Last week I was asked to be present when a local plumber was doing some 'maintenance' work for an elderly lady neighbour. He had replaced one radiator, flushed the crud out of the system, and finally added some corrosion inhibitor. Every rad had both the lockshield valve and the control valve fully opened during the flushing operation.
I watched him as he set about turning the system on, and his idea of balancing was to simply adjust each control valve until all the rads were working.
Now my knowledge of balancing radiators is simply from reading diy material online, but I am sure that his procedure is not correct.
I put it to him that the system could 'unbalance' if his customer decided to turn off some of the rads, - but he would not accept that. He had no idea that the lockshield valve was used for this purpose.
Am I right?