Constant Hot Water v Timed. Which is more Economical???

[EN4]

I have a Potterton Netaheat Profile 40e boiler and usually keep the hot water on constant. But we have a power shower for morning use and the kids have a bath in the evening.

The house is empty most of the day and we use a cold file dish washer and washing machine.

Is it more economical to keep the hot water set to constant or just have it timed to come on 2 hours in the morning and the same in the evening?

Thanks in advance for any input?

EN4

 

[cross thread]

take a meter reading when trying it both ways ,that way you have a deffinate answer

 

[EN4]

take a meter reading when trying it both ways ,that way you have a deffinate answer

But there are to many other variables.. numbers of cups of tea / food consumed etc?

Anyone got an idea from past experiences?

Cheers

EN4

 

[JohnD]

yes of course.

with a Profile you have a hot water cylinder, right?

Heat loss (energy used) is proportional to temperature difference x time

so having a cylinder at 60°C for 24 hours will lose more heat than if it is at 60°C for the eight hours you are at home and awake, and at a lower temperature when you are out. Set the timer so it comes on about half an hour before the first person wants a morning bath or shower, goes off 15 minutes before the last person leaves for work; comes on 15 minutes before the first person comes home, and it goes off after the last person has had their bath or shower at night. If you have a fully pumped system and a modern cylinder, the Netaheat should take it from cold to hot in 20 to 30 minutes. Adjust the cylinder stat so that it is no hotter than you need.

If your HW circuit is not pumped, you can set the stat a bit lower, as the extra heat held in the large iron heat exchanger will rise up after the boiler has gone out.

HOWEVER
it is very important to lag the hot pipes using Climaflex or similar stiff plastic foam tubular lagging, and to insulate the cylinder very well, preferably with factory fitted foam, else with two of those red fibreglass jackets. Insulate the pipes inside the airing cupboard, especially the one that comes out of the top of the cylinder, and any pipes under floorboards and in the loft. Insulate the hot pipes to the bath and sink. You will be surprised how much heat a round fat radiator (cylinder) or a long thin radiator (pipe) can weaste.

 

[electronicsuk]

It's a no-brainer, the water shouldn't be heated when not in use. There will be heat loss from the cylinder throughout the day. The hotter the cylinder, the greater the temperature differential between the outer skin of the cylinder and the ambient air, thus the cylinder will give up more of its heat to the air surrounding it. This will then result in the boiler constantly kicking in to bring the cylinder back up to temperature.