Hot water heating with central heating

[ricky101]

Hi,

Have a conventional boiler rated at 30-40,000 btu with 2 zone indirect heating to rads and hot water tank.

The rads have a total max load of 22,000 btu

Have generally always heated the hot water separately before the rads come on in the morning.

Are we really doing that wrong, am thinking that just heating the hot water effectively wastes about 20,000 btu (30,000btu min boiler output - 10,000btu for the hot water tank)

So my current thinking is we should always try to heat both rads and hot tank together for max efficiency .... yes ?

That said, is it almost just as or even more efficient to always have the hot water heating whenever the rad heating is on ( assuming the hot water cylinder thermostat is still functioning and controlling the valve)

 

[kbdiy]

How good is the insulation on your hot water cylinder? Having just renewed mine the recovery time has become much shorter (ie more efficient) and it retains the heat for longer (also more efficient). I have never found any particular difference in heating the water at different time and have always tried to match the water heating to the likely demand, likewise with the heating.

The only disadvantage I can see to running both at the same time is a situation where the hot water robs heat from the heating side. This is usually overcome by some kind of restrictor fitted to the hot water circuit to balance the output evenly between heating and hot water.

Otherwise I can't really see there being much difference either way. Comfort and convenience versus absolute economy is what it comes down to.