Most efficient way to heat a HWC in Y-Plan open-vented system

[Scarum]

This is possibly more of a physics question but I believe there are some would be professors on this forum so the question that's been racking my head is what would be the most efficient way to heat a HWC in Y-Plan open-vented system?

1/ heat the HWC at the same time as the radiators, or
2/ heat the HWC on its own i.e. separately.

If the former would turning the boiler thermostat up be necessary? The HWC has a second layer of insulation.

Thanks.

 

[Nige F]

1/ in the winter 2/in the summer 3/ don't bath, shower and only do that once a week

 

[stem]

Generally it's 'swings and roundabouts'. For example if you turn the boiler thermostat up, it will heat the hot water cylinder a bit quicker, but will consume more energy whilst it is running, albeit for a shorter time.

In addition, because the boiler, and the pipes to the cylinder will also have been heated to the higher temperature they will loose more heat to the environment in which they are located. If the boiler thermostat was set lower, the pipes and boiler will not be so hot, so loose less heat, but will be hot for a longer period of time so the heat losses overall will probably be pretty much the same.

If the boiler and pipework is already hot because the heating is on, then if you were to heat the water at the same time, you wouldn't be having to heat the system up from cold, so may make a tiny saving, but if in the winter the heat losses from the boiler and pipes contributed to the heat input to you home then you could argue perhaps not.

Then there's the issue of boiler efficiencies at different loads which may vary from boiler to boiler, so what's best for one may not be for another.....but that's a different kettle of fish.

The best way to keep running costs down are to have good thermostatic controls, and insulate, insulate, insulate.