Got to disagree with Croydoncorgi on the point of throttling DHW cylinder return flow, the coil is just another heat emitter, and customers, whilst they do want "hot water now" probably don't want it at the expense of heating. Remember the DHW coil is just a coil of 28mm pipe inside a tank, as the DHW heats up so the heat transferred to it reduces. This means the return water temperature rises which reduces boiler output, either by modulating it's burner pressure or by turning off.
All rads and cylinders are loads in parallel, the idea with balancing it to give each load a flow proportional to its size. In doing so three things will benefit.
1. All rads will heat evenly, giving quick warm-up and user comfort, therefore programmer "switch-on" can be set later and less gas used.
2. Boiler load will be higher, resulting in longer condensing periods and a large reduction in boiler short-cycling.
3. Boiler efficiency and reliability will be increased, as each boiler firing adds to thermal and electronic "stress".
So when a system is adequately balanced system return temperatures from all branches (except DHW) are substantially the same. I have excluded the DHW from this statement because of the dynamic nature of it's load, my opinion is that it should be set to give the required differential temperature with the cylinder under 40C.
TRV heads should be removed when balancing for reasons previously covered (very well) by others.
