We have just moved into a 3 storey house , that has gas central heatin boiler.
What is the ideal temp in 0c to operate this to heat the house.
weve been told different things by people we know , but im stil unsure.
I think that around 75 or 80c is right , yet someone else says 50c
also what would be ideal times for setting heating to ?? is is idea to have it on for say 2 hrs in am , and 2 hours at night , does tha use up more gas, or have it on for longer
If you have a conventional heating boiler, it should be run at its design temperature, which is around 80 degrees on the flow side. If it is run a lot cooler than that, there is a risk of condensation of flue products inside the boiler and consequent corrosion. Generally the boiler thermostat should not allow setting to temperatures low enough to cause a problem, but certainly 50 degrees or even 60 flow would take you to the point of internal condensation.
There is a newer type of boiler (condensing), which is now more or less mandatory to fit unless you have particularly unusual set of installation conditions. These can be 30% or so more efficient than some of the oldest conventional boilers and there is legislation on fitting them in new or replacement installations except in exceptional cases. In this type, the intention is that condensing does take place in the boiler, and the water is collected and fed to a drain. While these will work at the higher temperatures of the conventional boiler, they run more efficiently at lower temperatures.
However, if your system was originally designed for a conventional boiler, it is likely that the radiators will have been sized for 80 degree operation and 0 or -3 degrees outside. Unless they were oversized, running at 50 degrees may not give enough heat output in cold weather. This still means that a condensing boiler is worthwhile because for most of the year that level of heat output is not required and the boiler can run at a lower temperature and hence more efficiently
The other factor in low temperature operation would be that it would take longer to warm the house if it's really cold outside if radiators are run at 50 vs 80 degrees.
Switch on and running times are a personal choice. Of course running for longer uses more fuel, the other side of the coin is level of comfort.
One thing that you can do is to change the room thermostat for one with optimised start and perhaps night setback.
Optimised start is basically that the thermostat monitors how long it takes the heating system to raise the house temperature to the point you set. This is averaged over a few days. So for example, if you want it to be up to temperature at 0700 when you get up, it might need to start at 0615 on a cold day and so on.
Night set back means that instead of turning off the heating totally at night, it backs off the temperature by a few degrees. For example, you might set a setback of 6 or 7 degrees against a desired room temperature of 21 degrees and allow the temperature to fall to 14 or 15 during the night. Through much of the year, this doesn't use any or much extra energy, but in the coldest weather is pleasant if you need to get up during the night. Also, in some houses, it may actually prevent the temperature overshooting the set point by as much on the morning warm up and hence actually save fuel use overall.
If you don't have them, a useful investment is thermostatic radiator valves on the room radiators (all but the one where the room thermostat is). These allow finer control of room temperature and save fuel as well.
Using a programmable thermostat is perhaps the simplest way. That way you simply leave the heating "on" permanently - the stat then controls when it needs to run to reach your pre-set temps. Hence you can have it warmer for some times of the day, and cooler at others.
As for times, set it to whatever suits your lifestyle. When it's cold we generally have ours come on an hour or so before people get up, then it goes off after everyone leaves. It comes back on just before the kids get home, then off again about ten o-clock. Mostly though we don't use the timer - put it on when it feels cold for an hour.
We had a condensing boiler fitted last year and it is a lot more responsive than the back boiler we used to have. For showers - heat water for an hour in the morning, then off all day. If someone wants a shower, they set the water on for an hour and just go straight in - the water will still be hot from the morning.
If heating requirements are low, you lose a bit less from loft pipes going low. Also bolers are more effcient at lower temps I THINK. Not sure ..
But when it gets really cold you need the thing up around 60-70C to heat teh house at all..
If the house is well insulated and has good thermal mass inside the insulation, it makes very little difference to cost when you heat it - heat is retained well.
If its got low thermal mass and/or insulation then you want to only heat when you need it, and it will warm up fast.
The coldest, as well as the darkest, hour is just before the dawn.. I find that in winter, I want to start my underfloor heating about midday, so we have good output by 3pm. In a low mass house with poor insulation you can go to about 3pm. Frankly if its bloody cold I go to 24x7 because we are both in all day anyway.
OTOH is its a case of a low thermal mass house and everyone is out all day at work/school,. light up the boiler about half an hour before you get in. And run it to half an hour before bedtime, and get a good duvet or a willing wife..;-)
Personally I hate getting up into the cold, so heating on half and hour or more before getting is good, and time the water to heat up even earlier...and switch off half an hour before you leave for work.
Also with lower return temps a condensing boiler should be able to recover more of the latent heat of vaporisation, getting ever closer to the gross energy content of the gas burnt.
- The temperature drop across the radiator (flow and return).
- The temperture difference between the radiator and the room air temperature.
If you look at radiator manufacturer data sheets, you will see that they publish tables of numbers to allow you to work out what the actual heat output will be as opposed to the specified figures used in lab tests. The latter are done according to a standard which uses 90 degree flow. the tables work on the basis of Mean Water to Air temperature (MWTA) which is calculated by taking the mean water temperature (Flow + Return)/2 and subtracting room temperature from that.
You will end up with a factor that is multiplied by the nominal output to give the actual output under those operating conditions.
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Well, obviously if they're the same then there's no heat being dumped by the radiators - so either they're all wrapped in duvets or your house is already at the same temperature as the outflow from the boiler.
The house: The lowest temperature you can put up with _after_ you have put on a sweater!
The boiler: If you have a HW cylinder then set the flow temp to be around 10C higher than the HWC temp. The HWC temp should be set to at least 50C but otherwise as low as you can get away with on two counts: 1) The washing up 2) Making sure that there is enough HW for your needs, the cooler you store the HW the less HW you will have stored up. This is because you will be mixing it with less cold water as you use it.
If you have no HW cylinder then set the boiler as low as you can get away with but which still heats the radiators up enough to make the house comfortable.
Have the heating on as little as you can get away with. Try to heat the HW up only just before you need it.
Try things on middling setting and then adjust them a little at a time until they are what you want.
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