ChatterBank0 min ago
Central Heating/Hot Water
8 Answers
This has most probably been asked before but will check before I press the 'go' button. During the colder winter months I leave the CH on from 0530 to 2230, same applies to the HW. This means there is a seven hour period when power to both services is switched off. Must say both the house and the HW seem to maintain a satisfactory balance.
The question is : Is this the most economical option or should they be left on for the full 24hours? I have heard that by switching off, both services will cool and take longer to regain the thermostat level and so negate any advantages. I keep meaning to ask the BG engineer when he does my annual service, but always forget!!
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Im sure the BG engineer will tell you to leave it on 24 hours, so you use as much gas as possible! If your water storage tank is well lagged, it will not cool down very much during the night, I would carry on the way you are. In fact we have the boiler set to go off during the day as well, (when the house is empty), it comes back on at about 5pm, and heats up in about 15 mins, ready for when we get home. Then its on till bedtime, around 11, then off untill about 6, so its warm at 6.30 when we get up. I feel sure that is more economic than leaving it on all the time.
If there were no heat loss then, once up to temperature, there would in theory be no need to input any energy. Of course, there is heat loss and so energy (electricity) must be used to replace this heat loss.
Heat loss is a function of the difference between the water temperature and the air temperature. By keeping the heater on 24 hours a day, a high temp difference is maintained between water and air. Therefore maximum heat loss occurs and this has to be replaced. By turning off the heater for a while, the temp difference decreases as the water cools. Therefore the heat loss decreases. Therefore the energy that has to be 'put back' is less.
Thus, cheaper to have it turning off (though it might be more convenient to keep it on and always have hot water).
The above is the thermal loss argument, which stands up to the laws of physics.
The conflicting argument is that gas and oil boilers are less efficient when they are in the process of heating up from cold. This does not apply to electricity which converts all its input energy into heat. So boilers cause more loss of energy if switched off for a period. I don't know the answer - I think it depends on the system design. Take meter readings over a few nights perhaps?
Your house will always lose heat like a leaking bucket loses water so only have the heating on when you need it. Running it at other times is just throwing money away. If your house is reasonably insulated then the recovery time will be very quick and use a lot less fuel than keeping it going all day. The hotwater cylinder will heat up fairly quickly and then switch off on it's thermostat.
Many thanks to everybody for their info. I do have full loft insulation although no double glazing (please do not let this out of the bag!!!). It is a 1934 build on the east coast and one of the first things that attracted us was its apparent warmth. It seems a bit of experimenting is at hand, every little helps. Many thanks again.
Just one final suggestion.......why not fit a programmable room thermostat that you can pre-set to different temperatures for different times of the day. I've used one for years.....just fit and forget. You can always over-ride the settings if need be. Most types can be programmed separately for weekends if you're at work mid-week.
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