, to counteract the natural tendency for hot water to rise and flow to the higher radiators at the expense of radiators below.
It's easy to end up fiddling about for hours balancing a system ever more accurately, but it really doesn't matter that much. As long as all the radiators heat up within 15 minutes or so no-one is likely to realise a system is poorly balanced. In fact the settings are often lost once a few decorators have removed the radiators to decorate behind, then replaced them and fully opened the lockshield valves. Users rarely notice!