central heating - on longer or hotter?
 

Please can some one tell me which is most efficient if you want to get the
central heating up to say 22 degrees in time to get up in the morning....

Leave the thermostat on 22 degrees and have it come on earlier for longer
or
Put it on 26 &/or turn up heater temperature and let it come on later.

I've puzzled so much I'v econvinced myself both ways, but there must be a
scientific answer...
cheers

"keith" wrote
| Please can some one tell me which is most efficient if you want to
| get the central heating up to say 22 degrees in time to get up in
| the morning....
| Leave the thermostat on 22 degrees and have it come on earlier
| for longer or
| Put it on 26 &/or turn up heater temperature and let it come on later.
| I've puzzled so much I'v econvinced myself both ways, but there must
| be a scientific answer...

Turning the thermostat to 26 will make no difference to how much heat the
boiler will put out and thus no difference to how long it takes to heat the
room. It only affects at what degree of warmthness the CH turns off.

The only ways to get the room warmer earlier a
1. Turn the heating on earlier
2. Increase the heat output of the system by adding radiators if there is
spare boiler capacity, or increasing the size of the boiler

Owain

In an earlier contribution to this discussion,
keith wrote:

Please can some one tell me which is most efficient if you want to
get the central heating up to say 22 degrees in time to get up in the
morning....

Leave the thermostat on 22 degrees and have it come on earlier for
longer or
Put it on 26 &/or turn up heater temperature and let it come on later.

I've puzzled so much I'v econvinced myself both ways, but there must
be a scientific answer...
cheers

Not sure it's a question of efficiency! With the system running flat out it
will take a finite time to reach your desired 22 degrees. If you start it
too late to achieve this, you can set the stat to 50 if you like - it ain't
going to make any difference - 'cos if it doesn't even get to 22 it isn't
going to get to a level where the stat operates.

The problem is that the starting time needs to be different depending on how
cold it gets over night. The way to deal with this is to replace your manual
stat with a programmable stat such as the Honeywell CM67 with optimum start.
You tell that what temperature to achieve by when - and it works out for
itself when to start. You won't get much more efficient than that!
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Cheers,
Set Square
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Owain wrote:

Turning the thermostat to 26 will make no difference to how much heat the
boiler will put out and thus no difference to how long it takes to heat the
room. It only affects at what degree of warmthness the CH turns off.

The only ways to get the room warmer earlier a
1. Turn the heating on earlier
2. Increase the heat output of the system by adding radiators if there is
spare boiler capacity, or increasing the size of the boiler

Assuming the boiler thermostat isn't already up full of course, and the
OP did say "increase the heater temperature" - which suggests it isn't ;)
Albeit the effect of flow temp on warm up time depends on the Kw output
of the boiler, amount of water and number of rads in the system...


Lee


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Lee wrote:

Assuming the boiler thermostat isn't already up full of course, and the

Doh!, meant "is" not isn't.

Lee
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Email address is valid, but is unlikely to be read.

Owain wrote in message
...
"keith" wrote
| Please can some one tell me which is most efficient if you want to
| get the central heating up to say 22 degrees in time to get up in
| the morning....
| Leave the thermostat on 22 degrees and have it come on earlier
| for longer or
| Put it on 26 &/or turn up heater temperature and let it come on later.
| I've puzzled so much I'v econvinced myself both ways, but there must
| be a scientific answer...

Turning the thermostat to 26 will make no difference to how much heat the
boiler will put out and thus no difference to how long it takes to heat
the
room. It only affects at what degree of warmthness

That must be the most convoluted way of typing 'temperature' I'm ever likely
to come across :)

"Lee" wrote
| Assuming the boiler thermostat isn't already up full of course,
| and the OP did say "increase the heater temperature" - which
| suggests it isn't ;)

That would only make a difference if the boiler is cutting out whilst there
is still a demand for heat. That's possible with hot water only once the
cylinder reaches 50--70degC, but unlikely with heating as if the rooms are
still below 20deg and the radiator stats are open there should be ample
dumping of heat from the boiler to keep the boiler stat on even at low
settings.

Owain

That would only make a difference if the boiler is cutting out whilst
there
is still a demand for heat. That's possible with hot water only once the
cylinder reaches 50--70degC, but unlikely with heating as if the rooms are
still below 20deg and the radiator stats are open there should be ample
dumping of heat from the boiler to keep the boiler stat on even at low
settings.

That is only true of an old style non-modulating boiler that has been sized
to the house requirements. A modern modulating boiler is so overpowered
(typically 28kW) that it will very quickly be able to reach the set output
temperature, and bring the radiators up to temperature. Then the boiler stat
will act almost as a power setting for those radiators, long before the room
temperature rises anywhere near the room stat setting.

Christian.

Thanks to all for replies,

So it sounds like the most cost efficient way to wake up warm is to
put the gas burner temp high
(setting water tank thermostat medium for hot water)
put the CH thermostat on the temp i want to be at when we wake up,
and experiment with how early this has to be until it's right.

cheers